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61.
Shirahama T Kohno T Kaijima T Nagaoka Y Morimoto D Hirata K Uesato S 《Chemical & pharmaceutical bulletin》2006,54(5):665-668
Dimeric indole alkaloid, anhydrovinblastine, which can be obtained from catharanthine and vindoline in a high yield, was converted stereoselectively into vinblastine through alternating oxidation-reduction with oxygen and NaBH(3)CN in the presence of anti-vinblastine monoclonal antibody. 相似文献
62.
Let K denote a field, and let V denote a vector space over K with finite positive dimension. We consider a pair of linear transformations A : V → V and A∗ : V → V that satisfy (i) and (ii) below:
- (i)
- There exists a basis for V with respect to which the matrix representing A is irreducible tridiagonal and the matrix representing A∗ is diagonal.
- (ii)
- There exists a basis for V with respect to which the matrix representing A∗ is irreducible tridiagonal and the matrix representing A is diagonal.
63.
Fujihisa H Akahama Y Kawamura H Ohishi Y Shimomura O Yamawaki H Sakashita M Gotoh Y Takeya S Honda K 《Physical review letters》2006,97(8):085503
Despite many experimental and theoretical studies, the crystal structure of the epsilon phase of solid oxygen has not been determined. We performed powder x-ray diffraction experiments and the Rietveld analyses in this study to show that a new arrangement of the monoclinic space group C2/m could fit the diffraction patterns of the epsilon phase and obtained a structure that consisted of an O8 cluster with 4 molecules. The dependence of the lattice parameters, the molar volume, and the intermolecular distances on the pressure was investigated. 相似文献
64.
65.
Shigeo Kusuoka Kazumasa Kuwada Yozo Tamura 《Probability Theory and Related Fields》2010,147(3-4):649-674
The large deviation principle for stochastic line integrals along Brownian paths on a compact Riemannian manifold is studied. We regard them as a random map on a Sobolev space of 1-forms. We show that the differentiability order of the Sobolev space can be chosen to be almost independent of the dimension of the underlying space by assigning higher integrability on 1-forms. The large deviation is formulated for the joint distribution of stochastic line integrals and the empirical distribution of a Brownian path. As the result, the rate function is given explicitly. 相似文献
66.
The total synthesis and determination of the absolute configuration of (+)- and (−)-sundiversifolide have been achieved via intramolecular acylation and Wittig-lactonization as the key steps. The xanthanolide sesquiterpene lactones, 8-epi-xanthatin (1), dihydroxanthatin (2), and xanthatin (3) were also prepared, starting from a common intermediate derived from the synthesis of sundiversifolide. 相似文献
67.
68.
Valerie R. Kempf Kazumasa Wakamatsu Shosuke Ito John D. Simon 《Photochemistry and photobiology》2010,86(4):765-771
The morphological and chemical changes associated with the exposure of melanosomes to methyl iodide are assessed by a variety of analytical, imaging and spectroscopic methods. Scanning electron microscopy, light scattering and N2 adsorption measurements all indicate significant changes in the morphology of the pigment following methylation. Solid-state nuclear magnetic resonance (SS-NMR) spectroscopy and chemical degradation analysis reveals the methylation results in the introduction of ester groups into the pigment structures. Amino acid analysis further reveals that Arg, Cys, His, Ser and Tyr undergo methylation; the SS-NMR data provide additional evidence for the methylation of the sulfur of Cys. Methylation results in increased solubility of the melanosome; the absorption properties of the dissolved material are characterized by an absorption maximum at 225 nm, with a long tail throughout the UV-A and UV-B, indicating that the solubilized material is a combination of protein and pigment. The methylation-induced decomposition of the melanosomes provides new insights into both the observed increase in O-methyl derivatives of the indolic precursor to eumelanin in the urine of melanoma patients and how increased levels of biologic methylating agents in the brain induce symptoms that resemble Parkinson’s disease. 相似文献
69.
70.
Comparison of structural and chemical properties of black and red human hair melanosomes 总被引:1,自引:0,他引:1
Liu Y Hong L Wakamatsu K Ito S Adhyaru B Cheng CY Bowers CR Simon JD 《Photochemistry and photobiology》2005,81(1):135-144
Melanosomes in black and red human hair are isolated and characterized by various chemical and physical techniques. Different yields of 4-amino-hydroxyphenolanaline by HI hydrolysis (a marker for pheomelanin) and pyrrole-2,3,5-tricarboxylic acid by KMnO(4)/H(+) oxidation (a marker for eumelanin) indicate that the melanosomes in black hair are eumelanosomes, whereas those in red hair are mainly pheomelanosomes. Atomic force microscopy reveals that eumelanosomes and pheomelanosomes have ellipsoidal and spherical shapes, respectively. Eumelanosomes maintain structural integrity upon extraction from the keratin matrix, whereas pheomelanosomes tend to fall apart. The black-hair eumelanosomes have an average of 14.6 +/- 0.5% amino acids content, which is attributed to the internal proteins entrapped in the melanosomes granules. The red-hair melanosomes contain more than 44% of amino acid content even after extensive proteolytic digestion. This high content of amino acids and the poorly reserved integrity of red-hair melanosomes suggest that some proteins are possibly covalently bonded with the melanin constituents in addition to those that are entrapped inside the melanin species. Soluene solubilization assay indicates the absorbance of melanin per gram of sample, adjusted for the amino acid content, is a factor of 2.9 greater for the black-hair melanosomes than the red-hair melanosomes. Metal analysis reveals significant amounts of diverse heavy metal ions bound to the two types of melanosomes. The amount of Cu(II) and Zn(II) are similar but Fe(III) content is four times higher in the red-hair melanosomes. (13)C solid-state nuclear magnetic resonance spectra and infrared spectra are presented and are shown to be powerful techniques for discerning differences in the amino acid contents, the 5,6-dihydroxyindole-2-carboxylic acid:5,6-dihydroxyindole ratio, and the degree of cross-linking in the pigment. Excellent agreement is observed between these spectral results and the chemical degradation data. 相似文献