A modification of the nudged elastic band method for finding minimum energy paths is presented. One of the images is made to climb up along the elastic band to converge rigorously on the highest saddle point. Also, variable spring constants are used to increase the density of images near the top of the energy barrier to get an improved estimate of the reaction coordinate near the saddle point. Applications to CH4 dissociative adsorption on Ir~111! and H2 on Si~100! using plane wave based density functional theory are presented. © 2000 American Institute of Physics. @S0021-9606~00!71246-3#

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A climbing image nudged elastic band method for finding saddle points and minimum energy paths

The phenomenon of growth, decline and death—aging—has been the source of considerable speculation (1, 8, 10). This cycle seems to be a more or less direct function of the metabolic rate and this in turn depends on the species (animal or plant) on which are superimposed the factors of heredity and the effects of the stresses and strains of life—which alter the metabolic activity. The universality of this phenomenon suggests that the reactions which cause it are basically the same in all living things. Viewing this process in the light of present day free radical and radiation chemistry and of radiobiology, it seems possible that one factor in aging may be related to deleterious side attacks of free radicals (which are normally produced in the course of cellular metabolism) on cell constituents.* Irradiation of living things induces mutation, cancer, and aging (9). Inasmuch as these also arise spontaneously in nature, it is natural to inquire if the processes might not be similar. It is believed that one mechanism of irradiation effect is through liberation of OH and HO 2 radicals (12). There is evidence, although indirect, that these two highly active free radicals are produced normally in living systems. In the first place, free radicals are present in living cells; this was recently demonstrated in vivo by a paramagnetic resonance absorption method (3). Further, it was shown that the concentration of free radicals increased with increasing metabolic activity in conformity with the postulates set forth some years ago that free radicals were involved in biologic oxidation-reduction reactions (11, 13). Are some of these free radicals OH and/or HO2, or radicals of a similar high order of reactivity, and where might they arise in the cell? The most likely source of OH and HO2 radicals, at least in the animal cell, would be the interaction of the respiratory enzymes involved

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Aging: A Theory Based on Free Radical and Radiation Chemistry

/pdf/brownian-motion-in-a-field-of-force-and-the-diffusion-model-2nbbzrdubb.pdf

Brownian motion in a field of force and the diffusion model of chemical reactions

Stanford Moore, William Stein, and Anfinsen were awarded the Nobel Prize in Chemistry in 1972 for \"their contribution\n to the understanding of the connection between chemical structure and catalytic activity of the active center of the ribonuclease\n molecule.\" In his Nobel Lecture, Anfinsen provided a sketch of the rich history of research that provided the foundation\n for his work on protein folding and the \"Thermodynamic Hypothesis,\" and outlined potential avenues of current and\n future scientific exploration.

https://web.iitd.ac.in/~amittal/1973_Anfinsen_Science.pdf

Principles that Govern the Folding of Protein Chains

We demonstrate in this work that the surface tension, water-organic solvent, transfer-free energies and the thermodynamics of melting of linear alkanes provide fundamental insights into the nonpolar driving forces for protein folding and protein binding reactions. We first develop a model for the curvature dependence of the hydrophobic effect and find that the macroscopic concept of interfacial free energy is applicable at the molecular level. Application of a well-known relationship involving surface tension and adhesion energies reveals that dispersion forces play little or no net role in hydrophobic interactions; rather, the standard model of disruption of water structure (entropically driven at 25 degrees C) is correct. The hydrophobic interaction is found, in agreement with the classical picture, to provide a major driving force for protein folding. Analysis of the melting behavior of hydrocarbons reveals that close packing of the protein interior makes only a small free energy contribution to folding because the enthalpic gain resulting from increased dispersion interactions (relative to the liquid) is countered by the freezing of side chain motion. The identical effect should occur in association reactions, which may provide an enormous simplification in the evaluation of binding energies. Protein binding reactions, even between nearly planar or concave/convex interfaces, are found to have effective hydrophobicities considerably smaller than the prediction based on macroscopic surface tension. This is due to the formation of a concave collar region that usually accompanies complex formation. This effect may preclude the formation of complexes between convex surfaces.

Protein folding and association: insights from the interfacial and thermodynamic properties of hydrocarbons.

Advances in Quantum Chemistry. Volume 1.

The irradiation effects and the increase of neutron yield from the deuterium‐deuterium reaction in tantalum has been studied at a bombarding energy of 350 kev and a target current 100 μa. Saturation (the neutron yield becomes a steady maximum) is reached in a new target, maintained at temperatures below 45°C, after about 2 hours of steady bombardment or on the order of 1 coulomb of deuterons per square centimeter. The irradiated targets were annealed at temperatures from 45°C to 770°C. A thermal analysis shows that a prominent exothermic maximum in the annealing spectrum occurs at approximately 612°C. This maximum is associated with an increase in pressure, indicating an abrupt increase in diffusion of deuterium from the target at this temperature. From a study of diffusion of deuterium from the specimen at three temperatures, an activation energy of 0.24 ev is calculated for diffusion of deuterium in tantalum.X‐ray traces were taken of the specimen before and after bombardment and after annealing. These ...

Study of Irradiation Effects and the H2+H2 Buildup in Tantalum

There appears to be a tendency to convert pH values into "hydrogen ion concentrations" using the antilog of negative pH values The present communication describes the thermodynamic basis of pH to explain that the above procedure is erroneous and that pH values should be treated as primary variables Acidity expressed by the hydrogen ion concentrations measured by titrations (base excess or base deficit) has no bearing with the "hydrogen ion concentrations" derived by the antilog of negative pH

Hydrogen ion concentration versus pH.

A significant structure theory of monolayer physical adsorption is developed. The theory is tested with the adsorptions on graphite of gases Ar, , , and . A restricted rotation model is used for the polyatomic molecules , , and . The computed isotherms and heats of adsorption are in good agreement with experiment in all cases studied.

Significant Structure Theory of Physical Adsorption

The pH jump data of Bianchi and Strobel [(1968) Trans. N.Y. Acad. Sci. Ser. II, 30, 1082-1092] on desheathed frog sciatic nerve are fitted to rate equations. A general quantitation of synergism, summation, and antagonism of anesthetics and of excitation is given.

Henry Eyring

Papers

Advances in Quantum Chemistry. Volume 1.

Study of Irradiation Effects and the H2+H2 Buildup in Tantalum

Hydrogen ion concentration versus pH.

Significant Structure Theory of Physical Adsorption

Multiple factor analysis of the action of local anesthetics.