Cleavage of S-S Bond by Sm/cat. CoCl2 or Sm/cat. CoCl2 • 6H2O System: A Novel Method for the Synthesis of Thiolesters

Abstract

The Sm/cat. CoCl₂ or Sm/cat. &;Cl₂ ? 6H₂O system promoted disulfides to react with anhydrides or acyl chlorides to afford thiolesters in good yields under mild and neutral conditions.     

Isolation and Immobilization of Influenza Virus-Specific N-SA-α-2,3-Gal Receptors Using Magnetic Nanoparticles Coated with Chitosan and Maackia amurensis Lectin

Avian influenza viruses preferentially bind to sialic acid alpha-2,3-galactose (N-SA-α-2,3-Gal) receptors on epithelial cells. Herein, we describe a procedure we have developed for isolation of N-SA-α-2,3-Gal receptors from porcine trachea using magnetic nanoparticles (NPs) coated with chitosan (NP-Ch) and functionalized with Maackia amurensis lectin (NP-lectin). Magnetic nanoparticles were coated with chitosan in a one-step co-precipitation, and then M. amurensis lectin was immobilized covalently using glutaraldehyde. Lectin coated nanoparticles were incubated with sialic acid enriched fraction of tracheal homogenate, and N-SA-α-2,3-Gal receptor was extracted under magnetic field in two cycles. The presence of 66.4 kDa protein was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The interaction of immobilized receptor (NP-Ch-R) with M. amurensis lectin (NP-Ch-R-L) was demonstrated by Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA).     

Observation of noncovalent complexes to the avidin tetramer by electrospray ionization mass spectrometry

Intact avidin-biotin and avidin-biotin maleimide noncovalent complexes have been observed by electrospray ionization mass spectrometry (ESI-MS) by using an extended mass range quadrupole mass spectrometer. By utilizing mild ES1 interface conditions, the expected solution behavior of four biotin or biotin maleimide molecules noncovalently binding to each avidin tetramer can be preserved in the gas phase. The ESI-MS results show the appropriate mass additions of 973 ± 60 Da for biotin and 1802 ± 40 Da for biotin maleimide to the avidin tetramer species. These results support the hypothesis that substantial retention of higher order structure is possible in the gas phase by using gentle ESI conditions.     

Millimeter wave rotational spectrum of deuterofulminic acid,DCNO, in excited vibrational states

Rotational transitions of DCNO in the vibrational states 00002, 00003, 00020, and 00011 have been measured and analyzed. These results complete the presentation of assigned millimeter wave transitions of DCNO.The analysis of rotational l-type resonance in the 00002 and 00020 states is more satisfactory in the case of DCNO than in that of HCNO due to the absence of accidental resonances. The values obtained for the vibrational anharmonicity constant g₅₅ for 00002 and 00003 agree within experimental error with those found from the vibrational spectrum.An ambiguity in the assignment of the symmetry of the transitions in the four components of the 00011 vibrational state is discussed.     

Vinyl sulfones: inhibitors of SrtA, a transpeptidase required for cell wall protein anchoring and virulence in Staphylococcus aureus

Several small molecule vinyl sulfones were found to exhibit irreversible time-dependent inhibition of the Staphylococcus aureus sortase SrtA in vitro. A representative of these compounds was shown to impair the ability of S. aureus bacteria to bind fibronectin-coated surfaces through in vivo inhibition of SrtA-mediated linkage of fibronectin to the cell surface. These data highlight the potential use of small molecule vinyl sulfones as chemotherapeutics to prevent adhesion to and colonization of host tissues during S. aureus infection.     

Dynamic contrast-enhanced MRI of vascular changes induced by the VEGF-signalling inhibitor ZD4190 in human tumour xenografts

Dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) was used to examine the acute effects of treatment with an inhibitor of vascular endothelial growth factor (VEGF) signaling. ZD4190 is an orally bioavailable inhibitor of VEGF receptor-2 (KDR) tyrosine kinase activity, which elicits broad-spectrum antitumour activity in preclinical models following chronic once-daily dosing. Nude mice, bearing established (0.5-1.0 mL volume) human prostate (PC-3), lung (Calu-6) and breast (MDA-MB-231) tumor xenografts, were dosed with ZD4190 (p.o.) using a 1 day (0 and 22 h) or 7 day (0, 24, 48, 72, 96,120,144, and 166 h) treatment regimen. DCEMRI was employed 2 h after the last dose of ZD4190, using the contrast agent gadopentetate dimeglumine. Dynamic data were fit to a compartmental model to obtain voxelwise K(trans), the transfer constant for gadopentetate into the tumor. K(trans) was averaged over the entire tumor, and a multi-threshold histogram analysis was also employed to account for tumor heterogeneity. Reductions in K(trans) reflect reductions in flow, in endothelial surface area, and/or in vascular permeability. A vascular input function was obtained for each mouse simultaneously with the tumor DCEMRI data. ZD4190 treatment produced a dose-dependent (12.5-100 mg x kg(-1) per dose) reduction in K(trans) in PC-3 prostate tumors. At 100 mg x kg(-1), the largest concentration examined, ZD4190 reduced K(trans) in PC-3 tumors by 31% following 2 doses (1 day treatment regimen; p < 0.001) and by 53% following 8 doses (7 day regimen; p < 0.001). Comparative studies in the three models using a showed similar reductions in K(trans) for the lung and breast tumors using the histogram analysis, although the statistical significance was lost when K(trans) was averaged over the entire tumor. Collectively these studies suggest that DCEMRI using gadopentetate may have potential clinically, for monitoring inhibition of VEGF signaling in solid tumors.