Appeal No. 2005-2446 Page 3
Application No. 09/951,099
In a nutshell, according to appellants, two different pH-dependent mechanisms
contribute to the virtually complete inhibition of enzyme activity observed at high pH (e.g.,
pH 8 or 9) when the aminoglycol Tris is used as the complexing agent in the fracturing
fluid. Briefly, “[w]ithout the presence of an inhibitor, [like Tris,] a simple pH change from
9 to 4 altered the relative activity of [ß-mannanase] from 20% to 100%, based on the pH
profile of the enzyme” (id., pages 18 and 20). However, “an enzyme with 20% relative
activity [still] produces significant [unwanted] reduction in guar viscosity” (id., page 18).
But Tris itself acts as a pH-dependent reversible inhibitor of ß-mannanase, as appellants
discovered when comparing the effects of two different buffers (Tris versus sodium
phosphate) on enzymatic degradation of guar at pH 8 (id., pages 17 and 18). “Using
[Tris] inhibition in combination with a pH change, allowed [nearly complete control over]
pH-activated enzyme degradation to be achieved” (id., page 18), something that was not
observed with sodium phosphate buffer (id., page 17).
The Claims
Claims 1-5 and 7-10 are pending and the subject of appeal. Claims 6 and 11-55
are also pending, but have been withdrawn from consideration as directed to non-elected
subject matter. Additionally, in response to an election of species requirement,
appellants selected 2-amino-2-hydroxymethyl-1,3-propanediol, commonly known as Tris,
as the species of the compound of Formula I to be considered (Supplemental Response,
October 15, 2003). It is our understanding that examination of the claims has so far
been limited to that embodiment.
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