Purification of polypeptides

1. A process for the purification of a polypeptide comprising a vicinal-amino-thiol, vicinal-amino-hydroxyl, vicinal-diol or vicinal-diamino group, the process comprising:

(i) attaching the polypeptide to a purification matrix by contacting the polypeptide with a purification matrix comprising aldehyde or ketone groups under conditions which favour formation of a heterocyclic ring system,

(ii) washing the purification matrix, and

(iii) releasing the polypeptide from the purification matrix.

2. A process according to claim 1 , for the purification of a polypeptide comprising an N-terminal cysteinyl (Cys), threonyl (Thr) or seryl (Ser) amino acid, the process comprising:

(i) attaching the polypeptide to a purification matrix by contacting the polypeptide with a purification matrix comprising aldehyde or ketone groups under conditions favouring formation of a thiazolidine or oxazolidine ring,

(ii) washing the purification matrix to remove unbound material, and

(iii) releasing the polypeptide from the matrix by exposure to conditions which reverse thiazolidine or oxazolidine formation.

3. A process according to claim 2 , comprising the further step of cleavage of the N-terminal Cys, Thr, or Ser amino acid and optionally further N-terminal amino acids.

4. A process for the purification of a polypeptide comprising a group selected from

—CR(OH)—CR′(R″)—NH—CHR 1 CO—

—CR(NH 2 )—CR′(R″)—NH—CHR 1 CO—

wherein R 1 is the side chain of an amino acid,

R, R′ and R″ are selected from hydrogen, alkyl, aralkyl, aryl and heterocyclic groups, the process comprising the steps of

(i) attaching the polypeptide to a purification matrix by contacting the polypeptide with a purification matrix comprising aldehyde or ketone groups under conditions favouring formation of a heterocyclic ring,

(ii) washing the purification matrix to remove unbound material, and

(iii) releasing the polypeptide from the matrix by exposure to conditions which reverse heterocyclic ring formation.

5. A process according to claim 4 , comprising the further step of cleaving the group —R(OH)— or CR(NH 2 ) from the polypeptide with periodic acid or a salt thereof.

6. A process according to claim 4 , wherein the polypeptide comprises the group

HOCH 2 —CH 2 —NH—CHR 1 CO—.

7. A process for the purification of a polypeptide comprising a group selected from

T-L-CO—CR′(R″)—NH—CHR 1 —CO—

T-L-CR(OH)—CR′(R″)—NH—CHR 1 —CO— and

T-L-CR(NH 2 )—CR′(R″)—NH—CHR 1 —CO—,

wherein T is a capture tag group capable of binding, with or without the participation of the —CR—(OH)—,—CR(NH 2 )— or —CO— group, with a purification matrix,

L is a divalent linker moiety or may be absent,

R 1 is a side chain of an amino acid,

R, R′ and R″ are independently selected from hydrogen, alkyl, aralkyl, aryl and heterocyclic groups the process comprising the steps of

(i) attaching the polypeptide to a purification matrix by contacting the polypeptide with a purification matrix comprising a structure or chemical functionality capable of binding through the capture tag group,

(ii) washing the purification matrix to remove unbound material, and

(iii) releasing the bound polypeptide.

8. A process according to claim 7 , comprising the step of cleaving the group comprising

T-L-CO—, T-L-CR(OH)— or T-L-CR(NH 2 )—

from the polypeptide with periodic acid or a salt thereof.

9. A process according to claim 8 , wherein cleaving the group comprising

T-L-CO—, T-L-CR(OH)— or T-L-CR(NH 2 )—

from the polypeptide serves to release the polypeptide from the purification matrix.

10. A process according to claim 8 , wherein cleaving the group comprising

T-L-CO—, T-L-CR(OH)— or T-L-CR(NH 2 )—

from the polypeptide is performed subsequent to releasing the bound polypeptide from the purification matrix.

11. A polypeptide comprising a group selected from

T-L-CR(OH)—CR′(R″)—NH—CHR 1 —CO—

and

T-L-CO—CR′—(R″)—NH—CHR 1 —CO—,

wherein

T is a capture tag group capable of binding, with or without the participation of the

—CR—(OH)—, or —CO— group,

with a purification matrix,

L is a divalent linker moiety or may be absent,

R 1 is the side chain of an amino acid of the polypeptide,

R, R′ and R″ are independently selected from hydrogen, alkyl, aralkyl, aryl and heterocyclic groups,

and protected derivatives thereof.

12. A polypeptide according to claim 11 , wherein the capture tag group T is capable of binding with a purification matrix with the participation of the

—CR—(OH)—, or —CO— group.

13. A polypeptide according to claim 12 , comprising the group

HS—CH 2 —CH 2 —CH(OH)CH 2 NH——CHR 1 CO—.

14. A polypeptide according to claim 12 , comprising the group

H 2 N—CH 2 —CH 2 —CH(OH)CH 2 NH—CHR 1 CO—.

15. A polypeptide according to claim 12 , comprising the group

H 2 N—CH 2 —CH(OH)CH 2 NH—CHR 1 CO—.

16. A polypeptide according to claim 11 , wherein the capture tag group T is capable of binding with a purification matrix without the participation of the

—CR(OH), or —CO— group.

17. A polypeptide according to claim 16 , comprising the group

H-Cys-NH-CH 2 —CH 2 —CH(OH)—CH 2 NH—CHR 1 CO—.

18. A polypeptide according to claim 16 , comprising the group

H-Thr-NH—CH 2 —CH 2 13 CH(OH)—CH 2 NH—CHR 1 CO—.

19. A polypeptide according to claim 16 , comprising the group

H 2 N—O—CH 2 —CO—NH—CH 2 —CH 2 —CH(OH)—CH 2 NH—CH—R 1 CO—.

20. A polypeptide according to claim 11 , wherein the polypeptide is capable of binding with a purification matrix comprising aldehyde or ketone groups.

21. A process for removing the capture tag group T and, when present, the linker L from a polypeptide comprising a group selected from

T-L-CR(OH)—CR′(R″)—NH—CHR 1 —CO

T-L-CR(NH 2 )—CR′(R″)—NH—CH—R 1 —CO and

T-L-CO—CR′(R″)—NH—CHR 1 —CO,

the process comprising the step of treating the polypeptide with periodic acid or a salt thereof.

22. A process according to claim 21 , wherein the polypeptide is treated in solution.

23. A process according to claim 21 , wherein the polypeptide is treated while bound to a matrix and treatment serves to release the polypeptide from the matrix.

24. A process according to claim 4 , wherein a thiazolidine ring is formed upon attaching the polypeptide to a purification matrix.

25. A polypeptide comprising the group:

T-L-CR(NH 2 )—CR′(R″)—NH—CH R 1 —CO—

wherein

T is a capture tag group capable of binding, with the participation of the

—CR(NH 2 )— group

with a purification matrix,

L is a divalent linker moiety or may be absent,

R 1 is the side chain of an amino acid of the polypeptide,

R, R′ and R″ are independently selected from hydrogen, alkyl, aralkyl, aryl and heterocyclic groups,

and protected derivatives thereof.