Abstract: Raman scattering and low temperature specific heat (Cp ) measurements have been performed to investigate the low frequency vibrational dynamics of hen egg white dry lysozyme. The occurrence of low energy extra excitations have been revealed both in the light scattering spectrum and in the Cp /T3 vs. T plot. A perfect agreement in the frequency and temperature position of the Boson Peak in this protein has been observed. At temperature below 3 K it has been found a contribution to the specific heat similar to that revealed in glassy systems. This, together with the other analogies discovered between thermal…properties of amorphous and biological systems, suggests the possibility of making the most of the knowledge about the former in order to understand some glassy-like behaviours of proteins.
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Keywords: Boson Peak, lysozyme, protein, specific heat, Raman scattering, low frequency dynamics
DOI: 10.3233/SPE-2010-0464
Citation: Spectroscopy,
vol. 24, no. 3-4, pp. 201-205, 2010
Abstract: The investigations of the interaction between phospholipid bilayer and short-chain alcohols are relevant for the potential of lipid bilayer membranes to serve as model systems for studies of various biological processes including permeability of the plasma membrane and molecular mechanisms of anesthesia. Because the hydrophobic portion of an alcohol favorably interacts with lipid hydrocarbon chains, the polar hydroxyl group remains free to form hydrogen bonds with polar lipid atoms that are located near the water/lipid interface. Experiments on phospholipid membranes have shown that alcohols can induce an interdigitated phase and at high concentration even promote the assembly of some lipids…into non-bilayer structures within the membrane interior. In this paper we have investigated the DPPC:hexanol system at high alcohol concentration (two molecules per phospholipid) by means of calorimetric, Nuclear Magnetic Resonance, X-ray diffraction and density measurements. We have found that the presence of a high alcohol concentration shifts the membrane transition temperature to lower values, and has a disordering effect on the phospholipid acyl chains in the gel phase. The bilayer spacing and the area of polar head have been also derived for the liquid phase.
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