Synthesis of fullerene glycoconjugates through sulfide connection in aqueous media

[reaction: see text] A thiolate/alkyl halide coupling reaction in aqueous media provides a one-step synthesis of fullerene glycoconjugates bearing five carbohydrate groups in good yield by using stoichiometric amounts of reactants, without recourse to hydroxy group protection. The sulfide-connection methodology is also useful for synthesis of simpler amphiphilic fullerene molecules, such as one bearing five carboxylic acid groups.     

Adsorption, Migration and Reactions of Hydrocarbons on Zeolites Observed by Ftir Spectroscopy

The adsorption, migration and reactions of hydrocarbons on zeolites studied by FTIR spectroscopy are briefly reviewed. At low temperatures, alkyl-BAS (Brønsted acid sites) and -BAS complexes were first formed before protonation of olefins. For 1-butene, it underwent double bond migration (DBM) to form cis- and trans-2-butenes. With increasing temperature, oligomerization occurred and resulted in highly branched dimer, e.g., 3,4-dimethyl-3-hexene. Compared with 1-butene, isobutene can oligomerize at much lower temperature and formed dimerized alkoxy species, even on isolated silanols of zeolites. Upon adsorption of cyclic olefins such as 1-methylcyclopentene, alkenyl carbenium ions were formed at temperatures as low as 150 K. The adsorption of butenes on ferrierite indicates the existence of energy barriers for their intercalation into the pores. The H/D isotope exchange reaction of alkanes with acidic hydroxyl groups of zeolites will also be discussed.     

Unequal hydrolysis of salicylic acid-D-alanine and salicylic acid-L-alanine conjugate in rabbit intestinal microorganisms.

The behavior of salicylic acid-D-alanine conjugate (salicyl-D-alanine) following intravenous, oral and intracecal administration was examined in rabbits, then compared with that of salicylic acid-L-alanine conjugate (salicyl-L-alanine) as reported previously. Following intravenous administration, salicyl-D-alanine eliminated rapidly from the blood, and its blood concentration was almost identical with that of salicyl-L-alanine. In both cases, salicylic acid could not be detected in the blood, indicating that systemic de-conjugation of D-alanine might not occur. Unchanged salicyl-D-alanine was found in the blood mainly following oral and intracecal administration of salicyl-D-alanine. On the other hand, salicylic acid formed extensively following oral and intracecal administration of salicyl-L-alanine, suggesting that the presystemic de-conjugation of D-alanine and L-alanine was unequal. Furthermore, in vitro incubation of salicyl-D-alanine with cecal content, in which the major source of salicyl-L-alanine hydrolysis is found, showed that the hydrolysis of salicyl-D-alanine was negligible in rabbit intestinal microorganisms.     

Inhibition of angiogenesis by bleomycin and its copper complex.

The effects of bleomycin (BLM) and its copper complex on embryonic angiogenesis were studied in the chorioallantoic membranes of 4.5-day-old chick embryos. Copper-free BLM inhibited embryonic angiogenesis in a dose-dependent manner, with activity detectable at 1 ng/egg and maximal at 1000 ng/egg. Also, treatment with copper-BLM complex dose-dependently caused inhibition of embryonic angiogenesis in a lower dose range. Since tumor growth is believed to depend on angiogenesis, the present results may indicate that the antiangiogenic activity of BLM is, at least in part, implicated in the antitumor activity of the drug.     

Cross-checking of nanoelectrospray ionization mass spectrometry and computer simulation for the evaluation of the interaction strength of non-covalently bound enkephalins in solution

Nanoelectrospray ionization mass spectrometry (nanoESI-MS) and computer simulation were applied to the characterization of non-covalent interactions of [Leu5]-enkephalin (LE) and its optical isomers, [D-Tyr1, Leu5]-enkephalin (Y-LE), [D-Phe4, Leu5]-enkephalin (F-LE) and [D-Tyr1, D-Phe4, Leu5]-enkephalin (YF-LE). The dimer formation tendencies of the optical isomers of LE were evaluated by nanoESI-MS using quadruply deuterated LE (H2N-Tyr-(2,2-d2)Gly-(2,2-d2)Gly-Phe-Leu-COOH, d4-LE) as an internal standard. The relative interaction strengths of the optical isomers of LE were estimated to be Y-LE < F-LE < LE < YF-LE. Geometry optimization calculations were performed for interactions in vacuo and in water using a semi-empirical SCF method (PM3). The initial coordinate of the dimer structure of LE was taken from that obtained from single-crystalline x-ray diffraction analysis. Estimates of the interaction strengths of the dimer complexes were based on the heats of formation of a dimer complex (Hd) and the corresponding monomers (Hm) using the equation DeltaH = Hd - 2Hm. The values of DeltaH obtained from the calculations for interactions in water decreased in the order Y-LE > F-LE > LE > YF-LE. Since the smaller values of DeltaH correspond to stronger interactions between peptides, the results from computer simulations were qualitatively consistent with those obtained from the nanoESI experiments. The possibility of cross-checking these independent techniques was demonstrated using medium-sized molecules of biological importance. The agreement of the results from the two techniques suggested that nanoESI experiments, at least qualitatively, reflected the relative interaction strengths of non-covalently bound enkephalins in aqueous solution.     

Preparation of adsorbents for affinity chromatography using TSKgel Tresyl-Toyopearl 650M

The optimum conditions for the coupling of proteins were investigated using TSKgel Tresyl-Toyopearl 650M. They were dependent on the proteins coupled. For example, when soybean trypsin inhibitor was coupled at pH 8 the coupling was completed within 1 h and the subsequent adsorption capacity for trypsin was maximal. Longer coupling times decreased the adsorption capacity due to multi-point attachment. The adsorbents obtained were successfully used for affinity chromatography in a short time.     

Analysis of waterborne paints by gas chromatography-mass spectrometry with a temperature-programmable pyrolyzer

Gas chromatography-mass spectrometry (GC-MS) with a temperature-programmable pyrolyzer was used for the analysis of waterborne paints. Evolved gas analysis (EGA) profiles of the waterborne paints were obtained by this temperature-programmed pyrolysis directly coupled with MS via a deactivated metal capillary tube. The EGA profile suggested the optimal thermal desorption conditions for solvents and additives and the subsequent optimal pyrolysis temperature for the remaining polymeric material. Polymers were identified from pyrograms with the assistance of a new polymer library. The solvents were identified from the electron ionization mass spectra with the corresponding chemical ionization mass spectra. The additive was identified as zinc pyrithione by comparison with authentic standard. Zinc pyrithione cannot be analyzed by GC-MS as it is. However, the thermal decomposition products of zinc pyrithione could be detected. The information on the decomposition temperature and products was useful for the identification of the original compound.     

Deoxygenation of sugar trifluoromethanesulfonates by sodium metal in liquid ammonia and by photolysis

Several trifluoromethanesulfonyl(TFMS) derivatives of sugars were prepared and treated with sodium in liquid ammonia or subjected to ultraviolet irradiation. Three 3-$\text{O}$-TFMS derivatives gave the corresponding 3-deoxy compounds, but a 2-$\text{O}$-TFMS derivative gave a branched-chain sugar.