Mean-square helical hydrophobic moments in partially ordered proteins

✍ Scribed by Maher M. Hamed; Wayne L. Mattice

• Publisher: Wiley (John Wiley & Sons)
• Year: 1984
• Tongue: English
• Weight: 514 KB
• Volume: 23
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360230607

✦ Synopsis

Helical hydrophobic moment ratios, ( h 2 ) / ( H 2 ) ,

have been evaluated for 34 polypeptides under conditions where the helix content is dictated solely by the short-range interactions operative in aqueous media. The mean-square helical hydrophobic moment is denoted by

and ( H 2 ) is the averaged of the squared hydrophobicities. This ratio would he one in absence of any correlation in the hydrophobicities of amino acid residues in helices. The ( h 2 ) / ( H 2 ) tend to be substantially larger than values of the analogous ratio formulated for the mean-square dipole moments of typical synthetic polymers. For 24 of the 34 polypeptide chains considered, ( h 2 ) / ( H 2 ) is found to be greater than one, indicating a tendency to form helices with amphiphilic character. The ratio is exceptionally large in the case of the &hemolysins. It is also large for two other surface-active peptides, for two of the four apolipoproteins examined, and for myohemerythrin. A much smaller ( h 2 ) / ( H 2 ) is found for melittins. If melittins is to form helices with large ( h 2 ) / ( H 2 ) , the configurational statistics must be governed by effects in addition to those short-range interactions that occur when water is the solvent.