Abstract

MARCANO, Emildo; ALAYON, Johana  and  CISNEROS, José. Theoretical study of nonlinear optics properties in aminoacids. Revista de Investigación [online]. 2017, vol.41, n.90, pp.041-052. ISSN 1010-2914.

A theoretical study of the average polarizability (< α >) and first total hyperpolarizability (βtotal) for nine essential amino acids is presented. The calculations were carried out in gas phase, at Hartree Fock (HF) and Møller-Plesset (MP2) level using the 6-31+G (d,p) basis set. The maximum absorption bands, calculated at CAM-B3LYP/6-31+G (d, p), are between 122 nm and 153 nm, highlighting the Isoleucine with 129 nm. The main contribution for this λmax is associated with the transition HOMO-2 → LUMO + 4. Tryptophan stands out like structure with the best values of < α > (122.7 ua) and βtotal (302.0 ua). Increased < α > Trp → Phe substitution is due to the benzene ring by the indole moiety; latter introduces greater electron delocalization and charge separation in the structure. Similarly, the increase in the βtotal value can be justified by the presence of the indole moiety, because the nature of benzene centrosymmetric minimizes the contribution to the first hyperpolarizability in Phe. Similar arguments can explain the behavior of properties in the remaining amino acids.

Keywords : Amino acids; polarizability; hyperpolarizability; nonlinear optic.

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