The dynamics, structural properties, and energetics of hydration water around a sodium dodecyl sulphate micelle have been investigated using molecular dynamics simulation. A clear revelation of the slow dynamics of the hydration water has been made by separate measurements of the rotational and translational properties. Calculated diffusion coefficients fall within the range of experimentally observed quantities. The water-micelle head group (MHG) hydrogen bond is more stable (by an amount [Formula presented]) compared to the water-water hydrogen bond. The difference in stability of the water monomers forming different numbers of hydrogen bonds [Formula presented] with the MHG has clearly been shown from the analyses of their rotational relaxation, residence times, as well as the energy of interaction with different components of the system. The singly hydrogen-bonded water species is the most abundant and stable. The entropy plays the key role in controlling the relative abundance of the different species. © 2004 The American Physical Society.

CHAITALI MUKHOPADHYAY

Chemistry

S G DASTIDAR

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

An all-atom molecular dynamics simulation shows concentration-dependent like-charge ion pairing of the guanidinium ion in an aqueous solution of guanidinium chloride. We have observed two types of like-charge ion pairing for guanidinium ions, namely, stacked ion pairs and solvent-separated ion pairs. Interestingly, both of these like-charge ion-pair formations are dependent on the concentration of guanidinium chloride in water. The probability of stacked like-charge ion-pair formation decreases, whereas, the probability of solvent-separated like-charge pairing increases as the concentration of guanidinium chloride increases, which is shown from radial distribution functions and is confirmed from the energy calculations. Besides like-charge ion-pair formation, we also investigated guanidinium chloride induced changes in water structure. Hydrogen-bond analysis indicates that guanidinium chloride does not alter the strict-hydrogen-bonding patterns of water, whereas, it breaks the bend-hydrogen bond and the non-hydrogen-bonding patterns. Tetrahedral order, nearest neighbor orientation, and distance distribution of water molecules around a probe water molecule show the extent of water structure distortion. © 2013 American Physical Society.

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Concentration-dependent like-charge pairing of guanidinium ions and effect of guanidinium chloride on the structure and dynamics of water from all-atom molecular dynamics simulation

Alteration of the conformational and dynamic properties of peptides in the presence of micelles mimics the cellular events that take place during insertion and translocation of peptides in biological membranes. We have recently reported the alteration of the conformation of neuropeptides Leu- and Met-enkephalins in the presence of ganglioside GM1 micelles. Here, using pulsed-field gradient-stimulated echo diffusion NMR studies, we observe that the diffusion coefficients of the peptides are greatly reduced in the presence of GM1 micelles. Partition coefficient calculations indicate a nearly total incorporation of the peptides into the micelles. The binding epitope of the enkephalins, as established from the saturation transfer difference NMR spectroscopy, indicates involvement of the Tyr1, Gly3, and Phe4 residues. The involvement of the aromatic side chains of the Tyr1 and Phe4 indicates a possible hydrophobic nature of the interaction.

Journal of Physical Chemistry B

Pulsed-field gradient and saturation transfer difference NMR study of enkephalins in the ganglioside GM1 micelle

The enkephalins are endogenous neurotransmitters and bind with high affinity at the δ-receptor. Gangliosides, the major glycans of nerve cells, known to interact both with receptors and ligands on the cell surface, have been implicated to modulate the actions of opioid receptors by allosteric regulation (Wu, G.; Lu, Z. H.; Wei, T. J.; Howells, R. D.; Christoffers, K.; Leeden R. W. Ann NY Acad Sci 1998, 845, 126-138). We have studied the interactions between enkephalins and monosialylated ganglioside GM1 using NMR spectroscopy and fluorescence. The structural models of enkephalins in the presence of GM1 micelles were generated using two-dimensional 1H-ROESY experiments along with restrained molecular dynamics simulations. We report a conformational alteration of enkephalins in the presence of GM1 micelles. © 2003 Wiley Periodicals, Inc.

Biopolymers

Structural Alterations of Enkephalins in the Presence of GM1 Ganglioside Micelles

The dynamics of water around a biomolecular surface has attracted a lot of attention recently. We report here protein-solvent simulation studies of the small globular protein ubiquitin (human). The simulations are run unconstrained, without freezing the bonds. The mean square displacements of the water oxygen atoms show a sublinear trend with time. The diffusion coefficient data indicate that the water in the first hydration layer behaves like water at a temperature that is roughly [Formula presented] lower than the average temperature of the system [Formula presented] Both the dipolar second-rank relaxation and the survival time correlation function of the water layers show two decay constants, indicating contributions from fast and slow dynamics. A calculation of the interaction energy between the water layers and protein indicates that the interaction energy sharply decreases beyond 4 Å from the protein surface. © 2003 The American Physical Society.

Journal	Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Publisher	AMER PHYSICAL SOC
ISSN	1063-651X
Open Access	No