月腺大戟根中乙酰基间苯三酚衍生物

从月腺大戟（Euphorbia ebracteolata Hayata)根中分离出一种新的二苯甲烷化合物－双去甲基伪绵马素－AA和2,4－二羟基－6－甲氧基－3－甲基苯乙酮,并用光谱和化学方法确定前者的结构为3,3－二乙酰基－4,4－二甲氧基－2。25,6－四羟基二苯甲烷     

6_m2细胞转化与肌醇磷脂代谢相关性研究

肌醇磷脂代谢与V-mos癌基因转化细胞的相关性,迄今为止未见报导。本文用6m2细胞(Moloney鼠类肉瘤病毒(含V-mos)温度敏感突变株(MoMuSVts110)转化的NRK细胞)为模型,探讨了肌醇磷脂代谢与细胞转化的相关性。在33℃ (转化型温度)时,细胞内PIP(磷脂酰肌醇-4-磷酸)含量明显高于39℃(正常型温度),显示出转化型6m2细胞中存在一个提高的PI激酶活性。同时可见DG(二酰甘油)和IP_3(肌醇三磷酸)含量和蛋白激酶C(PKC)活性均明显高于正常型细胞。当细胞由39℃转至33℃10min,PIP、DG、IP_3含量和PKC活性均明显增加,并伴随有PKC活性由胞质向质膜上的转移。实验结果表明肌醇磷脂代谢参与了6m2细胞转化过程。文中对其作用机理进行了讨论。     

寡聚脱氧核苷酸d(G-C)_3的激光喇曼谱及其分析

用改进的固相磷酰三酯法合成了oligo-d(G-C)_3。以氩离子激光为激发光源,波长488nm.,在室温条件下,分别测定了纯化后的oligo-d(G-C)_3和其组分单体5’-dGMP和5’-dCMP的激光喇曼谱。观察到被测定的物质在300-2500cm~(-1)频率区间,各自都有其特征的谱形和喇曼峰。5’-dGMP和5’-dCMP谱中大多数特征峰在寡聚体的谱中消失,而在oligo-d(G-C)_3谱中出现了几处新的喇曼峰。经查证,峰832,851和899cm~(-1)系糖-磷酸主链的特征喇曼峰,另外几处峰与DNA的构象有关。实验结果表明oligo-d(G-C)_3在水溶液中(室温)主要以B-构象存在。     

人白血病细胞癌性促凝物(CP)的分离纯化及其特性的初步研究

用三步纯化法从人M_3型白血病细胞中分离纯化出人类肿瘤癌性促凝物(CP)。促凝活性回收率为24％,CP纯化倍数为2481倍。纯化CP在SDS-PAGE上为单一区带,其理化和酶学特性类似于动物肿瘤CP,分子量约为70 000,PI为4.8,在FVⅡ缺乏血浆中以及在含有组织因子(TF)抑制剂情况下仍能激活FX。CP促凝活性能被半胱氨酸蛋白酶抑制剂HgCl_2抑制,纯化CP能与抗动物肿瘤CP抗体形成免疫沉淀反应。     

cAMP-Dependent protein kinase inhibits the chloride conductance in apical membrane vesicles of hunman placenta

Summary The role of adenosine 3,5-monophosphate (cAMP) dependent protein kinase (PK-A) on the Cl^– conductance has been studied in the apical membrane vesicles purified from the chorionic villi of human placenta. In order to phosphorylate the cytosolic side of the membranes, vesicles have been hypotonically lysed, loaded with 100nm catalytic subunit of PK-A purified from human placenta and 1mm of the phosphatase resistant adenosine 5-thiotriphosphate (ATP-gamma-S) and resealed. Cl^– conductance has been measured by the quenching of the fluorescent probe 6-methoxy-N-(3-sulfopropyl) quinolinium (SPQ) at 23°C with membrane potential clamped at 0 mV. The actual volume of the resealed vesicles was measured in each experiment by trapping an impermeable radioactive molecule ([¹⁴C]-sucrose) and included in each Cl^– flux calculation. In 19 independent experiments, the mean Cl^– conductance in placental membranes in the absence of phosphorylation was 3.67±3.18 whereas with the addition of PK-A and ATP-gamma-S it was 1.97±1.75 nmol·sec^–1·(mg protein)^–1 (mean±sd). PK-A dependent phosphorylation reduced the Cl^– conductance in 14/19 experiments. The same protocol applied to the apical membranes of bovine trachea, where PK-A is known to activate the Cl^– channels, confirmed that the PK-A dependent phosphorylation increased the Cl^– conductance in 11/13 experiments, from 1.01±0.61 to 1.85±0.99 nmol·sec^–1·(mg protein)^–1(mean±sd). These studies indicate that the PK-A dependent phosphorylation inhibits one or more Cl^– channel(s) of the apical membranes of human placenta.     

Protein extraction by reverse micelles: a study of the factors affecting the forward and backward transfer of alpha-chymotrypsin and its activity

alpha-chymotrypsin is taken as a model protein to investigate three aspects of the protein extraction by reverse micelles: (1) the comparison between the two forward transfer techniques, i.e., the liquid-liquid and the solid state-liquid transfer; (2)the back-transfer, i.e., the capability of the protein to be recovered from the micellar solution; and (3) the maintainance of the enzyme activity at the end of the extraction cycle. Concerning the forward transfer from the liquid phase, we study first the effect of salt initially present in the aqueous phase on the equilibrium concentration of the extracted species; further, we study the forward protein extraction from the solid state, and the effect of pH, salt, and protein concentration on the transfer efficiency. Concerning the back transfer, we find the somewhat surprising result, that the percentage of protein back-extraction depends on the type and concentration of salt used for the forward transfer. Preliminary data concerning an alternative method for the back-transfer using silica gel to liberate the protein from the micellar environment, are presented. Finally, it is found that the enzyme activity depends again on the type and concentration of salt used for the forward transfer.     

Tunicamycin inhibits the initiation of DNA synthesis stimulated by prostaglandin F2α in Swiss mouse 3T3 cells

Tunicamycin, an inhibitor of the asparagine-linked protein N-glycosylation, blocks the initiation of DNA synthesis in Swiss 3T3 cells stimulated by prostaglandin F_2α alone or with insulin. This effect is exerted only when tunicamycin is added from 0 to 8 h after stimulation and it decreases the rate of entry into S phase. Blocking of labeled sugar incorporation to proteins occurs regardless of the time of PGF_2α stimulation. In contrast tunicamicin does not inhibit protein synthesis. These results suggest that N-glycoprotein synthesis early during the prereplicative phase is an important event controlling the mitogenic action of PGF_2α     

Electron microscopic and biochemical evidence that proline-β-naphthylamidase is composed of three identical subunits

Electron microscopy of pig intestinal proline-β-naphthyltamidase revealed that the enzyme is composed of 3 subunits, which are assembled in a trifoliolate shape, At pH 4.5 and 4°C, the enzyme dissociates reversibly into active subunits in 4h. Dissociation also occurs at higher pHs when the enyzme concentration is very low. The activity per mg protein of the native, trimeric enzyme is about 2.5-fold higher than that of the dissociated enzyme.