title: Quantum-mechanical DFT calculation supported Raman spectroscopic study of some amino acids in bovine insulin.
abstract: In this article Quantum mechanical (QM) calculations by Density Functional Theory (DFT) have been performed of all amino acids present in bovine insulin. Simulated Raman spectra of those amino acids are compared with their experimental spectra and the major bands are assigned. The results are in good agreement with experiment. We have also verified the DFT results with Quantum mechanical molecular mechanics (QM/MM) results for some amino acids. QM/MM results are very similar with the DFT results. Although the theoretical calculation of individual amino acids are feasible, but the calculated Raman spectrum of whole protein molecule is difficult or even quite impossible task, since it relies on lengthy and costly quantum-chemical computation. However, we have tried to simulate the Raman spectrum of whole protein by adding the proportionate contribution of the Raman spectra of each amino acid present in this protein. In DFT calculations, only the contributions of disulphide bonds between cysteines are included but the contribution of the peptide and hydrogen bonds have not been considered. We have recorded the Raman spectra of bovine insulin using micro-Raman set up. The experimental spectrum is found to be very similar with the resultant simulated Raman spectrum with some exceptions.
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
authors.forename: Bidisha
authors.initials: B
authors.lastname: Tah
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
authors.forename: Prabir
authors.initials: P
authors.lastname: Pal
authors.affiliation: Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur, West Bengal 721302, India.
authors.forename: Sourav
authors.initials: S
authors.lastname: Roy
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India.
authors.forename: Debodyuti
authors.initials: D
authors.lastname: Dutta
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India.
authors.forename: Sabyashachi
authors.initials: S
authors.lastname: Mishra
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
authors.forename: Manash
authors.initials: M
authors.lastname: Ghosh
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India. Electronic address: spgbt@iacs.res.in.
authors.forename: G B
authors.initials: GB
authors.lastname: Talapatra
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis*; D000818:Animals; D002417:Cattle; D061385:Insulins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman
chemical_list: D000596:Amino Acids; D061385:Insulins
keywords: Amino acid; Density functional theory; Insulin; Protein; Raman spectroscopy