A B3LYP investigation of the conformational and environmental sensitivity of carbon�Cdeuterium frequencies of aryl-perdeuterated phenylalanine and tryptophan

Carbon?Cdeuterium labeled amino acids can serve as sensitive probes for biophysical characterization. Although multiple research groups have used infrared spectroscopy in conjunction with alkyl backbone or side-chain deuterated amino acids for the biophysical characterization of conformational and/or environmental changes, it was not entirely clear to the authors that perdeuterated aryl rings would demonstrate a similar sensitivity toward conformational or environmental changes. In an effort to evaluate the sensitivity of aryl carbon?Cdeuterium (C?CD) IR frequencies, a B3LYP investigation of the sensitivity of aryl C?CD frequencies toward conformational and environmental changes was conducted for phenylalanine (Phe) and tryptophan (Trp). To compensate for the low molar absorptivity of C?CD frequencies, perdeuterated aryl rings were investigated, which are commercially available and can be readily compared to experimental data. B3LYP results suggest that aryl-deuterated Phe and Trp will exhibit moderate sensitivities toward conformational and environmental changes with frequency shifts upward of 13 and 26?cm^?1 for Phe and Trp, respectively. B3LYP predicts that conformational sensitivity arises from dipole changes and not orbital alignment changes. In an effort to mimic what might be observed experimentally, simulated IR spectra were created and show absorption band changes with conformational and environmental changes, which indicate that IR characterization of perdeuterated aryl rings in amino acids could serve as a biophysical tool.     

Elementary properties of minimal and maximal points in Zariski spectra

We investigate connections between arithmetic properties of rings and topological properties of their prime spectrum. Any property that the prime spectrum of a ring may or may not have, defines the class of rings whose prime spectrum has the given property. We ask whether a class of rings defined in this way is axiomatizable in the model theoretic sense. Answers are provided for a variety of different properties of prime spectra, e.g., normality or complete normality, Hausdorffness of the space of maximal points, compactness of the space of minimal points.     

Langmuir-Blodgett film structure

Langmuir-Blodgett (LB) films occupy a unique niche at the crossroads of materials science, complex fluids, and biophysics. They have many similarities to inorganic epitaxial films due to the layer by layer deposition process; however, the amphiphilic nature of the constituent molecules provides the connection to lyotropic liquid crystals and membranes. A great deal is known about LB film structure and thermodynamic behavior; both from classical studies as well as from recent experiments using sophisticated characterization techniques such as synchrotron X-ray scattering and scanning probe microscopy. This article summarizes the current understanding of these systems from a physical/structural point of view. Included are discussions of the deposition process, the layered nature of LB films, intralayer molecular packing, defects, stability, and phase transitions.     

Complexes of tri- and tetra-protonated forms of 1,4,8,12-tetraazacyclopentadecane with chloride,nitrate, iodate,and sulfate ions in aqueous media: II. Analysis of the underlying experimental and theoretical assumptions

In a previous paper [1] the complexation behavior of 1,4,8,12-tetraazacyclopentadecane with various anions was studied. This analysis depended on various assumptions involving the accuracy and the interpretation of the experimental data. In this paper these assumptions are examined using pH potentiometry,¹³C NMR, and conductometric techniques. The validity of each of the assumptions was confirmed.     

Solid-State 13C-NMR spectral evidence for charge transfer complex formation in aromatic diimides and dianhydrides

Solution and solid-state proton decoupled ¹³C-NMR spectra were determined on two diimides derived from 4, 4′-oxydiphthalic anhydride. Comparison of the individual diimide spectra to that of a mixture of the two diimides indicates that ordering of these materials occurs in the solid state via charge transfer complex formation. A similar study was conducted using two isomeric dianhydrides, 4, 4′-isophthaloyldiphthalic anhydride (IDPA) and 4, 4′-terephthaloyldiphthalic anhydride (TDPA). The solution spectra of these compounds are similar and are those which would be expected for these compounds. However, their solid state spectra differ from each other. The solid-state spectrum of TDPA resembles its solution spectrum, whereas, that of IDPA differs greatly from its solution spectrum and indicates charge transfer complex formation occurs with this molecule. This difference is explained in terms of the stereochemistry of the two isomeric dianhydrides.     

Design and optimal tuning of nonlinear PI compensators

In this paper, linear time-invariant single-input single-output (SISO) systems that are stabilizable by linear proportional and integral (PI) compensators are considered. For such systems, a five-parameter nonlinear PI compensator is proposed. The parameters of the proposed compensator are tuned by solving an optimization problem. The optimization problem always has a solution.Additionally, a general nonlinear PI compensator is proposed and is approximated by easy-to-compute compensators, for instance, a six-parameter nonlinear PI compensator. The parameters of the approximate compensators are tuned to satisfy an optimality condition. The superiority of the proposed nonlinear PI compensators over linear PI compensators is discussed and is demonstrated for two feedback systems.     

Graphitic‐Carbon Layers on Oxides: Toward Stable Heterogeneous Catalysts for Biomass Conversion Reactions

Conversion of biomass‐derived molecules involves catalytic reactions under harsh conditions in the liquid phase (e.g., temperatures of 250 °C and possibly under either acidic or basic conditions). Conventional oxide‐supported catalysts undergo pore structure collapse and surface area reduction leading to deactivation under these conditions. Here we demonstrate an approach to deposit graphitic carbon to protect the oxide surface. The heterogeneous catalysts supported on the graphitic carbon/oxide composite exhibit excellent stability (even under acidic conditions) for biomass conversion reactions.