Glycosyl phenylthiosulfonates (glyco-PTS): novel reagents for glycoprotein synthesis

Controlled site-selective glycosylation can be achieved by combining site-directed cysteine mutagenesis with chemical modification of the introduced thiol; a new class of more efficient chemoselective reagents, glycosyl phenylthiosulfonates, allow rapid glycosylations of representative simple thiols, peptides and proteins.     

Theoretical total ionization cross-sections of CH x,CF x,SiH x,SiF x ( ) and CCl 4 targets by electron impact

Total ionization cross-sections of electron impact are calculated for the molecular targets CH_x, CF_x, SiH_x, SiF_x (x = 1-4) and CCl₄ at incident energies 20-3 000 eV. The calculation is based on Complex Scattering Potential approach, as developed by us recently. This leads to total inelastic cross-sections, from which the total ionization cross-sections are extracted by reasonable physical arguments. Extensive comparisons are made here with the previous theoretical and experimental data. The present results are satisfactory except for the CF_x and SiF_x (x = 1-3) radicals, for which the experimental data are lower than most of the theories by more than 50%. Received 23 May 2002 / Received in final form 24 October 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: knjoshipura@yahoo.com     

Rapid breakdown anodization technique for the synthesis of high aspect ratio and high surface area anatase TiO2 nanotube powders

Clusters of high aspect ratio, high surface area anatase-TiO₂ nanotubes with a typical nanotube outer diameter of about 18 nm, wall thickness of approximately 5 nm and length of 5-10 μm were synthesized, in powder form, by breakdown anodization of Ti foils in 0.1 M perchloric acid, at 10 V (299 K) and 20 V (∼275 and 299 K). The surface area, morphology, structure and band gap were determined from Brunauer Emmet Teller method, field emmission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, photoluminescence and diffuse reflectance spectroscopic studies. The tubular morphology and anatase phase were found to be stable up to 773 K and above 773 K anatase phase gradually transformed to rutile phase with disintegration of tubular morphology. At 973 K, complete transformation to rutile phase and disintegration of tubular morphology were observed. The band gap of the as prepared and the annealed samples varied from 3.07 to 2.95 eV with increase in annealing temperature as inferred from photoluminescence and diffuse reflectance studies.     

A novel chelatofore functionalized spiropyran of the 2‐oxaindane series

A novel chelatofore functionalized spiropyran of the 2‐oxaindane series, namely 8‐formyl‐7‐hydroxy‐3′,3′‐dimethylspiro[2H‐chromene‐2,1′(3′H)‐2‐benzofuran], C₁₉H₁₆O₄, is reported. In the crystalline state, dimers are formed as a result of the π–π stacking of aromatic groups of the 2H‐chromene part of the molecule and C—H...O interactions. The C_spiro—O bond length in the pyran ring is 1.4558 (10) Å, which is longer than or equal to the bond length in thermo‐ and photochromic 2‐oxaindane spiropyrans synthesized previously, except for the 7,8‐benzo/6‐NO₂ derivative, in which this bond length is 1.465 (2) Å.     

正丙硫基芳氧基硫赶膦酰胺的合成

正丙硫基硫代膦酸酯类化合物具有较好的生物活性，其杀虫活性和杀螨活性尤为突出，八十年代以来国外已有商品化产品问世［１～３］。新近，美国氰胺公司还推出了一个含正硫基的有机膦酸酯类新品种ＢＡＳ－３０１，为广谱型杀线虫剂［４］。唐除痴研究小组报道了各种烷基硫...