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71.
R S Quinn M Rosenblatt S M Krane 《Biochemical and biophysical research communications》1976,71(1):300-306
Lysates of human skin fibroblasts harvested without the use of trypsin do not contain detectable proteolytic activity, but when trypsin is used, lysates may contain activity equal to 10 ng of trypsin/107 cells. The amount of cell lysate ordinarily examined for collagen prolyl and lysyl hydroxylase activity is sufficiently small that such amounts of trypsin have no observable effect on the unhydroxylated collagen substrate. Larger amounts of trypsin cause proteolysis of the unhydroxylated collagen substrate and a reduction of both prolyl and lysyl hydroxylation with lysyl hydroxylation more affected at low trypsin concentration than prolyl hydroxylation. 相似文献
72.
Biosynthesis of serum albumin in rat liver. Isolation and probable structure of ''proalbumin'' from rat liver. 总被引:2,自引:0,他引:2 下载免费PDF全文
1. Two methods are described for the preparation of 'proalbumin' in good yields from rat liver. 2. One of the methods does not depend on the use of specific antisera. 3. The product from both methods is identical as judged by electrophoresis on polyacrylamide gel, isoelectric focusing on pH gradients, ion-exchange chromatography and quantitative immunoelectrophoresis. The protein also appears to be radiochemically pure by these criteria. 4. The protein is free from serum albumin as judged by isoelectric focusing and co-chromatography on ion-exchange columns. It is judged to be free from other proteins by these same criteria and by specific precipitation with antibody. 5. It is converted into serum albumin by limited tryptic hydrolysis. The albumin so produced has the same N-terminal (glutamic acid) and C-terminal (alanine) amino acids as reported for rat serum albumin. 6. A hexapeptide is liberated from the N-terminal end of 'proalbumin' simultaneously. It contains three arginine, one phenylalanine, one valine and one glycine residues. 相似文献
73.
A comparison of the activity of phosphatidylinositol phosphodiesterase against substrate in dispersions and as monolayers at the air-water interface. 下载免费PDF全文
The activity of phosphatidylinositol phosphodiesterase, purified from rat brain, against substrate in three forms, (a) multibilayer liposomes, (b) single bilayer vesicles of phosphatidylinositol and (c) phosphatidylinositol oriented as monolayers at the air-water interface, was examined. The reaction rate was similar against the two substrate dispersions prepared with the same phospholipid concentration, although there was a large difference in substrate surface area available to the enzyme, and this similarity could not be accounted for by any differences in the microviscosity of the hydrocarbon region of the phospholipid bilayers. The reaction showed apparent zero-order reaction kinetics until about 10% of the substrate had been degraded, whereupon the rate decreased. The reaction against monolayers of phosphatidylinositol was linear throughout the entire digestion of the film, provided that more than 0.25 mg of enzyme was present in the subphase. The pH optimum was 6.6. Bivalent ions )Ca2+, Mg2+, Co2+, Ni2+ and Mn2+) facilitated enzyme penetration into substrate monolayers, but the enzyme was only activated by Ca2+ (optimal concentration, 1mM) and to a lesser extent by Mg2+. The reaction rate was independent of initial surface pressures of less than about 22mN-m(-1) but at higher pressures the rate decreased. This decrease could be prevented by the addition of 10mol of octadecylamine/90mol of phosphatidylinositol to the substrate monolayer; the amine did not increase the rate of reaction in films of less than 22mN-m(-1). 相似文献
74.
Evidence for the coupling of biosynthesis and secretion of serum albumin in the rat. The effect of colchicine on albumin production 下载免费PDF全文
1. By using isotopic-dilution techniques it was found that colchicine causes a slight increase in the proalbumin content of liver, from 0.63+/-0.06 to 0.83+/-0.10mg/g of liver, but has no effect on albumin content (0.50+/-0.05mg/g of liver). All the proalbumin and 67% of the albumin is found in vesicles from which they are liberated by detergents. 2. Colchicine inhibits secretion of albumin, decreases the rate of conversion of proalbumin into albumin and decreases the rate of incorporation of l-[1-(14)C]leucine into proalbumin. 3. Balance studies in vivo show that all the (14)C appearing in serum albumin can be accounted for by the flow of (14)C through the proalbumin, in the presence or absence of colchicine. 4. When cycloheximide is given to the rats, 2min after [(14)C]leucine, further synthesis of protein stops. The label in proalbumin disappears and the proalbumin content of the liver falls, so as to account for the albumin appearing in the plasma. This occurs both in the presence and in the absence of colchicine. By contrast, there is little change in liver albumin. Studies with isolated perfused livers are in agreement with the above. Lumicolchicine has no effect on any of these systems at doses at which colchicine exerts its action. 5. These results suggest that biosynthesis and conversion of proalbumin into albumin, and secretion of serum albumin are controlled at each step. 相似文献
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Birch Quinn T. Potter Phillip M. Pinto Patricio X. Dionysiou Dionysios D. Al-Abed Souhail R. 《Reviews in Environmental Science and Biotechnology》2020,19(2):275-336
Reviews in Environmental Science and Bio/Technology - The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small... 相似文献
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Ryan J. Quinn HakSoo Ha Timothy A. Volk Tristan R. Brown Steven Bick Robert W. Malmsheimer Marie‐Odile P. Fortier 《Global Change Biology Bioenergy》2020,12(9):728-741
Life cycle assessment (LCA) was combined with primary data from nine forest harvesting operations in New York, Maine, Massachusetts, and Vermont, from 2013 to 2019 where forest biomass (FB) for bioenergy was one of several products. The objective was to conduct a data‐driven study of greenhouse gas emissions associated with FB feedstock harvesting operations in the Northeast United States. Deterministic and stochastic LCA models were built to simulate the current FB bioenergy feedstock supply chain in the Northeast US with a cradle‐to‐gate scope (forest harvest through roadside loading) and a functional unit of 1.0 Mg of green FB feedstock at a 50% moisture content. Baseline LCA, sensitivity analysis, and uncertainty analyses were conducted for three different FB feedstock types—dirty chips, clean chips, and grindings—enabling an empirically driven investigation of differences between feedstock types, individual harvesting process contributions, and literature comparisons. The baseline LCA average impacts were lower for grindings (4.57 kg CO2eq/Mg) and dirty chips (7.16 kg CO2eq/Mg) than for clean chips (23.99 kg CO2eq/Mg) under economic allocation, but impacts were of similar magnitude under mass allocation, ranging from 24.42 to 27.89 kg CO2eq/Mg. Uncertainty analysis showed a wider range of probable results under mass allocation compared to economic allocation. Sensitivity analysis revealed the impact of variations in the production masses and total economic values of primary products of forest harvests on the LCA results due to allocation of supply chain emissions. The high variability in fuel use between logging contractors also had a distinct influence on LCA results. The results of this study can aid decision‐makers in energy policy and guide emissions reductions efforts while informing future LCAs that expand the system boundary to regional FB energy pathways, including electricity generation, transportation fuels, pellets for heat, and combined heat and power. 相似文献