Conformation of polypeptide in the, helix–coil transition region

✍ Scribed by T. M. Birshtein

• Publisher: Wiley (John Wiley & Sons)
• Year: 1969
• Tongue: English
• Weight: 96 KB
• Volume: 7
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1969.360070314

✦ Synopsis

Conformation of Polypeptide i n the Helix-Coil Transition Region

A recently published work by Go, Saito, and Ochiail presented a calculation of the mean values of the second (R2) and the fourth (R4) powers of the end-to-end distance of the polypeptide chain in the helix-coil transition region. The polypeptide chain followed the model of alternating rigid helical and gaussian coil-shaped segments freely joined to each other. The calculation has given (R4) # 513 (R2)2 and the authors draw the conclusion that the polypeptide conformation in the helix-coil transition region is not a gaussian one.

Considering the chain consisting of 2 p + 1 segments in which the segments having odd and even numbers are, respectively, helical and coil-shaped, Go et a1.l write:

Nevertheless this result is due to an error in calculations.

where the np subscript indicates that the averaging is made at the given number of the segments and the given number of the monomers in every segment and l k is the vector of length of the k-th segment. Evidently, the expression (1) is wrong since

In deriving eqs.

( 2 ) we took into account that a t k # m and