Syntheses and characterization of xylan esters

A series of low-molecular weight and high-molecular weight xylan esters with different alkyl chain lengths (C2–C12) were synthesized by heterogeneous and homogeneous reactions, respectively. Structure elucidation of these xylan esters was obtained by NMR analysis. The solubility of xylan in CHCl₃ improved after esterification. DSC results did not show a melting peak for all samples. However, WAXD diffractograms show the presence of diffraction peaks. The proposed structural model for xylan ester films is presented. TGA suggested that the thermal stability of xylan increased after esterification. Xylan esters with longer alkyl chains had higher decomposition temperatures. The mechanical properties of the xylan esters were dependent on the alkyl chain length. The tensile strength and elongation at break of these xylan esters ranged from 8 to 29 MPa and from 19 to 44%, respectively. Xylan esters in HFIP can be electrospun into nanofibers.     

Brillouin-Scattering Study of the Elastic Constants of ErVO4

The room-temperature elastic constants of ErVO₄ were considerably smaller than those of isostructural silicate and phosphate analogs. The generally "less-rigid" crystalline lattice and weaker metal-oxygen bond-strength in the RVO₄ (R = rare earth elements) phases indicates that these materials are of interest for potential applications as an interphase component in toughened oxide ceramic composites.     

Usefulness of myeloperoxidase as a biomarker for the ranking of pulmonary toxicity of nanomaterials

Background

In order to examine whether myeloperoxidase (MPO) can be a useful marker for evaluating the pulmonary toxicity of nanomaterials, we analyzed MPO protein in bronchoalveolar lavage fluid (BALF) samples obtained from previous examinations of a rat model. In those examinations we performed intratracheal instillation exposures (dose: 0.2–1.0 mg) and inhalation exposures (exposure concentration: 0.32–10.4 mg/m³) using 9 and 4 nanomaterials with different toxicities, respectively. Based on those previous studies, we set Nickel oxide nanoparticles (NiO), cerium dioxide nanoparticles (CeO₂), multi wall carbon nanotubes with short or long length (MWCNT (S) and MWCNT (L)), and single wall carbon nanotube (SWCNT) as chemicals with high toxicity; and titanium dioxide nanoparticles (TiO₂ (P90) and TiO₂ (Rutile)), zinc oxide nanoparticles (ZnO), and toner with external additives including nanoparticles as chemicals with low toxicity. We measured the concentration of MPO in BALF samples from rats from 3 days to 6 months following a single intratracheal instillation, and from 3 days to 3 months after the end of inhalation exposure.

Results

Intratracheal instillation of high toxicity NiO, CeO_2, MWCNT (S), MWCNT (L), and SWCNT persistently increased the concentration of MPO, and inhalation of NiO and CeO₂ increased the MPO in BALF. By contrast, intratracheal instillation of low toxicity TiO₂ (P90), TiO₂ (Rutile), ZnO, and toner increased the concentration of MPO in BALF only transiently, and inhalation of TiO₂ (Rutile) and ZnO induced almost no increase of the MPO. The concentration of MPO correlated with the number of total cells and neutrophils, the concentration of chemokines for neutrophils (cytokine-induced neutrophil chemoattractant (CINC)-1 and heme oxygenase (HO)-1), and the activity of released lactate dehydrogenase (LDH) in BALF. The results from the receiver operating characteristics (ROC) for the toxicity of chemicals by the concentration of MPO proteins in the intratracheal instillation and inhalation exposures showed that the largest areas under the curves (AUC) s in both examinations occurred at 1 month after exposure.

Conclusion

These data suggest that MPO can be a useful biomarker for the ranking of the pulmonary toxicity of nanomaterials, especially at 1 month after exposure, in both intratracheal instillation and inhalation exposure.

     

Computational Prediction of O-linked Glycosylation Sites That Preferentially Map on Intrinsically Disordered Regions of Extracellular Proteins

O-glycosylation of mammalian proteins is one of the important posttranslational modifications. We applied a support vector machine (SVM) to predict whether Ser or Thr is glycosylated, in order to elucidate the O-glycosylation mechanism. O-glycosylated sites were often found clustered along the sequence, whereas other sites were located sporadically. Therefore, we developed two types of SVMs for predicting clustered and isolated sites separately. We found that the amino acid composition was effective for predicting the clustered type, whereas the site-specific algorithm was effective for the isolated type. The highest prediction accuracy for the clustered type was 74%, while that for the isolated type was 79%. The existence frequency of amino acids around the O-glycosylation sites was different in the two types: namely, Pro, Val and Ala had high existence probabilities at each specific position relative to a glycosylation site, especially for the isolated type. Independent component analyses for the amino acid sequences around O-glycosylation sites showed the position-specific existences of the identified amino acids as independent components. The O-glycosylation sites were preferentially located within intrinsically disordered regions of extracellular proteins: particularly, more than 90% of the clustered O-GalNAc glycosylation sites were observed in intrinsically disordered regions. This feature could be the key for understanding the non-conservation property of O-glycosylation, and its role in functional diversity and structural stability.     

Survival of Vibrio parahaemolyticus serovar O3:K6 strains under acidic conditions

The survival of Vibrio parahaemolyticus serovar O3:K6 strains and other serovars in the presence of acetic, citric and hydrochloric acids were studied. There were no differences in resistance to these acids between serovar O3:K6 and the other serovars. At pH 5.6, citric acid was more effective in reducing the number of viable cells of V. parahaemolyticus than acetic acid. However, at pH 4.5, acetic acid was more effective than citric acid. The number of viable cells decreased quickly in the presence of rice vinegar or wine vinegar at pH 4.0.