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排序方式: 共有185条查询结果,搜索用时 15 毫秒
151.
Sekizaki H Kumagai A Itoh K Toyota E Horita K Noguchi Y Tanizawa K 《Bioorganic & medicinal chemistry letters》2003,13(21):3809-3812
The acyl trypsin was prepared by use of an inverse substrate, which is comprise of a photoresponsive 4-phenylazobenzoyl moiety. The acyl group in acyl trypsin has been shown to isomerize from trans-form (4t-trypsin) to cis-form (4c-trypsin)/from cis-form to trans-form by irradiation of UV-vis light. The deacylation rate of the cis-form (4c-trypsin) has been shown to be 18.6 times faster than that of the trans-form (4t-trypsin). 相似文献
152.
Five Japanese liverworts (Bazzania sp.) were examined for sesquiterpenes. B. japonica and B. pompeana contained two new drimane-type sesquiterpene esters, albicanyl 3,4-dihydroxycinnamate and albicanyl 2,4dihydroxycinnamate. Tridensenone, a new aromadendrane-type sesquiterpene ketone was isolated from B. tridens. The stereostructures of these new sesquiterpenes were elucidated mainly by spectrometry. Barbatane-, bazzanane- and cuparane-type sesquiterpenes were found in all of the five species investigated. These sesquiterpenes, along with the new drimane- and aromadendrane-type sesquiterpenes are useful chemosystematic markers. 相似文献
153.
Yoshinori Asakawa Reiko Matsuda Masao Toyota Shinske Hattori Guy Ourisson 《Phytochemistry》1981,20(9):2187-2194
Twenty-five Frullania species (liverworts) were chemically investigated. Fourteen species produce allergy-inducing sesquiterpene lactones. Eighteen species contain bibenzyls. The sesquiterpene lactones and bibenzyls are obtained as the major components and they are valuable chemosystematic markers of Frullania species. On the basis of their chemical constituents, Frullania species can be divided into five chemotypes: sesquiterpene lactone-bibenzyl type; sesquiterpene lactone type; bibenzyl type; monoterpene type and cyclocolorenone type. 相似文献
154.
Xiao Ping Zhu Jo Satoh M.D. Gen Muto Yoshiko Muto Mikio Sagara Kazuma Takahashi Hiroaki Seino Satoshi Hirai Takayuki Masuda Shun-ichi Tanaka Hitoshi Ishida Yutaka Seino Takayoshi Toyota 《Biotherapy》1996,9(4):189-197
Cytokine-inducers prevent insulin-dependent diabetes mellitus (IDDM) in animal models. We extended this therapy to non-insulin-dependent
diabetes mellitus (NIDDM), because it was reported that diabetes of KK-Ay mice, a model for NIDDM, was recovered by allogenic
bone-marrow transplantation that also prevented IDDM in animal models.
An i.p. or i.v. injection of streptococcal preparation (OK 432) lowered fasting blood glucose (FBG) levels and markedly improved
glucose tolerance test (GTT) in KK-Ay mice for more than 32 h regardless of the glucose loading routes (oral, i.v. or i.p.),
while an i.v. injection of BCG improved FBG and GTT for more than 4 wks without body weight loss. The improvement of FBG and
GTT with OK-432 was brought about in other NIDDM animals, GK rats and Wistar fatty rats. Among various cytokines possibly
induced by OK-432 and BCG, IL-1α, TNFα and lymphotoxin significantly improved FBG and GTT in KK-Ay mice, whereas IL-2 and
IFNγ did not. There were no differences between the OK-432-treated KK-Ay mice and control in histology of the pancreas, degree
of insulin-induced decrease in blood glucose levels, and muscle glycogen synthase activities. As to insulin secretion, there
is a tendency that the OK-432-treatment less than 1 week did not affect insulin levels during GTT, whereas the treatment more
than 2 weeks increased the insulin levels.
Thus, cytokine-inducers improved FBG and glucose tolerance of NIDDM animals probably via cytokines. The results imply a role
of the cytokines in glucose tolerance of NIDDM, although precise immune and metabolic mechanisms remain to be elucidated. 相似文献
155.
Haruo Sekizaki Kunihiko Itoh Eiko Toyota Kazutaka Tanizawa 《Journal of peptide science》2002,8(9):521-528
A procedure has been developed for the synthesis of oligopeptide amide using inverse substrates as acyl donors with amino acid amide instead of p-nitroanilide as acyl acceptor and trypsins of different origin (bovine, Streptomyces griseus and chum salmon trypsins) as the catalyst. The effectiveness of this procedure was demonstrated by the synthesis of a pentapeptide, Boc-[Leu5]-enkephalin amide, as a model compound. The method was the first enzymatic method shown to be successful at each successive coupling step for the synthesis of the oligopeptide. Bovine and chum salmon trypsins were superior to Streptomyces griseus trypsin as the catalyst. 相似文献
156.
Histamine H1 receptor binding capacities in the amygdalas of the amygdaloid kindled rat 总被引:1,自引:0,他引:1
The histamine H1 receptor binding capacity of the amygdalas of amygdaloid kindled rats was studied. In the kindled nonstimulated amygdala, significant decreases in K(D) and B(max) values compared with those of control amygdala were found 1 week after the last kindled seizure. One month after the last kindled seizure, the decreased K(D) value was sustained in the kindled nonstimulated amygdala. This decreased Bmax value 1 week after the last kindled seizure in nonstimulated amygdala may partly and transiently contribute to kindled seizure susceptibility. The decreased K(D) value in nonstimulated amygdala observed until 1 month after the last kindled seizure indicates the long-lasting increment of binding affinity of the pyrilamine binding site of the histamine H1 receptor in the steady state of kindled seizure susceptibility. 相似文献
157.
Cytoplasmic calcium increases in response to changes in the gravity vector in hypocotyls and petioles of Arabidopsis seedlings 总被引:1,自引:0,他引:1
Plants respond to a large variety of environmental signals, including changes in the gravity vector (gravistimulation). In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation is known to increase the cytoplasmic free calcium concentration ([Ca(2+)](c)). However, organs responsible for the [Ca(2+)](c) increase and the underlying cellular/molecular mechanisms remain to be solved. In this study, using Arabidopsis seedlings expressing apoaequorin, a Ca(2+)-sensitive luminescent protein in combination with an ultrasensitive photon counting camera, we clarified the organs where [Ca(2+)](c) increases in response to gravistimulation and characterized the physiological and pharmacological properties of the [Ca(2+)](c) increase. When the seedlings were gravistimulated by turning 180 degrees, they showed a transient biphasic [Ca(2+)](c) increase in their hypocotyls and petioles. The second peak of the [Ca(2+)](c) increase depended on the angle but not the speed of rotation, whereas the initial peak showed diametrically opposite characters. This suggests that the second [Ca(2+)](c) increase is specific for changes in the gravity vector. The potential mechanosensitive Ca(2+)-permeable channel (MSCC) inhibitors Gd(3+) and La(3+), the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), and the endomembrane Ca(2+)-permeable channel inhibitor ruthenium red suppressed the second [Ca(2+)](c) increase, suggesting that it arises from Ca(2+) influx via putative MSCCs in the plasma membrane and Ca(2+) release from intracellular Ca(2+) stores. Moreover, the second [Ca(2+)](c) increase was attenuated by actin-disrupting drugs cytochalasin B and latrunculin B but not by microtubule-disrupting drugs oryzalin and nocodazole, implying that actin filaments are partially involved in the hypothetical activation of Ca(2+)-permeable channels. These results suggest that the second [Ca(2+)](c) increase via MSCCs is a gravity response in the hypocotyl and petiole of Arabidopsis seedlings. 相似文献
158.
Berthold CL Toyota CG Richards NG Lindqvist Y 《The Journal of biological chemistry》2008,283(10):6519-6529
Formyl-coenzyme A transferase from Oxalobacter formigenes belongs to the Class III coenzyme A transferase family and catalyzes the reversible transfer of a CoA carrier between formyl-CoA and oxalate, forming oxalyl-CoA and formate. Formyl-CoA transferase has a unique three-dimensional fold composed of two interlaced subunits locked together like rings of a chain. We here present an intermediate in the reaction, formyl-CoA transferase containing the covalent beta-aspartyl-CoA thioester, adopting different conformations in the two active sites of the dimer, which was identified through crystallographic freeze-trapping experiments with formyl-CoA and oxalyl-CoA in the absence of acceptor carboxylic acid. The formation of the enzyme-CoA thioester was also confirmed by mass spectrometric data. Further structural data include a trapped aspartyl-formyl anhydride protected by a glycine loop closing down over the active site. In a crystal structure of the beta-aspartyl-CoA thioester of an inactive mutant variant, oxalate was found bound to the open conformation of the glycine loop. Together with hydroxylamine trapping experiments and kinetic as well as mutagenesis data, the structures of these formyl-CoA transferase complexes provide new information on the Class III CoA-transferase family and prompt redefinition of the catalytic steps and the modified reaction mechanism of formyl-CoA transferase proposed here. 相似文献
159.
The authors prepared the dimethyl and diphenyl esters of 9,9'-bianthryl-2,2'-dicarboxylic acid in racemic and enantiopure (M) forms. The enantiopure dimethyl ester forms inclusion compounds with various organic compounds such as benzene, methanol, phenol, and aniline whereas the racemic form does this only with benzene. No guest molecules are included by the racemic and enantiopure diphenyl esters. These effects of substituents and homochirality on the inclusion properties are discussed on the basis of X-ray structures of some inclusion and guest-free compounds. 相似文献
160.
To examine whether a primordial functional protein at the early stages of evolution has structural features, we carried out experimental evolution consisting of 25 cycles (generations) of mutation and selection toward DNA-binding function using a random-sequence polypeptide of 139 amino acid residues with no secondary structure as the initial sequence. In each generation, 16 clones were sampled arbitrarily for sequence analysis, and a phylogenetic tree was constructed. Polypeptide evolution proceeded from the initial point on branch I in 2 main directions of branches II and III. The initial and 2 evolved polypeptides (one at the 24th generation on branch III and the other at the 25th generation on branch II) were purified to examine their functional and structural properties. Although binding of the initial polypeptide to the target DNA was not detected by surface plasmon resonance measurements, the 2 evolved polypeptides bound to the DNA with dissociation constants of 1.6 and 1.0 microM, respectively, indicating an increase in affinity during the experimental evolution. Circular dichroism spectra of the evolved polypeptides, but not of the initial polypeptide, showed features characteristic of the polyproline II (PPII)-like structure, a left-handed helical structure commonly found in natural proteins, suggesting that the structure emerged through the experimental evolution. The same structural feature was found in another experimental evolution toward catalytic activity. These results demonstrate that the PPII-like structure is one of the common features that could have appeared in the early evolutionary stages of primordial functional protein. 相似文献