On the magnitude of the cotton effects of poly-L-glutamic acid

✍ Scribed by Jen Tsi Yang; William J. McCabe

• Publisher: Wiley (John Wiley & Sons)
• Year: 1965
• Tongue: English
• Weight: 256 KB
• Volume: 3
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360030208

✦ Synopsis

COMMUNICATION TO THE EDITORS

O n the Magnitude of the Cotton Eflects of Poly-L-glutarnic Acid

The recent improvement in spectropolarimeters makes it possible to measure the Cotton effects of polypeptides and proteins between 185 and 240 rnp.Ir2 The helical conformation, quite unlike the coiled form, shows a strong trough and peak at 233 and 108 mp. The reduced mean residue rotations, [m']233 and [112']198, have thus been suggested as two measiires of the helicity in protein moleciiles. At present, poly-L-glutamic acid (PGA) in aqueous solution is providing the reference values for the two conformations. The reported value for [m']233 (helix), however, varies from -13,000 to -18,000, thiis making siich an estimation very inc certain.^ Such a wide variation in reported results is puzzling because t,he PGA samples have all been prepared by the same meth0d.l We offer a comparative stitdy of 4 samples from 4 laboratories; all stork solutions were