Bonding in HNO-myoglobin as characterized by X-ray absorption and resonance raman spectroscopies

The EXAFS and resonance Raman spectra on the HNO-myoglobin adduct, 1, are consistent with the presence of HNO bound to a heme center. The three-dimensional structure about the heme center of 1 obtained from multiple-scattering (MS) analysis of the EXAFS of the heme protein yielded an Fe-N-O bond angle of 131 degrees and an Fe-N bond length of 1.82 A, which compare well with published values for model complexes containing RNO ligands. Resonance Raman spectra identified the nu(N=O) stretch at 1385 cm-1 (confirmed by 15N labeling), which corresponds well with those reported for small molecule HNO complexes. The wavelength of the nu(Fe-N) at 636 cm-1 of 1 is significantly higher than those of MbIINO and MbIIINO (554 and 595 cm-1, respectively). The XAFS, XANES, and resonance Raman data are all consistent with the structure deduced from the NMR experiments, providing more detail on the bonding between HNO and the metal center.     

Use of 13C NMR spectrometric data to produce a predictive model of estrogen receptor binding activity

We have developed a spectroscopic data-activity relationship (SDAR) model based on 13C NMR spectral data for 30 estrogenic chemicals whose relative binding affinities (RBA) are available for the alpha (ERalpha) and beta (ERbeta) estrogen receptors. The SDAR models segregated the 30 compounds into strong and medium binding affinities. The SDAR model gave a leave-one-out (LOO) cross-validation of 90%. Two compounds that were classified incorrectly in the SDAR model were in the transition zone between classifications. Real and predicted 13C NMR chemical shifts were used with test compounds to evaluate the predictive behavior of the SDAR model. The 13C NMR SDAR model using predicted 13C NMR data for the test compounds provides a rapid, reliable, and simple way to screen whether a compound binds to the estrogen receptors.     

Determination of the structures of antiinflammatory copper(II) dimers of indomethacin by multiple-scattering analyses of X-ray absorption fine structure data

Copper K-edge X-ray absorption spectroscopic (XAS) measurements were recorded for the veterinary antiinflammatory Cu(II) complexes of indomethacin (1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid = IndoH), of the general formula [Cu(2)(Indo)(4)L(2)] (L = N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methylpyrrolidone (NMP), and water), and [Cu(2)(OAc)(4)(OH(2))(2)] at room temperature and 10 K. The bond lengths and bridging O-C-O angles of the dimeric Cu(II) cage (Cu(2)O(10)C(8)) obtained from the multiple-scattering (MS) fitting of the X-ray absorption fine structure (XAFS) using a centrosymmetric model of [Cu(2)(Indo)(4)(DMF)(2)] gave Cu.Cu = 2.62(2) A, mean Cu-O(Ac) = 1.95(2) A, Cu-O(L) = 2.15(2) A, bridging O-C-O = 125(1) degrees, Cu displacement from plane 0.19 A compared with the XRD data Cu.Cu = 2.630(1) A, mean Cu-O(Ac) = 1.959 A, Cu-O(L) = 2.143(5) A, bridging O-C-O angles = 123.2(5) degrees, Cu displacement from plane 0.20 A. The excellent agreement between the XAFS- and XRD-derived data allowed the structures of related [Cu(2)(Indo)(4)L(2)] (L = DMA, NMP) complexes to be determined. All display a similar Cu(2)O(10)C(8) coordination geometry, which is independent of the nature of the axial ligand. While XAFS analysis of [Cu(2)(Indo)(4)(OH(2))(2)] and [Cu(2)(OAc)(4)(OH(2))(2)] indicates a coordination geometry similar to that of [Cu(2)(Indo)(4)L(2)] (L = DMF, DMA, NMP), removal of symmetry restraints in the MS model is required to obtain axial bond lengths comparable to those derived in the XRD structures of the acetate complex. For the Indo complex, the fitted bond lengths with the lower symmetry model give a mean Cu-L(OH2) bond distance within experimental errors of the value for [Cu(2)(Indo)(4)(DMSO)(2)] (2.16(2) A) (XRD). The difficulty in refining the Cu-O(OH2) distance of [Cu(2)(OAc)(4)(OH(2))(2)] and [Cu(2)(Indo)(4)(OH(2))(2)] using a centrosymmetric MS model is attributed to a symmetry reduction due to hydrogen-bonding effects characteristic of the aqua adducts, as is observed in the XRD structure of the acetate complex.     

EPR spectroscopic studies of the reduction of chromium(VI) by methanol in the presence of peptides. Formation of long-lived chromium(V) peptide complexes

The synthesis and characterization of the first Cr(V) complexes with non-sulfur-containing peptides, which may mimic the chemistry of the intermediates in the formation of Cr-induced peptide-DNA cross-links in vivo, are reported. The reduction of Cr(VI) with methanol in the presence of a number of non-sulfur-containing peptides produced relatively stable Cr(V)-peptide complexes, which were characterized by EPR spectroscopy and electrospray mass spectrometry. The reaction of Cr(VI) with methanol alone (in the absence of peptide ligands) resulted in the formation of two Cr(V)-methanol intermediates, with giso values of 1.9765 and 1.9687. The methanol reduction of Cr(VI) in the presence of the glycine peptides, triglycine, tetraglycine, and pentaglycine resulted in the formation of both Cr(V)-methanol and Cr(V)-peptide intermediates, while only the Cr(V)-peptide complexes were detected in the reactions with the alanine peptides trialanine, tetraalanine, and pentaalanine. Similar EPR signals were observed for all of the Cr(V)-peptide complexes with giso values between approximately 1.986 and approximately 1.979, and AN values of (2.1-2.6) x 10(-4) cm-1.     

Synthetic Approach to Kdo Glycosides Via Exo-Glycal Epoxides and Rationalization of the Stereo Chemical Outcome

Abstract

The use of epoxides obtained by dimethyldioxirane epoxidation of 2,3-anhydro-1,3-dideoxy-4,5:7,8-di-O-isopropylidene-D-manno-oct-1-enitol as glycosyl donors is described. This method offers a simple and stereoselective access to precursors of Kdo glycosides. The stereochemical outcome of the reaction is rationalized by means of semiempirical calculations of the transition states leading to glycosides formation.     

Preparation and characterization of nanocrystalline Ca-doped CeO2 by sol–gel process

The reactivity of CeO₂ is determined by grain size and oxygen vacancies, which can be achieved by doping elements with less oxidation state into CeO₂. In this study nanocrystalline Ca-doped CeO₂ sol was synthesized from the reaction of hydrate cerium (III) nitrate and calcium nitrate tetrahydrate in alcohol solution after being calcined at 600?°C. X-ray diffraction as well as selected area electron diffraction gave evidence that the synthesized Ca-doped CeO₂ samples were well crystalline and had a cubic fluorite structure. TEM observation revealed that Ca-doped CeO₂ was composed by nanoparticles with grain size around 8?nm. The Raman spectrum of pure CeO₂ consists of a single triple degenerate F_2g model characteristic of the fluorite-like structure. In the Ca-doped CeO₂ sample, two additional low-intensity Raman bands were detected, thus confirming the formation of the solid solution. The synthesized nanometric powder is expected to be used in solid oxide fuel cells as well as in the catalytic treatment of automobile exhaust fumes.     

An accurate empirical correlation for predicting natural gas compressibility factors

The compressibility factor of natural gas is an important parameter in many gas and petroleum engineering calculations. This study presents a new empirical model for quick calculation of natural gas compressibility factors. The model was derived from 5844 experimental data of compressibility factors for a range of pseudo reduced pressures from 0.01 to 15 and pseudo reduced temperatures from 1 to 3. The accuracy of the new empirical correlation has been compared with commonly used existing methods. The comparison indicates the superiority of the new empirical model over the other methods used to calculate compressibility factor of natural gas with average absolute relative deviation percent (AARD%) of 0.6535.     

Development of a body motion interactive system with a weight voting mechanism and computer vision technology

This study develops a body motion interactive system with computer vision technology. This application combines interactive games, art performing, and exercise training system. Multiple image processing and computer vision technologies are used in this study. The system can calculate the characteristics of an object color, and then perform color segmentation. When there is a wrong action judgment, the system will avoid the error with a weight voting mechanism, which can set the condition score and weight value for the action judgment, and choose the best action judgment from the weight voting mechanism. Finally, this study estimated the reliability of the system in order to make improvements.The results showed that, this method has good effect on accuracy and stability during operations of the human–machine interface of the sports training system.     

Necessary and Sufficient Optimality Conditions for Regular–Singular Stochastic Differential Games with Asymmetric Information

We consider a class of regular–singular stochastic differential games arising in the optimal investment and dividend problem of an insurer under model uncertainty. The information available to the two players is asymmetric partial information and the control variable of each player consists of two components: regular control and singular control. We establish the necessary and sufficient optimality conditions for the saddle point of the zero-sum game. Then, as an application, these conditions are applied to an optimal investment and dividend problem of an insurer under model uncertainty. Furthermore, we generalize our results to the nonzero-sum regular–singular game with asymmetric information, and then the Nash equilibrium point is characterized.