Patent ID: 8097591

Claim:
A method of producing a substantially unoxidized and isolated polysialic acid derivative having a defined degree of polymerization, a mixture of N-acetyl sialic acid and de-N-acetyl sialic residues, and a non-reducing end de-N-acetyl residue resistant to degradation by exoneuraminidase, the method comprising: providing a solution comprising a mixture of substantially unoxidized polysialic acid derivatives each having (i) a different degree of polymerization, (ii) a different mixture of N-acetyl residues and de-N-acetyl residues, and (iii) a non-reducing end N-acetyl sialic acid residue; subjecting said solution to ion exchange chromatography to generate fractions; and isolating from one or more of said fractions a substantially unoxidized polysialic acid derivative having a defined degree of polymerization, a mixture of N-acetyl sialic acid and de-N-acetyl sialic residues, and a non-reducing end de-N-acetyl residue resistant to degradation by exoneuraminidase, whereby said isolated polysialic acid derivative is produced.