Conformational analysis of alkali metal complexes of anionic species of aspartic acid, their interconversion and deprotonation: a DFT investigation

Gas-phase geometry-optimized structures of aspartate complexes of anionic species (Hasp(-)) with lithium, sodium and potassium metal cations and transition-state structures for their interconversions were obtained using the density functional theory computations at the B3LYP/6-311++G(d,p) level of theory. The metal ion affinities of Hasp(-) species and deprotonation energies of [Hasp-M] complexes, M=Li+, Na+ and K+, and their conformers were obtained. Relative energies of the [Hasp-M] complex conformers, reaction energies, thermodynamic properties, rate and equilibrium constants of their complexation are reported. Binding energies of the most stable complexes with Li+, Na+ and K+ are -168.53, -133.34 and -117.68kcal/mol, respectively. The most stable complex conformer as a tri-coordinated form for aspartate complex with Li(+) and bi-coordinated form for aspartate complexes with Na+ and K+ were found.     

Theoretical Investigation of Ethanol Conversion to Ethylene over H–ZSM–5 and Transition Metals–Exchanged ZSM–5

Abstract  

Reaction mechanisms of ethanol conversion to ethylene over H–ZSM–5, Cu–ZSM–5, Ag–ZSM–5, and Au–ZSM–5 catalysts were investigated using density functional theory calculations. Energetics, thermodynamic quantities, rate and equilibrium constants of ethanol conversion to ethylene were obtained using the B3LYP/LanL2DZ method. The catalytic abilities of these catalysts on the reaction rates of ethanol conversion to ethylene are in order: Au–ZSM–5 > > Ag–ZSM–5 > H–ZSM–5 > > Cu–ZSM–5.     

Purification and characterization of phytase from Klebsiella pneumoniae 9-3B

Phytase, an enzyme that catalyzes the hydrolysis of phytate, was purified from Klebsiella pneumoniae 9-3B. The isolate was preferentially selected in a medium which contains phytate as a sole carbon and phosphate source. Phytic acid was utilized for growth and consequently stimulated phytase production. Phytase production was detected throughout growth and the highest phytase production was observed at the onset of stationary phase. The purification scheme including ion exchange chromatography and gel filtration resulted in a 240 and 2077 fold purification of the enzyme with 2% and 15% recovery of the total activity for liberation of inorganic phosphate and inositol, respectively. The purified phytase was a monomeric protein with an estimated molecular weight of 45kDa based on size exclusion chromatography and SDS-PAGE analyses. The phytase has an optimum pH of 4.0 and optimum temperature of 50°C. The phytase activity was slightly stimulated by Ca(2+) and EDTA and inhibited by Zn(2+) and Fe(2+). The phytase exhibited broad substrate specificity and the K(m) value for phytate was 0.04mM. The enzyme completely hydrolyzed myo-inositol hexakisphosphate (phytate) to myo-inositol and inorganic phosphate. The properties of the enzyme prove that it is a good candidate for the hydrolysis of phytate for industrial applications.     

Conformational analysis of alkali metal complexes of aspartate dianion and their interactions in gas phase

The gas-phase geometry optimizations of mono and dinuclear complexes of dianionic species of aspartic acid, asp(2-) with lithium, sodium and potassium cations were carried out using density functional calculation at the B3LYP/6-311++G(d,p) level. The metal ion affinities (MIAs) of asp(2-) species and its complexes [asp-M](-), M=Li(+), Na(+) and K(+) were determined using the vibrational frequency calculations at the same level of theory. The most stable complex conformer for aspartate complexes with Li(+), Na(+) and K(+) alkali cations were found as a tri-coordinated form. All complexations of [asp-M](-) and [asp-M(2)] complexes were found to be exothermic reactions. Relative bond distances between the alkali metal cation M(+) and the binding atoms of aspartate ion in [asp-M](-) and [asp-M(2)] complexes are in decreasing order: K(+)>Na(+)>Li(+).     

Design model generation for reverse engineering using multi-sensors

Reverse engineering is the process of creating a design model and a manufacturing database for an existing part or prototype. The applications of reverse engineering are in redesigning of existing partstools or prototype parts where the CAD model of the part is not available. Reverse engineering, for the most part, is performed as an interactive process where the designer identifies the surface features from digitized data and then models the surfaces accordingly. This paper presents the algorithms and implementation results for a reverse engineering system which is intended to automatically create CAD representations of part prototypes. An integrated sensory system combining contact and non-contact sensors has been developed to digitize parts surfaces. The sensory system fuses data from machine vision and a coordinate measuring machine (CMM) in order to automatically digitize the part surface. Machine vision is used to capture the orthographic views of the part. The images of these orthographic views are processed and vectorized to create five views of the part in the form of an engineering drawing. The system utilizes the generated orthographic projections to automatically drive the CMM to capture a grid of point coordinates from the part surface. The CMM digitization process is guided by the segmentation provided from the orthographic views. The segmented data from the part surface is input to the surface modeling module of the system where parametric surfaces are fitted through the digitized points. The surfaces are then extended and intersected using the Hermite approximation method to develop the 3-D CAD model of the part. Accuracy and automation is achieved by combining global shape information obtained from part images with the accurate point data acquired by a CMM. Algorithms for surface segmentation, part digitization, surface extension, and surface intersection modeling are described in this paper.     

First-principles investigation of ZnO sodalite-like cage binding onto TiO2 (001) surface and its ability for CO oxidation to CO2

The binding of ZnO sodalite-like cage (ZnOSL) onto the anatase TiO₂ (001) surface to form ZnOSL/TiO₂ composite was investigated using the periodic DFT–B3LYP method. The strong binding for the ZnOSL onto TiO₂ (001) surface to form ZnOSL/TiO₂ composite was found, the binding energy of which is ?70.78 kcal/mol. The reaction mechanism of the oxidation of carbon monoxide by oxygen to form carbon dioxide gas over the ZnOSL/TiO₂ composite was investigated. The reaction energies for all reaction steps are reported.