Other evidence suggests a background absorbance value of .02. Engvall’s Example 1 includes
a second set of data immediately following the data used by Bergland in her calculations. Engvall
Specification, p. 12. The second set represents an experiment identical to the first except the
monoclonal bound to the substrate and the labeled monoclonal were the same. The results show an
absorbance of .02 at all antigen concentrations. This result is expected because both the bound and
labeled monoclonals were directed against the same determinant. When the labeled antibody was
added to the mixture there was nothing with which to react since the determinant had already been
utilized in reacting with the bound monoclonal. Because no reaction with the labeled monoclonal is
expected, the reported absorbance level might be a reasonable indicator of the background
absorbance. On cross examination, Bergland confirmed that the additional Example 1 data indicates
a possible background level of .02 (ER 1782):
Q. You assumed in this calculation at that the background was
.01 in your declaration, is that correct?
A. Yes.
Q. You say that is the normal background, is that correct?
A. Yes, in our system.
Q. Yet the data presented immediately below the data which you
have manipulated here in example 1 of the patent application
shows a uniform background level of .02, doesn’t it?
A. That is right.54
Langone similarly noted that the absorbance from the second set of data was a reasonable
background level. Langone, ER 3500.
While not necessary for our decision, we illustrate below the significance of even a small
change in the background absorbance level on the affinity constant determined using the Walker
technique. We have repeated Bergland’s calculations using .02, rather than .01, for the background
absorbance. Using this value, with all other values as used by Bergland, we have determined an
affinity constant of 3.6x10 liters per mole for the information in Engvall’s Example I. This value10
is an order of magnitude higher than that calculated by Bergland and about 360 times greater than
54
Prior to answering the last question, the witness noted some confusion about the question. The
following appears in the transcript immediately prior to the final answer (ER 1782):
A. Can you repeat? I didn’t understand.
Mr. Lipsey: Why don’t you read it back?
(Record read.)
27
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