• V D Gupta

      Articles written in Pramana – Journal of Physics

    • High resolution, rotation, vibration spectra of D2O in the region ofν1 andν3 bands

      V D Gupta

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      The infrared spectrum of D2O from 2400 to 3000 cm−1 has been analysed at a resolution better than 0·02 cm−1. It was recorded at the Fourier transform spectrometer of the Kitt Peak National Observatory, Tucson. Ground state constants of the reduced Watson-Hamiltonian, ground state energies and transition for theν1 andν3 bands are reported. The effect of strong Coriolis resonances on the spectra is discussed.

    • Molecular polarizabilities of some amino acids 1. Glycine and L-alanine

      V P Gupta V D Gupta C Mehrotra

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      Atom-dipole interaction model has been used to calculate the molecular polarizabilities, refractive indices along the direction of principal polarizabilities of glycine and L-alanine and the molar optical rotation of L-alanine. The results of the calculation have been compared with experimentally observed data from Kerr effect and polarimetric measurements.

    • Order-order transition in a macromolecular system—poly-L-proline I and II

      R C Agnihotri C Mehrotra V D Gupta Vandana Srivastava

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      Ising model formalism developed for order-disorder transition in poly-peptides has been modified for the study of order-order transition in a macromolecular system. A two-state theory is developed and applied to poly-L-proline I and II. Various transition curves for different chain lengths are obtained as a function of solvent composition. Transition curves and crossing point for a solvent system are in excellent agreement with the experimental data on poly-L-proline.

    • Fractional order phase transition in lipid bilayer: dipalmitoyllecithin

      R C Agnihotri C Mehrotra V D Gupta Vandana Srivastava

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      Dipalmitoyllecithin (DPL) shows an order ← → disorder pressure transition which is neither of first order nor of second order but can be treated as a fractional order (3/2 order) transition. The Ising model formalism is adopted for the study of such a system. A suitable equilibrium constant is defined which generates a 3/2 order transition. Transition curves are obtained and compared with the experimental curves of Liu and Kay. Reverse transition curves are also obtained and the system exhibits hysteresis effect. An approximate expression connecting transition pressures at different temperatures is obtained and the calculated and the experimental values are in good agreement.

    • Heat capacity and phonons in poly(L-leucine)

      Seema Srivastava Poonam Tandon V D Gupta Shantanu Rastogi S B Katti L Burman

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      Poly(L-leucine) is one of the polyamino acids having a bulky hydrophobic side-chain. For want of full phonon dispersion curves and density-of-states on this biopolymer Roleset al have interpreted their specific heat data in a limited way. In the present communication we report an analysis of the normal modes and their dispersion for poly(L-leucine) which leads to a very good agreement of the specific heat calculations with experimental measurements. It is observed that the main contribution to specific heat comes from the coupling of the back-bone skeletal and side-chain modes. Several other assignments have been revised. A special feature of some dispersion curves is their tendency to bunch in the neighbourhood of helix angle. It has been attributed to the presence of strong intramolecular interactions. Repulsion between the dispersion curves is also observed.

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