Full opinion text
OPINION MURRAY M. SCHWARTZ, Senior District Judge. I. Introduction Schering Corporation (“Schering”) and Biogen, Inc. (“Biogen”) (collectively “Scher-ing”) filed a patent infringement suit against Amgen, Inc. (“Amgen”), alleging Amgen infringed Biogen’s U.S. Patent No. 4,530,901 (“the ’901 Patent”), entitled “Recombinant DNA Molecules and Their Use in Producing Human Interferon-Like Polypeptides.” Amgen answered the Complaint alleging various affirmative defenses and counterclaimed seeking a declaratory judgment that the ’901 Patent is unenforceable, invalid, not infringed, and has been misused. Jurisdiction is proper under 28 U.S.C. § 1338(a). Pursuant to Markman v. Westview Instruments, Inc., 517 U.S. 370, 116 S.Ct. 1384, 134 L.Ed.2d 577 (1996), the Court now construes the scope and meaning of disputed claim language in the ’901 Patent. II. Factual Background A. History of Interferon The ’901 Patent relates generally to the synthesis of human alpha interferon (also referred to as “IFN-ot”), a naturally occurring human protein that functions as an antiviral and anti-tumor agent in human beings. The importance of interferon was first appreciated in the 1950s, and because of its ameliorative properties, became of interest as a pharmaceutical. Interferon may be produced by leukocyte cells (a type of white blood cell), fibroblast cells, or lymphoblastoid cells in the human body. The ’901 Patent, however, addresses primarily leukocyte interferon which is produced in the human body when these cells are exposed to viruses or other foreign invaders. Only minute amounts of interferon, however, can be extracted from the human cells which produce it. As a result, researchers explored alternative ways interferon could be produced in mass quantities. The ’901 Patent describes an alternative method by which to harvest alpha interferon: recombinant DNA technology. Briefly, the recombinant DNA technology at issue operates by: 1) identifying and isolating the DNA that contains the genetic code for manufacturing interferon in the human body; 2) inserting the isolated DNA into a bacterium which did not otherwise produce interferon; 3) growing the bacterium into enormous quantities, with each new bacterium containing the inserted interferon DNA; 4) utilizing the protein-making capacity of the bacteria cells to produce interferon; and 5) collecting the interferon from the bacteria to be used for pharmaceutical purposes. Dr. Charles Weissmann, the named inventor of the ’901 Patent, was the first person able to identify and isolate DNA bearing the genetic code for human alpha interferon using recombinant DNA technology. Human leukocyte cells were induced to make interferon by exposing them to a virus. A RNA (ribonucleic acid) mixture was collected from the induced cells, which contained among its constituents RNA encoding for alpha interferon. Double-stranded DNA fragments (cDNA or copy DNA) corresponding to the RNA segments in this mixture were then made according to methods known in the art. These cDNA segments were spliced into plasmids (circular loops of DNA found only in bacteria) which were in turn inserted into E. coli bacteria. Thousands of these transformed bacteria were then grown into colonies of billions of bacteria, each of which contained a copy of the plasmid that transformed the bacteria. Individual alpha interferon DNA was identified and isolated by systematically exposing the cDNA in the bacterial plasmid to the original RNA mixture. In this way, RNA complementary to the cDNA hybridized to the eDNA. The RNA, which hybridized to the cDNA, was then injected into frog oo-cytes (eggs) to determine if the RNA in question, when translated into protein, coded for interferon. Oocytes which contained the RNA coding for leukocyte interferon were effectively able to fight off viruses to which they were exposed, while the oocytes not coding for interferon died when exposed to the virus. In this general manner, the ’901 Patent identifies a number of DNA sequences that code for alpha interferon (“the DNA inserts”) which were each physically isolated by Dr. Weissmann. Each of these isolated DNA inserts, contained in a plasmid within a host cell, were then physically deposited with an official depository in Germany on January 7, 1980. The application for the ’901 Patent was subsequently filed on February 4, 1980. Later, Dr. Weissmann made further discoveries, including the fact that there are a number of different genes that code for different subtypes of alpha interferon. As a result, Biogen, three months later, filed a continuation-in-part application to cover this newly discovered subject matter. However, a patent never issued on this continuation-in-part application. B. The ’901 Patent The ’901 Patent issued to Biogen on July 23, 1985, after being assigned to it by the inventor, Weissmann. Schering was subsequently granted an exclusive license to practice the ’901 Patent. The independent claims of the ’901 Patent, Claims 1, 5, 8, 9, and 12, are directed to: a substantially pure DNA sequence containing the DNA coding on expression for a polypeptide of the IFN-a type (Claim 8); a recombinant DNA molecule that may be used to express an IFN-a type polypeptide in a host cell (Claim 1); a host cell transformed with a recombinant DNA molecule containing DNA coding on expression for a polypeptide of the IFN-a type (Claim 5); and methods for producing these polypeptides involving: 1) the preparation of a recombinant DNA molecule containing an IFN-a type DNA sequence, 2) transformation of a host cell with the DNA molecule, 3) culturing of the host, and 4) collection of the IFN-a type protein product (Claims 9 and 12). Schering contends Amgen’s consensus interferon product infringes all of these independent claims. Specifically, the following claim language is in dispute: 1. “A recombinant DNA molecule consisting of segments of DNA from different genomes” (Claims 1, 5, 9 and 12); 2. “which have been joined end-to-end outside of living cells” (Claims 1, 5, 9 and 12); 3. “which have the capacity to infect some host and to be maintained therein, and the progeny thereof’ (Claims 1, 5, 9 and 12); 4. “DNA sequences which hybridize to any of the foregoing DNA inserts,” (Claims 1, 5, 8, 9,12); 5. “A polypeptide of the IFN-a type,” (Claims 1, 5, 8, 9,12); 6. “(b) DNA sequences ... which code on expression for a polypeptide of the IFN-a type, and (c) DNA sequences which code on expression for a polypeptide of the IFN-a type coded for on expression by any of the foregoing DNA sequences .... ” (Claims 1, 5, 8, 9,12); and 7. “A substantially pure DNA sequence ... said DNA sequences coding on expression for only a single polypeptide chain,” (Claim 8). The Court, however, need only consider Claims 1 and 8, as they are representative of the claim disputes existing in the other independent claims. The disputed claim language will be construed according to the claim construction principles which are set out below. • III. Applicable Law for Claim Construction Patent infringement actions consist of two discreet and separate phases. In the first phase, the Court construes the scope and meaning of a patent, while in the second phase, the claim, as properly construed, is compared to the accused product. See Gentry Gallery, Inc. v. Berkline Corp., 134 F.3d 1473, 1476 (Fed.Cir.1998). The first phase is known as claim construction and is exclusively a matter of law to be determined by the Court. See Cybor Corp. v. FAS Technologies, Inc., 138 F.3d 1448, 1455 (Fed.Cir.1998) (in banc). The Court only addresses the claim construction phase in this opinion. Proper claim construction requires an examination of the claim language, the specification, and, if introduced, the prosecution history. See Phonometrics, Inc. v. Northern Telecom Inc., 133 F.3d 1459, 1464 (Fed.Cir.1998) (citing Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed.Cir.1996)). Foremost in importance is the asserted claim itself and, therefore, the claim language constitutes the appropriate starting point for the claim construction analysis. See id. (citations omitted); see also Vitronics, 90 F.3d at 1582 (a court “must look to the words of the claims themselves, both asserted and nonasserted, to define the scope of the patented invention.”). Particularly significant in this case is the principle that claim language is interpreted to ascertain the meaning that a person of ordinary skill in the art would give to the claims in dispute. See Wiener v. NEC Electronics, Inc., 102 F.3d 534, 539 (Fed.Cir.1996). The operative time for determining what meaning the disputed language of the claim has in the art is the date of the application for the patent. See id. While disputed claim language will normally be given its ordinary and customary meaning, “a patentee may choose to be his own lexicographer and use terms in a manner other than their ordinary meaning, as long as the special definition is clearly stated in the patent specification or file history.” Vitronics, 90 F.3d at 1582. Further, claims in the same patent are to be interpreted with reference to one another. See Southwall Technologies, Inc. v. Cardinal IG Co., 54 F.3d 1570, 1579 (Fed.Cir.), cert. denied, 516 U.S. 987, 116 S.Ct. 515, 133 L.Ed.2d 424 (1995). If the scope and the meaning of the claim language is ambiguous, the Court next considers the specification, which may be examined to more properly understand the metes and bounds of the claim. See Vitronics, 90 F.3d at 1582. The specification acts as a dictionary when it either expressly, or by implication, defines terms used in the claims. See id. As a result, the specification has been described as “often the single best guide to the meaning of a disputed term .... ” See id. When the specification explains and defines a term used in the claims, without ambiguity or incompleteness, there is no need to search further for the meaning of the term. See Multiform Desiccants, Inc. v. Medzam, Ltd., 133 F.3d 1473, 1478 (Fed.Cir.1998). The specification, however, cannot be used to import language into the claim limitation in a wholesale fashion. Although, “examples disclosed in the preferred embodiment may aid in the proper interpretation of a claim term, the scope of a claim is not necessarily limited by such examples.” Ekchian v. Home Depot, Inc., 104 F.3d 1299, 1303 (Fed.Cir.1997); Internet Am., 887 F.2d at 1053 (“[Interpreting what is meant by a word in a claim is not to be confused with adding an extraneous limitation appearing in the specification, which is improper.”). When the prosecution history is introduced into evidence, it informs the understanding of terms found in both the specification and the claim. See Multiform Desiccants, 133 F.3d at 1478 (“The evolution of restrictions in the claims, in the course of examination in the [Patent and Trademark Office], reveals how those closest to the patenting process — the inventor and the patent examiner — viewed the subject matter.”). Indeed, the prosecution history may limit, through prosecution history estoppel, the interpretation of the disputed language to meanings not expressly disclaimed by the inventor during the prosecution of the patents. See CVI/Beta Ventures, Inc. v. Tura LP, 112 F.3d 1146, 1152 (Fed.Cir.1997) (quoting Southwall, 54 F.3d at 1579), cert. denied sub nom. Marchon Eyewear v. Tura LP, - U.S. -, 118 S.Ct. 1039, 140 L.Ed.2d 105 (1998). Additionally, the prosecution history cannot enlarge, diminish or vary the limitations in the claims. See Markman, 52 F.3d at 980. “[I]f necessary to aid the court’s understanding of the patent,” the Court may consider extrinsic evidence. See Wright Medical Technology, Inc. v. Osteonics Corp., 122 F.3d 1440, 1443 (Fed.Cir.1997). Technical treatises and dictionaries are favored over other forms of extrinsic evidence. See Vitronics, 90 F.3d at 1584 n. 6. If, however, the intrinsic evidence unequivocally describes the meaning and scope of the disputed language, reliance on any extrinsic evidence is improper. See id. at 1583; Bell & Howell Document Management Products Co. v. Altek Systems, 132 F.3d 701, 705 (Fed.Cir.1997) (“The intrinsic evidence should usually be sufficient to enable one to determine the meaning of a claim term.”). As a result, the testimony of an inventor or his attorney concerning claim construction is entitled to little or no consideration. See Bell & Howell, 132 F.3d at 706. Lastly, the Court is not limited to picking between definitions supplied by the parties. The Federal Circuit has stated in this context: It may well be that often in some cases one side or the other will offer the correct claim interpretation to the judge. More often, however, it is likely that the adversaries will offer claim interpretations arguably consistent with the claims, the specification and the prosecution history that produce victory for their side. In any event, the judge’s task is not to decide which of the adversaries is correct. Instead the judge must independently assess the claims, the specification, and if necessary the prosecution history, and relevant extrinsic evidence, and declare the meaning of the claims. Exxon Chemical Patents, Inc. v. Lubrizol, Corp., 64 F.3d 1553, 1556 (Fed.Cir.1995). Specifically, as to declarations submitted by diametrically opposed experts, the Court expressly does not make factual findings or choose between them. The experts only inform the Court regarding their respective view on how the law should be interpreted. These claim construction principles will now be applied to the disputed claim language in the ’901 Patent. IV. Claim Construction of the ’901 Patent A. Claim 1 The language in dispute in Claim 1 can be more easily analyzed if subdivided into six distinct phrases: 1) “recombinant DNA molecule consisting of segments of DNA from different genomes,” 2) “joined end-to-end outside of the living cells,” 3) “capacity to infect some host and to be maintained therein, and the progeny thereof,” 4) “DNA sequences which hybridize to any of the foregoing DNA inserts,” 5) “a polypeptide of the IFN-a type,” and 6) “DNA sequences ... which code on expression for a polypeptide of the IFN-a type, and DNA sequences which code on expression for a polypeptide of the IFN-a type coded for on expression by any of the foregoing DNA sequences and inserts.” Each of these claim phrases will be examined in turn. 1. “recombinant DNA molecule consisting of segments of DNA from different genomes” This claim language can be more efficaciously explored by further dividing it into three smaller segments: a) “recombinant DNA molecule,” b) “consisting of,” and c) “segments of DNA from different genomes.” a. “recombinant DNA molecule” There is not, and there could not be, any dispute about the meaning of this term as it is specifically defined in the specification: Recombinant DNA Molecule or Hybrid DNA — A molecule consisting of segments of DNA from different genomes which have been joined end-to-end outside of living cells and the have the capacity to infect some host cell and being maintained therein. See Col. 7, lines 33-37. When the specification is acting as a dictionary, expressly defining a term used in the claims, it is “the single best guide to the meaning of the disputed term ....” See Vitronics, 90 F.3d at 1582. Accordingly, the Court adopts this definition for “recombinant DNA molecule.” Unfortunately, however, this definition is singularly unhelpful because it merely mimics the language in the claim that follows the term “recombinant DNA molecule.” Thus, it is necessary to construe the ensuing claim terms to gain an insight into the scope and meaning of this claim element. b. “consisting of’ Amgen argues “consisting of,” a term of art in patents, excludes the presence of non-recited elements. Schering counters that “consisting of’ is not used as a “transitional phrase,” but is part of Claim l’s “preamble,” and thus, there is no need to afford it its special patent law meaning. In patent law, there are terns whose meaning cannot be changed by individual parties. Two such phrases are “consisting of’ and “comprising.” See In re Gray, 19 C.C.P.A. 745, 53 F.2d 520, 521 (CCPA 1931). “Comprising” indicates the claim is open and additional elements not recited can be covered by the claim, whereas “consisting of’ indicates the claim is closed and no elements not recited may be included in the claim’s definition. See id.; Mannesmann Demag Corp. v. Engineered Metal Products Co., 605 F.Supp. 1362, 1379 (D.Del.1985), aff'd, 793 F.2d 1279 (Fed.Cir.1986); D. Chisum, 2 Patents § 8.06[1][b] at 8-99 to 8-102 (1984). However, in deciding whether to apply these “special meanings” in construing a claim, one must first ask whether a special clause such as “consisting of’ is part of the preamble, body or transition of the patent. See Regents of Univ. of Calif. v. Eli Lilly & Co., 39 U.S.P.Q.2d 1225, 1258 n. 15, 1995 WL 735547 (S.D.Ind.1995), aff'd in pertinent part, 119 F.3d 1559 (Fed.Cir.1997), cert. de nied, - U.S. -, 118 S.Ct. 1548, 140 L.Ed.2d 695 (1998); Chisum at § 8.06[1][b] at 8-99 (1998). Only if “consisting of’ is part of the transitional section of the claim will it be afforded the “special” limited meaning enunciated above. See Moleculon Research Corp. v. CBS, Inc., 793 F.2d 1261, 1271-72 & n. 8 (Fed.Cir.1986) (construing “comprising”). In the ’901 Patent, “consisting of’ in the disputed claim language is employed in the following manner: 1. A recombinant DNA molecule consisting of segments of DNA from different genomes which have been joined end-to-end outside of living cells and which have the capacity to infect some host and to be maintained therein, and the progeny thereof, comprising a DNA sequence selected from the group consisting of: (a) the DNA inserts_ (b) DNA sequences which hybridize (c) DNA sequences which code on expression .... See Col. 36, lines 4-5, 8-17 (emphasis added). After analyzing the pertinent language of this claim, the Court finds the first mention of “consisting of’ is clearly utilized as a transitional phrase in the claim, i.e., all the language coming after “consisting,” states, as a series of phrases, the structural elements which make up and form the nucleus of the invention. See Rosenberg § 14.05[3] at 14-32. Further, the term “recombinant DNA molecule” coming before this “consisting of’ language is not properly a one word preamble summarizing the invention expressed by the claims. See id., § 14.05[1] at 14-21. The fact that the second “consisting of’ phrase is also a transition phrase is inconsequential as neither the Court nor the parties have been able to point to a case which stands for the proposition that there cannot be two transitional phrases in one claim. Ergo, the “special meaning” ascribed to “consisting of’ when found in a transitional phase is appropriately applied to the first “consisting of’ phrase found in the claim language. The Court therefore finds “consisting of’ in Claim 1, Col. 36, line 4, indicates the claim is closed and no elements not recited in the claim may be included. c. “segments of DNA from different genomes” The crux of the dispute concerning this claim language, and which underlies many of the ensuing claim disputes between the parties, is whether the DNA segments that form the recombinant DNA molecule have to be from naturally-occurring genomes or may also be from non-naturally occurring genomes. Amgen argues this phrase must be construed narrowly such that the segments of DNA that make up the recombinant DNA molecule must be taken from the DNA of different naturally-occurring cells or viruses, e.g.,- segments of DNA from human beings and bacteria. Schering, on the other hand, maintains that the term “genome” should be interpreted broadly to mean the recombinant DNA molecules may be taken from both naturally occurring DNA sequences and from non-naturally occurring DNA sequences, such as those DNA sequences found in the engineered plasmids described in the specification. The term “genome” is defined in the specification: Genome — The entire DNA-of a cell or a virus. It includes inter alia the structural genes coding for the polypeptides of the substance, as well as operator, promoter and ribosome binding and interaction sequences, including sequences such as the Shine-Dalgarno sequences. See Col. 6, lines 57-62. It is unclear from this definition whether a genome is limited to DNA that originated in nature. Schering argues that the recombinant DNA molecules described in the ’901 Patent specification include DNA sequences that did not originate in nature; specifically, the pBR322 and pKT287 engineered plasmids that were used as cloning vehicles. See Col 27, lines 8-27; Col. 30, line 42. Because Schering asserts it is well-settled patent law that claims should be interpreted to encompass the embodiments of the specification, see Vitronics, 90 F.3d at 1583, it contends this claim language must be construed to include the engineered plasmids which did not originally occur in nature. Further, Schering finds support in the specification which states: A wide variety of host/cloning vehicle combinations may be employed in cloning the double stranded cDNA prepared in accordance with this invention. For example, useful cloning vehicles may consist of segments of chromosomal, non-chromosomal and synthetic DNA sequences, such as ... vectors derived from combinations of plasmids and phage DNAs such as plasmids which have been modified. See Col. 12, lines 3-14. The Court agrees with Sehering that the examples disclosed in the specification take DNA segments from the genome of both naturally occurring and non-naturally occurr ring cells. Not only does a recombinant DNA molecule’s genome not occur in nature, but at least one of the segments of DNA that make up this recombinant molecule may not come from nature. Specifically, the recombinant DNA molecules synthesized in the specification include either the pBR322 or pKT287 bacterial plasmids, which both parties agree, were engineered in the laboratory. See also D.I. 186 at 3, 6. Amgen argues, however, that even though the plasmid product is engineered in the laboratory, the plasmids consist of natural DNA, with the exception of one synthetic nucleotide in pKT287. Significantly, it is the bacterial genome as a whole, which is not naturally-occurring, and the desired interferon-type DNA sequence which are spliced together to form the recombinant DNA molecule. See Col. 36, lines 4-5. The combination of natural DNA with other non-natural constituents to foim the pKT287 and pBR322 plasmids is not part of the ’901 invention, but existed previously in the art. See Col. 13, lines 61-68 (pBR322); Col. 30, lines 42-43 (pKT287). Accordingly, regardless of whether the patent permits the splicing together of more than two segments of DNA from different genomes, as Amgen urges, the fact of the matter is that the preferred embodiment contemplates splicing an alpha interferon type segment with an engineered plasmid. The preferred embodiment must be covered by any interpretation of this claim language as an interpretation of a claim term which excludes a preferred embodiment is to be avoided. See Vitronics, 90 F.3d at 1582. The Court thus construes “segments of DNA from different genome” as permitting segments of DNA from genome of both naturally occurring cells or viruses and non-naturally occurring cells and viruses. The prosecution history further strengthens this conclusion. Under the doctrine of prosecution history estoppel, the prosecution history may limit the interpretation of the disputed language to meanings not expressly disclaimed by the inventor during the prosecution of the patents. See CVI/Beta Ventures, 112 F.3d at 1155 (quoting Southwall, 54 F.3d at 1579). This estoppel “may arise either from matters surrendered as a result of amendments to overcome patentability rejections ... or as a result of argument to secure allowance of a claim.” See Cybor, 138 F.3d at 1460. However, the reason for offering an amendment or an argument remains relevant to the application of an estoppel. See Litton Systems, Inc. v. Honeywell, Inc., 140 F.3d 1449, 1456 (Fed.Cir.1998). It is thus important for the Court to determine the reason a patentee submitted an argument or amendment during the prosecution of the patent. See Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 117 S.Ct. 1040, 1051, 137 L.Ed.2d 146 (1997). The originally filed claims recited: “DNA from whatever source obtained, including natural, synthetic, or semi-synthetic sources, related by mutation, including single or multiple, base substitutions, deletions, insertions, and inversions to any of the foregoing DNA sequences or inserts.” D.I. 172, Tab 1 at 64 (February 4, 1980). Amgen argues that because Biogen was forced to eliminate this language by the patent examiner, Biogen is now estopped from claiming synthetic and semi-synthetic sources for the DNA segments from different genomes. In rejecting this initial claim language, however, the examiner found over broad the use of the terms “related by mutation,” “multiple base substitutions,” “deletions,” “insertions,” and “inversions,” but significantly did not question the validity of the terms “synthetic” or “semi-synthetic.” See id., Tab 17 at 3 (November 29, 1982). Accordingly, the Court finds prosecution history estoppel does not bar an interpretation of “segments of DNA from different genomes” which includes both naturally occurring and non-naturally occurring DNA segments. For all of these reasons, the Court holds the claim language “segments of DNA from different genomes” refer to DNA segments or DNA sequences in genomes of cells or viruses which may be both naturally occurring and non-naturally occurring. Combining the above construed elements, the Court finds the claim language “[a] recombinant DNA molecule consisting of segments of DNA from different genomes” refers to a molecule which may consist of segments of DNA in genomes from both naturally occurring or non-naturally occurring cells or viruses. 2. “joined end-to-end outside of the living cells” The dispute concerning this claim language is whether this phrase is a product-by-process claim. Amgen argues it is and therefore, this claim language is a process limitation that requires the joinder of DNA end-to-end outside of the living cell. Scher-ing disagrees. It asserts this language is not in product-by-process form. Instead, Scher-ing argues that it is only a structural limitation as to the term “recombinant DNA molecule,” and therefore, this claim language may encompass an identical product made by a different process. “Product-by-process claims” are claims which describe the product more by the process used to obtain it than by its structure. See Hazani v. United States Int'l Trade Comm., 126 F.3d 1473, 1479 (Fed.Cir.1997). Although not referred to in the patent statute, product-by-process claims developed in response “to the need to enable an applicant to claim an" otherwise patentable product that resists definition other than by the process by which it is made.” See In re Thorpe, 777 F.2d 695, 697 (Fed.Cir.1985). The Court, however, is not persuaded that the phrase “joined end-to-end outside of living cells” is in produet-by-process form. Product-by-process claims recite how a product is made, not how it is used. See Mentor Corp. v. Coloplast, Inc., 998 F.2d 992, 997 (Fed.Cir.1993). This claim language, however, is best characterized as a pure product claim since the product is described by its structure rather than by the process used to obtain it. See Hazani, 126 F.3d at 1479. Accordingly, the Court finds “joined end-to-end outside of living cells” to be a structural limitation which may encompass identical products made by different processes. 3. “capacity to infect some host and to be maintained therein, and the progeny thereof’ Amgen contends this language requires that the joined segments of DNA must not only be able to infect a host cell and be maintained therein but also these same DNA segments must not be lost by its progeny. Sehering retorts that Amgen has misconstrued this phrase by not properly applying the comma in the phrase, which would actually make two separate phrases of the claim language. As a result, Sehering argues this claim language does not require the desired DNA segments to be maintained by the progeny of the initial host cells. The Court is persuaded that the comma does not act to distinguish between two separate phrases. As stated previously, Claim 1 reads in pertinent part: A recombinant DNA molecule consisting of segments of DNA from different genomes which have been joined end-to-end outside of living cells and which have the capacity to infect some host and to be maintained therein, and the progeny thereof .... See Col. 86, lines 4-8. Reading this claim language as a coherent whole, the claim language does require that the recombinant DNA molecules infect the progeny of the host, but does not require the recombinant DNA molecules be maintained in the progeny. If the claim language was to be construed otherwise, the sentence would have been written in the following manner: “... which have the capacity to infect some host and its progeny and be maintained therein .... ” Instead, the claim language merely reflects that the patentee wishes not only to cover the first generation of host cells that were infected by the recombinant DNA molecule but also the progeny which result from the reproduction of the host cells. While the purpose is not readily apparent, the claim language, as written, also takes into account the instance where even if the recombinant DNA molecule infects the progeny of the host, there is still a chance the recombinant DNA molecules may not be maintained in the progeny. As such, the Court finds “which have the capacity to infect some host and to be maintained therein, and the progeny thereof,” requires that the recombinant DNA segments infect the progeny of the host cells, but not necessarily to be maintained therein. 4. “DNA sequences which hybridize to any of the foregoing DNA inserts” This claim language contains two distinct claim terms which must be analyzed: a) “DNA inserts” and b) “hybridize.” The Court will consider each of these claim terms in turn. a. “DNA Inserts” Both parties agree that the “DNA inserts” refer to the inserts contained within the E. coli bacterial cells deposited with the Deutsche Sammlung von Mikroorganismen (“DSM”) in Germany. Amgen further seeks to establish that: 1) the inserts refer to the discrete sequences that are released from the deposited plasmids by using a restriction enzyme to cut the DNA insert and 2) the inserts are all derived from the same interferon gene. Schering asserts these added limitations are not part of the definition of “DNA inserts” and it is improper to read such limitations into the claim terms from the examples in the specification and from deposition testimony. The Court agrees with the parties that the DNA inserts are clearly set out in the ’901 Patent. Claim 1 reads in pertinent part: A recombinant DNA molecule ... comprising a DNA sequence selected from the group consisting of: (a) the DNA inserts of [Z-pBR322(Pst)/HcIF-4c (DSM 1699,] Z-pBR322(Pst)/HcIF-2h (DSM 1700), Z-pBR322 (Pst)/HeIF-SN35 (DSM 1701), Z-PBR322(Pst)/HcIF-Sn42 (DSM 1702) and ZpKT287(Pst)/HcIF-2h-AH6 (DSM 1703), (b) DNA sequences which hybridize to any of the foregoing DNA inserts .... Col. 36, lines 4-15. Although the DNA inserts described include the designation “(Pst)” to refer to the restriction site where the plasmid was cut, the claim language limits what is claimed to the “DNA inserts” of the recombinant DNA molecule. Importantly, the restriction enzyme, the plasmid, and the bacterial host in which the isolated DNA sequences are found, are not part of the ’901 invention. Further, there is no hint in either the claim or the specification that the DNA inserts are, or must be, derived from the same interferon gene. Although this might have turned out to be the ease, as illustrated by subsequent deposition testimony, such information was not known to anyone at the time the patent application was filed in January of 1980. Because the Court must construe claim language according to the meaning a person of ordinary skill in the art would ascribe to it at the time of the patent application, see Wiener, 102 F.3d at 539, it cannot conclude as part of the “DNA insert” definition that all DNA inserts had to be derived from the same interferon gene, as such knowledge was lacking in the relevant scientific community at the time of the ’901 Patent application. The Court therefore finds that the claim term “DNA inserts” refers to those DNA inserts deposited at the DSM and explicitly set out in the claim language of the ’901 Patent. b. “hybridize” Both parties agree that hybridization includes the process by which one strand of DNA or RNA binds and forms a double-stranded structure with a complementary strand of RNA or DNA. See supra note 7. Specifically, hybridization was used in this invention to identify DNA segments structurally similar to both RNA segments and DNA segments found to code on expression for proteins with the anti-viral characteristics of interferon. The parties also agree that hybridization between two complementary strands is affected by such factors as time of exposure, temperature, salt concentration, and the degree of homology (amount of complementary nucleotides) between the two segments. Although the parties do not dispute that the selection of hybridization conditions is critical to the performance of the hybridization, the parties cannot agree what specific hybridization conditions are required by the claim. Sehering argues that the conditions must be as stringent or more stringent than the conditions used by Dr. Weissmann in performing the hybridizations described in the patent specification. Amgen, on the other hand, contends the particular hybridization conditions disclosed in the specification must be used. Starting with the language of the patent itself, “hybridize” is not defined in the claim, nor is it defined in the specification. Specific conditions for the hybridization, however, are recited in the specification, see Col. 26, line 28 through Col. 27, line 2. Nevertheless, it is improper claim construction to import specification language into the claims. See Intervet Am., 887 F.2d at 1053. While claims are to be interpreted in light of the specification, it does not follow that extraneous limitations from the specification may be read into the claims. See CVI/Beta Ventures, 112 F.3d at 1158 (citing Sjolund v. Musland, 847 F.2d 1573, 1581 (Fed.Cir.1988)). As a result, the Court cannot agree with Amgen that the particular hybridization conditions disclosed in the specification are all that is covered by the ’901 Patent. Although the specification may not be properly used to add extraneous limitations to a claim, a limitation is not extraneous when there is a need to interpret what the patentee meant by a particular ambiguous word or phrase in the claim. See E.I. du Pont de Nemours & Co. v. Phillips Petroleum Co., 849 F.2d 1430, 1433 (Fed.Cir.), cert. denied, 488 U.S. 986, 109 S.Ct. 542, 102 L.Ed.2d 572 (1988). Such is the case here because both parties agree that the selection of hybridization conditions, such as time, temperature, salt concentration, and structural homology, is essential to the performance of the hybridization and to the overall invention. As the specification is the single best guide to the meaning and scope of the claims, see Vitronics, 90 F.3d at 1582, the Court therefore finds the claim term “hybridize” necessarily includes conditions at least as stringent as those set forth in the specification. Additionally, as more stringent conditions necessarily subsume less stringent hybridization conditions, such conditions are also properly within the patent. The Court therefore holds the claim language “DNA sequences which hybridize to” refers to hybridization of other DNA to DNA inserts deposited at the DSM, under conditions as stringent or more stringent than those that exist in the specification. Accordingly, combining the above two constructed phrases, the claim language “DNA sequences which hybridize to any of the foregoing DNA inserts” refers to DNA segments, which under conditions as least as stringent as those set forth in the specification of the ’901 Patent, are able to bind and form a double-stranded structure with those DNA inserts specified in the patent and deposited at the DSM. 5. “a polypeptide of the IFN-a type” Much paper has been devoted to this claim interpretation dispute. Unhappily, the Court will be no different. The language may be parsed into two queries: a) whether the “IFN-a” portion of the claim term “IFN-a type” refers to a single protein or multiple interferon proteins and b) whether the entire claim language, i.e, “IFN-a type,” may refer to a mature interferon protein. a. . Number of Interferon Subspecies To Which “IFN-a” Refers Schering asserts that it is “self-evident” that the claim language “IFN-a type” contains two related claim terms: “IFN-a” and “IFN-a type.” The term “IFN-a,” Schering submits, refers to proteins which have the same amino acid sequences as the amino acid sequence of the naturally occurring IFN-a proteins. As a consequence, Schering argues that “IFN-a” refers to all the sub-species of IFN-a. Schering points out that although originally referred to as “leukocyte interferon” in the patent, leukocyte interferon was later changed in the patent to “IFNa” to reflect a nomenclature change in the art adopted shortly after the patent was filed. Schering distinguishes “IFN-a type,” to mean DNA encoding IFN-a that may have adjacent to it DNA encoding additional amino acids, such as leaders, tails (linkers), or fusion partners. Amgen disagrees with Schering on almost every one of the above points. As an initial point, Amgen contends that “IFN-a type” is indefinite. Recognizing that the Court was unlikely to make a validity finding during claim construction, Amgen does agree that “IFN-a type” refers to DNA encoding both IFN-a and additional adjacent amino acids. Nevertheless, Amgen argues that polypeptides of “IFN-a type” must, not may, refer to DNA encoding for IFN-a and additional, adjacent amino acids. This is because Amgen asserts “IFN-a type” does not also include within it the term “IFN-a.” Amgen also vehemently contests the that this claim language covers all the subspecies of alpha interferon, most of which were not known at the time of the invention. Difficulty in analyzing this claim language stems from the fact that the language, “a polypeptide of the IFN-a type,” was not added to the claim of the ’901 Patent until after the patent application had been submitted and in fact, “IFN-a type” appears nowhere in the specification. Indeed, the nomenclature upon which “IFN-a type” is based was not developed, until six months after the patent application was filed. See Col. 1, lines 21-23 (“In this application the interferon nomenclature announced in Nature 286, p.110 (July 10, 1980) is used. E.g. leukocyte interferon is designated IFN-a.”). This specification language concerning the new nomenclature was added to the specification on February 24, 1983, three years after the initial patent application was filed. The prosecution history cites to a eo-pending, continuation-in-part S.N. 223,108 application filed in April of 1980, in which the change was also made to support this specification amendment. See D.I. 172, Tab 18 at 9. This cite to the then co-pending application, however, is unhelpful and misleading as this eopending application was filed: 1) later then the ’901 Patent application and 2) after additional interferon genes had been identified. The Court is thus left with the question of whether it is proper to consider this subsequently added specification language in interpreting this claim language. Schering responds with at least five separate arguments. First, Schering asserts the change from leukocyte interferon to IFN-a was a simple change in nomenclature and therefore, does not constitute new matter in violation of the patent statute. See 35 U.S.C. § 132 (“No amendment shall introduce new matter into the disclosure of the invention.”); see also 37 C.F.R. § 1.118(a) (“No amendment shall introduce new matter into the disclosure of an application after the filing date of the application_”). Amgen, unsurprisingly, disagrees. The new matter prohibition under § 132 is to be interpreted in the same manner as the identical new matter prohibition found in the reissue statute, 35 U.S.C. § 251. See Application of Oda, 58 C.C.P.A. 1353, 443 F.2d 1200, 1203 n. 2 (CCPA 1971). Because whether the statutory requirements of 35 U.S.C. § 251 have been met is a question of law, see Hester Industries, Inc. v. Stein, Inc., 142 F.3d 1472, 1479 (Fed.Cir.1998) (citing In re Clement, 131 F.3d 1464, 1468 (Fed.Cir.1997)), whether the new matter prohibition under § 132 is violated must also be a question of law. Nevertheless, the legal conclusion is based on underlying findings of fact, which will be sustained unless they are clearly erroneous. See Clement, 131 F.3d at 1468; In re Kemps, 97 F.3d 1427, 1430 (Fed.Cir.1996) (“The law of this circuit is clear: PTO factual determinations are reviewed under the ‘clearly erroneous’ standard.”). Additionally, the presumption of administrative correctness as applied to a new matter determination is “entitled to an especially weighty presumption of correctness.” See Brooktree Corp. v. Advanced Micro Devices, Inc., 977 F.2d 1555, 1574-75 (Fed.Cir.1992) (quoting In re Smythe, 480 F.2d 1376, 1385 n. 5 (CCPA 1973)). Despite this heavy burden, the Court is persuaded that the patent examiner’s allowance of this “new matter” was clearly erroneous and was incorrect as a matter of law. The patent examiner improperly relied on a subsequently filed, continuation-in-part application by Biogen to allow this amendment to the ’901 patent application. However, that continuation-in-part application was filed in April of 1980, both after the ’901 Patent application was filed, and more importantly, before even the terminology “IFN-a” was adopted. This fact is important because as Amgen correctly observes, the change from leukocyte interferon to IFN-a reflects more than a mere name change, it also represents a substantive modification in the way inter-ferons are to be classified. Relying on extrinsic evidence, as the Court must to aid its interpretation in this area because the intrinsic evidence of the record is muddled, the Nature article states: Interferons will be classified into types on the basis of antigenic specificities, type designations to be alpha, beta, and gamma, corresponding to previous designations of leukocyte (Le), fibroblast (F) and type II (immune) interferons, respectively. The old terminology of ‘leukocyte’, ‘fibroblast’, and ‘immune’ interferons were, by committee consensus, abolished, as they clearly were misnomers: both leukocytes and fibroblasts can produce each of these two types of interferon .... Interferon Nomenclature, Nature, vol. 286, p.110 (July 10, 1980). Before the new nomenclature, interferon classifications were cell-specific, i.e., leukocyte, fibroblast or immune; under the new nomenclature, non-cell specific definitions have been adopted, i.e., a, P, and y. Although leukocyte cells produces primarily what is now called alpha interferon, they also produce small amounts of the other types of interferon, including fibroblast interferon or beta interferon. Similarly, fibroblast cells produce primarily beta interferon, but also produce small amounts of alpha interferon. Thus, the substitution of “IFN-a” for “leukocyte interferon” was not a simple nomenclature change, but a change in scientific terminology that reflects an underlying scientific change in the concepts surrounding interferon proteins. Accordingly, the Court finds as a matter of law that the language and citation referring to the Nature article to be new matter under 35 U.S.C. § 132. See Manuel of Patent Examining Procedure, § 608.04(a) at M-326 (1997) (“Matter not in the original specification ... is usually new matter.”). The Court cannot therefore consider this specification language as rightfully part of the specification in its construction of this claim language. See Kolmes v. World, Fibers Corp., 107 F.3d 1534, 1539 (Fed.Cir.1997); In re Rasmussen, 650 F.2d 1212, 1214 (CCPA 1981); In re Bloch, 20 C.C.P.A. 1180, 65 F.2d 268, 269 (CCPA 1933). Second, Sehering submits that even if the Court is unwilling to consider this subsequently added specification language, this is not a significant fact as the Federal Circuit has in the past construed claim terms not found in the specification by relying on the prosecution history. See Ethicon v. United States Surgical, 93 F.3d 1572, 1581 (Fed.Cir.1996). Ethicon, however, did not concern a claim term that did not exist in the art until after the patent application was filed. This difference is significant because claim language must be construed from the point of view of one of skill in the art at the time the patent application was filed. See Wiener, 102 F.3d at 539 (emphasis added). When this patent application was filed, however, this nomenclature, which designates leukocyte interferon as IFN-a, had not yet been developed and IFN-a type was unknown in the art. Third, Sehering contends the prosecution history supports its construction of “IFN-a type.” Although the prosecution history is filled with references to “IFN-a type,” see, e.g., D.I. 172, Tab 30 at 8 (“Not a single one of the IFN-a type genes is isolated to date (between 12 and 15 genes) has an 80-nucleo-tide Haelll fragment, as recited by Colby.”), all such references were made after the patent application had been filed. Sehering asserts prosecution history statements are always made after a patent application has been filed and yet are routinely relied on to discern the meaning of claim language. Nonetheless, in those cases where prosecution history has been utilized, the claim language was not unknown in the art at the time the patent was filed. Further, the Court is disinclined, given principles of claim construction, to add, limit, or vary the scope of the claims based on post facto explanations found only in the prosecution history. See Markman, 52 F.3d at 980 (proper role of prosecution history is to inform scope and meaning of claim and specification, not to add, vary, or enlarge claim language). Fourth, Sehering argues that since leukocyte interferon was defined by its activity in the disclosure, any protein found to have the same activity must also be covered by the ’901 Patent, including the various subspecies of interferon. This simply cannot be. As an initial matter, even Sehering agrees that the patent does not cover the interferon proteins encoded by the isolated DNA sequences because such proteins are unpatentable as products of nature. See 35 U.S.C. § 101; Diamond v. Chakrabarty, 447 U.S. 303, 309, 100 S.Ct. 2204, 65 L.Ed.2d 144 (1980). The ’901 Patent covers only isolated DNA sequences and recombinant DNA methods for producing the interferon protein. Moreover, patents cannot cover physical phenomena occurring in nature, such as the biological or immunological effect of interferon on viruses. See Chakrabarty, 447 U.S. at 309, 100 S.Ct. 2204. Lastly, even if the Court were to find that leukocyte interferon should be defined as it is in the patent by its activity, the Court has previously determined that it would not take into account the IFN-a nomenclature change in the specification as it is new matter in violation of 35 U.S.C. § 132. For these reasons, then, the Court declines to define IFN-a by its activity. Fifth, Sehering argues that having identified one member of a gene family, it is entitled to claim the whole gene family. Sehering cites Oka v. Youssefyeh, 849 F.2d 581 (Fed.Cir.1988) for this proposition. Oka does indeed stand for the proposition that, “conception of a species within a genus may constitute conception of the genus.” See id. at 584 (emphasis added). The Federal Circuit went on to say, however, that where there is no evidence that the patented method could be used to derive the other species within the genus, there is no basis for the view that a description or method of making one is applicable to the other. See id. In the ease at bar, there was similarly no evidence, at the time of the invention, that the recombinant DNA method of procuring IFN-a-1 could be used to derive the other species in the genus. In fact, at the time of the ’901 invention, both Dr. Weissmann and Sehering have conceded that it was unknown in the art that there was more than one species of interferon. Thus, even though Dr. Weissmann had in fact derived, using a hybridization probe, the IFN-a-2 species among 185 positive colonies of transformed bacteria, he did not describe or isolate the separate species in the disclosure to the ’901 Patent. As such, there is no basis for the view that a description or method of making IFN-a-1 is applicable to the other species of interferon, including IFN-a-2. Thus, conception of the IFN-a-1 species within the IFN-a genus does not constitute conception of the entire IFN-a genus. Nevertheless, the Court is also unwilling to agree with Amgen that this language should be held invalid for lack of enablement in the specification or for indefiniteness, as claim construction does not concern itself with arguments of invalidity. See supra note 13. “[A] district court must exercise its power and duty to say what the claims mean.” See Digital Biometrics, 149 F.3d 1335, 1344. Because after consideration of the intrinsic evidence the exact meaning of the claim terms remains a mystery, “consideration of extrinsic evidence [is] necessary to determine the proper construction.” See id. at 1343. Having decided that extrinsic evidence is necessary to construe a claim term, another claim construction principle comes into play. See id. Because a patent applicant has the burden to “particularly point [ ] out and distinctly claim [ ] the subject matter which the applicant regards as his invention,” 35 U.S.C. § 112, ¶ 2, “if the claim is susceptible to a broader and narrower meaning, and the narrow one is clearly supported by the intrinsic evidence while the broader one raises questions of enablement under § 112, ¶ 1, [a court should] adopt the narrower of the two.” See Digital Biometrics, 149 F.3d at 1343 (citing Athletic Alternatives, Inc. v. Prince Mfg., Inc., 73 F.3d 1573, 1581 (Fed.Cir.1996); Ethicon, 93 F.3d at 1581). Technical publications in the art make clear that “IFN-a” does indeed refer to what was previously termed “leukocyte interferon.” See Nature at 110. Despite that fact, the Court is unwilling to conclude that “IFN- ¥” necessarily includes all IFN-a subspecies. Even though the ’901 Patent specification refers to both F IF [fibroblast interferon] and Le IF [leukocyte interferon], the patent specification did not differentiate between different subtypes of leukocyte interferon. See Col. 1, lines 36-43. Nor does the fact that the specification refers to the “polymorphic” nature of leukocyte interferon lead the Court to another conclusion. See Col. 2, lines 34-35. “Polymorphic” only means that the same polypeptide may manifest itself in slightly different structural variations, not that there are separate subspecies. In addition, in both Weissmann’s deposition testimony and in Schering’s Opening Brief on Claim Construction, it is candidly admitted that at the time of Dr. Weissmann’s invention, Dr. Weissmann did not recognize the existence of multiple alpha interferon subtypes. See D.I. 163 at 27; D.I. 176, Ex. L at 319. There is therefore no evidence in the intrinsic or extrinsic record that the inventor, Dr. Weiss-mann, knew at the time of the invention that there were various subspecies of interferon protein. Schering responds in its Opening Brief, however, that, “[a]lthough the Weissmann Inserts apparently all code for a single alpha interferon subtype (which became known as IFN-alpha-1), one skilled in the art could have isolated the DNA coding for the other naturally occurring alpha interferon subtypes ... following the hybridization procedures described in the patent specification.” See D.I. 163 at 8. In fact, during oral argument, Schering made the observation that the hy-bridizations disclosed in the specification led to the discovery of 185 positive colonies, one of which later turned out to be the DNA sequence for IFN-a-2. See Col. 27, lines 61-66. Through this logic, Schering attempts to convince the Court to adopt a broader meaning for the term “IFN-a” by including sub-species not specifically disclosed in the specification, but enabled in the specification. The Court is not persuaded. There remains a significant question as to whether the specification does disclose and enable the production of the other interferon sub-species. Specifically, although another sub-species was eventually found to exist as part of the hybridization probe carried out in the disclosure, that sub-species was not identified or isolated in the disclosure of the ’901 Patent. Accordingly, because this claim language is susceptible to a broader and narrower meaning, and only the narrow one is clearly supported by the intrinsic evidence while the broader one raises questions of enablement under § 112, ¶ 1, the narrower of the two meanings must be adopted under applicable claim construction principles. See Digital Biometrics, 149 F.3d at 1343. Consequently, the Court construes the “IFN-a” portion of the claim term “IFN-a type” to refer to a single, naturally-occurring leukocyte interferon protein known at the time of the ’901 invention, now referred to as IFN-a-1. b. Whether “IFN-a Type” May Refer To Mature Proteins A closely related question to whether IFN-a corresponds to more than one protein is whether the claim term “IFN-a type” covers: 1) DNA sequences coding for the mature form of the interferon protein, i.e., interferon itself; 2) the immature form, i.e., interferon with a leader sequence attached,; 3) a fusion protein, i.e., interferon with additional adjacent amino acids from another gene or tails attached; 4) some combination of the first three; or 5) even a protein with less than the full alpha interferon sequence. Schering asserts that since “IFN-a” refers to a mature leukocyte interferon protein, it follows that “IFN-a type” may refer to either an immature protein, a fused protein or a mature protein. Amgen disagrees and maintains the ’901 Patent covers only immature proteins and fused proteins, but not mature proteins. Because the parties agree that “IFN-a type” covers immature proteins and fused proteins, the Court will focus its analysis on whether “IFN-a type” may refer to mature proteins as well. The ’901 Patent is silent as to the import of the word “type” in the claim language. Nevertheless, “IFN-a” by itself, without the word “type” appended, appears nowhere in the claim language. If Schering had wanted its patent to read on both “IFN-a” and “IFN-a type” polypeptides, it could have written the claim language to reflect that both forms of the polypeptide were covered. It is therefore irrelevant that “IFN-a” may indeed correspond to a mature IFN-a-1 protein. Supporting this reading of the claim language is the fact that polypeptides of the “IFN-a type” are all that is supported by the intrinsic evidence of the patent. For instance, the specification recites: [A]ntibodies directed against human Le IF [leukocyte interferon] specifically inhibit the IF [interferon] of polypeptides produced in E. coli transformed with certain recombinant DNA molecules containing the HcIF-2h DNA sequences. The apparent lower affinity for the IF produced in E. coli may reflect structural differences between the latter and natural Le IF, for example, absence of carbohydrate moiety, presence of signal sequence, or fusion to part of the p-laetamase sequence. Col. 34, lines 50-58; see also Col. 30, lines 26-32. This passage reflects that the inventor was aware that he had not isolated the interferon gene alone, but had produced variations with structural differences, including interferon with a signal sequence (immature proteins), with parts of another gene (fused proteins), or a protein with less than the full alpha interferon sequence. Additionally, the specification points out that Dr. Weiss-mann had to fuse nucleotide “tails” to the DNA in order to insert the DNA sequences into the plasmid cloning vector. See Col. 14, lines 12-48. In fact, Schering admits that the DNA inserts deposited at the DSM are DNA sequences coding on expression for immature or fused forms of IFN-a-1. See D.I. 163 at 8, 30. Nevertheless, Schering cites to the following language in the specification for the proposition that the ’901 Patent teaches how to produce a mature protein: It is thus of advantage to separate the specific coding sequences for the desired protein from their adjacent nucleotide sequences and fuse them instead to other known expression control sequences so as to favor higher levels of expression .... Therefore, to improve the production of a particular polypeptide in an appropriate host, the gene coding for that polypeptide may be prepared as before and removed from a recombinant DNA molecule containing it and reinserted into a recombinant DNA molecule closer to its former expression control sequence or under control of one of the above expression control sequences. Such methods are known in the art. Col. 32, lines 30-35; 53-59. Although this language deals with eliminating fusion proteins, this segment of the specification does not deal with the elimination of the leader sequence. Notably absent from this description is any mention of the leader sequence or any mention of the distinction between immature and mature proteins. Stating it is “of advantage” to separate the specific coding sequence for the desired protein is not tantamount to saying that the leader sequence is also eliminated, especially since the subsequent method outlined in the specification does not say the leader sequence will be thereby eliminated or that even all of the fused proteins will be eliminated. As a consequence, the patent does not teach how to produce the interferon protein alone without additional, adjacent amino acids attached. In any event, a crucial distinction must be made in claim construction between importing an additional limitation into the claim, which is improper, and looking to the specification to aids its interpretation of a term already in the claim, an entirely appropriate practice. See Ethicon, 93 F.3d at 1578. In this instance, even assuming for the sake of argument that “IFN-a” does refer to the mature form of leukocyte interferon, the fact of the matter is that “IFN-a” does not appear in the claim. Only “IFN-a type” does. Thus, by reading “IFN-atype” to refer to the mature form of the protein, the Court in effect would be improperly importing the term “IFN-a” into the claim. This type of m claim construction is improper and impermissible. Further, although there are numerous passages from the prosecution history which utilize the term “IFN-a type,” see, e.g., D.I. 172, Tab 18, at 14-15, there is no intrinsic evidence that this term was understood in the manner utilized in the prosecution history at the time the ’901 patent application was filed, i.e., January of 1980. Without some basis in fact that “IFN-a type” had the same meaning when the patent application was filed, the Court is unwilling to vary the scope of this claim language based on the p