Compounds and methods for treatment of thrombosis

A purified Factor XI protein comprising amino acids 370–607 as set forth in SEQ ID NO:

• 15 and one or more of the following mutations:
• (a) a mutation of a residue of said protein that disrupts post-translational N-linked glycosylation when said protein is recombinantly expressed in an organism,
• (b) a mutation that eliminates a free, reactive sulfhydryl group of a cysteine residue present in said protein, or
• (c) a mutation of the NH2— or COOH-terminal residue of said protein, wherein said mutation of the NIH2— or COOH-terminal residue of said protein promotes crystallization of said protein relative to wild-type Factor XI lacking said mutation.