J. At. Mol. Sci. doi: 10.4208/jams.022214.041814a Vol. 5, No. 4, pp. 279-288 November 2014 Structural, vibrational and electronic properties of cis and trans conformers of 4-hydroxy-l -proline: a density functional approach Ambrish K. Srivastava a , Anoop K. Pandey b , Shashi K. Gangwar a , and Neeraj Misra a ∗ a Department of Physics, University of Lucknow, Lucknow, Uttar Pradesh- 226007, India b Department of Physics, Govt. D.P.G. College, Dantewada, Chhattishgarh-494449, India Received 22 February 2014; Accepted (in revised version) 18 April 2014 Published Online 29 October 2014 Abstract. 4-hydroxy-l -proline is formed by hydroxylation of proline, an amino acid found in protein, whose inhibition results in hair problems in human, causing scurvy disease. We report a theoretical study on cis and trans conformers of 4-hydroxy-l - proline using first principle density functional approach at B3LYP/6-31+G(d,p) level. The equilibrium structures of both conformers are obtained to analyze their vibrational properties. The calculated vibrational modes are assigned and interpreted on the basis of potential energy distribution analysis. A good correlation has been obtained be- tween calculated frequencies and corresponding experimental values from FTIR spec- tra. The electronic properties of both conformers are also calculated and discussed. PACS: 31.15.A, 31.15.es, 31.15.V Key words: 4-hydroxy-l -proline, cis-trans conformers, vibrational analysis, density functional theory 1 Introduction 4-hydroxyproline or 4-hydroxy-l -proline (4HLP) is a non native amino acid which differs from proline, a proteinogenic amino acid, by the presence of a hydroxyl (−OH) group attached to the gamma carbon. It was isolated from hydrolyzed gelatin by Hermann Emil in the beginning of 20th century. Although, it is not directly incorporated into proteins, it comprises about 4% of all amino acids found in animal tissue, an amount greater than ∗ Corresponding author. Email address: neerajmisra11@gmail.com (N. Misra) http://www.global-sci.org/jams 279 c 2014 Global-Science Press