Electronic spectra of a homo-molecular dimer cation, (C6H5CN)2+, are measured by photodissociation spectroscopy in the gas phase. Broad features appeared in the 450–650 nm region are characteristic
of π3 → πCN transitions of the C6H5CN+ chromophore. No intense band is observed in the 650–1300 nm region, where other aromatic dimer cations usually show charge
resonance bands. Two component molecules of (C6H5CN)2+ cannot take a parallel sandwich configuration suitable for the resonance interaction, because of geometrical constraints
due to other stronger interactions. 相似文献
Treatment of N(3)-[(2-cyano-2-ethoxycarbonyl)vinyl]amino-N(4),N(4)-dimethylaminomethylenehydrazones of aromatic carbonyl compounds with hot acetic acid resulted in the formation of symmetrical gem-bis-(3-dimethylamino-1,2,4-triazol-1-yl)methanes, (3-dimethylamino-1,2,4-triazol-1-yl)arylmethyl acetates, and (3-dimethylamino-1,2,4-triazol-1-yl)alkenes of a gem-diaryl type depending upon whether the carbonyl compound was aldehyde or ketone. 相似文献
The reaction of amino-N(4),N(4)-dimethylaminornethylenehydrazones 1 of some aliphatic carbonyl compounds with ethyl ethoxymethylenecyanoacetate 2 gave directly symmetrical gem-bis(3-dimethylamino-1, 2, 4-triazol-1-yl)alkanes 4 and (3-dimethylamino-1, 2, 4-triazol-1-yl)alkenes 5 at room temperature, with the former being major product. On the other hand, the reaction of amino- N (4)-methylaminomethylenehydrazone homologue 1 of aliphatic ketone with 2 gave ethyl 2-alkyl-5-methylamino[1, 2, 4]triazolo[1, 5-c]pyrimidine-8-carboxylate 7 as the only product with elimination of alkane. 相似文献
Poly(L-lysine)s having an Nepsilon-substituted tetrapeptide, Lys-Gly-Tyr-Gly, were synthesized by the coupling of the protected tetrapeptide active ester, Boc-Lys(Z)-Gly-Tyr(Bzl)-Gly (4-hydroxyphenyl)dimethylsulfonium methylsulfate and Nepsilon-group of the poly(L-lysine) side chain. The Nepsilon-substituted tetrapeptide functions as the substrate of tyrosinase and is responsible for the enzyme-mediated interpolymer cross-linking. The degree of Nepsilon-substitution (DS) was mostly controlled by changing the stoichiometry between the Nepsilon-amino groups of the parent poly(L-lysine) and the protected tetrapeptide active ester. Two kinds of samples having DS values of 8.6 and 18 mol-% were prepared. The resulting cationic Nepsilon-(Lys-Gly-Tyr-Gly)-poly(L-lysine) (abbreviated as PLL(GYGK)) was spun into hybrid fibers with the anionic polysaccharide gellan via a polyionic complexation reaction at the interface between aqueous solutions of the two polymers. The mechanical strengths of the PLL(GYGK)-gellan hybrid fibers were superior to those of the original poly(L-lysine)-gellan fibers. The mechanical strength of the hybrid fibers further increased upon the tyrosinase-mediated cross-linking reaction of the PLL(GYGK). This result indicates that the covalent cross-bridge formation between the Nepsilon-substituted peptides significantly contributed to reinforcement of the hybrid fibers. The present study affords a new methodology for reinforcement inspired by a biological process. 相似文献
A polymeric aminoglycoside was prepared by a facile chemoenzymatic reaction. Boc‐protected aminoglycoside, amikacin, was chemoselectively esterified with divinyl sebacate at a hydroxyl group in the C6″ position by protease from Bacillus subtilis. The resulting 3,6′,3″,4?‐tetra‐N‐Boc‐6″‐O‐vinyl sebacate was copolymerized with maltitol 6‐vinyl sebacate to yield a polymeric amikacin. The polymeric amikacin showed a modest inhibitory effect on in vitro protein synthesis, and a little antibiotic activity in minimum inhibitory concentration (MIC) assay in the presence of protease.
The synthesis of Boc‐protected amikacin ester by an enzyme‐catalyzed (protease) esterification. 相似文献
E. coli cells were inactivated with visible light in the presence of toluidine blue as a photo-sensitizer. This photodynamic effect was partially protected with α-tocopherol. Not only pH but the concentration of the buffer during irradiation also affected the survival. The addition of osmotic stabilizers such as KCI, glycerol and polyethyleneglycol to the buffer increased the survival. The difference in singlet oxygen production in these reaction mixtures could not be related to these features. Furthermore, the survival was also dependent upon both irradiation temperature and cultivation temperature of the cells. These results with E. coli cells support the notion that one of the primary targets of toluidine blue sensitized photodynamic inactivation is cytoplasmic membrane, although other factors than cytoplasmic membrane also influence the survival of the cells. 相似文献
Raman spectra of the Li+, Na+, K+, NH+4, Mg2+, Ca2+, Sr2+, Ba2+, Pb2+ complexes of 12-crown-4 and also 12-crown-4 in various states are observed. The spectra of 12-crown-4 change remarkably by complex formation with cations. Normal vibration calculations of various conformations of 12-crown-4 are carried out. On the basis of the observed spectra and the results of the calculations, the conformation of 12-crown-4 in the Li+, Na+, K+, NH+4, Mg2+ complexes is found to have approximate D2d symmetry, while that in the Ca2+, Sr2+, Ba2+ complexes is found to have approximate C2V symmetry. 相似文献
Model potential parameters and basis sets, presented previously for the transition metal atoms Sc through Hg, are tested in calculations of the transition metal compounds (CuF, CuCl, Cu2, TiCl4, ZrCl4, CoF63?, CoF62?, AgH, AuH, CrF6, ScO, ZrO, Cr2, Mo2). Calculated values of the bond distances, vibrational frequencies, and some transition energies (for Cu2 and CoF62?) are compared with those given by all-electron calculations with basis sets of high quality. Singlet-triplet splittings in Cu2 and correlation energies in CrF6n? (n = 0, 1, and 2) are also examined. The satisfactory results obtained by these calculations strongly support the contention that the model potential method is a reliable and economical alternative to the ab initio Hartree-Fock-Roothaan method. 相似文献
Abstract Solid state NMR measurements are carried out for polymorphs and inclusion complexes of 4,5-bis(4-methoxyphenyl)-2-(3-nitrophenyl)-1H-imidazole. Observed 13C and 15N chemical shifts are characteristic of each polymorph A, B, C and D. In addition, 15N chemical shift was a good index for understanding hydrogen bond. VT measurements revealed that B transforms to C between 93 and 113°C. From PSTMAS and 1H solid echo measurements for AcOET inclusion complex, host molecules have almost same structure as B and guest molecules have the highest mobility of all inclusion complexes. 相似文献