On the two forms of bacteriorhodopsin

In our previous work [(1993) FEBS Lett. 313, 248-250; (1993) Biochem. Int. 30,461-469] M-intermediate formation of wild-type bacteriorhodopsin was shown to involve two components differing in time constants (τ₁ = 60–70 μs and τ₂ = 220–250 μs), which were suggested to reflect two independent pathways of M-intermediate formation. The contribution of the fast M was 4-times higher than the slow one. Our present research on M-intermediate formation in the D115N bacteriorhodopsin mutant revealed the same components but at a contribution ratio of 1:1. Upon lowering the pH, the slow phase of M-formation vanished at a pK of 6.2, and in the pH region 3.0–5.5 only the M-intermediate with a rise time of 60 μs was present. A 5–6 h incubation of D115N bacteriorhodopsin at pH 10.6 resulted in the irreversible transformation of 50% of the protein into a form with a difference absorbance maximum at 460 nm. This form was stable at pH 7.5 and had no photocycle, including M-intermediate formation. The remaining bacteriorhodopsin contained 100% fast M-intermediate. The disappearance of the 250-μs phase concomitant with bR460 formation indicates that at neutral pH bacteriorhodopsin exists as two spectroscopically indistinguishable forms.     

Four fish species new to the Omo-Turkana basin,with comments on the distribution ofNemacheilus abyssinicus (Cypriniformes: Balitoridae) in Ethiopia

Four fish species,Pollimyrus isidori (Mormyridae),Barbus paludinosus, Labeo forskalii (Cyprinidae), andNemacheilus abyssinicus (Balitoridae), new to the Omo-Turkana basin, were recorded from the Gojeb River, a tributary of the Omo River (south-western Ethiopia). Occurrence of the latter species in the upper reaches of the Blue Nile and of the Omo drainage substantiates the belonging of the upper parts of these water systems to the Abyssinian highlands ichthyofaunal province.     

The dynamics of continuous microbial culture described by cell age distribution and concentration of one substrate

A mathematical model has been considered in which the known equation of McKendrick and Von Foerster for cell age distribution is combined with that for substrate concentration. The dependence of cell division rate on cell age has been taken as a step function. The interrelation between culture parameters describing the substrate consumption and cell division has been found. The shape of cell age distribution as well as the values of substrate and cell concentrations in steady and transient states have been investigated. Stationary regimes at the initial culture state synchronized by ages have been found to be established as damped oscillations and age waves. Under definite conditions the transition from one steady growth regime to another includes sharp single-time age synchronization of the culture.     

大鼠肝癌中α_2-巨球蛋白等几种分泌性蛋白基因表达的变化

用Northern blot方法对二乙基亚硝胺所诱发的大鼠肝癌中内源性蛋白酶抑制因子α_2-巨球蛋白(α_2-M)、非特异性免疫抑制剂α_1-酸性糖蛋白(α_1-AGP)及雄性激素正调控的α-2u球蛋白(α-2u)三种分泌性蛋白基因表达情况进行了分析。结果表明在大部分(14/16)肝癌样品中α_2-M RNA水平显著降低;而α_1-AGP RNA水平显著高于正常对照水平;α-2u RNA水平明显下降,但在某些雄性大鼠肝癌样品中该基因却有一定程度的表达。这些结果说明,一些肿瘤宿主血浆中α_2-M水平的显著下降及α_1-AGP水平的明显升高分别是由于基因表达活性的下降及升高所致。α-2u基因表达的异常提示,在癌变过程中机体的内分泌功能发生了某些变化。     

Natural history of small mammals of subtropical montane areas in central Taiwan

Based on samples collected in 1989–90, I report on several aspects of the natural history of species of small mammals from seasonal montane areas in subtropical central Taiwan, including their reproduction, demography, sex ratio and body size. The climatic seasonality in the areas is striking. The wet season lasts from May through September and the dry season from October through April. The phenology of plant life is related to this seasonality: vegetative growth occurs primarily in the wet season, but fruit and seed production is concentrated in the dry season. Variation in the reproduction and demography are analysed between the wet and the dry season for six species, Apodemus semotus, Niviventer culturatus. Eothenomys melanogaster, Microtus Kikuchii, Anourosorex syuamipes and Soriculus fumidus . Two murid rodents. A semotus and N. culturatus. are capable of breeding year-round, whereas the microtine rodents, E. melanogaster and M. Kikuchii , have discrete breeding seasons. The shrews, A. squamipes and S. fumidus are both seasonal breeders. but they differ in the timing of their breeding cycles. While S. fumidus breeds primarily in the late dry season, A. syuamipes reproduces in the wet season. Finally, seasonal variation in reproduction is discussed in relation to phylogenetic and physio-ecological characteristics of these six species.     

Cloning, sequence analysis and expression of gene alyVI encoding alginate lyase from marine bacterium Vibrio sp. QY101.

The gene (alyVI) encoding an alginate lyase of marine bacterium Vibrio sp. QY101, which was isolated from a decaying thallus of Laminaria, was cloned using a strategy of combined degenerate PCR and long range-inverse PCR (LR-IPCR), then sequenced and expressed in Escherichia coli. Gene alyVI was composed of a 1014 bp open reading frame (ORF) encoding 338 amino acid residues. The calculated molecular mass of alyVI product is 38.4 kDa, but a signal peptide is cleaved off, leaving a mature protein of 34 kDa. AlyVI was purified from culture supernatants to electrophoretic homogeneity using affinity chromatography. AlyVI was most active at pH 7.5 and 40 degrees C in the presence of 1 mM ZnCl2. A nine-amino-acid consensus region (YXRESLREM), which was only found in polyguluronate lyases, was also observed in the amino-terminal region of AlyVI. However, AlyVI could degrade both M block and G block. These results indicate that a novel alginate lyase-encoding gene has been cloned.     

Solid-phase synthesis of triple-helical collagen-model peptides

Summary The triple-helical conformation of collagen has been proposed to be important for mediation of cellular activities, such as adhesion and activation, extracellular matrix assembly, and enzyme function. We have developed synthetic protocols that allow for the study of biological activities of specific collagen sequences in triple-helical conformation. These methods primarily involve solid-phase assembly and covalent linkage of three peptide chains. The resultant triple-helical peptides have sufficient thermal stabilities to permit structural and biological characterization under physiological conditions. The present article critically reviews the various approaches for constructing synthetic triple-helices.This paper is based on a presentation given at the Symposium on Peptide Structure and Design as part of the 31st Annual ACS Western Regional Meeting held in San Diego, CA, USA, October 18–21, 1995.     

马桑内酯对培养的海马神经元γ-氨基丁酸和谷氨酸的影响——免疫细胞化学研究

用免疫细胞化学方法,观察研究了马桑内酯(CL)对培养的海马神经元内γ-氨基丁酸(GABA)和谷氨酸(Glu)神经元的影响.结果表明:CL作用后,GABA免疫反应阳性神经元数目减少,反应强度减弱;Glu免疫反应阳性神经元数目变化不明显,但反应增强.推测:CL可能引起海马神经元兴奋性增高是使动物模型致痫的基础,其机理可能与阻断GABA的合成途径有关.     

Genetic variation at storage protein-coding loci of common wheat (cv ‘Chinese Spring’) induced by nitrosoethylurea and by the cultivation of immature embryos in vitro

Electrophoretic patterns of seed storage proteins, the high-molecular-weight glutenins and gliadins, were studied in 468 plants of the common wheat cultivar Chinese Spring regenerated from callus culture of immature embryos, in 115 plants grown from seeds treated with nitrosoethylurea and in 260 control plants. From 5 to 21 single grains were analysed from each plant. In these three groups, the frequency of inherited mutations causing the loss of all proteins controlled by a locus (null-mutations, probably caused by a chromosomal deficiency) was 0.69%, 2.07%, and 0.05% per locus (the differences were statistically significant), respectively, while that of mutations causing the loss of a single protein band was 0.11%, 0.33%, and 0.05%, respectively. The loss of all of the gliadins controlled by Gli-B1 or GH-B2 (mutations were probably caused by a deletion of satellites of the corresponding chromosomes), was significantly higher than the loss of gliadins controlled by genomes A and D. Gene mutations altering the electrophoretic mobility of a single protein band in the pattern were found only in the second group of plants (0.44%). Therefore, chemical mutagenesis which produced not only more mutations than cultivation of immature wheat embryos in vitro, but also a higher ratio of mutations that altered DNA sequences, can be considered as an easier and comparatively more promising way for obtaining new improved variants of loci controlling biochemical characteristics in wheat. Somaclonal variation, on the other hand, was probably mainly caused by chromosomal abnormalities and could therefore hardly be considered as a useful tool in wheat breeding.