Interaction between chondroitin-6-sulfate and poly-L-arginine in aqueous solution

✍ Scribed by R. A. Gelman; D. N. Glaser; J. Blackwell

• Publisher: Wiley (John Wiley & Sons)
• Year: 1973
• Tongue: English
• Weight: 536 KB
• Volume: 12
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1973.360120603

✦ Synopsis

Abstract

The interactions between chondroitin‐6‐sulfate and poly‐L‐arginine in aqueous salt solution have been investigated by circular dichroism techniques. In the presence of chondroitin‐6‐sulfate, at neutral pH, poly‐L‐arginine adopts the α‐helical conformation rather than “charged coil” form observed in the absence of mucopolysaccharide. This interaction is at a maximum when the ratio of arginine to disaccharide residues is 2:1. Elevation of the temperature leads to a sharp melting transition at 76.0 ± 1.0°C. This behavior is in marked contrast to that for poly‐L‐lysine‐chondroitin‐6‐sulfate interactions, which are at a maximum at a 1:1 residue ratio and have a melting transition at 47.0 ± 1.0°C. These results indicate a stronger interaction for poly‐L‐arginine than for poly‐L‐lysine. The positive arginine side chains appear to interact with both the negative sulfate and carboxyl residues, while those of the lysines are involved only with the sulfates. Poly‐L‐ornithine at neutral pH shows no conformation directing interaction with chondroitin‐6‐sulfate, although a small proportion of α‐helix is formed on dilution of the mixture with methanol. The extent of the interaction of cationic polypeptides with chondroitin‐6‐sulfate increases in the order poly‐L‐ornithine, poly‐L‐lysine, poly‐L‐arginine, i.e., in the order of increasing side‐chain length.