Appeal No. 2000-0630
Application No. 07/780,717
desirability of the modification. In re Gordon, 733 F.2d 900, 902, 221 USPQ 1125, 1127
(Fed. Cir. 1984).
We agree with the examiner that Sano reasonably suggests truncating recombinant
streptavidin to solve aggregation problems. Nevertheless, we do not agree that the
evidence suggests truncation at exactly residue 16 - we see no nexus between the
teachings of Sano and those of Hendrickson, despite the statement in Hendrickson that
“residues 16-133 are sufficient to complete the J-barrel structure.” Hendrickson does not
discuss solubility of streptavidin. Sano, on the other hand, suggests that hydrophilic amino
acid residues in the C-terminal region, and possibly in the N-terminal region, are
responsible for unwanted aggregation. The aggregating recombinant streptavidin shown
in Figure 1 of Sano contained seven foreign amino acids fused to streptavidin downstream
of residue 15; streptavidin residue 15 is alanine. If, as the examiner suggests, the
motivation for truncating streptavidin is to remove residues responsible for aggregation -
and Sano suggests that hydrophilic amino acids are involved in aggregation - then the
reference provides no particular motivation to remove alanine residue 15, because it is not
hydrophilic. Without a reason to remove residue 15, one would not arrive at applicant’s
claimed product consisting of residues 16-133.
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