Appeal No. 2005-2446 Page 6
Application No. 09/951,099
According to Dawson, “suitable hydratable polysaccharides are the
galactomannan gums, glucomannan gums, guars, derived guars and cellulose
derivatives” (id., column 3, lines 21-24). “Suitable enzyme breakers include, for
example, the cellulases . . . [which] specific[ally] [ ] degrade the particular polymeric
linkage found on the polysaccharide polymer backbone of the crosslinked gel, for
instance, the 1,4 linkage between mannose in galactomannans” (id., column 4, lines
11-21). Finally, according to Dawson, “[a]ny conventional buffer can be used to adjust
the pH, for instance aqueous potassium carbonate” (id., column 5, lines 1-2).
The examiner acknowledges that “Dawson differs from the claims in not disclosing
the use of . . . ‘Tris’[ ] as the buffer in the [alkaline] pH adjustment step” (Examiner’s
Answer, page 4), but relies on Segel’s list of “acids and bases that are useful in
preparing buffers for enzyme assays” as evidence that “Tris is an extremely well known
buffer, conventionally used in processes employing enzymes” (id.). Moreover, the
examiner notes that Tris “has an alkaline pKa of 8.1 and is therefore capable of providing
buffering power in the alkaline range initially required in Dawson’s fracturing fluid” (id.).4
According to the examiner, “the artisan of ordinary skill clearly would have recognized
Tris as being a conventional buffer suitable for processes employing enzymes, [thus,] the
claimed substitution of Tris into Dawson’s process must be . . . considered obvious” (id.,
pages 4 and 5).
Appellants argue that the examiner’s conclusion is unfounded because, among
other things, “[t]he only specific reference to Tris buffer systems having a particular pH in
4 We note that the pKa value provided here is for Tris at 25°.
Page: Previous 1 2 3 4 5 6 7 8 9 Next
Last modified: November 3, 2007