盐酸胍诱导的α淀粉酶去折叠与再折叠

利用蛋白质内源荧光和酶活性两种信号以及荧光偏振,HPLC和停流等方法研究了盐酸胍诱导的α淀粉酶去折叠与重折叠的平衡转变和动力学。实验结果表明α淀粉酶去折叠与重折叠是两个不同的过程;变性与复性过程中可能伴有聚集体生成;去折叠与重折叠均为双相过程,重折叠大约始于2秒之后。     

A New Antiroll Device for Cryostat Wax Sectioning

A new antiroll device has been developed to replace the antiroll guide plate for cryostat wax sectioning. With this device, a continuous ribbon of 3-4 μm sections can be obtained. The sections are flat, uncreased. and compression is reduced to a minimum.     

Influence of the route of administration on the pharmacokinetics of pirprofen enantiomers in the rat

The pharmacokinetics of the enantiomers of the non-steroidal anti-inflammatory drug pirprofen were studied in male Sprague-Dawley rats after oral and intravenous (iv) doses of the racemate. No significant differences were detected between the enantiomers after oral or iv dosing in t_½, Vd, or ∑Xu. However, the R:S area under the plasma concentration (AUC) ratio after oral doses (0.92 ± 0.13) was slightly but significantly lower than after matching iv doses (1.05 ± 0.036). The absolute bioavailability of the active S-enantiomer (78.5%) after oral doses was higher than the inactive R-enantiomer (69.3%). The plasma protein binding of both enantiomers was saturable over a fivefold range of plasma concentrations. At higher plasma concentrations, the S-enantiomer was less bound than the R-enantiomer. In an in vitro experiment using everted rat jejunum, no chiral inversion was discernible. The dependency of the AUC ratio of the enantiomers on the route of administration may be due to stereoselective first-pass metabolism. © 1993 Wiley-Liss, Inc.     

Sub-Cellular Distribution of Zinc in Different Vegetative Organs and Their Contribution to Grains Zinc Accumulation in Rice Under Different Nitrogen and Zinc Supply

Journal of Plant Growth Regulation - Zinc is an important micronutrient for the growth and development of human body and plants. Proper use of nitrogen fertilizer and foliar application of Zn have...     

Research Progress on Anti-Inflammatory Mechanisms of Black Ginseng

In recent years, black ginseng, a new type of processed ginseng product, has attracted the attention of scholars globally. Ginsenoside and ginseng polysaccharide, the main active substances of black ginseng, have been shown to carry curative effects for many diseases. This article focuses on the mechanism of their action in anti-inflammatory response, which is mainly divided into three aspects: activation of immune cells to exert immune regulatory response; participation in inflammatory response-related pathways and regulation of the expression level of inflammatory factors; effect on the metabolic activity of intestinal flora. This study identifies active anti-inflammatory components and an action mechanism of black ginseng showing multi-component, multi-target, and multi-channel characteristics, providing ideas and a basis for a follow-up in-depth study of its specific mechanism.     

Effect of exogenous gibberellin A4/7 on tracheid production, longitudinal growth and the levels of indole‐3‐acetic acid and gibberellins A4, A7 and A9 in the terminal shoot of Pinus sylvestris seedlings

Synchronously dividing cultures of the unicellular green alga Scenedesmus obtusiusculus were cultivated for 24 or 70 h in medium high (1000 μM) or low (60 μM) in phosphorus. Aliquots of AlCl₃ (0, 37, 74, 111, 148, 185, or 222 μmol) were added daily to 1 l cell suspension at the end of the cell division phase. Algae were also grown in media with different pH, adjusted with HCl, in the absence of AlCl₃.
Effects of Al on cell metabolism vary with the intracellular Al concentration and with the concentration of Al available per cell. When the concentration of phosphorus is low, internal concentrations of Al are high and the chlorophyll content and the net dry matter production per cell increase, whereas the photosynthesis and the cell division are increased. Presence of Al in a low P medium decreases the pH of the medium down to 4.5. There are only small effects of Al in the presence of P, due to precipitation of most of the Al with P in the medium.
Despite the Al-induced decrease of the pH of the culture medium, effects caused by Al cannot be explained as a pH effect. Instead, the Al effect may, at least to some extent, be related to a decrease in availability of P in the metabolism, due to formation of aluminium phosphate inside the cell.     

The CD95 (Fas/APO-1) receptor is phosphorylatedin vitro andin vivo and constitutively associates with several cellular proteins

Different CD95 (Fas/APO-1) isoforms and phosphory lated CD95 species were identified in human T and B cell lines. We had shown previously that the CD95 intracellular domain (IC), expressed as a glutathione S-transferase (GST) fusion protein in murine L929 fibroblasts, was phosphorylatedin vivo. GST-CD95IC was phosphorylatedin vitro by a kinase present in extracts from the human lymphocytic cell lines Jurkat and MP-1 and from murine L929 cells. Phosphoamino acid analysis indicated that phosphorylation occurred at multiple threonine residues and also at tyrosine (Tyr232 and Tyr291) and serine. Amino acids 191 to 275 of CD95 were sufficient for phosphorylation at threonine, tyrosine and serine and also mediated interaction with a 35 kDa cellular protein. Immuno-precipitation of CD95 and chemical cross-linking revealed CD95-associated proteins of approximately 35, 45 and 75 kDa. GST-CD95IC affinity chromatography detected binding of the 35 and 75 kDa protein species. The 75 kDa species may correspond to the CD95-associated proteins RIP or FAF1 and the 35 kDa protein may represent a TRADD analogue. These data indicate that several cellular proteins interact with CD95, possibly in a multi-protein complex, and that a kinase activity is associated with CD95 not onlyin vitro but alsoin vivo. Therefore, receptor phosphorylation may play a role in CD95 signal transduction. This work was in part supported by a grant from the Health Research Council of New Zealand (to JW).     

矩阵的加号逆理论在参数估计中的应用

本文从矩阵的加号逆理论出发,根据求矛盾线性方程组最佳逼近解的方法,建立起一种新的参数估计方法,同时给出了显著性检验方法,这种方法更简单更精确．     

Ce~（3＋）与G－肌动蛋白结合引起的构象变化及对聚合的影响

用Ａｅｄａｎｓ标记肌动蛋白单体Ｇ－Ａｃｔｉｎ上Ｃｙｓ３７４残基作为探针,研究了稀土离子Ｃｅ~（３＋）与Ｇ－Ａｃｔｉｎ的结合及引起的微构象变化。Ｃｅ~（３＋）在低浓度（Ｃｅ~（３＋）／Ａｃｔｉｎ摩尔比＜１）和Ｃａ~（２＋）竞争Ｇ－Ａｃｔｉｎ上二价离子的高亲合位点。Ｃｅ~（３＋）取代Ｃａ~（２＋）引起Ａｅｄａｎｓ荧光强度增强与Ｍｇ~（２＋）取代Ｃａ~（２＋）的结果相同。Ｃｅ~（３＋）／Ａｃｔｉｎ＞ｌ则导致Ａｅｄａｎｓ荧光强度下降。说明Ｃｅ~（３＋）在高低两种浓度条件下结合的位点及对Ｃｖｓ３７４的微构象的影响不同。时间分辩测得的Ａｅｄａｎｓ荧光寿命也支持这一结论。ＣＤ谱结果表明Ｃｅ~（３＋）／Ａｃｔｉｎ＜０．４,Ａｃｔｉｎ的二级结构增加,大于０．４又导致其失去。Ｃｅ~（３＋）－Ａｃｔｉｎ在有／无游离ＡＴＰ时用聚合液诱导的聚合结果表明,无游离ＡＴＰ时,极低浓度Ｃｅ~（３＋）促进聚合,高浓度虽有促进但有所减弱;有游离ＡＴＰ时,Ｃｅ~（３＋）／Ａｃｔｉｎ在实验范围内促进聚合。     

人胸腺素α原cDNA的克隆及在大肠杆菌中的表达

采用基因工程方法制取人胸腺素α原获得成功。用２０ｕｇ／ｍｌ植物血球凝集素（ＰＨＡ）和５００Ｕ／ｍｌ重组人白细胞介素２（ＩＬ－２）联合刺激人胎儿胸腺细胞,从中提取总ＲＮＡ,经反转录ＰＣＲ获得了人胸腺素α原ｃＤＮＡ;将之克隆入ｐＵＣ１９中,序列测定表明与已报道序列一致,进一步将之亚克隆入原核表达载体ｐＢＶ２２０,转化大肠杆菌ＤＨ５ａ．观察到在不改变氨基酸编码的前提下,增加胸腺素ａ原上游引物中Ａ、Ｔ含量,可以明显提高胸腺素α原的表达量,同时,不同培养基对它的表达也有影响。胸腺素α原在大肠杆菌中以可溶形式表达,不需复性。初步活性测定显示,它可明显刺激人外周血淋巴细胞Ｅ－玫瑰花结形成率。重组人胸腺素α原在大肠杆菌中表达,为其临床应用及基础研究奠定了基础。