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Like-chargeion-pair formation in an aqueous solution of guanidiniumchloride (GdmCl) has two important facets. On one hand, it describesthe role of the arginine (ARG) side chain in aggregation and dimerformation in proteins, and on the other hand, it lends support forthe direct mechanism of protein denaturation by GdmCl. We employ all-atommolecular dynamics simulations to investigate the effect of GdmClconcentration on the like-charge ion-pair formation of guanidiniumions (Gdm+). From analyses of the radial distribution function(RDF) between the carbon atoms of two guanidinium moieties, the existenceof both contact pairs and solvent-separated pairs has been observed.Although the peak height corresponding to the contact-pair state decreases,the number of Gdm+ions in the contact-pair state actuallyincreases with increasing GdmCl concentration. We have also investigatedthe effect of the concentration of Gdm+on the structureof water. The effect of GdmCl concentration on the radial and tetrahedralstructures of water is found to be negligibly small; however, GdmClconcentration has a considerable effect on the hydrogen-bonding structureof water. It is demonstrated that the presence of chloride ions, notGdm+, in the first solvation shell of water causes thedistortion in the hydrogen-bonding network of water. In order to establishthat Gdm+not only stacks against another Gdm+but also directly attacks the ARG residue of a protein or peptide,simulation of an ARG-rich peptide in 6 M aqueous solution of GdmClhas been performed. The analyses of RDFs and orientation distributionsreveal that the Gdm+moiety of the GdmCl attacks the samemoiety in the ARG side chain with a parallel stacking orientation. [ABSTRACT FROM AUTHOR]

The article responds to B. G. Desai's comments on their work, emphasizing the consideration of a 50-year timeframe to set an ambitious Human Development Index (HDI) target for India. It authors stress the need for a high standard of living, the challenges of state-wise HDI variations, the importance of "energy footprint," and their view on a reasonable energy consumption target for the country.

Atomistic molecular dynamics simulations have been employed to study the self-ion (H + and OH - ) distribution at the interface between long-chain C 16 -OH alcohol (cetyl alcohol) monolayer and water. It is well known that the free air-water interface is acidic due to accumulation of the hydronium (H 3 O + ) ions at the interface. In the present study, we have observed that contrary to the air-water interface, at the long-chain alcohol monolayer-water interface, it is the hydroxide (OH - ) ion, not the hydronium ion (H 3 O + ) that gets accumulated. By calculating the potential of mean forces, it is confirmed that there is extra stabilization for the OH - ions at the interface relative to the bulk, but no such stabilization is observed for the H 3 O + ions. By analyzing the interaction of the self-ions with other constituents in the medium, it is clearly shown that the favorable interaction of the OH - ions with the alcoholic -OH groups stabilizes this ion at the interface. By calculating coordination numbers of the self-ions it is observed that around 50% water neighbors are substituted by alcoholic -OH in case of the hydroxide ion at the interface, whereas in the case of hydronium ions, only 15% water neighbors are substituted by the alcoholic -OH. The most interesting observation about the local structure and H-bonding pattern is that the hydroxide ion acts solely as the H-bond acceptor, but the hydronium ion acts only as the H-bond donor.