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Titolo:
Influence of lysine content and pH on the stability of alanine-based copolypeptides
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 Cornell Univ, Ctr Theory, Ithaca, NY 14853 USA Cornell Univ Ithaca NY USA14853 l Univ, Ctr Theory, 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
Titolo Testata:
BIOPOLYMERS
fascicolo: 3, volume: 58, anno: 2001,
pagine: 235 - 246
SICI:
0006-3525(200103)58:3<235:IOLCAP>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
OCCURRING AMINO-ACIDS; MONTE-CARLO METHOD; POISSON-BOLTZMANN EQUATION; CHARGE-CHARGE INTERACTIONS; HYDROGEN-BOND INTERACTIONS; SHORT TEMPLATED PEPTIDES; BOUNDARY-ELEMENT METHOD; MULTIPLE-MINIMA PROBLEM; HELIX FORMATION; CONFORMATIONAL-ANALYSIS;
Keywords:
lysine; alanine; alpha-helices; copolymers; conformational energy calculations; electrostatic interactions; hydration; hexadecapeptides; pH dependence;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
59
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., "Influence of lysine content and pH on the stability of alanine-based copolypeptides", BIOPOLYMERS, 58(3), 2001, pp. 235-246

Abstract

To account for the relative contributions of lysine and alanine residues to the stability of cu-helices of copolymers of these two residues, conformational energy calculations were carried our for several hexadecapeptides atseveral pHs. All the calculations considered explicitly the coupling between the conformation of the molecule and the ionization equilibrium as a function of pH. The total free energy function used in these calculations included terms that account for the solvation free energy and free energy of ionization. These terms were evaluated by means of a fast multigrid boundary element method. Reasonable agreement with experimental values was obtained for the helix contents and vicinal coupling constants ((3)J(HN alpha)). Thehelix contents were found to depend strongly on the lysine content, in agreement with recent experimental results of Williams et al. (Journal of the American Chemical Society. 1998, Vol. 120 pp. 11033-11043) In the lowest energy conformation computed for a hexadecapeptide containing 3 lysine residues at pH 6 the lysine side chains are preferentially hydrated; this decreases the hydration of the backbone CO and NH groups. thereby forcing the latter to form hydrogen bonds with each other in the helical conformation. The lowest energy conformation computed for a hexadecapeptide containing 6 lysine residues at pH 6 show's a close proximity between the NH: groups of the lysine side chains, a feature that was previously observed in calculations of short alanine-based oligopeptides. The calculation on a blocked 16-mer of alanine shows a 7% helix content based on the Boltzmann averaged vicinal coupling constants computed from the dihedral angles phi, consistent with previous experimental evidence on triblock copolymers containing a central block of alanines, and with earlier theoretical calculations. (C) 2001 John Wiley & Sons, Inc.

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Documento generato il 02/07/20 alle ore 20:03:43