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Titolo:
Physical reasons for the unusual alpha-helix stabilization afforded by charged or neutral polar residues in alanine-rich peptides
Autore:
Vila, JA; Ripoll, DR; Scheraga, HA;
Indirizzi:
Cornell Univ, Baker Lab Chem & Chem Biol, Ithaca, NY 14853 USA Cornell Univ Ithaca NY USA 14853 b Chem & Chem Biol, Ithaca, NY 14853 USA Univ Nacl San Luis, Fac Ciencias Fis Matemat & Nat, Inst Matemat Aplicada San Luis, Consejo Nacl Invest Cient & Tecn, RA-5700 San Luis, Argentina Univ Nacl San Luis San Luis Argentina RA-5700 A-5700 San Luis, Argentina Cornell Univ, Ctr Theory, Ithaca, NY 14853 USA Cornell Univ Ithaca NY USA14853 l Univ, Ctr Theory, Ithaca, NY 14853 USA
Titolo Testata:
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
fascicolo: 24, volume: 97, anno: 2000,
pagine: 13075 - 13079
SICI:
0027-8424(20001121)97:24<13075:PRFTUA>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
AMINO-ACIDS; TRIFLUOROETHANOL; WATER; POLYPEPTIDES; PH;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
22
Recensione:
Indirizzi per estratti:
Indirizzo: Scheraga, HA Cornell Univ, Baker Lab Chem & Chem Biol, Ithaca, NY 14853 USA Cornell Univ Ithaca NY USA 14853 Biol, Ithaca, NY 14853 USA
Citazione:
J.A. Vila et al., "Physical reasons for the unusual alpha-helix stabilization afforded by charged or neutral polar residues in alanine-rich peptides", P NAS US, 97(24), 2000, pp. 13075-13079

Abstract

We have carried out conformational energy calculations on alanine-based copolymers with the sequence Ac-AAAAAXAAAA-NH2 in water, where X stands for lysine or glutamine, to identify the underlying source of stability of alanine-based polypeptides containing charged or highly soluble polar residues in the absence of charge-charge interactions. The results indicate that ionizable or neutral polar residues introduced into the sequence to make them soluble sequester the water away from the CO and NH groups of the backbone, thereby enabling them to form internal hydrogen bonds. This solvation effect dictates the conformational preference and, hence, modifies the conformational propensity of alanine residues. Even though we carried out simulations for specific amino acid sequences, our results provide an understanding of some of the basic principles that govern the process of folding of these short sequences independently of the kind of residues introduced to make them soluble. In addition, we have investigated through simulations the effect of the bulk dielectric: constant on the conformational preferences of these peptides. Extensive conformational Monte Carte searches on terminally blocked 10-mer and 16-mer homopolymers of alanine in the absence of salt werecarried out assuming values for the dielectric constant of the solvent epsilon of 80, 40, and 2. Our simulations show a clear tendency of these oligopeptides to augment the a-helix content as the bulk dielectric constant of the solvent is lowered. This behavior is due mainly to a loss of exposure of the CO and NH groups to the aqueous solvent. Experimental evidence indicates that the helical propensity of the amino acids in water shows a dramatic increase on addition of certain alcohols, such us trifluoroethanol. Our results provide a possible explanation of the mechanism by which alcohol/water mixtures affect the free energy of helical alanine oligopeptides relative to nonhelical ones.

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Documento generato il 07/07/20 alle ore 21:45:47