Preliminary crystallographic studies of lobster D-glyceraldehyde-3-phosphate dehydrogenase and the modified enzyme carrying the fluorescent derivative

When the active-site carboxymethylated D-glyceraldehyde-3-phosphate dehydrogenase is irradiated with ultraviolet light in the presence of NAD+, a fluorescent NAD derivative that is covalently linked to the enzyme is obtained. A preliminary crystallographic study of this fluorescent derivative, as well as of the native and the carboxymethylated enzymes from Palinurus versicolor, showed that they are isomorphous and belong to space group C2 as reported for the native enzyme from Palinurus vulgaris. The three forms of the enzyme, although they have identical unit cell parameters, differ considerably in their diffraction patterns, indicating marked differences in conformation in spite of the fact that they differ chemically only in a restricted region around the active site.     

Cloning and Expression of a 5-Hydroxytryptamine7 Receptor Positively Coupled to Adenylyl Cyclase

Abstract: In a number of different cell types, phosphorylation of a 63-kDa protein has been shown to increase rapidly in response to stimuli that lead to an increase in intracellular calcium. Here, a stimulus-sensitive protein at this molecular weight is identified in PC12 cells and rat cortical synaptosomes as phosphoglucomutase. In addition, the added phosphate is shown to be in an oligosaccharide terminating in phosphodiester-linked glucose. In synaptosomes, incorporated radioactivity, following incubation with [¹⁴C]glucose or the [β-³⁵S]phosphorothioate analogue of UDP-glucose, was found to increase within 5 s of stimulation and return to baseline within 25 s. Despite the many pathways utilizing glucose, this was the only detectable protein glycosylation observed in synaptosomes. These results indicate that cytoplasmic glycosylation is reversible and rapidly regulated, and suggest that phosphoglucomutase undergoes an alteration in function and/or topography in response to increases in intracellular calcium.     

几种常用杀虫剂对蚜虫天敌——瓢虫的影响

作者等就11种常用杀虫剂对蚜虫的重要天敌——瓢虫进行了毒性测定,观察了它们对瓢虫的各个虫态的影响。 供试药剂 20％乐果乳剂、50％敌敌畏乳剂、50％对硫磷乳剂、50％内吸磷乳剂、25％三硫磷乳剂、50％杀螟硫磷乳剂、50％磷胺液剂、20％酚开普敦乳剂、6％丙体六六六乳剂、6％丙体六六六可湿性粉(W、P)、2.5％鱼籐精乳剂。 供试瓢虫 异色瓢虫Leis axyridis,室内饲养;龟纹瓢虫Propylaea japonica,田间采回。     

The insulin A and B chains contain sufficient structural information to form the native molecule

Refolding studies show that native insulin can be reformed from A and B chains only. This suggests that the A and B chains contain the necessary structural information and that the C peptide is not required for this process.     

3-磷酸甘油醛脱氢酶胍变性时的活力及构象变化

酵母3-磷酸甘油醛脱氢酶在盐酸胍溶液中的内源荧光及剩余活力的变化结果提示:apo酶及holo酶的活力在胍浓度为0.5M左右可完全丧失.同时伴有内源荧光强度的下降,光谱宽度的增加和335nm最大发射峰的红移(提示了色氨酸残基的暴露).与已经报导的肌肉酶(内源荧光强度在胍浓度为0.4—1.2M范围相对稳定)不同,酵母酶内源荧光在此浓度范围内表现为逐渐降低.在0.7M胍溶液中,内源荧光变化动力学过程只能测出一相,而酶失活动力学过程为快慢两相,快相动力学速度常数至少大于内源荧光降低速度常数三个数量级以上.以上结果提示:低浓度胍可引起该酶的完全失活,活性部位的空间构象比酶分子的构象更易受到变性剂的扰乱;有一个色氨酸残基位于或靠近酶的活性部位.     

Preparation, properties, and uses of two fluorogenic substrates for the detection of 5'-(venom) and 3'-(spleen) nucleotide phosphodiesterases

A new method for ³H-labeling of native collagen and a specific microassay for collagenase activity are presented. Acid-soluble type I collagen derived from rat tail tendons was reacted with pyridoxal phosphate and then reduced with NaB³H₄ to yield [³H]collagen with a specific activity of more than 10 μCi/mg. With respect to rate of hydrolysis, trypsin susceptibility, and gelling properties this collagen compares favorably with biosynthetically labeled preparations. It was shown that chemical labeling procedures such as this, or N-acetylation with acetic anhydride, do not adversely affect properties of collagen which are important for its use as substrate in specific assays. The microassay employs 50-μl [³H]collagen gels (1 mg/ml) dispensed in microtest plates. At 36°C this assay combines rapid rate of hydrolysis with low trypsin susceptibility. As little as 1 ng of clostridial collagenase activity can be measured reproducibly. The high specific activity of the [³H]collagen allowed us to explore microassay conditions employing minute quantities of substrate in solution. These studies indicated that native type I collagen whether labeled or not, is cleaved in the helical region by trypsin at subdenaturation temperatures. It was concluded that, in order to remain specific, collagenase assays with collagen in solution as with collagen in fibrils must be performed at 10–12°C below the denaturation temperature, i.e., at 35–37°C with collagen gels and 27–29°C with collagen in solution.     

A fluorogenic method for the demonstration of human serum 5′-nucleotide phosphodiesterase isozymes after polyacrylamide gel electrophoresis

A rapid fluorogenic method for the demonstration of 5′-nucleotide phosphodiesterase in human serum has been developed. This method uses the substrate 4-methylumbelliferyl 5′-thymidylate impregnated in agarose gels or filter paper strips. Zymograms are developed in less than 30 min at 25°C, and the sensitivity of this method has been compared with that of the indigogenic method.     

On the chemical basis of chromosome banding patterns.

A comparative study of the staining characteristics of four reagents for human chromosomes has been carried out. The four reagents are: (I) quinacrine mustard, as an alkylating agent, (II) the dihydroxy derivative of quinacrine mustard, (III) quinacrine, and (IV) 9-amino-6-chloro-2-methoxyacridine. The last reagent does not possess the amino substituted side chain even though it has the same intercalating nucleus. Comparison of the first three compounds in their staining and banding behavior suggested the initial step leading to banding may be the displacement of the nucleoprotein sites in hcromosomes. The Q and G banding could be blocked experimentally by treating the chromosome preparation with dimethylamine solution. This result may suggest that these sites have weaker basic proteins (nonhistone proteins?). The use of compound IV, which does not have the side chain in the molecule but does have the same intercalating chromophore, did not lead to banding and gives indirect support to this hypothesis. A combined use of compound IV and quinacrine may be useful for the determination of total DNA vs. banding DNA.