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961.
David Kessel W.Barkley Butler Vaidyanathan K. Iyer Jerome P. Horwitz 《Biochemical and biophysical research communications》1982,109(1):45-48
An estrogen-bridged adenine derivative was equitoxic to both the P388 murine leukemia and an adriamycin-resistant subline, . The drug rapidly altered several P388 and membrane properties resulting in impaired nucleoside transport and increased membrane hydrophobicity. Resistance to anthracyclines in is associated with an operational barrier to drug retention which was reversed by exposure to the estrogen-bridged adenine derivative. These results suggest further exploration of the estrogen-bridged purines as chemotherapeutic agents. 相似文献
962.
963.
Indole, tryptophan, tryptamine and skatole were isolated from the leaves of Tecoma stans. Anthranilic acid was also identified in its free form, in contrast to its glucoside, in Jasminum grandiflorum. The presence of both indole and anthranilic acid in the leaves of Tecoma stans indicates that they are the true substrate and product of indole oxygenase from the leaves of Tecoma stans. 相似文献
964.
Milind C. Mahajan Prashant S. Phale Chelakara S. Vaidyanathan 《Archives of microbiology》1994,161(5):425-433
Pseudomonas putida CSV86, a soil bacterium, grows on 1- and 2-methylnaphthalene as the sole source of carbon and energy. In order to deduce the pathways for the biodegradation of 1- and 2-methylnaphthalene, metabolites were isolated from the spent medium and purified by thin layer chromatography. Emphasis has been placed on the structural characterisation of isolated intermediates by GC-MS, demonstration of enzyme activities in the cell free extracts and measurement of oxygen uptake by whole cells in the presence of various probable metabolic intermediates. The data obtained from such a study suggest the possibility of occurrence of multiple pathways in the degradation of 1- and 2-methylnaphthalene. We propose that, in one of the pathways, the aromatic ring adjacent to the one bearing the methyl moiety is oxidized leading to the formation of methylsalicylates and methylcatechols. In another pathway the methyl side chain is hydroxylated to-CH2OH which is further converted to-CHO and-COOH resulting in the formation of naphthoic acid as the end product. In addition to this, 2-hydroxymethylnaphthalene formed by the hydroxylation of the methyl group of 2-methylnaphthalene undergoes aromatic ring hydroxylation. The resultant dihydrodiol is further oxidised by a series of enzyme catalysed reactions to form 4-hydroxymethyl catechol as the end product of the pathway. 相似文献
965.
We discuss the derivation of atomic-level potentials of mean force from the known protein structures and their applicability for structural evaluation applications. In the derivation process, rigorous density estimation methodology is used to estimate the probability density functions (PDFs) for the distributions of interatomic distances in the protein structures. Potentials of mean force are then derived from these density functions using simple Boltzmann's relation. We also test the potentials against pairs of current and superseded protein structures in the Protein Data Bank. Using PDF potentials to evaluate each structure pair, we are able to identify, with high accuracy, which of the two structures is of higher resolution or better quality. This result shows that the PDF potentials are sensitive to details in protein structures as the current and superseded atomic coordinates generally do not differ by more than 1 A in root-mean-square deviation, and that the PDF potentials could potentially be used for X-ray structure refinement and protein structure prediction. 相似文献
966.
S H Low S H Wong B L Tang V N Subramaniam W J Hong 《The Journal of biological chemistry》1991,266(20):13391-13396
Dipeptidyl peptidase IV (DPPIV) is a type II membrane glycoprotein that is predominantly localized to the apical plasma membrane in various epithelial cells. In order to understand in more detail the biogenesis and sorting of DPPIV, the cDNA for rat DPPIV was inserted into a mammalian plasmid expression vector so that DPPIV expression was driven by a control region composed of the SV40 early promoter region fused to the enhancer of the Rous sarcoma virus. Madin-Darby canine kidney cells transfected with this construct were found to express the DPPIV protein. In these transfected cells, the majority of DPPIV was present on the apial cell surface. This observation suggests that the information for apical surface localization is inherent in the DPPIV molecule itself and that this sorting information is decipherable in the epithelial cells of a different species. DPPIV is transported efficiently from the endoplasmic reticulum to the Golgi apparatus as assessed by pulse-chase experiments. Furthermore, evidence is presented which suggests that the majority of DPPIV is sorted intracellularly to the apical cell surface. The same protein has, however, been reported to be sorted by an indirect pathway through transcytosis from the basolateral to the apical cell surface in hepatocytes (Bartles, J.R., Feracci, H., M., Stinger, B., and Hubbard, A.L. (1987) J. Cell Biol. 105, 1241-1251). This study suggests that the same protein can take two different pathways in different cell types for its correct apical cell surface localization. 相似文献