Rungtiva Palangsuntikul

Global and local optimization of auxiliary basis sets for RI-MP2 calculations

Optimization approaches using several global and local algorithms (genetic algorithms, direct search and implicit filtering) in the search for a global minimum are applied to optimize auxiliary basis sets for quantum chemistry ab initio calculations. We optimize mixed Poisson and density auxiliary basis sets for RI-MP2, by minimizing a suitable objective function ΔI. For H, B, C, N, O and F optimized auxiliary basis sets are reported for cc-pVXZ (X = D, T and Q). The auxiliary basis sets optimized in this work are all even-tempered series. As results from these approaches, we never observed errors (ΔI/|EMP2|) greater than 0.55 μEh per atom. In more than 90% of all cases the errors were smaller than 0.009 μEh. Moreover, these approximations affect molecular MP2 energies by less than 30 μEh per atom. In contrast to traditional attempts to optimize auxiliary basis sets, this approach is faster and more reliable.

Screening of 64 Tryptamines at NMDA, 5-HT1A, and 5-HT2A Receptors: A Comparative Binding and Modeling Study

Tryptamine (T) and several T derivatives (Ts) inhibit in a voltage-dependent manner the NMDA receptor (NR). This effect is influenced by substituents at various positions, but has not yet been subjected to a detailed SAR study. Here, 64 Ts have been tested as inhibitors of [3H]MK-801 binding to NRs on rat brain membranes. For comparison, they were also tested as inhibitors of [3H]8-OHDPAT binding to 5-HT1A and of [3H]ketanserin binding to 5-HT2A receptors. Since most of these Ts have not been tested before at any of these receptors, we start with a review of the effects of Ts on 5-HT1A and 5-HT2A binding sites. NRs were inhibited with IC50s from 2 to 7 μM by Ts with alkyl or halogen at positions 2, 5, and/or 7. Inhibition by some Ts was attenuated more than 10-fold by 30 μM spermine. The most potent inhibitors at 5-HT1A receptors were 5-carboxamido-T (IC50 0.00015 μM) and serotonin (0.0016 μM), at 5-HT2A receptors 2-Me-4,7-Cl2-T (1.2 μM) and 2,7-Me2-4-Cl-T (2.0 μM). Fujita-Ban modified Free-Wilson analyses pointed to the individual significance of particular substituents. Also QSARs based on molecular operating environment descriptors resulted in sound correlations at all 4 targets. No similarities between the NR and 5-HT receptors could be found. At the NR, only L-Trp-NH2 bound 10 times better than at both 5-HT receptors studied. L-Trp-NH2 may be a structural lead to endogenous non-competitive NR antagonists.

Holographic Quantitative Structure-Activity Relationships of Tryptamine Derivatives at NMDA, 5HT 1A and 5HT 2A Receptors

Tryptamine derivatives (Ts) were found to inhibit the binding of [3H]MK-801, [3H]ketanserin and [3H]8-OH-DPAT to rat brain membranes. [3H]MK-801 labels the NMDA (N-methyl-D-aspartate) receptor, a ionotropic glutamate receptor which controls synaptic plasticity and memory function in the brain, whereas [3H]ketanserin and [3H]8-OH-DPAT label 5HT2A and 5HT1A receptors, respectively. The inhibitory potencies of 64 Ts (as given by IC50 values) were correlated with their structural properties by using the Holographic QSAR procedure (HQSAR). This method uses structural fragments and connectivities as descriptors which were encoded in a hologram thus avoiding the usual problems with conformation and alignment of the structures. Four correlation equations with high predictive ability and appropriate statistical test values could be established. The results are visualized by generation of maps reflecting the contribution of individual structural parts to the biological activities.

Investigation of damaged interior walls using synchrotron-based XPS and XANES

Evidence of internal sulfate attack in field exposure was demonstrated by the damaged interior wall of a three-year-old house situated in Nakhon Ratchasima Province, Thailand. Partial distension of the mortar was clearly observed together with an expansion of a black substance. Removal of the black substance revealed a dense black layer. This layer was only found in the vicinity of the damaged area, suggesting that this black material is possibly involved in the wall cracking. By employing synchrotron-based X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) techniques, the unknown sample was chemically identified. The S 2p and O 1s XPS results mutually indicated the existence of sulfate species in the materials collected from the damaged area. The XANES results indicated the presence of ferrous (II) sulfate, confirming sulfate-induced expansion and cracking. The sulfate attack in the present case appeared to physically affect the structure whereas the chemical integrity at the molecular level of the calcium silicate hydrate phase was retained since there was a lack of spectroscopic evidence for calcium sulfate. It was speculated that internal sulfate probably originated from the contaminated aggregates used during the construction. The current findings would be beneficial for understanding the sulfate-attack mechanism as well as for future prevention against sulfate attack during construction.

A Novel NAD+/MWNTs Nanocomposite-Based Electrochemical Biosensor for Measuring Mevalonic Acid

A novel, simple and precise electrochemical biosensor, was developed for measuring mevalonic acid (MA) concentration, which is thought to be a good indicator of HMG-CoA reductase activity. This sensor is based on noncovalent-linking NAD+/MWNTs nanocomposite coated on a screen-printed electrode (SPE). The resulting biosensor exhibited excellent electrocatalytic activity, fast response and good stability to MA. At the NAD+/MWNTs-modified SPE, the current is linear with the concentration of MA being within a concentration range from 18.1 to 145 μM with a limit of detection down to 4.25 μM (S/N = 3), and the sensor exhibited a sensitivity of 92.2 μA/mM.

In Situ X-ray Absorption Near Edge Structure Study of Amorphous-TiO2 Phase Transformation.

The in situ X-ray absorption near edge structure (XANES) measurement and linear combination fitting were applied to monitor phase transformation of titanium dioxide. In this study, TiO2 (TiSG) was prepared by a sol-gel method.using titanium isopropoxide as a precursor. At low preparation temperature, the results revealed the formation of an amorphous structure. To obtain the anatase phase, the calcination at 843 K was necessary. Using phase fraction plot, TiO2 phase-transition can be observed at temperatures between 748 and 778 K and remain unchanged at 873 K.

Nanobiocomposite-Based Bienzyme Screen-Printed Electrode for Glucose Monitoring

Multi-walled carbon nanotubes (MWNTs) were coated first with methylene blue (MB) by noncovalent adsorption and then by horseradish peroxidase (HRP) and glucose oxidase (GOD) by covalent-linking. The MB-MWNTs/GOD/HRP composites formed stable films on screen-printed electrodes (SPE). The electrochemical and electrocatalytic behaviors of the bienzyme modified SPE were studied using cyclic voltammetry (CV) and amperometry. Using the MB-MWNT/GOD/HRP composites, glucose could be calibrated by amperometry at −0.35 V vs. SCE. The optimized response (at pH 7.0) had a sensitivity of 2.4 mA.M−1 and a limit of detection (3×S/N) of 35 µM. Tests of the portable bienzyme sensor demonstrate its imperviousness to the effects of ascorbic acid, uric acid and p-acetaminophen, as well as its ability to measure glucose concentrations ranging from 0.25 to 2 mM.