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排序方式: 共有873条查询结果,搜索用时 15 毫秒
21.
Summary Polypeptides, synthesized from a mixture of amino acid amides by microwave heating during repeated hydration-dehydration cycles, showed hydrolase- and oxidoreductase-like catalytic activities. Poly(GAVDH), polypeptides synthesized from an equimolar mixture (each 0.1 M) of glycinamide,l-alaninamide,l-valinamide,l-aspartic acid -amide, andl-histidinamide, catalyzed the hydrolysis of PNPAc. The hydrolytic rate of PNPAc with poly(GAVDH) was the quadruple of that ofl-histidine alone. Though the kcat values of different resulting polypeptides were 103–106 times less than those of native hydrolases, the Km value of the polypeptides further containing phenylalanine residues was nearly equal to that of the esterase. This result indicates the presence of hydrophobic interaction between a substrate and the polypeptides. Resulting polypeptides also showed catalytic activity for the reduction of ferricyanide ion [Fe(CN)3–] with NADH. The polypeptides seemed to have a strong affinity for adenine nucleotides, because the reaction was inhibited by adenine derivatives such as NAD+ and AppA. A hypothesis for the emergence of primitive protein enzymes is discussed. 相似文献
22.
Hiroshi Yanagawa Kiyotsugu Kojima Masahiko Ito Nobuhiko Handa 《Journal of molecular evolution》1990,31(3):180-186
Summary Amino acid amides effectively reacted to produce polypeptides in response to microwave heating during repeated hydration-dehydration cycles. The polypeptides, formed from a mixture of glycinamide, alaninamide, valinamide, and aspartic acid -amide, had molecular weights ranging from 1000 to 4000 daltons. Amino acids were incorporated into the polypeptides in proportion to the starting concentrations, with the exception of glycine whose incorporation was 1.5 times higher than that of the other amino acids. The polypeptides had some definite secondary structure, such as -helix and -sheet, in aqueous solution. This reaction provides not only a convenient method for abiotic peptide formation but also a convenient method for the chemical synthesis of peptides. 相似文献
23.
A sulfated glucosylceramide from rat kidney 总被引:6,自引:0,他引:6
N Iida T Toida Y Kushi S Handa P Fredman L Svennerholm I Ishizuka 《The Journal of biological chemistry》1989,264(10):5974-5980
A novel sulfated glycosphingolipid containing a sulfated glucosyl residue was isolated from rat kidney and purified to homogeneity by column chromatographies with DEAE-Sephadex and silica beads. By compositional analyses, permethylation studies, one- and two-dimensional proton magnetic resonance spectroscopy, infrared spectroscopy, negative secondary ion mass spectrometry, solvolysis, and immunostaining on thin layer chromatogram, the structure of this glycolipid was proposed to be HSO3-3Glc beta 1-1Cer (where Cer is ceramide). The ceramide portion consisted of 4-D-hydroxysphinganine as the sole long chain base, and the fatty acid consisted of predominantly tetracosanoic acid, deduced from both composition analysis and negative secondary ion mass spectrometry. The yield of glucosyl sulfatide was about 5 nmol/g of tissue, being about three times as much as that of lactosylceramide sulfate. 相似文献
24.
N Kojima K Handa W Newman S Hakomori 《Biochemical and biophysical research communications》1992,189(3):1686-1694
E-selectin has a "multi-recognition" capability in terms of epitope binding specificity, depending on adhesion conditions (static vs. low- or high-shear stress dynamic systems). Specifically, (i) adhesion based on expression of alpha 2-->3 sialylated Le(x) (SLe(x)) is prominent under static or low shear stress dynamic conditions; (ii) adhesion under high shear stress dynamic conditions does not depend on the known SLe(x) species, but rather on Lex with an adjacent unidentified sialosyl substitution, which shows different susceptibility to sialidases and antibodies compared to known SLe(x). 相似文献
25.
Keiko Tadano-Aritomi Harumi Kubo Philip Ireland Takeshi Kasama Shizuo Handa Ineo Ishizuka 《Glycoconjugate journal》1996,13(2):285-293
A novel mono-sulfated glycosphingolipid based on the gangliotriaose core structure was isolated from rat kidney. The isolation procedure involved extraction of lipids with chloroform/methanol, mild alkaline methanolysis, column chromatographies with anion exchangers and silica beads. The structure was characterized by compositional analysis, FTIR spectroscopy, methylation analysis,1H-NMR spectroscopy and negative-ion liquid secondary ion mass spectrometry (LSIMS) using the intact glycolipid and its desulfation product. The two dimensional chemical shift correlated spectroscopy provided information on the sugar sequence as well as anomeric configurations, and indicated the presence of a 3-O-sulfatedN-acetylgalactosamine within the molecule. Negative-ion LSIMS with high- and low-energy collision-induced dissociation defined the sugar sequence and ceramide composition, confirming the presence of a sulfatedN-acetylgalactosamine at the non-reducing terminus. From these results, the complete structure was proposed to be HSO3-3GalNAc1-4Gal1-4Glc1-1Cer (Gg3Cer III3-sulfate, SM2b).
Abbreviations: Abbreviations for sulfated glycolipids [17] follow the modifications of the nomenclature system of Svennerholm for gangliosides [37], and the designation of the other glycosphingolipids follows the IUPAC-IUB recommendations [38]. Cer, ceramide; LacCer, lactosylceramide, Gal1-4Glc1-1Cer; Gg3Cer, gangliotriaosylceramide, GalNAc1-4Gal1-4Glc1-1Cer; Gg4Cer, gangliotetraosylceramide, Gal1-3GalNAc1-4Gal1-4Glc1-1Cer; iGb4Cer, isoglobotetraosylceramide, GalNAc1-3Gal1-3Gal1-4Glc1-1Cer; Gb4Cer, globotetraosylceramide, GalNAc1-3Gal1-4Gal1-4Glc1-1Cer; SM4s, galactosylceramide sulfate, GalCer I3-sulfate; SM3, lactosylceramide sulfate, LacCer II3-sulfate; SM2a, Gg3Cer II3-sulfate; SM2b, Gg3Cer III3-sulfate; SB2, Gg3Cer II3,III3-bis-sulfate; SM1a, Gg4Cer II3-sulfate; SM1b, Gg4Cer IV3-sulfate; SB1a, Gg4Cer II3,IV3-bissulfate; GLC, gas-liquid chromatography; GC-MS, gas chromatography-mass spectrometry; DQF, double quantum filtered; COSY, chemical-shift-correlated spectroscopy; LSIMS, liquid secondary ion mass spectrometry; CID, collision-induced dissociation; MS/MS, tandem mass spectrometry. 相似文献
26.
Toshio Ariga Shama Bhat Takashi Kanda Masanaga Yamawaki Tadashi Tai Yasunori Kushi Takeshi Kasama Shizuo Handa Robert K. Yu 《Glycoconjugate journal》1996,13(2):135-145
We analysed the glycolipid composition of glioma cells (N-370 FG cells), which are derived from a culture of transformed human fetal glial cells. The neutral and acidic glycolipid fractions were isolated by column chromatography on DEAE-Sephadex and analysed by high-performance thin-layer chromatography (HPTLC). The neutral glycolipid fraction contained 1.6 µg of lipid-bound glucose/galactose per mg protein and consisted of GlcCer (11.4% of total neutral glycolipids), GalCer (21.5%), LacCer (21.4%), Gb4 (21.1%), and three unknown neutral glycolipids (23%). These unknown glycolipids were characterized as Lewisx (fucosylneolactonorpentaosyl ceramide; Lex), difucosylneolactonorhexaosyl ceramide (dimeric Lex), and neolactonorhexaosyl ceramide (nLc6) by an HPTLC-overlay method for glycolipids using specific mouse anti-glycolipid antibodies against glycolipid and/or liquid-secondary ion (LSI) mass spectrometry. The ganglioside fraction contained 0.6 µg of lipid-bound sialic acid per mg protein with GD1a as the predominant ganglioside species (83% of the total gangliosides) and GM3, GM2, and GM1 as minor components. Trace amounts of sialyl-Lex and the complex type of sialyl-Lex derivatives were also present. Immunocytochemical studies revealed that GD1a and GalCer were primarily localized on the surface of cell bodies. Interestingly, Lex glycolipids and sialyl-Lex were localized not only on the cell bodies but also on short cell processes. Especially, sialyl-Lex glycolipid was located on the tip of fine cellular processes. The unique localization of the Lex glycolipids suggests that they may be involved in cellular differentiation and initiation of cellular growth in this cell line. 相似文献
27.
The in-gel competitive reassociation (IGCR) procedure was successfullyapplied to construct a comprehensive library enriched in DNAfragments containing C5mCGG sequences from mouse liver and braingenomic DNA. For IGCR, methylation-insensitive restriction enzyme(Msp I) digests were used as target DNA and methylation-sensitiverestriction enzyme (Hpa II) digests as competitor DNA. Southernblot analysis indicated that 60 to 70% of the clones in thelibrary were derived from the methylated sites and overall enrichmentwas 200- to 1000-fold. IGCR was further applied to constructa library for the sites differentially methylated between brainand liver DNA. In the library, approximately 20% of the HpaII sites exhibited different degrees of methylation betweenthese tissues. 相似文献
28.
Direct binding to and tyrosine phosphorylation of the alpha subunit of the type I interferon receptor by p135tyk2 tyrosine kinase. 总被引:9,自引:2,他引:7
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O Colamonici H Yan P Domanski R Handa D Smalley J Mullersman M Witte K Krishnan J Krolewski 《Molecular and cellular biology》1994,14(12):8133-8142
29.
The rapid activation of stress-responsive neuroendocrine systems is a basic reaction of animals to perturbations in their environment. One well-established response is that of the hypothalamo-pituitary-adrenal (HPA) axis. In rats, corticosterone is the major adrenal steroid secreted and is released in direct response to adrenocorticotropin (ACTH) secreted from the anterior pituitary gland. ACTH in turn is regulated by the hypothalamic factor, corticotropin-releasing hormone. A sex difference exists in the response of the HPA axis to stress, with females reacting more robustly than males. It has been demonstrated that in both sexes, products of the HPA axis inhibit reproductive function. Conversely, the sex differences in HPA function are in part due to differences in the circulating gonadal steroid hormone milieu. It appears that testosterone can act to inhibit HPA function, whereas estrogen can enhance HPA function. One mechanism by which androgens and estrogens modulate stress responses is through the binding to their cognate receptors in the central nervous system. The distribution and regulation of androgen and estrogen receptors within the CNS suggest possible sites and mechanisms by which gonadal steroid hormones can influence stress responses. In the case of androgens, data suggest that the control of the hypothalamic paraventricular nucleus is mediated trans-synaptically. For estrogen, modulation of the HPA axis may be due to changes in glucocorticoid receptor-mediated negative feedback mechanisms. The results of a variety of studies suggest that gonadal steroid hormones, particularly testosterone, modulate HPA activity in an attempt to prevent the deleterious effects of HPA activation on reproductive function. 相似文献
30.
Molecular phylogeny in the Lardizabalaceae 总被引:1,自引:0,他引:1
Rumiko Kofuji Kunihiko Ueda Kazuo Yamaguchi Tatemi Shimizu 《Journal of plant research》1994,107(3):339-348
Eleven species belonging to seven genera in the Lardizabalaceae were analyzed in terms of restriction fragment length polymorphism
(RFLP) of chloroplast DNA and the sequence of the chloroplast gene,rbcL, of Lardizabalaceae and its related families. Phylogenetic trees inferred from parsimony, neighbor joining and maximum likelihood
methods based on RFLP data showed that two South American genera,Boquila andLardizabala, and three East Asian genera,Akebia, Holboellia andStauntonia are closely related to each other, respectively. On the other hand, the parsimony, neighbor joining and maximum likelihood
trees constructed using sequence data of therbcL gene showed thatAkebia, Stauntonia, Boquila andLardizabala clustered as(((Akebia, Stauntonia), Boquila), Lardizabala). This difference may be attributable to fewer informative sites inrbcL genes than in RFLP in this family.Decaisnea diverges at the very base of the Lardizabalaceae. 相似文献