诺卡氏菌属GS-17耐热茁霉多糖酶的提纯和性质

诺卡氏菌属GS-17(Nocardia sp.GS-17)的耐热茁霉多糖酶(Pullulanase EC.3.2.1.41)的粗酶液经中空纤维柱超滤浓缩、羟基磷灰石柱层析和Pullulan-Sepharose 6B亲和层析,得到凝胶电泳均一的纯酶,比活提高264倍.酶作用最适温度为55℃,最适PH6.2,分子量140000,等电点pI为6.0.该酶水解茁霉多糖、支链淀粉和可溶性淀粉,但不水解糖原.酶在50℃作用于茁霉多糖的米氏常数K_m为0.90mg/ml,最大反应速度V_(max)为57μmol·min~(-1)·mg~(-1).Zn~(2 )、Fe~(3 )、Hg~(2 )、Cu~(2 )、Pb~(2 )和环状糊精对酶有抑制作用,Ca~(2 )对酶有激活作用.经蛋白质侧链化学修饰研究表明,色氨酸残基位于酶的活性位区.该酶是由1129个氨基酸残基组成的单肽链,酶的N末端序列经测定为:Ala-Gly-His-Gly-Pro-Asp-Val-Gln-Asp-Gly-     

EVOLUTIONARY SHIFTS IN THE SPECTRAL PROPERTIES OF SPIDER SILKS

We measured the reflectance properties of unpigmented silks spun by a systematic array of primitive (Deinopoidea) and derived (Araneoidea) aerial, web-spinning spiders, as well as silks spun by Araneomorphae and Mygalomorphae spiders that do not spin aerial webs. Our data show that all of the primitive aerial web spinners produce catching silks with a spectral peak in the ultraviolet (UV), and cladistic analysis suggests that high UV reflection is the primitive character state for silk spectral properties. In contrast, all of the derived aerial web spinners produce silks that are spectrally flat or characterized by reduced reflectance in the UV. Correlated with the evolution of these catching silks is a 37-fold increase in species number and apparent habitat expansion. This suggests that the unique silk proteins spun by the araneoids have been important to their ecological and evolutionary diversity.     

Effect of gliadins and HMW and LMW subunits of glutenin on dough properties in the F6 recombinant inbred lines from a bread wheat cross

The storage proteins of 64 F₂-derived F₆ recombinant inbred lines (RILs) from the bread wheat cross Prinqual/Marengo were analyzed. Parents differed at four loci: Gli-B1 (coding for gliadins), Glu-B1 (coding for HMW glutenin subunits), Glu-A3/Gli-A1 (coding for LMW glutenin subunits/gliadins) and Glu-D3 (coding for LMW glutenin subunits). The effect of allelic variation at these loci on tenacity, extensibility and dough strength as measured by the Chopin alveograph was determined. Allelic differences at the Glu-B1 locus had a significant effect on only tenacity. None of the allelic differences at either the Glu-A3/Gli-A1 or Glu-D3 loci had a significant effect on quality criteria. Allelic variation at the Gli-B1 locus significantly affected all of the dough properties. Epistatic effects between some of the loci considered contributed significantly to the variation in dough quality. Additive and epistatic effects each accounted for 15% of the variation in tenacity. Epistasis accounted for 15% of the variation in extensibility, whereas additive effects accounted for 4%. Epistasis accounted for 14% of the variation in dough strength, and additivity for 9%. The relative importance of epistatic effects suggest that they should be included in predictive models when breeding for breadmaking quality.     

A 43 kDa protein inserted at the plasma membrane-cytoskeleton interface in rumen entodiniomorphid ciliates

Summary The P-43 ofEudiplodinium and homologous proteins in three other entodiniomorphid species, free-living ciliates, flagellates, and HeLa cells, were identified at the plasma membrane-cytoskeleton interface. Proteins cross-reacting with MAb B6 were also located at the ciliary inner surface of the plasma membrane. Due to the strong adhesion of the plasma membrane to the underlying cytoskeleton, classical extraction with detergents, urea, NaOH, and PTA, failed to separate the two components completely. However, the extraction properties of P-43, associated with its membrane-cytoskeleton interactive functions, suggest that this unglycosylated protein may present some analogies with proteins of the intermediate filaments. Their ubiquity and localization suggest that P-43 and MAb B6 crossreacting proteins may not be strictly epiplasmic but could be amphitropic proteins, strongly anchored to both the plasma membrane and the underlying microfilament framework, via protein-protein binding or by direct insertion in the lipid bilayer.Abbreviations BSA bovine serum albumin - Con A concanavalin A - EDTA ethylene diamine tetraacetic acid - EM electron microscopy - IF intermediate filaments - MAb monoclonal antibody - MET 2-mercaptoethanol - MW molecular weight - PAb polyclonal antibody - PBS phosphate buffered saline - PMSF phenylmethylsulfonyl fluoride - PTA phosphotungstic acid - SDS sodiumdodecyl sulfate - TAME Na-p-tosyl-arginine methyl ester - TLCK Na-p-tosyl-lysine chloromethyl ketone     

Hydrodynamic characteristics and equilibrium rigidity of pullulan molecules

The hydrodynamic characteristics of the polysaccharide pullulan (polymaltotriose) in water have been investigated and its molecular characteristics have been determined. Experimental values varied over the following ranges: velocity sedimentation coefficient (S): 0.9 < S < 11.2, translational diffusion coefficient (10⁷ cm² s⁻¹): 1.1 < D < 14.7 and intrinsic viscosity (cm³ g⁻¹): 6.7 < [η] < 164, which corresponds to a change in molecular weight (× 10³) in the range 3.9 < M_SD < 644. On the basis of analysis of the literature and our experimental data, excluded volume effects have been shown to have a prevailing influence on the chain length of these polysaccharides. The equilibrium rigidity and hydrodynamic chain diameter of pullulan were evaluated on the basis of the theory of hydrodynamic properties of a wormlike necklace, taking into account excluded volume effects. At low M (< 30 × 10³) the translation friction data (in contrast to viscometric data) cannot be described in the framework of the theory of linear molecules.     

Protein dynamics: conformational disorder,vibrational coupling and anharmonicity in deoxy-hemoglobin and myoglobin

In this work we study the temperature dependence of the Soret band lineshape of deoxymyoglobin and deoxyhemoglobin, in the range 300–20 K. To fit the measured spectra we use an approach originally proposed by Champion and coworkers (Srajer et al. 1986; Srajer and Champion 1991). The band profile is modelled as a Voigt function that accounts for the coupling with low frequency vibrational modes, whereas the coupling with high frequency modes is responsible for the vibronic structure of the spectra. Moreover, owing to the position of the iron atom out of the mean heme plane, inhomogeneous broadening brings about a non-Gaussian distribution of 0–0 electronic transition frequencies. The reported analysis enables us to isolate the various contributions to the overall bandwidth, and their temperature dependence points out the relevance of low frequency vibrations and of large scale anharmonic motions starting at temperatures higher than 170 K. Information on the mean iron-heme plane distance and on its temperature dependence, as well as on the heme pocket conformational disorder, is also obtained.Abbreviations Cc Carbon monoxide - Hb Human deoxyhemoglobin A - HbCO human carbonmonoxyhemoglobin A - SWMb spermwhale deoxymyoglobin - SWMbCO spermwhale carbonmonoxymyoglobin - HbO₂ human oxyhemoglobin A - SWMb³⁺-H₂O spermwhale aquometmyoglobin     

Soil-eating byAlouatta andAteles

Among 12 species of New World monkeys studied in La Macarena Region and the River Caquetá basin of Colombia, onlyAlouatta seniculus andAteles belzebuth were frequently observed to eat soil. They do this at particular sites on the ground called salados by local people. They also eat termite nests found on tree trunks. OnlyAteles drink the water of salado sites. The chemical properties of 17 soil samples and 5 water samples were analyzed. The results are discussed in relation to the question of whyAlouatta andAteles eat soil.     

菜心溶菌酶的提纯及酶学性质

菜心（ＢｒａｓｓｉｃａｃａｍｐｅｓｔｒｉｓＬ．ｓｓｐ．ｃｈｉｎｅｎｓｉｓｖａｒ．ｕｔｉｌｉｓ）叶子高速捣碎后,滤液经酸碱处理,硫酸铵分步沉淀,凝胶柱层析等步骤分离纯化溶菌酶,酶比活力达３４１４．６Ｕ／ｍｇ,纯化倍数为１９７．４。菜心溶菌酶在较宽的温度或ｐＨ值范围均有活性,最适温度为６０℃,最适ｐＨ值为５．８,底物Ｋｍ值为８７μｇ／ｍＬ。该酶对热和酸碱的稳定性较高,巯基和酪氨酸残基不是该酶活性中心的必需基团。