Scientific Results

Conformational Analysis of Gly-Ala-NHMe in D2O and DMSO Solutions: A Two-Dimensional Infrared Spectroscopy Study

Year: 2013

Authors: Candelaresi M., Ragnoni E., Cappelli C., Corozzi A., Lima M., Monti S., Mennucci B., Nuti F., Papini A.M., Foggi P.

Autors Affiliation: Heriot-Watt University, Edinburgh Campus, Edinburgh, Scotland EH14 4AS; LENS, Polo Scientifico Universitario, Via Nello Carrara 1, 50019 Sesto F.no (FI), Italy; Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy; Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy; Technical University of Denmark-Department of Chemistry, Kemitorvet, Kongens Lyngby, DK 2800, Denmark; INO−CNR, Polo Scientifico Universitario, Via Nello Carrara 1, 50019 Sesto F.no (FI), Italy; CNR ICCOM, Area della Ricerca, Via G. Moruzzi 1, 56124 Pisa, Italy; French-Italian Laboratory of Peptide & Protein Chemistry & Biology (www.peptlab.eu) Dipartimento di Chimica, Università di Firenze, Polo Scientifico Universitario, Via delle Lastruccia 13, 50019 Sesto F.no (FI), Italy; Laboratoire SOSCO EA 4505, Université de Cergy-Pontoise, 5 Mail Gay Lussac, 95031 Cergy-Pontoise, France; Dipartimento di Chimica, Università di Perugia, Via Elce di Sotto 8, 06100 Perugia, Italy

Abstract: A relevant number of experiments on short peptides has been performed in recent years. One of the major problems rises from the simultaneous presence of slightly different conformers at equilibrium in solution. In the present paper, the conformational characteristics of the Gly-L-Ala-Methyl amide dipeptide in D2O and DMSO solutions are investigated by nonlinear IR spectroscopy. The pump probe scheme with ultrashort midinfrared pulses, in the Amide I region, is used to determine the mutual orientation of the two C=O bonds and the dynamics due to solute solvent interactions. The coupling between Amide I modes is evaluated from both linear and 2D spectra. The interconversion between the different conformations occurs on time scales longer than the vibrational lifetime, and the spectral diffusion observed in 2D spectra is attributed to the solvent dynamics. Quantum mechanical calculations and molecular dynamics simulations are performed to identify the most stable geometries. By comparing the experimental and the theoretical data, we establish the prevalence of beta-like polar conformers in both water and DMSO solvents.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY B

Volume: 117 (46)      Pages from: 14226  to: 14237

More Information: The authors wish to remember Robin M. Hochstrasser, recently deceased, who gave the largest contribution to the development of 2DIR spectroscopy. The authors acknowledge the Italian \”Ministero dell\’Universit√† e della Ricerca\” (PRIN 2008BFJ34R, FIRB RBFR10Y5VW, and EFOR L. 191/2009 art. 2 comma 44) and the \”Ente Cassa di Risparmio di Firenze\” for their financial support. Moreover, A.M.P. thanks the ANR Chaire d\’Excellence 2009-2013 for financial support to PeptLab.
KeyWords: 2D-IR; polyproline-II structure; molecular-dynamics simulations; polarizable continuum model; vibrational spectroscopy
DOI: 10.1021/jp406139t

Citations: 3
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