Full opinion text
MEMORANDUM AND ORDER WOLF, District Judge. I. SUMMARY.80 II. STANDARD FOR SUMMARY JUDGMENT.81 III. FACTS.82 A. Technical Background.82 B. The Axel Patents Licensed by Biogen.83 C. The Berlex Patents.84 D. The ’779 Patent .85 E. The Prosecution of the Berlex Patents.85 1. The 1982 Application.85 2. The 1984 Amendments.86 3. The 1985 CIP Application.87 4. The 1990 Divisional Application.90 5. The 1992 Preliminary Amendment.90 6. The 1994 Amendments.92 7. The 1994 Application Leading to the ’779 Patent.93 F. Biogen’s Avonex Process and Product.94 IV. BERLEX’S MOTION FOR SUMMARY JUDGMENT CONCERNING LITERAL INFRINGEMENT OF THE ’567 PATENT.94 V. BIOGEN’S MOTION FOR SUMMARY JUDGMENT CONCERNING INFRINGEMENT OF THE ’567 PATENT UNDER THE DOCTRINE OF EQUIVALENTS.104 VI. BERLEX’S MOTION FOR SUMMARY JUDGMENT CONCERNING LITERAL INFRINGEMENT OF THE ’779 PATENT.112 VII. BIOGEN’S MOTION FOR SUMMARY JUDGMENT CONCERNING INFRINGEMENT OF THE ’779 PATENT UNDER THE DOCTRINE OF EQUIVALENTS.118 VIII. CONCLUSION AND ORDER.121 I. SUMMARY These three, consolidated cases concern whether Biogen, Inc. (“Biogen”) infringes patents owned by Berlex Laboratories, Inc. (“Berlex”). The issues presented relate to the use of recombinant DNA technology to produce human beta interferon (“interferon” or “IFN”) protein in Chinese hamster ovary cells (“CHO” cells), cells which have been adapted to grow in laboratory or manufacturing conditions. Beta interferon is used to treat multiple sclerosis. Both Avonex, which is marketed by Biogen, and Betaseron, which is marketed by Berlex, are beta interferon products which have been approved by the United States Food and Drug Administration for the treatment of multiple sclerosis. Berlex is a New Jersey subsidiary of Schering AG, a German pharmaceutical company. Berlex is the co-assignee of the U.S. Patents No.’s 4,966,843 (the “’843 Patent”), 5,376,567 (the “’567 Patent”), and 5,795,779 (the “ ’779 Patent”). Biogen is a Massachusetts company that is principally engaged in the business of developing and manufacturing pharmaceutical products through genetic engineering. Berlex alleges that in producing Avonex Biogen infringes Berlex’s ’567 and ’779 Patents both literally and under the doctrine of equivalents. Berlex seeks damages for the past infringement which it alleges and a permanent injunction to prevent future infringement. Biogen requests a declaratory judgment that it does not infringe the ’567 or ’779 Patents. Alternatively, Biogen contends that if Ber-lex’s proposed claim construction is adopted by the court the ’567 Patent is invalid because it lacks the legally required adequate written description. In addition, Biogen asserts that both the ’567 and ’779 Patents should not be enforced because Berlex engaged in inequitable conduct in prosecuting the applications which led to the issuance of each patent by the United States Patent and Trademark Office (the “PTO”). The parties engaged in extensive discovery for several years. At least one party has moved for summary judgment on each issue of the foregoing issues. The parties conducted two “tutorials” to educate the court on the relevant science, which is summarized in § III A, infra. The parties agree that there are no material disputed facts concerning whether Biogen infringes the ’567 Patent either literally or under the doctrine of equivalents. They also agree that there are no disputed material facts concerning whether the ’779 Patent is infringed literally. While Berlex argues that there is a genuine factual dispute concerning whether Biogen infringes the ’779 Patent under the doctrine of equivalents, the court finds that this is not correct. See § VII, infra. As there are no material facts genuinely in dispute, the questions concerning infringement of the ’567 and ’779 Patent are ripe to be resolved on the pending motions for summary judgment. In essence, issues of claim construction are dispositive in these cases. Biogen infringes each of the claims at issue, either literally or under the doctrine of equivalents, if the claim constructions advocated by Berlex are correct. Biogen does not infringe either the ’567 or ’779 Patent if Biogen’s proffered claim constructions are correct. Claim construction is an issue to be decided by the court. Thus, the court held a “Markman hearing,” for the purpose of deciding how to construe the relevant claims, in connection with the hearings on the motions for summary judgment which were conducted on March 7, 8, 9, 10, and 13, 2000. For the reasons described in detail in this Memorandum, the court concludes that Biogen’s proposed construction of each of the claims at issue is correct. Thus, Biogen is entitled to summary judgment on its request for a declaratory judgment that it does not infringe either the ’567 Patent or the ’779 Patent. The court understands that these decisions resolve these cases, subject to possible appeal. The court is, therefore, not deciding Biogen’s motions for summary judgment on the questions whether the ’567 and/ or ’779 Patents are invalid or unenforceable. In view of the foregoing, the parties are being ordered to confer; to inform the court, by September 8, 2000, whether they agree that final judgment should now be entered for Biogen; and if so, to submit a proposed form of judgment. II. STANDARD FOR SUMMARY JUDGMENT The court’s discretion to grant summary judgment is governed by Fed.R.Civ.P. 56. Rule 56 provides, in pertinent part, that the court may grant summary judgment only if “the pleadings, depositions, answers to interrogatories, and admissions on file, together with the affidavits, if any, show that there is no genuine issue as to any material fact and that the moving party is entitled to judgment as a matter of law.” Fed.R.Civ.P. 56(c); see also Karlin Tech. Inc. v. Surgical Dynamics, Inc., 177 F.3d 968, 970 (Fed.Cir.1999). The facts must be viewed in the light most favorable to the non-moving party. Rodime PLC v. Seagate Tech., Inc., 174 F.3d 1294, 1301 (Fed.Cir.1999), cert. denied, - U.S. -, 120 S.Ct. 933, 145 L.Ed.2d 812 (2000). “When a party fails to make a showing sufficient to establish the existence of an element essential to that party’s case, and on which that party bears the burden of proof at trial, there can no longer be a genuine issue as to any material fact ... and the moving party is entitled to judgment as a matter of law.” Smith v. Stratus Computer, Inc., 40 F.3d 11, 12 (1st Cir.1994), cert. denied, 514 U.S. 1108, 115 S.Ct. 1958, 131 L.Ed.2d 850 (1995) (citation omitted). “[S]ummary judgment is as appropriate in a patent case as in any other.” Avia Group Int’l, Inc. v. L.A. Gear Calif., Inc., 853 F.2d 1557, 1561 (Fed.Cir.1988) (citations and internal quotations omitted). In determining the merits of a motion for summary judgment, the court is compelled to undertake two inquiries: (1) whether the factual disputes are genuine, and (2) whether any fact genuinely in dispute is material. Anderson v. Liberty Lobby, 477 U.S. 242, 247-48, 106 S.Ct. 2505, 91 L.Ed.2d 202 (1986). “As to materiality, the substantive law will identify which facts are material. Only disputes over facts that might affect the outcome of the suit under the governing law will properly preclude the entry of summary judgment.” Id. To determine if the dispute about a material fact is “genuine,” the court must decide whether “the evidence is such that a reasonable [factfinder] could return a verdict for the nonmoving party.” Id. III. FACTS A. Technical Background The relevant facts, which unless otherwise noted are not in genuine dispute, include those set forth below. The history of events relating to this litigation is described chronologically in this section of this Memorandum to place them in context. At the risk of redundancy, the salient facts are repeated, and in some instances amplified, in the following sections which analyze each of the motions for summary judgment being decided. Using recombinant DNA technology, proteins such as interferon can be produced in “host” cells which normally do not produce those proteins. Foreign DNA encoding the interferon protein is introduced into the host cell on a “DNA construct,” which is also sometimes referred to as a “plasmid” or “vector.” A DNA construct is an engineered piece of DNA that serves as a vehicle to facilitate transfer of a gene into the host cell. Once introduced into a eukaryotic cell, the DNA construct may integrate into the chromosome of the host cell. If stably integrated, the “gene of interest,” in this case the interferon gene, can be “transcribed” into “RNA.” That RNA may be “translated” into protein by the host cell. If the process is successful, progeny of the host cell will also have the gene of interest and produce the protein. The process of introducing a foreign gene into a cell is known as “transfection.” The term “transform” is often used interchangeably with “transfect,” although “transform” implies that the foreign DNA has been successfully incorporated in the host cell. In this Memorandum the terms “transform” and “transformation” refer to the successful introduction of foreign genes into the chromosome of a host cell. Multiple genes can be introduced into a host cell simultaneously, in a process called “co-transformation.” Co-transformation is valuable because successful transformation is a rare event. Typically less than one cell in 100,000 successfully integrates a foreign gene. Thus, identification of CHO cells transformed with the interferon gene is both difficult and important. To facilitate detection of transformed cells, scientists can introduce a “selectable marker gene,” as well as the gene of interest, into a host cell. A selectable marker gene encodes a protein required by the cell to survive in certain growth conditions. Cells lacking this marker gene are used as hosts. After transformation has been attempted, scientists place the cells in medium which is nutritionally deficient or toxic to cells which did not integrate the marker gene and, therefore, do not produce the protein it encodes. A cell which has been transformed to include the selectable marker gene will survive in this medium because the transformed cell will compensate for the nutritional deficiency or toxicity. A cell which has not been transformed will die. In essence, the cells which have been transformed to contain the selectable marker gene will live and be identifiable as transformed. When co-transformation is attempted, if the selectable marker gene has been successfully introduced, the interferon gene may have been successfully introduced as well. Thus, the marker gene facilitates the identification of cells that have been transformed to include interferon. Co-transformation can be attempted by placing two genes on a single DNA construct and introducing it into the cell. This is called “linked co-transformation,” or co-transformation with a “single construct”. See Exhibit A hereto. Alternatively, co-transformation can be attempted by placing two genes on different DNA constructs, and simultaneously introducing them into the cell. Id. This is referred to as “unlinked co-transformation” or co-transformation employing “multiple constructs”. See Exhibit B hereto. Berlex uses a single construct to introduce interferon and marker genes into CHO host cells. Biogen employs multiple constructs to accomplish this. The legal implications of this difference are at the heart of the instant litigation. After either linked or unlinked co-transformation is accomplished, the host cell is grown in a “culture medium” in order to allow the gene of interest, in this case interferon, to be expressed as a protein. A “culture medium” is a solution that contains the nutrients required for maintenance and growth of the cell. When mon-olayer cultures, which are cultures that are grown on the surface of a plate or roller bottle with a layer one cell thick, are used, the monolayers can be grown to “confluen-cy.” “Confluency” is the point at which the cells touch each other, and thus reach the maximum density of the cells in that medium. To stimulate the production of the maximum amount of interferon, the transformed cells may be “superinduced.” “Superinduction” involves treating the transformed cells with certain toxic chemicals which induces production of a high level of interferon, but ultimately kill the host cells. The concentration of interferon in a medium is typically measured by International Units per milliliter. This is abbreviated as “IU/ml.” After superinduction, the interferon produced is harvested. It is then available for use in products such as Avonex and Beta-seron. B. The Axel Patents Licensed by Biog-en In 1979, Drs. Richard Axel, Michael Wigler, and Saul Silverstein published an article in the journal Cell disclosing the unlinked co-transformation procedure. See M. Wigler, et al., “Transformation of Mammalian Cells with Genes from Procar-yotes and Eucaryotes,” 16 Cell 777 (1979), Affidavit of David B. Bassett in Supp. of Biogen, Inc.’s Mots, for Summ. J. (“Bas-sett Aff.”) Ex. .26, at BG0029574. Among other things, the authors wrote that: “This paper demonstrates the feasibility of co-transforming cells with two physically unlinked genes. Co-transformed cells can be identified and isolated when one of these genes codes for a selectable marker.” Id. In 1980, Drs. Axel, Wigler, Silverstein, and others published another article discussing linked co-transformation. See M. Wigler, et al., “Transformation of Mammalian Cells With an Amplifiable Dominant-Acting Gene,” 77 Proc. Natl Acad. Sci. 6:3567, 3569 (1980), Bassett Aff. Ex. 31. Drs. Axel, Wigler, and Silverstein were granted patents, two of which (the Axel ’216 and ’665 Patents) are prior art to Berlex’s patents. The initial patent describes experiments using both linked and unlinked co-transformation. U.S. Patent No. 4,399,216, (the Axel “ ’216 Patent”) at 2:32-35, 5:3-6, 5:24-28, 5:63-68, 6:62-66, 7:27-31, 8:36-44, Bassett Aff. Ex. 8. The experiments also identify interferon as the gene of interest, DHFR as a selectable marker gene, and CHO cells as host cells. Id. The application for this patent was filed on February 25, 1980, and the patent issued on August 16, 1983. Id. at BG0017365. A subsequent Axel patent, deriving from the same application, claims a “Chinese Hamster Ovary cell ... wherein the proteinaceous material is interferon protein-” U.S. Patent No. 5,179,017 (the “Axel ’017 Patent”), at 42:49-51, Bas-sett Aff. Ex. 9. In addition, the inventors were issued an International patent with a specification which was identical to that of the ’216 and ’017 Patents. International Patent Application No. PCT/US81/00240 published Sept. 3, 1981 (the “Axel International Patent”); Letter from W.F. Lee and R.W. Clary to Judge Wolf (Aug. 10, 2000). The Axel ’216 Patent, the Axel ’017 Patent, and the Axel International Patent are sometimes referred to as the “Axel Patents.” Biogen has a license from Columbia University, the assignee of the Axel Patents, to produce interferon by using unlinked co-transformation and CHO cells in its production of Avonex. As indicated earlier, the parties dispute whether Berlex’s patents, which are described below, are limited to the use of linked co-transformation — the expression of human interferon in CHO cells transformed by employing a single DNA construct comprising multiple genes — or whether it is broader and also encompasses unlinked co-transformation where interferon and marker genes are inserted into a host cell as parts of two distinct DNA constructs. C. The Berlex Patents As also indicated earlier, Berlex owns three patents pertinent to this litigation. The ’843 Patent issued on October 30, 1990. ’843 Patent, Bassett Aff. Ex. 1, at BG0035689. It is literally restricted to the use of a single DNA construct comprising both interferon and marker genes to express human interferon in CHO cells. Id. Berlex has not sued Biogen for infringement of the ’843 Patent. The ’567 Patent, entitled “Expression of Interferon Genes in Chinese Hamster Ovary Cells,” was issued to Berlex on December 27, 1994, based upon a continuation application filed in the ’843 Patent prosecution. ’567 Patent, Bassett Aff. Ex. 2. Berlex asserts that the claims of the ’567 Patent claims fall into three distinct categories, which it characterizes as: (a) construct claims; (b) cell claims; and (c) method claims. Biogen contends that all of the claims of the ’567 Patent are limited to the use of a single construct. The claims Berlex characterizes as the construct claims of the ’567 Patent (Claims 1, 2-9, 15-21, 40, 41, and 90) explicitly recite a single DNA construct containing both interferon and DHFR genes as the means of transforming CHO cells. ’567 Patent, Bassett Aff. Ex. 2, 27-32. Berlex does not allege that Biogen literally infringes these claims, but argues instead that Biogen infringes them under the doctrine of equivalents. The claims Berlex characterizes as cell claims (Claims 10-13, 36-39, 66-69) pertain to CHO cells which have been transformed with human interferon. The broadest of these cell claims, Claims 66-69, describe CHO cells “having incorporated therein an expressible gene encoding human - or 13-interferon,” without reciting any specific construct configuration for achieving transformation. Id. at 30:37-39. Berlex contends that Biogen literally infringes claims 66-69. Claims 10-13 and 36-39, describe CHO cells having incorporated into their chromosomes a single DNA construct bearing both interferon and marker genes. Id. at 27:49-63; 28:61-29:3. Berlex charges Biogen with infringing these claims under the doctrine of equivalents. Claims 42 and 70 are the broadest of the claims that Berlex characterizes as method claims. They describe methods of interferon production in CHO cells, without specifying the use of a single DNA construct comprising an interferon gene and a marker gene. Id. at 29:18-24 (Claim 42), 30:49-55 (Claim 70). Berlex asserts that Biogen literally infringes these and similar or dependent claims (Claims 42^45, 52, 56, 58, 64, 70, 72, and 78). D. The ’779 Patent This litigation commenced in May 1996. In March 1998, Berlex submitted to the PTO claims which emerged as the ’779 Patent. The ’779 Patent is entitled “Human Interferon-p (IFN-p) Produced in Chinese Hamster Ovary (CHO) Cells.” It was issued to Berlex on August 18, 1998.-’779 Patent, Bassett Aff. Ex. 3. All claims of the ’779 Patent expressly require a cell culture composition directly resulting from the secretion of interferon from transformed CHO cells with an interferon concentration of between 150,000-600,000 IU/ ml. Id. at 28:6-30:19. Berlex contends that Biogen literally infringes Claim 1 and representative dependent claims (Claims 2, 8, 9, 11, 12, 21, 25, 26, and 37) of the ’779 Patent because Biogen’s product passes through the 150,-000-600,000 IU/ml range before achieving concentrations of 1,200,000-1,600,000 IU/ ml. Alternatively, Berlex contends that Biogen infringes the ’779 Patent under the doctrine of equivalents. E. The Prosecution of the Berlex Patents 1. The 1982 Application On November 1, 1982, Drs. Francis P. McCormick, Michael A. Innis, and Gordon M. Ringold (the “inventors” or the “applicants”) filed with the PTO U.S. Patent Application No. 06/438,991 (the “1982 application”), . entitled “Expression of Interferon Genes in Animal Cells.” Bassett Aff. Ex. 4, at 5. Dr. Ringold has testified in this case that he was aware of, and had performed, unlinked co-transformation pri- or to the collaboration with Drs. McCormick and Innis which produced the Berlex patents. Deposition of Gordon M. Ringold (“Ringold Dep.”), Battin Decl. Ex. 15, at 68-69. In fact, the work underlying the original application was based on the hypothesis that linked co-transformation would increase the frequency of successful co-transformation. Id. at 65, 588. Dr. Ringold believed that linked co-transformation distinguished his work from what he understood to be Axel’s unlinked co-transformation procedure. Id. The claims of the original 1982 application expressly required a single DNA construct containing: (1) a replication sequence; (2) a selectable marker sequence; and (3) an interferon gene for expression of interferon in mammalian cells. Bassett Aff. Ex. 4, at 23. The original claims did not expressly require a “linkage” of those three elements. Id. 2. The 198k Amendments In May 1984, the Examiner rejected the pending claims as anticipated and obvious in light of the prior art. Id. at 45-48. In order to avoid the prior art, on September 14, 1984, the inventors amended the claims to require a linkage of the three elements. Id. at 75-77. It was this linkage of the selectable marker and IFN on the same DNA construct which the inventors claimed led to the “unexpected,” positive results of their invention. Id. at 82. More specifically, the inventors claimed that the linkage of the interferon gene and selectable marker gene on a single DNA construct solved problems of human interferon toxicity to CHO cells, and the contamination of human interferon with hamster interferon. They wrote to the PTO that: applicants’ invention resides in the construction of a plasmid which, when introduced into CHO cells which are selected and grown so as to express interferon, produces human interferon in large quantities and to the exclusion of any hamster interferon [citation omitted]. It was well known at the time of filing this application that human interferon is toxic to animal cells so that it inhibits cell growth as it is produced.... Thus, it was completely unexpected that the CHO cells did not die as the human interferon was being produced.... Furthermore, it was well known that mammalian host cells produced mixtures of animal and human IFN when transformed with a recombinant DNA containing a human interferon gene. Therefore, it was unexpected that only human interferon was produced by the CHO cells.... Id. at 81-82 (emphasis in original). High levels of expression of human interferon without hamster interferon and without human interferon toxicity to CHO cells was the unexpected result according to the inventors. Id. The inventors asserted that this result was due to the linkage of the interferon gene and the selectable marker gene on a single DNA construct. They stated that: These unexpected and advantageous results were accomplished by linking the interferon gene with the gene containing the selectable marker on a single DNA construct so that coamplification of the genes occurred. In the prior art co-transformation was generally used, wherein two plasmids with the separate genes were cotransformed into the host. Thus, the instant DNA construct differs from what was done previously, and the results obtained on transforming the host with this construct were totally surprising. Id. at 82 (emphasis in original). As the foregoing statement reflects, the applicants distinguished the Axel patent on the basis of their single DNA construct configuration and the linkage of the interferon gene and the marker gene on that construct. They went on to emphasize this point, stating that the Axel process: involves co-transformation where two separate DNA constructs with unlinked genes are integrated into the plasmid. In contrast, applicants’ process deals with coamplification where the interferon gene and selectable marker gene are linked on the same DNA construct. Id. at 83 (emphasis in original). 3. The 1985 CIP Application On July 31,1985, Cetus Corporation, the original assignee of the ’843 Patent, filed a continuation-in-part (CIP) application. The text of this application is the specification of both of Berlex’s patents at issue in this case. The 1985 CIP application was entitled “Expression of Interferon Genes in Chinese Hamster Ovary Cells.” 1985 CIP, Bassett Aff. Ex. 5, at 5. All claims of the 1985 CIP application expressly recited a single, three part DNA construct including both interferon and marker genes. Id. at 46:2-49:17. All of the experimental examples describe CHO cells that had been transformed with a single DNA construct. Id. at 29:14-44:4. None of the examples describe transformation utilizing separate constructs. Id. The Background of Invention generally describes the use of interferons as therapeutic agents, and the efficacy of expressing IFN in bacterial cells, using recombinant DNA technology. Id. at 5:4-7:10. It refers to the Axel International Patent, which it said, “broadly describes processes for inserting DNA into eukaryotic cells and for producing proteinaceous material, but provides no enabling details regarding suitable DNA fragments, hosts, transforming vectors, methods for transformation, promoter and control sequences which facilitate expression, and other essential components.” Id. at 7:2-7 (emphasis added). The applicants thus deemed not only “hosts” but also “suitable DNA fragments,” “transforming vectors,” and “methods for transformation” as “essential components” for enabling interferon expression. The CIP application added to the specification a new Summary of Invention section. The Summary of Invention explicitly describes a single DNA construct with an operable linkage of several genes as being the invention. It states: [T]he present invention provides a DNA construct for the expression of the human interferon gene in Chinese hamster ovary cells or progeny thereof comprising an operable linkage of: (a) a nucleotide sequence from a cloning vector which allows for replication in a prokaryotic cell; (b) a first gene capable of transcription and translation in Chinese hamster ovary cells or progeny thereof operably linked to a selectable marker for the selection of Chinese hamster ovary (CHO) cell transformants or progeny thereof; and (c) a human interferon gene capable of transcription and translation in Chinese hamster ovary cells or progeny thereof. Id. at 7:12-22 (emphasis added). “[0]ther aspects” of the invention were similarly described as requiring the use of the single construct comprising both genes. The Summary states: “In other aspects, the invention provides for transforming vectors carrying the DNA construct, suitable CHO hosts transformed with the cloning vector, and expression control sequences for expressing the DNA fragments.” Id. at 7:23-26 (emphasis added). The Summary of Invention also describes a method of producing IFN in CHO cells comprising “introducing into a Chinese hamster ovary cell or progeny thereof the above-described DNA construct.” Id. at 7:29-30 (emphasis added). Thus, in the Summary the applicants described their invention as the single, three-part DNA construct. The DNA eon-struct is never characterized as possessing fewer than three elements. The Summary does not describe the invention as the expression of interferon in CHO cells generally. Indeed, Berlex agrees that the foregoing passages in the summary describe a single construct. Mar. 7, 2000 Tr. at 68. The Summary concludes: In preferred embodiments, DNA fragments which code for one or more IFNs are isolated from appropriate human cells; introduced into CHO cells by DNA transfection, or by penetration of viral vectors carrying, the DNA fragment, or by transfection of cloned plasmids into cells that express T-antigens; and expressed by the host cells; and the expressed product is isolated and purified. Id. at 8:11-16. Four figures in the specification represent DNA constructs used for the expression of IFN in CHO cells. Figs. 1-4, Id. at 52-63. Each of these figures depicts interferon and marker genes operably linked on a single DNA construct. Id. at 52-53, 8:18-26. No drawing depicts a marker gene on one vector, and an interferon gene on another vector. Id. The 1985 application also added a definition of “operable linkage” to the Description of the Preferred Embodiments. It said: The term “operably linked” or “operable linkage” as used herein regarding DNA sequences or genes refers to the situation wherein the sequences or genes are juxtaposed in such a manner so as to permit their ordinary functionality. For example, a promoter operably linked to a coding sequence refers to those linkages where the promoter is capable of controlling the expression of the sequence. The sequence operably linked to a selectable marker has the same significance: i.e., it permits the selectable marker to be positioned in the transcript so as to participate in the selection procedure after the sequence has been expressed in the host. Similarly, an operable linkage of sequences and genes signifies that the sequences and genes are so positioned in a DNA construct as to permit expression of the sequences in the desired manner. Id. at 11:21-33 (emphasis added). Thus, the inventors tied the concept of operable linkage to the use of a single DNA construct. Id. The Description of the Preferred Embodiments defines the term “DNA construct” as “any suitable cloning vector, including, for example, plasmids, viruses such as SV40, polyoma virus, bovine papil-loma virus, mouse mammary virus and the like, and bacteriophages.” Id. at 12:6-9. The Description continues: The method of effecting expression of heterologous genes in CHO host cells or progeny thereof generally involves preparing DNA constructs as defined above operably linked to a nucleotide sequence for replicating in a prokaryotic cell, preferably E. col% a marker gene operably linked to a CHO cell selectable marker for the selection of transformants or progeny thereof, and operably linked to a promoter and start and stop codons; and an interferon gene from a human source, operably linked to an endogenous or heterologous promoter and translation sequences (start and stop co-dons) for expression of the interferon gene in CHO cells or progeny thereof. This DNA construct is then introduced in CHO cells or progeny thereof, preferably in a culture, by any technique, including any of the three techniques described below, the transformed cells are selected and then grown under selective conditions whereby the interferon gene is expressed; and the interferon so produced is isolated and purified. Id. at 12:33-13:13 (emphasis added). Later, the Description states: “In accordance with the present invention, any approach may be used to introduce the cloned DNA into CHO cells and to select and grow the transformed cells for expression of the protein. Among the approaches for trans-fection are the following three approaches”: (1) transfection, where foreign DNA is precipitated from solution and enters cells in this insoluble form; (2) introduction of DNA through a virus which can penetrate the cell membrane; and (3) transfection of cloned plasmids into cells that express SV40 regulatory proteins (T-antigens). Id. at 27:7-28:16. Dr. John Hiscott, one of Berlex’s experts, has opined that viral transfection “would not be expected to involve use of a selectable marker gene.” Rebuttal Expert Report of Dr. John Hiscott (“Hiscott Reb. Rpt.”), Decl. of Jennifer L. Gillum (“Gillum Decl.”), Ex. 2, at 51. However, Dr. His-cott does not assert that transfection with a virus could not employ a selectable marker. Moreover, counsel for Berlex acknowledged at oral argument that the above quoted language at columns 27 and 28 is “inconsistent]” with the language appearing in columns 12 and 13, which states that “[t]his DNA construct” is introduced into the cells according to one of these three approaches. Mar. 7, 2000 Tr. at 76. The Description of Preferred Embodiments also emphasizes the use of CHO cells. It states: Chinese hamster ovary cells or progeny thereof are used as the host cells herein. They do not coproduce endogenous (hamster) IFN constitutively or by induction, whether a promoter endogenous to IFN or a heterologous promoter for IFN is employed, in contrast to other eukaryotic hosts such as mouse cells. Furthermore, CHO cells are largely resistant to the anti-cellular activity of the human IFNs produced. When CHO cells are transformed with IFN gene under its own promoter control, expression levels for IFN are high for induction and low for constitutive production. With heterologous promoters, no detectable induction is observed, but only constitutive production of IFN. 1985 CIP, Bassett Aff. Ex. 5, at 12:22-32. CHO cells facilitated the recombinant expression of human interferon without contamination from the endogenous host. The Description of the Preferred Embodiments identifies the potential use of various cloning vectors, selectable marker genes, and promoters. Id. at 13:14-30; 26:24-32. It does not state however, that the singular DNA configuration is not critical to the invention, and does not identify any alternative to using a single construct. Indeed, the specification never suggests the use of multiple DNA constructs or constructs comprising fewer than three elements. The specification concludes: The foregoing description of the preferred embodiments of the instant invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in the light of the above teaching. Id. at 45:4-9. Finally, the Abstract describes the disclosed invention as single DNA constructs bearing both interferon and marker genes operably linked for the expression of human interferon in CHO cells. Id. at 50. It summarizes the disclosure as follows: DNA constructs are prepared which op-erably link human interferon genes, selective, eukaryotic marker genes, and promoter and expression control sequences for the expression of human interferon in Chinese hamster ovary (CHO) cells or progeny thereof. Id. In an Amendment and Response under 37 C.F.R. § 1.111 submitted on May 18, 1988, the inventors distinguished prior art on the ground that the prior art “does not disclose the coamplification and expression of linked structural or selectable marker genes.” Id. at 87, 89, 91. In Remarks filed with the amendment, the applicants represented that: The present invention is a DNA construct for human interferon gene expression and a method for producing human interferon from Chinese Hamster Ovary (CHO) cells. The DNA construct comprises: a nucleotide sequence from a cloning vector which permits replication in prokaryotes, a gene that is capable of transcription and translation in CHO cells operably linked to a marker which is capable of selecting CHO transfor-mants, and a human interferon gene that is capable of transcription and translation in CHO cells. Id. at 88 (emphasis added). On August. 12, 1988, the Examiner withdrew his rejections to the 1982 Application based on prior art. Bassett Aff. Ex. 4, at 205. Ultimately, on October 30, 1990, the CIP Application issued as the ’843 Patent. • ’843 Patent, Bassett Aff. Ex. 1, at BG0035689. Consistent with the limited disclosure of the application, it is undisputed that all of the claims of the ’843 Patent are literally restricted to the use of a single DNA construct comprising both interferon and marker genes. Id. at 28:1-30:11; Blx. Tech. Mem. at 24. Berlex does not claim that Biogen infringes the ’843 Patent. 4. The 1990 Divisional Application On June 29,1990, Cetus filed a divisional application, Application No. 07/546,519. Bassett Aff. Ex. 6, at 9. Although it was eventually abandoned, both the ’567 and ’779 Patents descend from this application. Blx. Invalidity Opp. at 12. This application characterized the disclosure as a single, three-part DNA construct. It stated: “The present invention provides a method for producing human interferon in Chinese hamster ovary (CHO) cells or progeny thereof. A DNA construct is made comprising” a replication sequence, a selectable marker gene, and an interferon gene. Bassett Aff. Ex. 6, at 114. 5. The 1992 Preliminary Amendment Berlex acquired rights to the ’843 Patent in 1991, and assumed control of the pending divisional patent application. Robert Chaoora Dep., Bassett Aff. Ex. 21, at 53-54; Cetus-Berlex Technology Ownership and Royalty Agreement, Bassett Aff. Ex. 18. On April 30, 1992, Berlex filed a preliminary amendment, adding new claims which Berlex contends are not limited to linked co-transformation involving a single DNA construct that includes both an interferon and a marker gene. For example, new claim 29 recited: A DNA construct for expression in a Chinese hamster ovary cell or progeny thereof comprising a human interferon gene, said construct being effective for transcription and translation of said gene when introduced into a Chinese hamster ovary cell or progeny thereof. Bassett Aff. Ex. 6, at 156 (emphasis added). Claim 51 described: A method for the production of human interferon or a mutein thereof in a Chinese hamster ovary cell or progeny thereof comprising: (a) introducing into a Chinese hamster ovary cell or progeny thereof a DNA construct for expression in a Chinese hamster ovary cell or progeny thereof comprising a human interferon gene or a gene coding for a mutein of human interferon which retains the biological activity of said interferon, said construct being effective for transcription and translation of said gene when introduced into a Chinese hamster ovary cell or progeny thereof; (b) selecting a resultant transformed cell; and (c) growing a selected transformant under conditions whereby the interferon gene in said construct is expressed. Id. at 158 (emphasis added). Claim 103 recited: “A Chinese hamster ovary cell or a progeny thereof having incorporated into its chromosome a DNA construct of claim 30.” Id. at 163 (emphasis added). As Berlex emphasizes, none of the claims recites a marker gene, and none explicitly requires the use of a single DNA construct that includes both an interferon and a marker gene. Berlex asserted to the PTO that these claims were “different” than the single construct claims of the ’843 Patent. Notably, Berlex did not state that the claims were “broader.” More specifically, Berlex wrote the PTO that: The foregoing claims are being added to cure an inadvertent oversight during ancestor prosecution leading to U.S. Patent 4,966,843.... it is noted that all claims of this application are of a scope different from that of each claim of ’843. The oversight cured above involves the unnecessary language in the ’843 claims concerning prokaryotic cell nucleotide sequences and selectable marker-related sequences. Whereas such sequences are useful in various cloning experiments and procedures, they clearly are not necessary to a prime aspect of ’843, i.e., “production in Chinese hamster ovary cells” (page 1, line 9). Since the prior art in the parent makes clear the nonobviousness of the combination of an expressible heterologous gene operably incorporated into Chinese hamster ovary cells, it is important that the claims reflect this nonobvious scope. Otherwise, infringers might attempt to avoid the literal scope of the claims, e.g., by simply preparing and/or using DNA constructs which omit components unnecessary for patentability and/or practical expression after selection of a favorable cell line is effected. Id. at 164. On October 5, 1992, the Examiner rejected these new claims as unpatentable in light of the ’843 Patent, under the doctrine of obviousness-type double patenting. Id. at 173, 175. The Examiner stated: Although the conflicting claims are not identical, they are not patentably distinct from each other. In the parent patent, the c[la]ims recite the DNA construct by listing each element of the vector construct. The instant application seeks to remove the detailed language of the construct elements, and replaces it with functional language. This functional language effectively limits the claims to the vector construct of the ’843 application. The DNA construct, either described by its “physical elements or by its function, is the same in the prior patent and the instant application. Therefore, it would be obvious from the patent, which describes the functional characteristics of the vector in the specification, to arrive at the vector claimed in the instant application. Id. at 175-76 (emphasis added). The functional language referenced by the Examiner included phrases such as “effective for transcription and translation,” “introduced into,” and “having incorporated into.” Thus, as interpreted by the Examiner, requiring the DNA construct to have the function of being effective for the production of interferon was equivalent to requiring the structure described in the ’843 Patent: a single DNA construct that included both an interferon gene and a marker gene. Berlex did not dispute the Examiner’s assessment. Rather, on April 16, 1993, in an effort to avoid the Examiner’s rejection, Berlex filed a “terminal disclaimer,” attempting to cause the ’567 Patent to expire when the ’843 Patent was due to expire. Id. at 185. Following the filing of the terminal disclaimer, on October 19,1993, the Examiner held claims 29 through 46 (all of what Berlex calls the “construct claims” then pending which did not reference “mu-teins”) allowable over the prior art, and rejected claims 47 through 109 (the so called “method” and “cell” claims, and construct claims requiring muteins). Id. at 193-95. At an interview between the Examiner and Berlex’s attorneys on September 14, 1994, Berlex voluntarily agreed to narrow the DNA construct claims explicitly to recite a DHFR gene, even though most of the construct claims had been found allowable without such narrowing. Id. at 200, Anthony Zelano Dep. (“Zelano Dep”), Second Decl. of Richard W. Clary (“2d Clary Decl”) Ex. 6, at 212. The Examiner’s Interview Summary Record memorializing the agreement states that, “Construct claims will be narrowed to include DHFR marker.” Bassett Aff. Ex. 6, at 200. Initially, she wrote only that “claims will be narrowed.” At Berlex’s request she added the words “construct” and “to include DHFR marker.” 6. The 199Ip Amendments On September 21, 1994, Berlex filed an Amendment narrowing all of the claims reciting a single construct which had previously been allowed to recite also the presence of a DHFR marker gene. Id. The remaining claims were modified to eliminate all reference to “muteins,” but continued not to require explicitly a marker gene. Id. Berlex also added 39 claims, some of which did not recite the use of a single DNA construct. Id. at 208-11. Each of these so called cell and method claims did not refer expressly to the single DNA construct limitation, but included language such as “having incorporated therein,” “effective for expression,” and “under conditions whereby the interferon gene in said construct is expressed.” Id. at 205 (Claim 42). This was functional language described by the Examiner two years earlier as equivalent to the structural language describing the single, three-part DNA construct of the ’843 Patent. See, e.g., Id. at 175; ’567 Patent, Bassett Aff. Ex. 2, at 29:21-25 (Claim 42). In the remarks accompanying the September 21, 1994 amendment, Berlex stated that “[t]he claims continue to reflect the pioneering invention of the first expression of interferon (IFN) genes in Chinese hamster ovary (CHO) cells.” Bassett Aff. Ex. 6, at 213; see also id. at 217-18. Noting that all references to muteins had been eliminated, Berlex stated that: “the remaining breadth of the claims, including broad method claims, such as 51 and 71, and CHO cell claims, such as 104 and 108, has essentially already been found allowable.” Id. at 214. Berlex also noted that “[platentability and breadth of the current claims reflect the non-obviousness of the first expression of human IFN in CHO cells and do not depend on any particular nucleic acid construct configuration.” Id. at 223 (emphasis added). In making this statement, Berlex was evidently attempting to persuade the Examiner that previous attempts to distinguish Axel’s work and patents based on the erroneous assertion that Axel disclosed only unlinked transformation were unnecessary. Rather, Berlex stated: “It is not relevant whether the Axel et al. prior art patent disclosures of record actually employ only unlinked co-transformed genes in their work. (Axel et al. do generieally disclose linked such genes. See, e.g., column 7, lines 3-31, of, e.g., U.S. Patent No. 4,399,216.)” Id. While asserting that interferon expression did not depend on “any particular nucleic acid construct configuration,” Berlex did not state that it did not depend on a single construct. On November 16, 1994, the Examiner listed all of the claims being allowed. Id. at 336. The Examiner wrote, in the “Reasons for Allowance”: Applicants!] claims are directed to a DNA construct comprising a vector, an interferon gene, and a dhfr marker gene. The construct is expressed in CHO cells. The instant claims are similar to the claims in parent Patent 4,966,-843 (’843), however the instant claims recite the marker gene to be dhfr, whereas the ’843 claims do not. Since a terminal disclaimer has been filed over the ’843 claims, the instant claims are held allowable. Id. at 336 (emphasis added). Significantly, the Examiner referred to “[a]pplicants[’] claims,” which encompassed all of what Berlex calls its construct, cell, and method claims. She did not limit this statement only to Berlex’s construct claims. On November 25, 1994, Berlex responded to the Examiner’s statement. In its “Comments on Statement of Reasons for Allowance,” Berlex wrote that “as is factually clear from the involved texts of record, the claims of both this application and ’843 reflect aspects other than those mentioned by the examiner, e.g., for this application, methods and cells, no need for a proka-ryotic sequence, etc” Brooks Decl. Ex. 23, at MW0001135 (emphasis added). This statement indicates that Berlex recognized that the Examiner’s Reasons for Allowance seemed to limit the ’567 Patent to a single construct using DHFR as the marker gene. Berlex evidently wished to reassert a broader interpretation. Berlex’s November 25, 1994 comments, however, are not included in the file history of the ’567 Patent which is in the record in this case. See Bassett Aff. Ex. 6. Although the PTO received the comments, Brooks Decl. Ex. 23, at MW0001137, they do not appear in the certified copies of the file wrapper made available to the public by the PTO. Mar. 8, 2000 Tr. at 18. Thus, the public would not have had notice of Berlex’s position. 7. The 1994 Application Leading to the ’779 Patent On August 12, 1994, Berlex filed the application, based on the specification for the ’843 and ’567 Patents, which culminated in the ’779 Patent. Bassett Aff. Ex. 7, at 1. As indicated earlier, in May 1996, the instant litigation was commenced. On October 28, 1996, the pending claims were rejected as obvious over prior art, including the Axel ’216 Patent. Id. at 112, 115— 16. On March 27,1997, about nine months after the inception of this litigation, Berlex canceled all of its pending claims and added new claims, which it characterized as “composition” or “product claims.” The new claims covered a cell culture composition resulting directly from the secretion of interferon from transformed CHO cells, in which the amount of interferon is 150,000 to 600,000 IU/ml of medium. Id. at 121-25. In its Remarks in support of the new claims, Berlex stated that “[t]he values recited in the claims are in reference to the bioassay for antiviral activity described in Table 1 of the application.” These values are measurable from samples removed at any time from the claimed culture composition. Id. at 216. A copy of Table 1 is attached as Exhibit C hereto. Table 1 disclosed only one instance in which a cell composition with an interferon level as high as 150,000-600,000 IU/ml was achieved. Bassett Aff. Ex. 3; Ex. C hereto. The Table explicitly explains that level was achieved after the transformed CHO cells had been grown to confluence and superinduction had been employed to stimulate the production of interferon. Id., n. 3. Berlex also stated in support of its new claims that: [T]he achievement by this invention of amounts of 3-interferon as high as 600,-000 IU/ml is strikingly superior and unexpected .... There is nothing in any of the prior art which would lead a skilled worker to have expected this result. ... The only reason applicants have chosen to place an upper limit on the literal scope is to enhance a fast allowance by minimizing potential issues. In fact, a claim scope which literally includes values higher than 600,000 IU/ml, is clearly justified.... As for the lower limit, in view of the Paragraph No. 9[of] the accompanying declaration by Dr. Jan Vilcek, it can be seen that the value of 150,000 IU is although precise, somewhat arbitrary. Thus, a scope of equivalents less than this value is warranted. Id. at 129-30. In his declaration submitted to the PTO pursuant to 37 C.F.R. § 1.132, Dr. Vilcek stated that: I know that as of November 1, 1982 the amounts of human fibroblast IFN obtained from animal cell cultures under conditions optimized for the achievement of maximal yields were generally from 10,000 to 50,000 IU/ml.... The highest amount of human fibroblast IFN produced in any animal cell system at that time that I know about, including from human fibroblast cell strains and from mammalian recombinant systems, was 102,000 IU/ml, reported in a paper I published in 1978 (Vilcek et al., pages 101-118, in Human Interferon: Production and Clinical Use, Stinebring and Chappie, eds., Plenum Press, 1978).... At the time, there appeared to be an upper limit to the amount of IFN that could be produced and secreted by animal cells. Vilcek Decl. (Mar. 27, 1997), Bassett Aff. Ex. 7, at 133-34. On June 10, 1997, the Examiner allowed some claims of the '779 Patent, stating that the Vilcek Declaration was “sufficient to overcome the rejection” for obviousness. Bassett Aff. Ex. 7, at 171-72. On September 9, 1997, Berlex first advised the Patent Office of the instant litigation involving the ’567 Patent, which commenced on May 3, 1996. Id. at 189-94. The ’779 Patent issued on August 18, 1998. ’779 Patent, Bassett Aff. Ex. 3. F. Biogen’s Avonex Process and Product Biogen produces Avonex from interferon that has been secreted from transformed CHO cells. As indicated earlier, in contrast to Berlex, Biogen utilizes a process of unlinked co-transformation. Blx’s LR 56.1 Statement of Undisputed Facts in Connection with its Mot. for Summ. J. that Bg Literally Infringes Certain Claims of U.S. Patent Nos. 5,367,567 and 5,795,779 (“Blx Literal Infringement Facts”) ¶ 9. More specifically, Biogen introduces interferon into CHO cells on one DNA construct and the DHFR selectable marker on a separate construct. It has been stipulated that the nine bioassays performed for Biogen by Dr. Wendy Jones are reliable. Stipulation (Jan. 14, 2000). Those nine tests resulted in the measurement of 1,200,000 IU/ml two times, 1,500,000 IU/ml six times, and 1,600,000 IU/ml one time. Id. In the process of achieving an interferon concentration of 1,200,000-1,600,000 IU/ml, Biogen’s product goes through the 150,000-600,000 IU/ml range. Mar. 10, 2000 Tr. at 41. IV. BERLEX’S MOTION FOR SUMMARY JUDGMENT CONCERNING LITERAL INFRINGEMENT OF THE ’567 PATENT Berlex has moved for summary judgment on its assertion that some, but not all, of the claims in the ’567 Patent are literally infringed by Biogen. As discussed previously, the ’567 Patent includes some claims that do not expressly refer to the use of a single DNA construct containing both an interferon gene and DHFR as the selectable marker. Thus, Berlex contends that Biogen’s use of multiple constructs to introduce interferon and DHFR into cells literally infringes those claims. Biogen asserts, however, that each of the claims in the ’567 Patent include terms which require clarification by reference to the specification and prosecution history. Biogen argues that when the specification and prosecution history are consulted, a person of ordinary skill in the relevant art would understand that each of the claims in the ’567 Patent is limited to the use of a single DNA construct and, therefore, Biog-en’s method of producing Avonex does not literally infringe the ’567 Patent. “An infringement analysis entails two steps. The first step is determining the meaning and scope of the patent claims asserted to be infringed. The second step is comparing the properly construed claims to the device accused of infringing.” Kraft Foods, Inc. v. International Trading Co., 203 F.3d 1362, 1366 (Fed.Cir.2000) (citation and internal quotations omitted). Claim construction is a question of law to be decided by the court. Markman v. Westview Instruments, Inc., 517 U.S. 370, 372, 116 S.Ct. 1384, 134 L.Ed.2d 577 (1996) (“Markman II ”). The parties agree that there are no facts material to the question of whether the ’567 Patent is literally infringed that are genuinely in dispute. Thus, after the court construes the claims at issue, the question of literal infringement may be resolved as a matter of summary judgment. Athletic Alternatives, Inc. v. Prince Mfg. Inc., 73 F.3d 1573, 1578 (Fed.Cir.1996). For the reasons described below, the court concludes that Biogen’s proposed claim construction is correct and that each of the claims of the ’567 Patent requires the use of a single DNA construct that includes an interferon gene and a DHFR marker gene. Therefore, Biogen’s method of introducing interferon genes and DHFR marker genes into cells on separate DNA constructs does not literally infringe the ’567 Patent. Accordingly, Berlex’s motion for summary judgment on this issue is being denied. Instead, judgment must be entered for Biogen on the claim of literal infringement of the ’567 Patent. In construing the claims of the ’567 Patent, the court has considered the purposes of the patent laws and patents, as well as the principles of claim construction enunciated primarily by the Court of Appeals for the Federal Circuit. These include the following. The Patent Clause [of the Constitution] reflects a balance between the need to encourage innovation [by granting monopoly power over the production, use, and sale of the patented product] and the avoidance of monopolies which stifle competition without any concomitant advance in the “Progress of Science and useful Arts.” ... the federal patent laws have embodied a careful balance between the need to promote innovation and the recognition that imitation and refinement are both necessary to invention itself and the very lifeblood of a competitive economy. Bonito Boats, Inc. v. Thunder Craft Boats, Inc., 489 U.S. 141, 146, 109 S.Ct. 971, 103 L.Ed.2d 118 (1989). “A patent is a government grant of rights to the patentee.” Markman v. Westview Instruments, Inc., 52 F.3d 967, 978 (Fed.Cir.1995) (en banc) (“Markman I”). Among other things, it gives the patentee rights, for a limited period of time, to exclude others from using the invention claimed. Id. In order not to stifle innovation and competition unduly, however, “[t]he public generally, and in particular, the patentee’s competitors, are entitled to clear and specific notice of what the inventor claims as his invention.” Exxon Chem. Patents, Inc. v. Lubrizol Corp. (“Luorizol”), 64 F.3d 1553, 1563 (Fed.Cir.1995) (Plager, J., concurring). See also Markman I, 52 F.3d at 978. Such clear notice informs a competitor, who may be contemplating an expensive investment, of what is permissible. It also provides that competitor assurance that “if infringement litigation occurs, [ ] a judge, trained in the law, will similarly analyze the text of the patent and its associated public record and apply the established rules of construction, and in that way arrive at the true and consistent scope of the patent owner’s rights to be given legal effect.” Id. at 979. A patent’s claims define the scope of the protection that the patent provides. Renishaw PLC v. Marposs Societa’ per Azioni, 158 F.3d 1243, 1248 (Fed.Cir.1998). “[T]he claim construction inquiry, therefore, begins and ends in all eases with the actual words of the claim.” Id. Evidently because the primary audience is potential competitors seeking notice of what is protected and what is permissible, the words used in the claims must be construed from the perspective of the person ordinarily skilled in the field of invention. The Toro Co. v. White Consol. Indus., Inc., 199 F.3d 1295, 1299 (Fed.Cir.1999). Claims must be read in the context of the specification and prosecution history, as a person skilled in the art would read them. Markman I, 52 F.3d at 979-80; Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed.Cir.1996); Bell Communications Research, Inc. v. Vitalink Communications Corp., 55 F.3d 615, 619 — 20 (Fed.Cir.1995). “[T]he specification is always highly relevant to the claim construction analysis. Usually, it is dispositive; it is the single best guide to the meaning of a disputed term.” Vitronics, 90 F.3d at 1582. See also Bell Communications, 55 F.3d at 621. If a term used in a claim has “a clear and well-defined meaning” for those skilled in the art, “limitations from the specification are not to be read into the claims.” Comark Communications, Inc. v. Harris Corp., 156 F.3d 1182, 1186-87 (Fed.Cir.1998). “[T]here must be a textual reference in the actual language of the claim with which to associate a proffered claim construction.” Johnson Worldwide Assoc., Inc. v. Zebco Corp., 175 F.3d 985, 990 (Fed.Cir.1999). However, as the Court of Appeals for the Federal Circuit has held in a series of recent decisions, terms as seemingly straightforward as “protecting,” “frame,” “included,” and “when” may require clarification by reference to the specification and prosecution history. See Kraft Foods, 203 F.3d at 1368 (“protecting”); Wang Labs., Inc. v. America Online, Inc., 197 F.3d 1377, 1380 (Fed.Cir.1999) (“frame”); Toro, 199 F.3d at 1299 (“included”); Renishaw, 158 F.3d at 1250 (“when”). The foregoing cases indicate that the context of the words in claims is critical to understanding their meaning. “[T]he interpretation to be given a term can only be determined and confirmed with a full understanding of what the inventors actually invented and intended to envelop with the claim.” Renishaw, 158 F.3d at 1250. The specification and prosecution history illuminate what was invented and intended to be covered by a claim. See Comark, 156 F.3d at 1187 (specification should be consulted “to ascertain the meaning of a claim term as it is used by the inventor in the context of the entirety of his invention”). “There is presumed to be a difference in meaning and scope when different words or phrases are used in separate claims. To the extent that the absence of such difference in meaning and scope would make a claim superfluous, the doctrine of claim differentiation states the presumption that the difference between claims is significant.” Id. (quoting Tandon Corp. v. United States Int’l Trade Comm’n, 831 F.2d 1017, 1023 (Fed.Cir.1987)). That presumption, however, is re-buttable. Comark, 156 F.3d at 1187. “[T]he doctrine of claim differentiation does not serve to broaden claims beyond their meaning in light of the specification and does not override clear statements of scope in the specification and the prosecution history.” Toro, 199 F.3d at 1302. The court has construed the claims of the ’567 Patent by applying the foregoing principles. The court has considered the language of the claims at issue in light of the other intrinsic evidence — the specification and prosecution history. Read in context, those claims contain terms that require clarification. Thus, the court has employed the specification and prosecution history, as well as the words of the claims themselves, to determine what the claims would communicate to a person skilled