Propriedades eletrônicas, ópticas e vibracionais da região C- Terminal da fosfolipase A2 Lys 49.

Abstract

In this work, we present a study of the electrical properties, optical, vibrational and thermodynamic of the C-terminal Phospholipase A2 Lysine region 49 (PLA2 Lys 49). This was done by means of quantum calculations by Density Functional Theory (DFT), using the approach of Local Density Approximation (LDA) and the approach of the Generalized Gradient Approximation (GGA). They were also made calculations based on the model tight binding. The PLA2 Lys 49 composes myotoxins group that presents a little or no catalytic activity and still are able to act on the cell membrane by providing an alternative mechanism of cell's death. The C-terminal region of these proteins, in particular the region between amino acids 115-129 is identi_ed as responsible for the damage the membranes. Little is known about the characteristics that propitiate to this region such capacity and how are their interaction with the cell membrane. This work constitutes a characterization of the physical properties of this region. Searching, therefore, establish a relationship between the physical properties expressed by this region and its potential for cell damage. An initial results obtained in this study were current-voltage curves (I-V) for nine di_erent peptides corresponding to regions 115-129 PLA2 from di_erent snake species. The (I-V) curves were obtained by the model tight binding. They demonstrate that the peptides studied have semiconductor characteristics. They also have similarity with experimental results obtained by LOMONTE et al., 2003. Using the DFT were performed the calculations of the area accessible to the solvent, the electron density, population analysis of load, orbital border, and density of states. They were also carried out calculations of vibrational properties as infrared spectrum, optical properties and thermodynamic properties such as heat capacity, entropy, enthalpy and free energy. The electronic properties show that there is a possibility the interaction of the C-terminal region with the membrane it's predominantly electrostatic. The load population analysis showed that the amino acid Lysine 122 has load zero. This indicates that it may not have important role as described in the literature. The consequences obtained for the solvent accessible area indicates that a peptide with the largest area available to interact with the membrane not cause greater damage. The optical results presented absorption peaks in the visible region. These results together with the results vibrational serve like a "digital"to identify the studied peptides. The Thermodynamic results presented in this work can be used in future research involving PLA2 Lysine 49.