Molecular structure and vibrational assignments of L-tyrosine: a detailed experimental and density functional theoretical study

Introduction Urolithiasis is a relatively common condition in humans. Dietary habits are considered the prime reasons for urolithiasis. During the last half of this century its prevalence has dramatically increased in all industrialized countries. From 3 to 20% of overall population will form at least one urinary stone during a life time of 70 years. Crystal induced kidney disease is a frequent occurrence in human pathology. It is becoming more and more apparent that knowledge of kidney stone composition and structure appears to be the key for establishing the etiology of stone diseases. To identify pathological conditions responsible for stone formation, it is necessary to carefully examine the structure and determine both the qualitative and quantitative crystalline composition of urinary stones. Proteins are the basic constituents of all living organisms and composed of organic molecules called amino acids which are joined covalently by peptide bonds. The building blocks of proteins are the 20 naturally occurring amino acids. These relatively simple molecules are interesting molecules themselves and much more work has been done both experimentally and theoretically in trying to understand these molecules. As building blocks of proteins, amino acids are indispensible agents of biological functions. Due to their important biological function, amino acids have been a subject of spectroscopic studies. All α -amino acids except glycine have the same basic design i.e an amino group, a carbonyl group, and a side chain or R group, all bonded to the central carbon atom. The side chains of the 20 amino acids vary in size, shape, charge, hydrogen bonding capacity and chemical reactivity. In the main part of the -amino acid skeleton, three internal rotational degrees of freedom exist i.e rotation about the N-C, C-C and C-O bond. Tyrosine is one of the three aromatic amino acids. Its side chain consists of a CH2 group bonded in para position on a phenol ring. Despite its biological importance, detailed data on the conformational behaviour and spectroscopic data of neutral isolated tyrosine are not found much in literature. Matrixisolation FTIR spectroscopic study and theoretical calculations of the vibrational properties of tyrosine were carried out by Guido Maes et al [1]. In our former report of research we have demonstrated the influence of sodium fluoride on the crystallization and spectral properties of L-tyrosine [2]. Apart from the chemical and biochemical interests of Ltyrosine, the structural and vibrational studies are of pharmacological importance because this molecule acts as a precursor of several neurotransmitters. A deficiency in the neurotransmitter synthesis can lead to physical and mental burnout and fatigue as well as Dementia, Phynylketonuria, and Molecular structure and vibrational assignments of L-tyrosine: a detailed experimental and density functional theoretical study M.Thenmozhi, R.Mathammal and C. Sekar Department of Physics, Sri Sarada College, Salem 636 016, TN, India. Department of Physics, Periyar University, Salem 636 011, TN, India. Department of Bioelectronics and Biosensors, Alagappa University, Karaikudi-630 003, TN, India.