The starting point rules and stability of nomenclature

Changes in the rules are contraproductive and in contradiction to the Preamble of the International Code of Botanical Nomenclature (Voss & al. 1983), especially if the consequences are insufficiently researched before binding, basic, retroactive alterations are introduced. The most confusing and upsetting alterations concern those accepted at Sydney with regard to the starting point rule, Art. 13.1 (d). It is recommended that Proposal 42 (Taxon 1984) be accepted at Berlin.     

聚乙二醇修饰的单克隆抗体的某些生物活性

 不久前我们报道了PEG-1900修饰的McAb的某些理化性质,本文主要报道经PEG-1900修饰的McAb在某些生物活性方面的变化。与天然的McAb相比,修饰的McAb有以下的变化:(1)抗原性与免疫原性下降;(2)抗体活性下降;(3)在体内存活的时间延长;(4)对温度及pH的抵抗力增强。修饰的酶与天然的酶相比,酶活性有所下降,但下降的程度要比修饰的McAb小得多。     

Molecular genetics of F1-ATPase fromEscherichia coli

We have reviewed recent molecular biological studies on F₁-ATPase ofEscherichia coli and emphasized the advantages of using the bacterium in studies on this important enzyme. All subunits had homologies of varied degrees with those from other organisms. Mutations of F₁ subunits caused defects in catalysis and assembly. Defects of the mutant enzymes were studied extensively together with the determination of the amino acid substitutions. Extensive molecular biological studies may help greatly in understanding the normal mechanism and assembly of the complex.     

Differences in open state of NBA-modified cardiac Na+ channels

Patch clamp recordings from neonatal cardiac Na⁺ channels treated with N-bromoacetamide (NBA, 5–50 x 10^-mol/l) showed modified Na⁺ channel activity. By chemical removal of inactivation, repetitive openings with an increased life time and burst-like activity occurred. NBA-modified Na⁺ channels differ in life time and may attain either a slightly (mean open time 3.1±0.2 ms) or a strongly (mean open time 15.2±1.4 ms) prolonged open state. This strongly suggests a heterogeneous population of NBA-modified Na⁺ channels in newborn rat cardiocytes.     

Chloroplast thylakoid membrane proteins having buried amine buffering groups

Some chloroplast thylakoid membrane proteins have anomalously low pK_a (near 7.8) amine groups, indicating that the buffering groups may be buried in hydrophobic regions and/or close to other positive charges. Other work has shown that the low pK_a amine group array is not in ready equilibrium with either the inner or outer bulk aqueous phases (Laszlo, J.A., Baker, G.M. and Dilley, R.A. (1984) J. Bioenerg. Biomembranes, 16, 37–51). Acetic anhydride reacts with the neutral amine and has been used as a probe for labeling the low pK_a amines. The buried array of buffering groups can be labeled with [³H]acetic anhydride in the dark only after the membranes were made leaky to protons with uncoupler addition. Sodium dodecyl sulfate/urea-polyacrylamide gel electrophoresis was used to separate the polypeptides and identify those that show the uncoupler-dependent labeling increase. Included in that group are polypeptides known to be associated with Photosystem II having M_r 17000, 22000 and 31000, some of the light-harvesting pigment proteins with M_r 24000–28000, the CF₀ component with M_r 8000 and some polypeptides associated with Photosystem I. A protein with M_r 15000 showed very large changes in labeling, but the identity of this polypeptide is unknown. The arrays of buried amine buffering groups are diversely distributed among membrane proteins and it is not clear what role, if any, they play in membrane function.     

Self-adaptive modification of red-cell membrane lipids in lecithin: Cholesterol acyltransferase deficiency. Lipid analysis and spin labeling

In a patient with lecithin: cholesterol acyltransferase deficiency, free cholesterol was markedly increased, and esterified cholesterol was diminished. In the patient's plasma, an increase in phosphatidylcholine (PC) and a decrease in sphingomyelin were observed. Concomitantly, an increase in a shorter acyl chain 16:0 was noted in PC, sphingomyelin and phosphatidylethanolamine (PE). In contrast to these results, longer chains such as 22:0 and 24:0 were decreased, especially in sphingomyelin. Unsaturated double bonds such as 18:1 was also increased in PC and PE. In the red-cell membrane lipids, the increase in free cholesterol was counteracted by an increase in PC and by a decrease in sphingomyelin and PE, reflecting changes in the patient's plasma lipids. Increased 16:0 (in PC) and decreased 18:0 and 24:0 were observed. The increased plasma free cholesterol due to metabolic defect (lecithin:cholesterol acyltransferase deficiency) led to decreased red-cell membrane fluidity. This effect appeared to be counteracted by changing phospholipid composition (increased PC and decreased sphingomyelin and PE), by increasing shorter chains (16:0), by decreasing longer chains (18:0 and 24:0) and by increasing unsaturated double bonds (18:2). These results can be interpreted as a self-adaptive modification of lecithin:cholesterol acyltransferase deficiency-induced red-cell membrane abnormalities, to maintain normal membrane fluidity. This speculation was supported by the ESR spin-label studies on the patient's membrane lipids. The normal order parameters in intact red cells and in total lipid liposomes were decreased if cholesterol-depleted membrane liposomes were prepared. Thus, the hardening effect of cholesterol appeared to be counteracted by the softening effects described above. Overall membrane fluidity in intact red cells of the lecithin:cholesterol acyltransferase-deficient patient was maintained normally, judged by order parameters in ESR spin-label studies.     

记北京双桥古菱齿象下颌骨上的砍痕现象

1986年7月,北京市第五制药厂在双桥一号机井里打捞出一件古菱齿象下颌骨。承蒙该制药厂污水处理总队负责人杨宝贵、赵宗治两同志将采集的化石标本给我们研究,谨此致谢。回到室内后,在修理过程中,在距右侧颏孔14.2毫米处呈现出一条痕迹,经观察、对比,确认其痕迹系人工所致。但由于其他工作未能将观察结果及时报道,一直拖到     

Light/Dark Modulation: Regulation of Chloroplast Metabolism in a New Light

Light-dark modulation of chloroplast enzymes is achieved by covalent redox-modification of protein thiols/disulfides mediated by ferredoxin/thioredoxin reductase and thioredoxins. Light-dependent electron flow leads to reduction of particular chloroplast proteins, while photosynthetically evolved oxygen effects their continuous reoxidation. The oxidized and the reduced forms, respectively, differ greatly in their catalytic properties. The rate of reduction of each target enzyme is specifically fine-controlled by metabolites. By this combined mode of producing a defined ratio of active to inactive enzyme during steady-state each of the enzymes is adjusted to the immediate requirements of the chloroplast. Upon changes of the metabolic situation the system can respond in a flexible manner as is known from comparable regulatory mechanisms such as protein phosphorylation/dephosphorylation in animals and bacteria. From sequence comparisons between various light-dark modulated chloroplast enzymes and their non-regulated counterparts from other organelles or non-photosynthetic organisms, the presence of extra-peptides in the otherwise highly homologous sequences has been estabüshed for the chloroplast enzymes. However, no general pattern in the primary structure of those extra-sequences can be recognized. By the acquisition of “regulatory peptides” during evolution a new type of metabolic control was created in a compartment uniquely occurring in organisms performing oxygenic photosynthesis.     

Functional characteristics of the cardiac sarcolemmal monocarboxylate transporter

Summary We have previously shown that a mechanism for transportingl-lactate is located in cardiac sarcolemmal membranes (Am. J. Physiol. 252:C483–C489, 1987). This mechanism has now been shown to transport pyruvate also. The transporter recognizes a wide range of monocarboxylic acids with chain lengths of three to six carbons, as evidenced by their ability to inhibitl-lactate uptake into sarcolemmal vesicles. The ability of the monocarboxylate analogues to inhibit depends strongly on the nature of substituents, particularly at the second carbon.l-lactate and pyruvate transport are not affected by dicarboxylates other than oxaloacetate. The transporter is inhibited by the protein modifiers diethylpyrocarbonate, dinitrofluorobenzene, and phenylisothiocyanate. Diethylpyrocarbonate inhibition is not reversed by hydroxylamine, nor is dinitrofluorobenzene inhibition reversed by thiol reagents, suggesting that the target residues are not histidine, or tyrosine or cysteine, respectively. Several monocarboxylates effectively protect the transporter from inhibition by the modifying reagents, suggesting that the modified residue(s) may be at or near the binding site. Alternatively, the target amino acid(s) in the transport protein may become inaccessible due to a conformation change triggered by the substrate analogues. Overall, the results suggest that a sensitive free amino group, associated with substrate binding, is attacked by the protein-modifying reagents.