To obtain an indication of the tendencies of amino acids to leave water and enter a truly nonpolar condensed phase, distribution coefficients between dilute solution in water and dilute solution in wet cy- clohexane have been determined for each of the common amino acid side chains at pH 7; they are found to be closely related to the inside-outside distributions of the side chains observed in globular proteins. There was no evidence that excess water enters cyclohexane in association with these solutes. Cyclohexane-to-water distribution coefficients can be combined with vapor-to-water distribution coefficients reported earlier to yield vapor-to-cyclohexane distribution coefficients. Vapor-to-cyclohexane distribution coefficients provide an experimental index of susceptibility to attraction by dispersion forces, and the corresponding free energies are found to be linearly related to side-chain surface areas. Observations using different solvents and variously substituted side chains suggest that alcohols such as 1-octanol exert a specific attraction on the side chain of tryptophan. When less polar phases are used as a reference, leucine, isoleucine, valine, phenylalanine, and methionine are found to be more hydrophobic than tryptophan.

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Comparing the polarities of the amino acids: side-chain distribution coefficients between the vapor phase, cyclohexane, 1-octanol, and neutral aqueous solution

The structure of MO 1/2 TeO 2 (M = Li, Na, K, Rb, Cs and Tl) binary glasses has been studied by means of Raman spectroscopy. The glasses having low alkali content have a continuous network constructed by sharing corners of TeO 4 trigonal bipyramids (tbp's) and TeO 3 + 1 polyhedra having one non-bridging oxygen atom (NBO). In the glasses containing 20–30 mol% alkali oxide, TeO 3 trigonal pyramids (tp's) having NBOs are formed in the continuous network. When alkali content exceeds 30 mol%, isolated structural units, such as Te 2 O 2− 5 ion, coexist in the continuous network. The fraction of TeO 4 tbp's decreases with increasing alkali content. The glasses, which contain nearly 50 mol% alkali oxide, are composed of a continuous network constituted by TeO 3 + 1 polyhedra and TeO 3 tp's, and of isolated structural units, such as Te 2 O 2− 5 and TeO 2− 3 ions. The structure of thallium tellurite glasses having less than 30 mol% TlO 1/2 is similar to that of alkali tellurite glasses containing equal amounts of MO 1/2 . The fraction of TeO 3 tp's having NBOs in the thallium tellurite glasses, when TlO 1/2 content is equal to or higher than 40 mol%, is larger than that in the corresponding alkali tellurite glasses. In the 66TlO 1/2 ·34TeO 2 glass, most of tellurium atoms are in a form of isolated TeO 2− 3 ion. A new hypothesis is also given for a mechanism for the basic structural changes in the tellurite glasses.

Raman spectra of MO1/2TeO2 (M = Li, Na, K, Rb, Cs and Tl) glasses

High-level ab initio calculations were carried out to evaluate the interaction between the π face of benzene and ammonia as a model of NH/π interaction. The intermolecular interaction energy was calculated from the extrapolated MP2 interaction energy at the basis set limit and a CCSD(T) correction term. The calculated interaction energy (−2.22 kcal/mol) is considerably smaller than that of the hydrogen bond between waters. The monodentate complex is slightly more stable than the bidentate and tridentate complexes. The potential energy surface is very flat near the minimum, which shows that the major source of the attraction is a long-range interaction. The HF interaction energy of the monodentate complex (0.13 kcal/mol) is repulsive. The large gain in the attraction by electron correlation correction (−2.36 kcal/mol) indicates that the dispersion interaction is significantly important for the attraction. The electrostatic energy (−1.01 kcal/mol) is also important for the attraction. The benzene−water (OH/...

Origin of the Attraction and Directionality of the NH/π Interaction: Comparison with OH/π and CH/π Interactions

We present a zero-dimensional kinetic model of CO2 splitting in non-equilibrium plasmas. The model includes a description of the CO2 vibrational kinetics (25 vibrational levels up to the dissociation limit of the molecule), taking into account state-specific VT and VV relaxation reactions and the effect of vibrational excitation on other chemical reactions. The model is applied to study the reaction kinetics of CO2 splitting in an atmospheric-pressure dielectric barrier discharge (DBD) and in a moderate-pressure microwave discharge. The model results are in qualitative agreement with published experimental works. We show that the CO2 conversion and its energy efficiency are very different in these two types of discharges, which reflects the important dissociation mechanisms involved. In the microwave discharge, excitation of the vibrational levels promotes efficient dissociation when the specific energy input is higher than a critical value (2.0 eV/molecule under the conditions examined). The calculated energy efficiency of the process has a maximum of 23%. In the DBD, vibrationally excited levels do not contribute significantly to the dissociation of CO2 and the calculated energy efficiency of the process is much lower (5%).

https://iopscience.iop.org/article/10.1088/0963-0252/23/4/045004/pdf

Splitting of CO2 by vibrational excitation in non-equilibrium plasmas: a reaction kinetics model

Study of triplet states and short-lived negative ions by means of electron impact spectroscopy

General anharmonic force constants of carbon dioxide

A new method for the adjustment of vibrational force constants is presented. It avoids some of the divergence difficulties which may be encountered in perturbation and least‐squares procedures. The new method employs an efficient computer program to adjust an initial set of force constants in accordance with the requirement that each successive adjustment leads to a smaller sum of squared deviations between calculated and observed eigenvalues. Several variants of the procedure are given, and their application to a number of actual cases is discussed in detail.

Isao Suzuki

Papers

General anharmonic force constants of carbon dioxide

Erratum: Method of Adjusting Force Constants and Its Application to H2O, H2CO, CH2Cl, and Their Deuterated Molecules

General anharmonic force constants of nitrous oxide

The internal rotation in anilides about the peptide bond as axis

Infrared spectra and force constants of CH2Cl2, CHDCl2, and CD2Cl2