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101.
Human serum albumin. Spectroscopic studies of binding and proximity relationships for fatty acids and bilirubin. 总被引:14,自引:0,他引:14
Binding and proximity relationships of hydrophobic ligands on human serum albumin have been studied using absorption, fluorescence, circular dichroism, and electron paramagnetic resonance spectroscopy. The ligands studied were bilirubin, two conjugated linear polyene fatty acids, cis-parinaric acid and cis-eleostearic acid, and three nitroxide derivatives of stearic acid with doxyl groups at positions 5, 10, and 12, respectively. Binding of polyene fatty acids was monitored by absorption peak shifts, induced circular dichroism, enhancement of fluorescence, and energy transfer between albumin's single tryptophanyl residue and the polyene chromophore. Induced circular dichroism studies indicate excitonic ligand-ligand interaction between bound fatty acids. Fluorescence enhancement of cis-parinaric acid was analyzed using a stepwise multiple equilibrium model, and six binding constants in the range 10(8) to 10(6) M-1 were obtained, in agreement with previous measurements for other fatty acids. The temperature dependence of the equilibrium constants indicates that the binding enthalpy is nearly zero. Fluorescence energy transfer was similarly used to quantitate bilirubin binding to albumin. Energy transfer, nitroxide quenching of fluorescence, and electron paramagnetic resonance spectroscopy were used to elucidate binding geometries which support and extend proposed structural models for albumin. It is suggested that the first two fatty acids bind side-by-side in an antiparallel fashion in domain III of human serum albumin. 相似文献
102.
Marvin H. Bernstein Inez Sandoval Michael B. Curtis Dennis M. Hudson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1979,129(2):115-118
Summary During heat stress in domestic pigeons (Columba livia, mean mass 0.43 kg) brain temperature (T
B) varied in parallel with colonic temperature (T
c). The difference between these (T
C–T
B=T) averaged 0.7°C and was not significantly altered when the animal breathed through a trachael cannula bypassing the buccopharyngeal cavity. When we sealed the nares and beak in bypass animals, T was significantly reduced but was nevertheless maintained at 0.4°C. When the eyes were sealed as well, however, T was reversed, amounting to –0.4°C. Conversely, with eyes sealed but beak and nares open, T was indistinguishable from that in controls. These results suggest a role for the cornea in evaporative cooling, at least when respiratory evaporation is impaired, and are consistent with the hypothesis that buccopharyngeal and corneal evaporation are coupled to brain cooling. The probable mechanism for this coupling is the flow of venous blood from evaporative surfaces through theretia mirabilia in the temporal areas. Here heat is transferred from the warmer arterial blood flowing through theretia toward the brain to the centrally flowing, cooler venous blood. 相似文献
103.
Rajendra M. Srivastava Norman Hudson Fred R. Seymour Bernard Weissmann 《Carbohydrate research》1978,60(2):315-326
The earlier preparation of cyclohexylammonium (phenyl α-l-idopyranosid)-uronate has been improved, and (4-methylumbelliferyl α-l-idopyranosid)uronic acid (14), a more sensitive substrate for α-l-iduronidase, has been synthesized by an analogous route. Zinc chloride-catalyzed condensation of 4-methylumbelliferone with 1,2,3,4,6-penta-O-acetyl-α-l-idopyranose (4) in 1,2-ethanediol diacetate gave crystalline 4-methylumbelliferyl 2,3,4,6-tetra-O-acetyl-α-l-idopyranoside (7). O-Deacetylation and catalytic oxidation gave 14, characterized as a cyclohexylammonium salt. The starting material 4 was prepared, in 21 % yield from l-glucose, by conversion of the intermediate 1,2,3,4,6-penta-O-acetyl-β-l-glucopyranose to 2,3,4,6-tetra-O-acetyl-β-l-glucopyranosyl chloride and acetoxonium ion rearrangement, as described for the D-series. 相似文献
104.
105.
A new method of in situ hybridization 总被引:27,自引:0,他引:27
Jerry E. Manning N. Davis Hershey Thomas R. Broker Maria Pellegrini Herschel K. Mitchell Norman Davidson 《Chromosoma》1975,53(2):107-117
A new method for gene mapping at the chromosome level using in situ hybridization and scanning electron microscopy is described and has been applied to mapping the rRNA genes of Drosophila melanogaster. Biotin is covalently attached to Drosophila rRNA via a cytochrome c bridge at a ratio of one cytochrome-biotin per 130 nucleotides by a chemical procedure. Polymethacrylate spheres with a diameter of ca. 60 nm are prepared by emulsion polymerization and are covalently attached to the protein avidin at a ratio of 5–20 avidins per sphere. The biotin-labeled rRNA is hybridized to denatured DNA in a chromosome squash. Upon incubation with a sphere solution, some of the biotin sites become labeled with spheres because of the strong non-covalent interaction between biotin and avidin. The chromosome squash is examined in the scanning electron microscope (SEM). Polymer spheres, which are visible in the SEM, are observed to label the nucleolus, where the rRNA genes are located.Contribution number 5121 from the Department of Chemistry. 相似文献
106.
Bovine glomerular basement membrane was extracted with 6 M guanidinium chloride and the soluble material fractionated on a Bio-Gel A-1.5m column in 1% Na dodecyl-SO4. A single component was obtained by reduction of a selected column fraction with 2-mercaptoethanol followed by chromatography on an analytical Bio-Gel A-1.5m column and shown to be homogenous by electrophoresis and ultracentrifugation. It consists of 90% protein and 8.6% carbohydrate by weight. The amino acid composition is characterized by the presence of low amounts of hydroxyproline and hydroxylysine, and substantial amounts of aspartic acid, glutamic acid, half-cystine, and glycine. It contains all the monosaccharide constituents present in the whole basement membrane indicating the presence of both heteropolysaccharide and disaccharide units; the presence of the latter unit was demonstrated unequivocally by ion exchange chromatography. The component contains 1 heteropolysaccharide unit and 4 dissaccharide units/molecule of Mr equals 70,000. The molecular weight of component VII was determined by several methods. Molecular weight values of 68,000 +/- 3,000 and 72,000 +/- 2,000 were determined in 6 M guanidinium chloride by the methods of sedimentation equilibrium and gel filtration chromatography, respectively, and values of 136,000 +/- 3,100 and 140,000 +/- 2,000 were determined in 1% Na dodecyl-SO4 by the methods of polyacrylamide gel electrophoresis and gel filtration chromatography, respectively. Circular dichroism spectra indicate that component VII assumes a random coil conformation in 6 M guanidinium chloride and a more disordered conformation in 1% Na dodecyl-SO4 than standard proteins used in calibration of polyacrylamide gels and gel filtration column. These results indicate that the minimal molecular weight of component VII is about 70,000 and that the anomalous behavior in Na dodecyl-SO4 is due in part to its conformation. 相似文献
107.
Adenyl cyclase and cyclic nucleotide phosphodiesterase activities were assayed in homogenates of hind leg skeletal muscle from dystrophic and normal mice. Adenyl cyclase activity was stimulated 2.5 times by epinephrine and 6 times by fluoride over the basal activity in both dystrophic and normal mice. The activity of adenyl cyclase from dystrophic muscle of mice was significantly higher than that of normal mice under all the conditions tested (i.e. basal, epinephrine and fluoride). Cyclic nucleotide phosphodiesterase from skeletal muscle of mice has two Km's (2.1 and 11 mumol/l) which suggests the existence of either two forms of enzyme or a single enzyme with negative cooperativity. The activity of this enzyme was significantly elevated in the skeletal muscle of dystrophic mice compared to the normal controls. The available evidence suggests that the same cyclic nucleotide phosphodiesterase is responsible for the hydrolysis of both cyclic AMP and cyclic GMP. 相似文献
108.
Lack of Genic Similarity between Two Sibling Species of Drosophila as Revealed by Varied Techniques 下载免费PDF全文
Jerry A. Coyne 《Genetics》1976,84(3):593-607
Acrylamide gel electrophoresis was performed on the enzyme xanthine dehydrogenase in sixty isochromosomal lines of Drosophila persimilis from three geographic populations. Sequential electrophoretic analysis using varied gel concentrations and buffers revealed twenty-three alleles in this species where only five had been described previously. These new electrophoretic techniques also detected a profound increase in divergence of gene frequencies at this locus between D. persimilis and its sibling species D. pseudoobscura. The implications of these results for questions of speciation and the maintenance of genetic variability are discussed. 相似文献
109.
V W Lee I A Cumming D M de Kretser J K Findlay B Hudson E J Keogh 《Journal of reproduction and fertility》1976,46(1):1-6
Plasma LH, FSH and testosterone concentrations were measured by radioimmunoassays in male crossbred Merino/Corriedale sheep from birth to 45 weeks of age. FSH levels were 11 and 22 ng/ml at birth, increased to peak levels (mean value of 47 ng/ml) at 5 weeks and fluctuated between 25 and 35 ng/ml for the next 40 weeks. Similarly, LH (less than 0-5 ng/ml) and testosterone (less than 38 ng/100 ml) levels were low at birth and were significantly elevated by 5 weeks of age. LH values varied betwen 0-9 and 3-0 ng/ml for the next 30 weeks and then a secondary rise occurred reaching levels of 2-4 ng/ml by the 41st week after birth. Concentrations of LH subsequently fell to levels observed in adult rams. Testosterone levels rose gradually between the 5th and the 25th week, and then increased rapidly to values of 270-517 ng/100 ml by the 41st week after birth, a time coincident with the peak LH levels. Histological examination of testicular biopsies demonstrated that Sertoli cell maturation occurred 17-21 weeks after birth and was followed by activation of spermatogenesis leading to the presence of spermatozoa in the seminiferous epithelium by 39-42 weeks of age. 相似文献
110.
Derek A. Hudson 《Life sciences》1975,16(1):117-129
Uptake or “binding” of Ca2+ ions by microvillous membranes occurs in the absence or presence of ATP. In its absence uptake is independent of temperature (3–37°C), reduced by the presence of other cations and is dependent upon pH and the number and type of “binding” sites of which there are at least two classes. Under certain conditions uptake of Ca2+ is increased by ATP. The degree of stimulation is dependent upon both the concentration of Ca2+ and ATP, the time and temperature of incubation and is partly dependent upon the presence of Mg2+ ions. 相似文献