Appeal No. 2002-0456 Page 2
Application No. 09/155,995
11. A porous, cross-linked polysaccharide gel obtainable by the following steps:
a) preparing a solution or dispersion of the polysaccharide,
b) adding a bifunctional cross-linking agent having one active site and one
inactive site to the solution or dispersion from step a),
c) reacting hydroxylgroups of the polysaccharide with the active site of the cross-
linking agent,
d) forming a polysaccharide gel,
e) activating the inactive site of the cross-linking agent,
f) reacting the activated site from step e) with hydroxylgroups of the
polysaccharide gel, whereby cross-linking of the gel takes place.
Claims 1-20 stand rejected under 35 U.S.C. § 103 as unpatentable over
Lindgren1 alone, and over Lindgren “in view of appellant’s own admissions.” Examiner’s
answer, pages 3-6.
We reverse both of these rejections.
BACKGROUND
“Gel matrices of polysaccharides have long been used as separation media . . .
[in] chromatographic separation methods.” Specification, page 1. As further explained
in the specification (pages 1-2):
Generally, chromatographic separations are carried out in columns
packed with the separation matrix in [the] form of particulate beads.
Separation media of a fast kinetics with rapid flow rates results in a high
productivity and may be achieved by a reduction in the particle size.
However, small beads result in a higher back pressure due to the
narrowing of the convective flow channels between the particles in a
packed bed. To be able to separate large molecules the particles should
have large pores, but large pores may result in a weakened structure of
the particles. As the polysaccharides are soft materials the particles may
easily collapse, especially at high flow rates . . . It is well known to
increase the stability of polysaccharide particles by cross-linking the
polymer . . . [stabilizing] the polysaccharide gel matrices by chemically
binding the polymer chains with each other at their respective free
hydroxyl groups. The cross-linking takes place between the hydroxyl and
the functional groups of the cross-linkers. This affects the particle rigidity,
but to a lesser extent or not at all the size of the pores . . .
1 U.S. Patent No. 4,973,683 to Lindgen, issued November 27, 1990.
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