Lysine polypeptide conformational study

Mezo, G., Kajtar, J., Nagy, I., Szekerke, M., and Hudecz, F. (1997) Carrier design Synthesis and conformational studies of poly[L-lysine] based branched polypeptides with hydroxyl groups. Biopolymers 42, 719-730. 

Spin-lattice relaxation times and 13C chemical shifts were used to study conformational changes of poly-L-lysine, which undergoes a coil-helix transition in a pH range from 9 to 11. In order to adopt a stable helical structure, a minimum number of residues for the formation of hydrogen bonds between the C = 0 and NH backbone groups is necessary therefore for the polypeptide dodecalysine no helix formation was observed. Comparison of the pH-dependences of the 13C chemical shifts of the carbons of poly-L-lysine and (L-Lys)12 shows very similar values for both compounds therefore downfield shifts of the a, / and peptide carbonyl carbons can only be correlated with caution with helix formation and are mainly due to deprotonation effects. On the other hand, a sharp decrease of the 7] values of the carbonyl and some of the side chain carbons is indicative for helix formation [854]. 

Blackwell and his co-workers have used circular dichroism spectroscopy to study the interactions of glycosaminoglycans with collagen, and with synthetic cationic polypeptides. In the absence of glycosaminoglycans, poly-L-lysine and poly-L-arginine exist in an extended charged coil conformation. Glycosaminoglycans bind to these cationic polypeptides and cause them to assume an a-helical conformation. In a series of systematic studies (76-83). Blackwell and his co-workers... 

Susi et al. (1967) have observed spectra of poly-L-lysine, poly-L-glutamic acid, )S-lactoglobulin, myoglobin, and a -casein in the region of absorption of the amide I band in HjO and DjO solutions, and in the solid state. Their results indicated that characteristic frequencies exhibited by specific conformations of the synthetic polypeptides studied are not transferable to corresponding conformations of globular proteins. 

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