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Role of the phonon-phonon interaction highly anharmonic systems: the hydrated amino acids case


Two special dynamical transitions of universal character have been recently observed in macromolecules (lysozyme, myoglobin, bacteriorhodopsin, DNA, and RNA) at TD=180 - 220K and T*= 100 K. The first represents the threshold of biological activity and the transition from an anharmonic to harmonic dynamical regime of motion in hydrated biomolecules. The second represents the onset of a secondary harmonic characteristic behavior. Despite their relevance, a complete understanding of the nature of these transitions and their consequences for the bio-activity of the macromolecule is still lacking. Specifically one could cite as important open questions (i) the nature of the relaxation mechanisms evolved in the molecular interactions and their hydration dependence; (ii) the thermodynamic nature of the transitions; (iii) the dependence of TD and T* on the hydration level; (iv) role of the phonon-phonon interactions and relative contributions from intrinsic and extrinsic anharmonicites; (v) role of the local environment of the water site; (vi) how the raised points above change when considering bio-inactive optical isomers (dextrogyres). The objective of the present project is contribute to elucidate the questions raised above having as system study the optical isomers (dextrogyre and levogyre) and the racemic mixture of the amino acids cysteine (C3H7NO2S), cystine (C6H12N2O4S2), proline (C5H9NO2) and hydroxyproline (C5H9NO3) with several hydration levels. The methodology will consist in study the temperature dependence (10-300 K) of the thermodynamic (specific heat), structural (X-Ray diffraction), and Raman-active phonon spectra aimed with computational simulations of the physical properties (DFT calculations). (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
LIMA, T. A.; SATO, E. T.; MARTINS, E. T.; HOMEM-DE-MELLO, P.; LAGO, A. F.; COUTINHO-NETO, M. D.; FERREIRA, F. F.; GILES, C.; PIRES, M. O. C.; MARTINHO, H.. Anharmonic transitions in nearly dry L-cysteine I. JOURNAL OF PHYSICS-CONDENSED MATTER, v. 24, n. 19, . (11/06618-0)

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Filed patent(s) as a result of this research project

APARATO PARA AJUSTE DE INTENSIDADE LUMINOSA BR1020160099927 - Universidade Federal do ABC (UFABC) . Herculano Da Silva Martinho ; Taciana Deprá Magrini Alva ; Arnaldo Rodrigues Santos Junior ; Marcella Pecora Milazzotto ; Marcela Sorelli Carneiro Ramos ; Marcelo Augusto Christoffolete - May 2016, 03