Investigation on the Biaxial Flexural Strength of Universal Shade Resin-Based Composites.

The biaxial flexural strength of universal shade and conventional dental resin-based composites before and after alkaline degradation was investigated. Disk samples were prepared from these resin-based composites, and some of the specimens were immersed in 0.1 M NaOH solution to create deteriorated samples.

Primary Signet Ring Cell Carcinoma of Rectum Diagnosed by Boring Biopsy in Combination with Endoscopic Mucosal Resection.

A 46-year-old man with severe back pain visited our hospital. Magnetic resonance imaging revealed extensive bone metastasis and rectal wall thickness. Colonoscopy revealed circumferential stenosis with edematous mucosa, suggesting colon cancer.

1H NMR investigations of the molecular nature of cobalt(II) ions in human saliva.

High-resolution (1)H NMR spectroscopy demonstrated that addition of Co(II) ions to isolated human salivary supernatants (HSSs) gave rise to its complexation by a variety of biomolecules. The relative efficacies of these complexants/chelators in this context were classifiable by the influence of added Co(II) on their line-widths and chemical shift values, and also the added Co(II) concentration-dependence of these spectral modifications. Those which were most affected by the addition of this metal ion were lactate > formate ≈histidinate > succinate, this order reflecting the ability of these complexants to compete for the available Co(II) in terms of (1) thermodynamic equilibrium constants for the formation of their complexes and (2) their HSS concentrations.

Local suppression of ferroelectricity at PbTiO3 surface steps: a density functional theory study.

Ab initio (first-principles) density functional theory (DFT) calculations are performed within the local density approximations (LDA) to investigate the ferroelectricity at PbTiO(3) surface steps consisting of (001) and (100) surfaces with a spontaneous polarization along [100]. For both the PbO- and TiO(2)-terminated surface steps, the [100] polarization is suppressed and the [001] polarization appears at their upper terraces, which results in a rotation of polarizations at the surface steps. The polarization rotation is induced by the local variation of the covalent Pb-O bond due to the charge redistribution at the surface steps.

Intra- and intermolecular reaction selectivities of γ-substituted adamantanylidenes.

A study of adamantanylidenes having a γ-substituent (R) was undertaken to gauge how inductive and steric effects of remotely positioned functional groups influence intra- and intermolecular product selectivity. 3H-Diazirines were thermolyzed or photolyzed to generate the corresponding carbenes. On rapid heating, the resulting carbenes isomerized to 2,4-didehydroadamantanes by intramolecular 1,3-CH insertions.

First-principles study on ferroelectricity at PbTiO3 surface steps.

We performed ab initio density functional theory calculations to investigate ferroelectricity at PbTiO(3) surface steps consisting of (100) and (001) surfaces with the polar axis in the [010] direction. Ferroelectricity was enhanced at PbO-terminated surface steps due to enhanced covalent Pb-O bonding because of the low coordination number of Pb atoms at the step edge. In contrast, ferroelectric distortions were suppressed at TiO(2)-terminations, because of electron transfer from Pb-O sites to Ti-O sites.

Theoretical study on the mechanism and diastereoselectivity of NaBH4 reduction.

As the first step to understand the reaction mechanism and diastereoselectivity of sodium borohydride reduction of ketones, ab initio Car-Parrinello molecular dynamics simulation has been performed on a solution of NaBH4 in liquid methanol. According to pointwise thermodynamic integration involving constrained molecular dynamics simulations, it was strongly suggested that Na+ and BH4(-) are associated in the solvent forming contact ion pairs. Thus we propose a new transition state structure model that contains complexation of the carbonyl oxygen with sodium cation.

Perturbational formulation of principal component analysis in molecular dynamics simulation.

Conformational fluctuations of a molecule are important to its function since such intrinsic fluctuations enable the molecule to respond to the external environmental perturbations. For extracting large conformational fluctuations, which predict the primary conformational change by the perturbation, principal component analysis (PCA) has been used in molecular dynamics simulations. However, several versions of PCA, such as Cartesian coordinate PCA and dihedral angle PCA (dPCA), are limited to use with molecules with a single dominant state or proteins where the dihedral angle represents an important internal coordinate.

Diagnosis of infections in newborns using a new particle-mediated immunoassay for serum C-reactive protein.

C-reactive protein (CRP) levels were measured using a new particle-mediated immunoassay. Tests for precision and linearity of this method gave satisfactory results. The minimum sensitivity of the assay was 1 ng/ml.

The importance of lone pair delocalizations: theoretical investigations on the stability of cis and trans isomers in 1,2-halodiazenes.

The relative and thermodynamic stabilities of cis and trans isomers of 1,2-dihalodiazenes (XN=NX; X = F, Cl, or Br) were examined using high level ab initio and density functional theory (DFT) calculations. For 1,2-dihalodiazenes, it was found that the cis isomers were more stable than the corresponding trans isomers, despite the existence of several cis destabilizing mechanisms, such as steric exchange between halogen lone pairs and dipole-dipole electrostatic repulsions (Delta(trans-cis) = 3.15, 7.

An ultrasensitive new DNA microarray chip provides gene expression profiles for preoperative esophageal cancer biopsies without RNA amplification.

Objectives: Gene expression profiling using pretreatment biopsies has been limited due to their small sample sizes. This study evaluated the usefulness of an ultrasensitive new DNA microarray chip, which has a unique array structure, for the clinical diagnosis of esophageal cancer using preoperative biopsies.

Methods: Paired cancer and normal esophageal epithelial tissues from 56 patients who underwent esophagectomy and from 48 patients who underwent preoperative endoscopy were studied.

Direct observation of conformational folding coupled with disulphide rearrangement by using a water-soluble selenoxide reagent--a case of oxidative regeneration of ribonuclease A under weakly basic conditions.

Oxidative regeneration pathways of bovine pancreatic ribonuclease A (RNase A), which has four SS linkages, were studied at 25 degrees C and pH 8.0 by using trans-3,4-dihydroxy-1-selenolane oxide (DHS(ox)), a new selenoxide reagent with strong oxidation power. The short-term folding study using a quench-flow instrument ( approximately 1 min) revealed that early intermediates (1S, 2S, 3S and 4S) are formed stochastically and irreversibly from the reduced protein (R) and do not have any stable structures.

Equilibrium and kinetics of the folding and unfolding of canine milk lysozyme.

The equilibrium and kinetics of canine milk lysozyme folding/unfolding were studied by peptide and aromatic circular dichroism and tryptophan fluorescence spectroscopy. The Ca2+-free apo form of the protein exhibited a three-state equilibrium unfolding, in which the molten globule state is well populated as an unfolding intermediate. A rigorous analysis of holo protein unfolding, including the data from the kinetic refolding experiments, revealed that the holo protein also underwent three-state unfolding with the same molten globule intermediate.

Experimental and theoretical studies on the nature of weak nonbonded interactions between divalent selenium and halogen atoms.

To investigate the nature of weak nonbonded selenium...

Nature of nonbonded Se...O interactions characterized by 17O NMR spectroscopy and NBO and AIM analyses.

To investigate the nature of nonbonded Se...

Het-PDB Navi.: a database for protein-small molecule interactions.

The genomes of more than 100 species have been sequenced, and the biological functions of encoded proteins are now actively being researched. Protein function is based on interactions between proteins and other molecules. One approach to assuming protein function based on genomic sequence is to predict interactions between an encoded protein and other molecules.

Origin of stereochemical reversal in Meyers-type enolate alkylations. Importance of intramolecular Li coordination and solvent effects.

[reaction: see text] The origin of exclusive exo-stereochemistry in the alkylation of Meyers-type enolate 2 has been studied. It was found that the intramolecular complex with a strong Li..

Origin of facial diastereoselection. Evidence for negative role of antiperiplanar hyperconjugation effects in the transition state of carbene insertion.

[reaction: see text] Quantitative analysis of the transition state (TS) structures of the insertion reactions of 5-X-2-adamantanylidenes (X = H, OH, NH(2), SiMe(3)) into MeOH or cyclohexane revealed that the magnitude of antiperiplanar hyperconjugative stabilization involving the incipient bond effects (the AP effect) decrease at TS, strongly suggesting that the AP effect contributes "net destabilization" of TS (i.e., increase in activation energy), in sharp contrast to the proposals of the Felkin-Anh and the Cieplak models.

The SAAP force field. A simple approach to a new all-atom protein force field by using single amino acid potential (SAAP) functions in various solvents.

A simple strategy to compose a new all-atom protein force field (named as the SAAP force field), which utilizes the single amino acid potential (SAAP) functions obtained in various solvents by ab initio molecular orbital calculation applying the isodensity polarizable continuum model (IPCM), is presented. We considered that the total energy function of a protein force field (E(TOTAL)) is divided into three components; a single amino acid potential term (E(SAAP)), an interamino acid nonbonded interaction term (E(INTER)), and a miscellaneous term (E(OTHERS)), which is ignored (or considered to be constant) at the current version of the force field. The E(INTER) term consists of electrostatic interactions (E(ES')) and van der Waals interactions (E(LJ')).

Statistical and theoretical investigations on the directionality of nonbonded S...O interactions. Implications for molecular design and protein engineering.

Weak nonbonded interactions between a divalent sulfur (S) atom and a main-chain carbonyl oxygen (O) atom have recently been characterized in proteins. However, they have shown distinctly different directional propensities around the O atom from the S..

Quantitative evaluation of weak nonbonded Se...F interactions and their remarkable nature as orbital interactions.

To evaluate weak intramolecular nonbonded Se...