Modalities of Protein Denaturation and Nature of Denaturants

Denaturation of protein is a biological phenomenon in which a protein loses its native shape due to the breaking or disruption of weak chemical bonds and interactions which makes the protein biologically inactive. It is the process where properly folded proteins formed under physiological conditions is transformed to an unfolded protein under non-physiological conditions. The process of denaturation of proteins can occur under different physiological and chemical conditions. Denaturation can be reversible or irreversible. Denaturation mostly takes places when the protein is subjected under external elements like inorganic solutes, organic solvents, acids or bases, and by heat or irradiations. The denaturing agents or denaturants widely used in protein folding or unfolding experiments are urea and guanidinium chloride (GdmCl). In denaturation, the alpha-helix structure and beta sheets structure of the native protein are disrupted and unfolds it into any random shape. We can also say that denaturation occurs due to the disruption of bonding interactions which are responsible for secondary structure and the tertiary structure of the proteins.

Photogeneration of Organic Free Radicals in Liquid Solutions

In this brief review we consider the generation of free radicals by irradiation with UV-light solutions of compounds with weak chemical bonds. Bond dissociation energies (BDE) are compared with the energies of photons. Light sources used in industry and academia are listed. Free radicals can be produced by photodissociation and by bimolecular chemical reactions between the electronically- excited state of a molecule and a quencher. Important examples are presented. A special effort is devoted to light-emitting diodes (LED) which gain a wide application in this century. We cited books on the free radicals and photochemistry as an introduction as well as recent publications dated 2020.

Leading Interaction Components in the Structure and Reactivity of Noble Gases Compounds

The nature, strength, range and role of the bonds in adducts of noble gas atoms with both neutral and ionic partners have been investigated by exploiting a fine-tuned integrated phenomenological–theoretical approach. The identification of the leading interaction components in the noble gases adducts and their modeling allows the encompassing of the transitions from pure noncovalent to covalent bound aggregates and to rationalize the anomalous behavior (deviations from noncovalent type interaction) pointed out in peculiar cases. Selected adducts affected by a weak chemical bond, as those promoting the formation of the intermolecular halogen bond, are also properly rationalized. The behavior of noble gas atoms excited in their long-life metastable states, showing a strongly enhanced reactivity, has been also enclosed in the present investigation.

The effect of translation on the binding energy for transition-metal porphyrines adsorbed on Ag(111) surface

The characteristics of interaction between six transition-metal porphyrines and the Ag(111) surface are detailed here as resulted from DFT calculations. Van der Waals interactions as well as the strong correlation in 3d orbitals of transition metals were taken into account in all calculations, including the structural relaxation. For each system we investigate four relative positions of the metallic atom on top the surface. We show that the interaction between the transition metal and silver is the result of a combination between the dispersion interaction, charge transfer and weak chemical interaction. The detailed analysis of the physical properties, such as dipolar and magnetic moments and the molecule–surface charge transfer, analyzed for different geometric configurations allows us to propose qualitative models, relevant for the understanding of the self-assembly processes and related phenomena.