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81.
Alternating poly(Glu-Leu) was synthesized by the condensation of the corresponding dipeptide p-nitrophenyl ester at high concentration. It exhibits a random coil structure in pure water at neutral pH. Addition of monovalent cations, such as NH+4 to a final 0.1 M solution, induces a transition to a water soluble β-structure. The salt effect is quite selective since no transition was observed with Li+, Na+ or Cs+ ions. Addition of 0.5 equiv. of calcium, cobalt or manganese chlorides per glutamyl residue induces similar coil to β-sheet transitions. No polymer precipitation was observed at these very low salt concentrations. Addition of 0.5 equiv. of Cu2+ or 0.15 equiv. of Fe3+ induces a coil to α-helix transition. Molecular modeling has been used to understand tentatively the main factors controlling the different conformations observed with the various metal ions. © Munksgaard 1997. 相似文献
82.
6-取代苯基哒嗪的3位γ-氨基丁酸衍生物的合成及抗惊活性 总被引:1,自引:0,他引:1
GABA的合成类似物是开发新型抗惊剂和抗癫痫药物的新领域。由芳香醛与吗啉、氰化钾反应形成的α-芳基-α-(4-吗啉)乙腈,可对α,β-不饱和腈或酯进行1,4-加成,生成1,4-酮酸型化合物。此物与肼缩合,再经芳构化即得6-芳基-3(2H)哒嗪酮。后者再经氯化后。与GABA缩合,制备3-(N-GABA)-6-芳基哒嗪类及其分子内脱水产物3-(N-丁内酰胺)-6-芳基哒嗪类化合物。本文应用此法合成了17个上述苯代哒嗪的GABA衍生物,并初步测验了它们的抗惊(MES)活性。活性最强的是3-(N-GABA)-6-(2′,4′-二氯苯基)哒嗪(ED50=21.05mg/kg)。 相似文献
83.
Cinolazepam is reduced at the Dropping Mercury Electrode (DME) over the entire pH range in Britton Robinson buffers (BRB) containing 20% DMF as a solubilizer. A well-defined cathodic wave is obtained over the pH range 3-5, which is very suitable for analytical purposes. The wave was characterized as being irreversible, diffusion-controlled and free from adsorption phenomena. In acid buffers, 4 electrons are consumed in the reduction process, while in alkaline buffers the electrode reaction is somewhat complicated. Tablets containing 40 mg cinolazepam were analysed using the polarographic and a developed HPLC method. The results obtained with both methods are in good accordance as revealed by statistical analysis. The details of the complicated mechanism of the reduction process at the DME are still under investigation but elucidated in principle. 相似文献
84.
85.
Andrew KC Lam Ken KH Cheng Rex K Lam Christina FC Lau SY Yau 《Clinical & experimental optometry》1996,79(4):167-172
Myopic crescent, refractive error and axial length were previously investigated in Hong Kong Chinese subjects. The myopic crescent was found to correlate with axial length and myopic refraction. In this study, three groups of Hong Kong Chinese with different degrees of myopia were assessed for optic disc ovalness, refractive error and axial length. The axial length was significantly correlated with the degree of myopia, indicating that the myopia was axial in nature. The regression line shows that 0.44 mm of axial elongation would give about one dioptre of increase in myopia. The elliptical ratio of the optic disc was defined as the maximal disc diameter divided by the minimal disc diameter. All three groups showed an oval disc with vertical axis greater and an increased ovalness for the high myopic group with an elliptical ratio from 1.11 in low myopia to 1.29 in high myopia. There is a small amount (about four degrees) of temporal rotation of this vertical oval orientation, which is independent of the amount of myopia. This result shows an association between axial elongation of the globe and optic disc ovalness, in addition to the previously described temporal myopic crescent. Therefore, in myopic subjects, a vertically oval disc may be associated with a myopic refraction rather than glaucoma. 相似文献
86.
E A Gomaa M H Belal M B Ashour 《Bulletin of environmental contamination and toxicology》1979,22(6):717-725
The effect of the insecticide Temik on the persistence of the herbicides Cotoran and Cobex was investigated in cultivated cotton fields. Temik was applied to the soil which had also been treated with Cotoran or Cobex. Residues were determined at 15 day intervals for four months. Temik was found to inhibit the degradation of both compounds as long as it persisted. As Temik disappeared the degradtation of Cotoran and Cobex increased, attaining after the 15th day the rates shown by Cotoran and Cobex when applied in isolation. 相似文献
87.
The utriculo-endolymphatic valve: its functional significance. 总被引:3,自引:0,他引:3
A study was made of the anatomical structure and functional significance of the ultriculo-endolymphatic (UE) valve in man. The material consists of 170 human temporal bones of which 75 were chosen to show normal structure through nine decades of life, 29 with endolymphatic hydrops, 22 with developmental defects and 44 with pertinent staining characteristics of the endolymphatic fluid. The studies show that the UE valve is ideally suited to preserve the humoral and anatomical features of the pars superior (utricle and canals) from the developmental, disease, and traumatic susceptibilities of the pars inferior (cochlear duct and saccule). Its function probably is to permit the occasional egress of excessive accumulation of endolymph to be processed in the endolymphatic sac and to accomplish this while preserving the normal endolymph volume and membrane anatomy of the utricle and canals. 相似文献
88.
89.
A simple and sensitive spectrophotometric method is described for the assay of naphazoline, clemizole, penicillin G sodium, and piperazine. The method was based on the formation of a charge transfer complex between these drugs as n-donors and chloranil, the pi-acceptor. Conformity to Beer's law enabled the assay of dosage forms of these drugs. Compared with official methods, the results obtained were of equal accuracy. A more detailed investigation of th naphazoline-chloranil complex was made with respect to its composition, association constant, and free energy change. 相似文献
90.
Inhibition of calcineurin phosphatase activity in adult bone marrow transplant patients treated with cyclosporine A 总被引:2,自引:1,他引:1
Pai SY; Fruman DA; Leong T; Neuberg D; Rosano TG; McGarigle C; Antin JH; Bierer BE 《Blood》1994,84(11):3974-3979
In vitro studies have demonstrated that cyclosporine A (CsA) acts by inhibiting the phosphatase activity of calcineurin, an important mediator of T-cell activation. The relationship of CsA administration in vivo, calcineurin activity, and graft-versus-host disease (GVHD) has yet to be studied. The calcineurin activities of mononuclear cells isolated from 62 bone marrow transplant recipients and 12 normal volunteers were determined and analyzed with respect to administration of CsA, presence or absence of CsA in plasma, and presence or absence of GVHD. Of 62 patients, 33 were taking CsA and 29 were not. Early posttransplant (< 100 days), the calcineurin activity of patients on CsA was significantly lower than that of patients not on CsA (P = .0004) and than that of normal volunteers (P < .0001). Similarly, late posttransplant (> 100 days), the calcineurin activity of patients taking CsA was inhibited compared with normal volunteers (P < .05). The calcineurin activity of patients with acute GVHD who were taking CsA was lower than that of patients on CsA without acute GVHD matched for time posttransplant (P = .02). Calcineurin activity in patients on CsA with chronic GVHD was similar to those without chronic GVHD on drug. In conclusion, calcineurin activity is significantly suppressed by in vivo administration of CsA. The lower calcineurin activity of patients on CsA with acute GVHD suggests that CsA-resistant GVHD is not the result of inadequate suppression of calcineurin activity. These data suggest that if inhibition of calcineurin is the only physiologic target of CsA administration, simply increasing doses of CsA or treatment with other inhibitors of calcineurin, such as FK506, would not be expected to ameliorate GVHD. 相似文献