UniCa UniCa News Notizie Jože Grdadolnik - National Institute of Chemistry, Ljubljana, Slovenia

Jože Grdadolnik - National Institute of Chemistry, Ljubljana, Slovenia

From dipeptides to protein structure; backbone structures of 19 dipeptides in aqueous solution
22 maggio 2013
Dipartimento di Scienze Chimiche e Geologiche
 
 
Il Prof. Jože Grdadolnik (National Institute of Chemistry, Ljubljana, Slovenia) terrà il giorno mercoledì 22 maggio 2013 alle ore 11:00 presso l’aula 3 della Cittadella Universitaria di Monserrato il seguente seminario:
 
 
From dipeptides to protein structure; backbone structures of 19 dipeptides in aqueous solution
 
 
A basic unsolved problem in protein structure research is how to make accurate calculations of the folding energetics of flexible peptides. Even the simplest problem, calculation of the Phi,Psi map of the alanine dipeptide, is beyond the reach of standard force fields. The first necessary step in producing a force field that will reliably describe the folding energetics of flexible peptides is to obtain accurate experimental data for the fractional populations in the major backbone conformations. The three major basins are PII (positioned approximately at -75o, 145o), β (-120o, 120o) and αR (-60o, -40o). These backbone conformations reveal three distinct bands in amide III region that appear in both infrared and Raman spectra near 1309 cm-1  (PII), 1299 cm-1 (αR), and 1288 cm-1 (β), respectively. The assignment of the bands was checked by changing temperature, pH, and solvent. The distributions of the PII, αR, and β conformations depend on the type of side-chain. The PII is the prevailing conformation of alanine and leucine dipeptides; however, threonine, and histidine dipeptides adopt predominantly the β conformation. The least populated conformation of dipeptides in aqueous solution is the αR conformation (exception is glycine dipeptide). The experimental populations of dipeptides derived from the infrared spectra and Raman spectra agree well with the 3JHNα NMR coupling constants and are in accord with the electrostatic screening model of conformational preferences of residues. The distributions of the conformations of dipeptides in aqueous solution can be used to develop new and more accurate force fields for simulating structures and dynamics of proteins.
 
 
Il seminario sarà in lingua inglese
 
Tutti gli interessati sono invitati.
Mariano Casu
Prof. Associato di Chimica Fisica
Università di Cagliari
Dipartimento di Scienze Chimiche e Geologiche
Cittadella Universitaria di Monserrato
09042 Monserrato (CA) - Italy - 
Tel: 0706754416
Cell: 3393221050
Email: mcasu@unica.it: people.unica.it/marianocasuWeb

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