Stability enhancement and circular dichroism spectral anomaly as an indication of non-covalent interactions in histidine- and tyrosine-containing ternary copper(II)—amino acid systems

Visible absorption and CD spectral and potentiometric studies on the His- and Tyr-containing ternary copper(II) complexes Cu(A)(L-B), where A refers to L-His, D-His, or L-Tyr and B to Lys, Tyr, Trp, Phe, Ala, Val, Arg, Glu, Asn, Gln, Ser, or Thr, were made to study ligand-ligand interactions in the complexes. While the CD spectral magnitudes in the d—d region are additive in the absence of side chain interactions and can be estimated from the magnitudes for the ternary systems involving DL-A or DL-B, deviation from the additivity was observed for Cu(L-His)(L-B) (B = LysH, Tyr, Trp, or Phe) and Cu(L-Tyr)(L-Trp). From the stability constants determined at 25 °C and I = 0.1 M (KNO₃), the equilibrium constants, K, for the following hypothetical equilibria were calculated to be large (0.14–0.60) for formation of Cu(L-/D-His)(L-B)(B = Tyr or Trp) and Cu(D-His)(L-Phe) with Cu(en)(L-Ala) as standard: $Cu(A)(L?Ala)+Cu(en)(L?b)\stackrel{K}{?}Cu(A)(L?B)+Cu(en)(L?Ala)$ The positive values indicate the stabilization due to the stacking between the imidazole ring of His and the aromatic side chain of L-B. Solvent dependence of the CD spectra for Cu(L-His)(L-LysH) and Cu(L-His) L-Trp) further supported the existence of the intramolecular electrostatic and hydrophobic interactions.     

Decreased Cerebrospinal Fluid Glutamine Levels in Patients with Benign Brain Tumors

Abstract: CSF glutamine concentrations were studied in 12 patients with benign brain tumors (meningioma, craniopharyngioma, or osteofibroma), 12 patients with malignant brain tumors (astrocytoma, medulloblastoma, pinealoblastoma, or chondrosarcoma), 9 patients with non-cerebral tumors, and a reference group of 24 patients. The mean ± SD levels in the benign tumor group (424 ± 124 μ M ) were significantly lower (p < 0.0004) than those in the reference group (642 ± 195 μ M ). There was no significant difference between the CSF glutamine concentrations in the malignant cerebral tumor group (643 ± 210 μ M ) or noncerebral tumor group (599 ± 127 μ M ) and those in the reference group. In patients with benign brain tumors there was indication of an inverse linear relationship between the logarithm of CSF glutamine concentration and tumor diameter.     

Development of a high-frequency transforming vector for Aspergillus nidulans

The pyr4 gene of Neurospora crassa, which codes for orotidine-5'-phosphate decarboxylase, is capable of transforming an Aspergillus nidulans pyrG mutant by chromosomal integration, despite low homology between the transforming DNA and the recipient genome. Integration of pFB6, a plasmid carrying pyr4 and capable of replication in Escherichia coli, was not observed at the pyrG locus. The efficiency of transformation was considerably enhanced (50-100 fold) by inclusion in the transforming vector of a 3.5-kb A.nidulans chromosomal sequence, ans1. Although this sequence was isolated on the basis of replicating activity in Saccharomyces cerevisiae, there was no evidence for such activity in A.nidulans. Part of the ans1 fragment appears to be reiterated in the A.nidulans genome, though it is not yet clear whether this is directly responsible for the high transformation frequency. The efficiency of transformation of A.nidulans by plasmids bearing ans1, using an improved protocol, was approx. 5 X 10(3) stable transformants per microgram of plasmid DNA.     

菠萝叶膜脂脂肪酸组成的温度效应及其与抗寒性的关系

生长在不同季节的菠萝叶膜脂脂肪酸的配比存在着明显差异;随着大气温度的下降,18:1含量显著减少,18:2和18:3含量增加。不同品种均表现出一致的变化趋势。致害低温破坏了膜脂,使较不抗寒品种的16:0含量增加,18:2和18:3含量减少;较抗寒品种这种变化则较不显著。适当低温锻炼能改变膜脂脂肪酸的代谢过程,16:0和18:1含量减少,18:3含量增加。当处于更低温度时,除了16:0和18:1继续减少外,有一部分18:2也脱饱和而转变为18:3。因之明显地增加了膜脂中18:3的含量和脂肪酸的不饱和度,从而有利于抗寒性的提高。而品种间的抗寒性差异亦是在此低温期间表现出来。     

Calcium compartments and fluxes are affected by the src gene product of Rat-1 cells transformed by temperature-sensitive Rous sarcoma virus

Total cellular calcium content (determined by atomic absorption spectrometry) of Rat-1 cells transformed by temperature-sensitive Rous sarcoma virus decreases with cell density, but is found not significantly different at permissive and at non-permissive temperature. Kinetic analysis of 45Ca efflux from preloaded cells exhibits three separable pools of exchangeable calcium. The ratio of pool size of the fast-exchanging Ca-compartment (bound to cell surface) to pool size of the intermediate Ca-compartment (cytoplasmic) was found to decrease from 2.5 to 1.3 upon shift from non-permissive to permissive temperature. The slowly exchanging Ca-pool (presumably mitochondrial) did not change significantly upon temperature shift. These and further data demonstrate a close correlation between distribution of cellular Ca among different cellular compartments and characteristics of cellular proliferation, both attributable to the function(s) of a single oncogene.     

广谱肾综合征出血热病毒单克隆抗体的A35的生物学性状

具有中和及血凝抑制活性的、能和世界各地分离到的肾综合征出血热病毒(HFRSV)发生反应的、广谱的单克隆抗体(McAb),对HFRSV的诊断和分子生物学研究都有重要意义。 本文着重比较了HFRSV McAbA5、A19、A25-1、A25-7和A35的生物学性状,并观察了对感染动物的实验治疗效果。     

似鳡属的系统地位及种的分化(鲤形目:鲤科)

似鳡属(Luciocyprinus Vaillant)是鲤科鱼类中属于鲃系(陈湘粦等,1984)的一个属,下咽齿3行,臀鳍无硬刺,具分枝鳍条5根。过去只记载一个种,外形很像鳡鱼,是由于摄食习性相同而导致的趋同现象(林人端,1981),故称似鳡,在广西俗称墨线鳡,云南俗称杆条鱼。分布于西江水系,包括云南中南部的湖泊,与鳡鱼分布于同一水系,但各占一定的水域,互不重叠。 关于似鳡的拉丁名称,惯用Fustis vivus Lin,是林书颜1932年定的新属新种,     

Dependent competing risks: a stochastic process model

Analyses of human mortality data classified according to cause of death frequently are based on competing risk theory. In particular, the times to death for different causes often are assumed to be independent. In this paper, a competing risk model with a weaker assumption of conditional independence of the times to death, given an assumed stochastic covariate process, is developed and applied to cause specific mortality data from the Framingham Heart Study. The results generated under this conditional independence model are compared with analogous results under the standard marginal independence model. Under the assumption that this conditional independence model is valid, the comparison suggests that the standard model overestimates by 4% the effect on life expectancy at age 30 due to the hypothetical elimination of cancer and by 7% the effect for cardiovascular/cerebrovascular disease. By age 80 the overestimates were 11% for cancer and 16% for heart disease. These results suggest the importance of avoiding the marginal independence assumption when appropriate data are available — especially when focusing on mortality at advanced ages.     

Genetic diversity and environmental associations of wild barley,Hordeum spontaneum (Poaceae), in Iran

Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267–0.500, and of genetic diversity,He = 0.134, range = 0.069–0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02–0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted.     

Introduction of a nitrogen-fixing cyanobacterium into tobacco shoot regenerates

Tobacco (Nicotiana tabacum L.) shoots associated with the nitrogen-fixing cyanobacterium Anabaena variabilis Kütz. (ATCC 29413) were regenerated in mixed cultures of tobacco callus and the cyanobacterium. The cyanobacteria were localized inside the tissues as well as on the surface of regenerated shoots, formed heterocysts, and were capable of acetylene reduction.