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Research has been conducted on the chiral allylic alcohol epoxidation. The study of this epoxidation has been carried out via the use of the density functional theory method and the role of the metal-alcoholate bonding in the allylic alcohol diastereoselective epoxidation has been investigated.

DFT/B3LYP calculations are carried out on complexes formed by N(H)4(super + ) with aromatics to characterize the forces involved in such interactions and to gain further insight in to the nature and diversity of cation-aromatic interactions. The calculated results indicate that the protanated heterocyclic N(H)3 hydrogen-bond complexes produce the largest enthalpies.

Zinc metalloenzyme carbonic anhydrase III catalyzes the dehydration of HCO-3, which yields maximal turnover rates. The process of translocating a proton to zinc-bound hydroxide in the active site restricts the maximal turnover rates. A proton donor, histidine, is positioned at location 64 by employing site-directed mutagenesis. The rate at which the intramolecular proton transfers to the zinc-bound hydroxide is determined by employing 18O exchange between CO2 and water, and calculated by mass spectroscopy. A range of values of pKa of the zinc-bound water is seen in a sequence of site-specific mutants.

The carbonic anhydrase III isoform of carbonic anhydrase is less efficient compared with carbonic anhydrase II in catalyzing the hydration of carbon dioxide. Phenylalanine 198 in human carbonic anhydrase III was replaced with seven other amino acids and the catalytic properties of the mutant enzymes were analyzed by stopped-flow spectrophotometry and mass spectrometry. The mutants showed enhanced maximal values of kcat/Km for the hydration of CO2 with five of the mutants having pKa of the zinc-bound water increased compared to the wild carbonic anhydrase.

The effect of hexamethylphosphoric triamide (HMPA) on lithium phenolates is investigated. Results show that HMPA effects different changes in the solution structures of organic lithium compounds. These changes include an increase and decrease in aggregation and triple ion formation. These changes are observed to depend on the basicity of the anion, steric factors and the polarity of the mother solvent.

Formaldehyde-induced cross-links of Lys, Cys, His, and Trp with dG, dA, and dC were characterized to understand the mechanism underlying the formation of DNA-protein cross-links (DPCs) as a primary genotoxic effect. The results obtained for the structures would provide a basis to study the characteristics and properties of DPCs formed in vivo and also help to identify biomarkers for the evaluation of formaldehyde exposure both at the site of contact and at distant sites.

A comprehensive study is presented for a series of 'b' fragment ions ([b.sub.2] to [b.sub.8]) based on the simplest amino acid residue glycine in order to examine the effect of peptide chain length on the appearance of macrocycle fragment structures. The results have shown that in some cases larger macrocycle structures are stable.

The formation of sequence-specific intra- and intermolecular triplexes using antiCG, antiGC, and antiTA is demonstrated. The results indicate that oligoTRIPs bind to mixed purine-pyrimidine sequences in intramolecular and intermolecular systems.

The interaction properties if tetramethylammonium(TMA) with aromatic compounds such as benzene and pyrrole are theoretically analysed, based on B3LYP density-functional theory (DFT) and ab initio second order Moller-Plesset perturbation theory (MP2) calculations. The TMA-aromatic interactions are mainly due to typical cation-pi interaction and the dispersion interaction.

The density functional theory (DFT) and MP2 methods are employed at the 6-31G and 6-311G basis set levels to investigate the interaction between tetramethylammonium and benzene, and to deduce binding geometries and ESP CHELPG atomic charges in order to modify the atomic charge parameters of existing molecular mechanics force fields. The suitable modification of the atomic charges based on calculated CHELPG charges, enable it to represent cation-pi interactions without reprogramming.

The quantum chemical calculations were performed on the complexes formed by silicane and ammonium in order to investigate the binding characteristics and nature of the dihydrogen bond. The calculation results reveal that the dihydrogen-bond angle is ~180.0degrees and that the bond length is ~1.60A.

Recent advances in upconversion technology have enabled optogenetic neural stimulation using remotely applied optical signals, but limited success has been demonstrated for neural inhibition by using this method, primarily due to the much higher optical power and more red-shifted excitation spectrum that are required to work with the appropriate inhibitory opsin proteins. To overcome these limitations, core-shell-shell upconversion nanoparticles (UCNPs) with a hexagonal phase are synthesized to optimize the doping contents of ytterbium ions (Yb3+) and to mitigate Yb-associated concentration quenching. Such UCNPs' emission contains an almost three-fold enhanced peak around 540-570 nm, matching the excitation spectrum of a commonly used inhibitory opsin protein, halorhodopsin. The enhanced UCNPs are utilized as optical transducers to develop a fully implantable upconversion-based device for in vivo tetherless optogenetic inhibition, which is actuated by near-infrared (NIR) light irradiation without any electronics. When the device is implanted into targeted sites deep in the rat brain, the electrical activity of the neurons is reliably inhibited with NIR irradiation and restores to normal level upon switching off the NIR light. The system is further used to perform tetherless unilateral inhibition of the secondary motor cortex in behaving mice, achieving control of their motor functions. This study provides an important and useful supplement to the upconversion-based optogenetic toolset, which is beneficial for both basic and translational neuroscience investigations. [ABSTRACT FROM AUTHOR]

Thepilot test is an important procedure that ultimately leadsto implementation of an optimized catalytic process. A global reactionrate was calculated from the intrinsic kinetic rate with the effectivenessfactor, and the calculated value is fitted well with the experimentaldata, which indicates that the global reaction rate is reliable. Further,a scale-up HCl oxidation experiment has been carried out in a single-tubereactor with an inner diameter of 22 mm using shaped CeO2–CuO/Y as the catalyst. A one-dimensional fixed-bed modelbased on the global reaction rate was adopted to properly describethe reaction behavior in the single-tube reactor. The results havelaid a valuable foundation for the industrial reactor designationand the process optimization of HCl oxidation. [ABSTRACT FROM AUTHOR]

Biosensors based on nanomaterials have been used for detection of various biological molecules with high sensitivity and selectivity. Herein, we developed a simple and ultrasensitive electrochemical DNA biosensor using long-range self-assembled DNA nanostructures as carriers for signal amplification, which can achieve an impressive detection limit of 5 aM human immunodeficiency virus (HIV) DNA even in complex biological samples. In this study, we designed two auxiliary probes. A cascade of hybridization events between the two auxiliary probes can lead to long-range self-assembly and form micrometer-long one-dimensional DNA nanostructures. In the presence of target DNA, each copy of the target can act as a trigger to connect a DNA nanostructure to a capture probe on the electrode surface. Then, a great amount of redox indicator [Ru(NH3)6]3+ can be electrostatically bound to the DNA nanostructures and eventually result in significantly amplified electrochemical signals. [ABSTRACT FROM AUTHOR]