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131.
132.
Rate constants for deactivation of DF in vibrational states n = 1 to 7 in collisions with DF (0) are calculated semiclassically in the temperature range from 300 K to 3000 K. The variation with the temperature agrees quite well with experiments for n = 1, although the theoretical rates are 30% lower than the experimental values for temperatures above 1200 K and 75% lower at 300 K. This difference is discussed. Single quantum transitions dominate. At 300 K the mechanism is predominantly a V—V transfer for n = 2 and a V-T/R transfer for n = 7, while both mechanisms contribute for n = 3–6. Collision complexes are important for both V—V and V-T/R energy transfer. Rotational relaxation times are calculated for HF and DF. 相似文献
133.
134.
Díaz-Mochón JJ Bialy L Keinicke L Bradley M 《Chemical communications (Cambridge, England)》2005,(11):1384-1386
Enzymatic modifications of split and mix libraries were followed by "pulling down" onto a 2-dimensional DNA microarray, via PNA tagging; this allowed complete library interrogation of all members of the split and mix library. 相似文献
135.
Mikkelsen LM Krintel SL Jiménez-Barbero J Skrydstrup T 《The Journal of organic chemistry》2002,67(18):6297-6308
Studies are reported on the assembly of the branched C-trisaccharide, alpha-D-Man-(1-->3)-[alpha-D-Man-(1-->6)]-D-Man, representing the core region of the asparagine-linked oligosaccharides. The key step in this synthesis uses a SmI(2)-mediated coupling of two mannosylpyridyl sulfones to a C3,C6-diformyl branched monosaccharide unit, thereby assembling all three sugar units in one reaction and with complete stereocontrol at the two anomeric carbon centers. Subsequent tin hydride-based deoxygenation followed by a deprotection step produces the target C-trimer. In contrast to many of the other C-glycosylation methods, this approach employes intact carbohydrate units as C-glycosyl donors and acceptors, which in many instances parallels the well-studied O-glycosylation reactions. The synthesis of the C-disaccharides alpha-D-Man-(1-->3)-D-Man and alpha-D-Man-(1-->6)-D-Man is also described, they being necessary for the following conformational studies of all three carbohydrate analogues both in solution and bound to several mannose-binding proteins. 相似文献
136.
Lise M. Mikkelsen Christina M. Jensen Bettina Hj Peter Blakskjr Troels Skrydstrup 《Tetrahedron》2003,59(52):10541-10549
Attempts were made to promote the carbonyl coupling of cyclohexanone to 4-pyridylthioesters of N-carbamate-protected amino acids with the one electron reducing agent, samarium diiodide. Such reactions proved unsuccessful due to the inability of the ketyl-type radical anion intermediate to be reduced to the corresponding dianion at −78°C. Nevertheless, these results explain our recently published work on the high efficiency of the SmI2-mediated acyl-type radical additions of the same thioesters with electron deficient alkenes [J. Am. Chem. Soc. 2003, 125, 4030]. A study was also undertaken to examine methods for the stereoselective reduction of N-carbamate-protected amino ketones to either the syn- or anti-vicinal amino alcohols. In most cases, LiAl(O-t-Bu)3H and (S)-Alpine-Hydride were found to effectively provide the anti- and syn-amino alcohols, respectively. The SmI2-promoted reduction of the same ketones afforded a majority of the syn-isomer with selectivities of approximately 5:1. However, in one case, the SmI2-promoted reduction was found to be more effective than that of (S)-Alpine-Hydride. 相似文献
137.
The analytical performance of three acetylcholinesterase (AChE) screen-printed biosensors designed for the detection of pesticides are evaluated. Bioencapsulation of the enzyme in a sol-gel composite and immobilization by metal-chelate affinity were compared with the entrapment of the enzyme in a photopolymerisable polymer. A very low amount of enzyme ranging between 0.8 and 1.2 mIU was immobilized on the electrode surface in each approach. The sensors exhibited a storage stability of over 6 months when the enzyme was encapsulated in a polymer film. Pesticide concentrations in the range of 10−8 to 10−9 M paraoxon, dichlorvos and chlorpyrifos ethyl oxon could be detected according to each configuration by following an incubation time of 20 min. 相似文献
138.
Differential cross sections for rotational excitation in D2 + CO collisions are calculated at six scattering angles using an electron gas surface and a semiclassical scattering theory in which the translational and the rotational motion of CO are treated classically whereas the D2 rotation is quantized. 相似文献
139.
Summary 2 D-, 3 D-, and 4 D-pyridine were prepared by the action of Zn, D2O and D2SO4 on the corresponding halopyridines. The infrared absorption curves showed that the samples obtained were practically pure. The microwave spectra were taken and interpreted. Based on the data so obtained and on data for ordinary pyridine the magnitudes of the 10 geometrical parameters of pyridine were calculated for 7 different models. Only one of these, however, is consistent with valence-theory aspects.
Zusammenfassung Durch Einwirkung von Zink, Deuteriumoxyd und Deuteriumsulfat auf die entsprechenden Halogenpyridine wurden 2-D-, 3-D- und 4-D-Pyridin hergestellt. Die davon hergestellten IR-Absorptionskurven erwiesen die Reinheit dieser Präparate, deren Kurzwellenspektren aufgenommen und interpretiert wurden. Auf Grund dieser Spektren und der entsprechenden Daten für gewöhnliches Pyridin wurde die Größe der 10 geometrischen Parameter für 7 Modelle von Pyridin errechnet. Nur eines davon stimmt mit den Forderungen der Valenztheorie überein.
Résumé On a préparé les 2 D-, 3 D- et 4 D-pyridine par action de Zn, D2O et D2SO4 sur les halopyridines correspondantes. Les produits obtenus sont pratiquement purs ainsi que le montrent les spectres d'absorption infra-rouge. On a enregistré et interprété les spectres de micro-ondes. A partir de ces données et des données relatives à la pyridine ordinaire, on a calculé 10 paramètres géométriques de la pyridine pour 7 modèles différents. Un seul de ces modèles cependant est acceptable du point de vue de la théorie des valences.相似文献
140.