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1.
The yeast Trichosporon adeninovorans secretes two multiple forms of β-glucosidase at a high rate if grown in a medium containing cellobiose. Following mutagenesis a mutant strain resistant to 2-deoxy-D-glucose was selected. This strain produced more β-glucosidase activity and had acquired a strong resistance against repression by glucose. The β-glucosidases were separated one from each other by chromatography on hydroxylapatite and by gel filtration. Both enzymes have similar properties. The optimal temperature for their activity was 60 to 63°C and the enzymes displayed highest activity at pH of 4.5. The molecular weight of β-glucosidase I was found to be 570,000 and that for β-glucosidase II was 525,000. The Km value for cellobiose was determined to be 4.1 mM for β-glucosidase I and 3.0 mM for β-glucosidase II. 相似文献
2.
Are there two DNA methyltransferase gene families in plant cells? A new potential methyltransferase gene isolated from an Arabidopsis thaliana genomic library.
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Using the 1kb 3' terminal DNA fragment of the mouse methyltransferase cDNA as a probe and low stringent hybridisation conditions, a new potential methyltransferase (MTase) gene family was isolated from an Arabidopsis thaliana genomic DNA library. One clone (MTase-11), which gave the strongest signal at the Northern blot, was entirely sequenced (11483 bp) and further characterised. Under consideration of the likely open reading frames and our preliminary cDNA experiments we propose that the clone 11 gene encodes for an approximately 90 kD protein. As deduced form the DNA sequence this protein contains all conserved sequence motifs specific for the 5m cytosine MTases. MTase-11 gene expression was demonstrable in callus and during germination but not in one month old plants or in leaves. 相似文献
3.
Effects of low-chloride solutions on action potentials of sheep cadiac purkinje fibers 总被引:2,自引:0,他引:2
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The rapid repolarization during phase 1 of the action potential of sheep cardiac purkinje fibers has been attributed to a time- and voltage-dependent chloride current. In part, this conclusion was based on experiments that showed a substantial slowing of phase 1 when larger, presumably impermeant, anions were substituted for chloride in tyrode’s solution. We have re- examined the electrical effects of low-chloride solutions. We recorded action potentials of sheep cardiac purkinje fibers in normal tyrode’s solution and in low-chloride solutions made by substituting sodium propionate, acetylglycinate, methylsulfate, or methanesulfonate for the NaCl of Tyrode’s solution. Total calcium was adjusted to keep calcium ion activity of test solutions equal to that of control solutions. Propionate gave qualitatively variable results in preliminary experiments; it was not tested further. Low-chloride solutions made with the other anions gave much more consistent results: phase 1 and the notch that often occurs between phases 1 and 2 were usually unaffected, and the action potential duration usually increased. The only apparent change in the resting potential was a transient 3-6 mV depolarization when low-chloride solution was first admitted to the chamber, and a symmetrical transient hyperpolarization when chloride was returned to normal. If a time- and voltage-dependent chloride current exists in sheep cardiac purkinje fibers, our results suggest that it plays little role in generating phase 1 of the action potential. 相似文献
4.
Stefan Schleifenbaum Torsten Prietzel Gabriela Aust Andreas Boldt Sebastian Fritsch Isabel Keil Holger Koch Robert M?bius Holger A. Scheidt Martin F. X. Wagner Niels Hammer 《PloS one》2016,11(3)
Introduction
Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens.Materials and Methods
Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens.Results
Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin.Discussion
Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin. 相似文献5.
Leisan F. Galiullina Holger A. Scheidt Daniel Huster Albert Aganov Vladimir Klochkov 《生物化学与生物物理学报:生物膜》2019,1861(3):584-593
Statins are drugs that specifically inhibit the enzyme HMG-CoA reductase and thereby reduce the concentration of low-density lipoprotein cholesterol, which represents a well-established risk factor for the development of atherosclerosis. The results of several clinical trials have shown that there are important intermolecular differences responsible for the broader pharmacologic actions of statins, even beyond HMG-CoA reductase inhibition. According to one hypothesis, the biological effects exerted by these compounds depend on their localization in the cellular membrane. The aim of the current work was to study the interactions of different statins with phospholipid membranes and to investigate their influence on the membrane structure and dynamics using various solid-state NMR techniques. Using 1H NOESY MAS NMR, it was shown that atorvastatin, cerivastatin, fluvastatin, rosuvastatin, and some percentage of pravastatin intercalate the lipid-water interface of POPC membranes to different degrees. Based on cross-relaxation rates, the different average distribution of the individual statins in the bilayer was determined quantitatively. Investigation of the influence of the investigated statins on membrane structure revealed that lovastatin had the least effect on lipid packing and chain order, pravastatin significantly lowered lipid chain order, while the other statins slightly decreased lipid chain order parameters mostly in the middle segments of the phospholipid chains. 相似文献
6.
Lars?Thomas Julian?Kahr Peter?Schmidt Ulrike?Krug Holger?A.?Scheidt Daniel?HusterEmail author 《Journal of biomolecular NMR》2015,61(3-4):347-359
In contrast to the static snapshots provided by protein crystallography, G protein-coupled receptors constitute a group of proteins with highly dynamic properties, which are required in the receptors’ function as signaling molecule. Here, the human neuropeptide Y2 receptor was reconstituted into a model membrane composed of monounsaturated phospholipids and solid-state NMR was used to characterize its dynamics. Qualitative static 15N NMR spectra and quantitative determination of 1H–13C order parameters through measurement of the 1H–13C dipolar couplings of the CH, CH2 and CH3 groups revealed axially symmetric motions of the whole molecule in the membrane and molecular fluctuations of varying amplitude from all molecular segments. The molecular order parameters (Sbackbone = 0.59–0.67, SCH2 = 0.41–0.51 and SCH3 = 0.22) obtained in directly polarized 13C NMR experiments demonstrate that the Y2 receptor is highly mobile in the native-like membrane. Interestingly, according to these results the receptor was found to be slightly more rigid in the membranes formed by the monounsaturated phospholipids than by saturated phospholipids as investigated previously. This could be caused by an increased chain length of the monounsaturated lipids, which may result in a higher helical content of the receptor. Furthermore, the incorporation of cholesterol, phosphatidylethanolamine, or negatively charged phosphatidylserine into the membrane did not have a significant influence on the molecular mobility of the Y2 receptor. 相似文献
7.
8.
Engel KM Schröck K Teupser D Holdt LM Tönjes A Kern M Dietrich K Kovacs P Krügel U Scheidt HA Schiller J Huster D Brockmann GA Augustin M Thiery J Blüher M Stumvoll M Schöneberg T Schulz A 《PloS one》2011,6(12):e29400
G protein-coupled receptors (GPCR) are involved in the regulation of numerous physiological functions. Therefore, GPCR variants may have conferred important selective advantages during periods of human evolution. Indeed, several genomic loci with signatures of recent selection in humans contain GPCR genes among them the X-chromosomally located gene for GPR82. This gene encodes a so-called orphan GPCR with unknown function. To address the functional relevance of GPR82 gene-deficient mice were characterized. GPR82-deficient mice were viable, reproduced normally, and showed no gross anatomical abnormalities. However, GPR82-deficient mice have a reduced body weight and body fat content associated with a lower food intake. Moreover, GPR82-deficient mice showed decreased serum triacylglyceride levels, increased insulin sensitivity and glucose tolerance, most pronounced under Western diet. Because there were no differences in respiratory and metabolic rates between wild-type and GPR82-deficient mice our data suggest that GPR82 function influences food intake and, therefore, energy and body weight balance. GPR82 may represent a thrifty gene most probably representing an advantage during human expansion into new environments. 相似文献
9.
The recent, synchrotron-based vibrational technique nuclear resonance vibrational spectroscopy (NRVS) is introduced. The method can be used for a number of M?ssbauer active isotopes including 57Fe, which has yielded most of the results to date. The NRVS experiment can be thought of as M?ssbauer spectroscopy with vibrational sidebands. Importantly, the NRVS experiment provides the complete set of bands corresponding to modes that involve motion of the iron atom. The method has a selectivity reminiscent of that of resonance Raman spectroscopy, but with the significant advantage that NRVS is not subject to the optical selection rules of Raman or infrared spectroscopy. Indeed, NRVS provides the ultimate limit in selectivity because only the vibrational dynamics of the probe nucleus contribute to the observed signal. All iron-ligand modes will be observed, including many that had not been previously observed. For hemes, these include in-plane iron vibrations that have not yet been reported by resonance Raman studies and the iron-imidazole stretch that has not been identified in six-coordinate porphyrins. Other modes that can be investigated include that of heme doming that is expected to be a low-frequency mode. The experimental setup at a beam line and sample requirements for iron-based derivatives are presented. Both powder and polarized single-crystal measurements can be made. The general features of data extraction and analysis are given. Data for heme and heme proteins are given. Examples of assignment of spectra for nitrosyl and carbonyl derivatives are given. These data demonstrate the importance of peripheral substituents on the vibrational spectrum of heme derivatives. Delocalization of modes appears to be common. Although this technique has only been available for a relatively short time, this early progress report indicates that NRVS has significant potential for probing the dynamics of Fe-containing molecules of biological interest. 相似文献
10.