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1.
Auromomycin and macromomycin from the organism Streptomyces macromomyceticus have been crystallized. The X-ray diffraction pattern of crystals of each molecule is consistent with space group P21212 with cell parameters for auromomycin, and for macromomycin. Diffraction analysis of auromomycin is in progress. 相似文献
2.
The metabolism of pregnenolone in subcellular fractions of the testes of the macaque (Macaca fascicularis) has been studied using capillary gas chromatography to characterize and quantify the metabolites, after their conversion into the O-methyloxime and/or trimethylsilyl ether derivatives. The microsomal incubations yielded the greatest quantities of metabolites, with lesser amounts in the mitochondrial fraction. The cytosolic fraction contained no significant quantity of metabolites after incubation, except for 5alpha-androst-16-en-3 beta-ol. This, and other odorous androst-16-enes, found in the microsomal fraction, are of particular interest in the context of animal communication because of their possible pheromonal role. Pregnenolone was converted into androst-5-ene-3 beta,17 beta-diol, androst-4-ene-3,17-dione and testosterone, suggesting that both classical pathways for testosterone synthesis were operating. Testosterone was further converted into 5 alpha-reduced androstanediols, especially in the microsomal fraction. 相似文献
3.
Pulsatile flow of Casson's fluid through stenosed arteries with applications to blood flow 总被引:1,自引:0,他引:1
The effects of non-Newtonian nature of blood and pulsatility on flow through a stenosed tube have been investigated. A perturbation method is used to analyse the flow. It is of interest to note that the thickness of the viscous flow region is non-uniform (changing with axial distance). An analytic relation between viscous flow region thickness and red cell concentration has been obtained. It is important to mention that some researchers have obtained an approximate solution for the flow rate-pressure gradient equation (assuming the ratio between the yield stress and the wall shear to be very small in comparison to unity); in the present analysis, we have obtained an exact solution for this non-linear equation without making that assumption. The approximate and exact solutions compare well with one of the exact solutions. Another important result is that the mean and steady flow rates decrease as the yield stress theta increases. For the low values of the yield stress, the mean flow rate is higher than the steady flow rate, but for high values of the yield stress, the mean flow rate behaviour is of opposite nature. The critical value of the yield stress at which the flow rate behaviour changes from one type to another has been determined. Further, it seems that there exists a value of the yield stress at which flow stops for both the flows (steady and pulsatile). It is observed that the flow stop yield value for pulsatile flow is lower than the steady flow. The most notable result of pulsatility is the phase lag between the pressure gradient and flow rate, which is further influenced by the yield stress and stenosis. Another important result of pulsatility is the mean resistance to flow is greater than its steady flow value, whereas the mean value of the wall shear for pulsatile flow is equal to steady wall shear. Many standard results regarding Casson and Newtonian fluids flow, uniform tube flow and steady flow can be obtained as the special cases of the present analysis. Finally, some applications of this theoretical analysis have been cited. 相似文献
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1. Glycoproteins were isolated from the plasma of sheep, goat, cow, buffalo and monkey. They were homogeneous by electrophoresis; on ultracentrifugation, a faster-sedimenting fraction, to an extent of 5–8% only, was observed in each case. 2. Similar physical properties were exhibited by these glycoproteins and they each have a molecular weight of about 105000. 3. In chemical composition, differences have been observed and the glycoproteins can be classified into three groups: (a) sheep and goat glycoproteins; (b) cow and buffalo glycoproteins; (c) monkey glycoprotein. Glucose, galactosamine and N-terminal amino acid were absent from these proteins. 4. These glycoproteins were trypsin inhibitors and prolonged the clotting time of plasma. 相似文献
6.
The polyamines stimulated tyrosine hydroxylase in whole homogenates of bovine caudate nuclei approximately 2 fold. TheV
max forl-tyrosine increased by 2.3 fold while theK
m
s forl-tyrosine and for the cofactor (DMPH4) were unchanged.l-Aromatic amino acid decarboxylase from whole rat brain homogenate was stimulated by about 40% in the presence of polyamines. These findings suggest that increased polyamine levels associated with increased cellular synthetic activity can modify the synthesis of neurotransmitters. 相似文献
7.
L C Sieker L H Jensen T S Samy 《Biochemical and biophysical research communications》1976,68(2):358-362
The antitumor protein, neocarzinostatin, has been crystallized and examined by X-ray diffraction. Crystals of this globular protein are of space group P212121 with cell parameters a = 27.4Å, b = 33.9Åand c = 102.0Å. There is one molecule of approximately 27Ådiameter per asymmetric unit. Crystals soaked in a K2HgI4 solution give diffraction patterns significantly different from native crystal diffraction patterns. 相似文献
8.
Abstract— It has been reported that myelin basic protein (MBP) forms a specific complex with S-100 protein in the presence of either Ca2+ or Mn2+, as detected by Immunoelectrophoresis. We have now studied the binding of Ca2+ and Mn2+ to these two proteins. We find that MBP binds 1 mol of Mn2+/mol of protein, and this binding produces an increment in its fluorescence, indicating a conformational change. Ca2+ does not bind to MBP nor does it affect the fluorescence of MBP. S-100 protein, as has been reported, binds about 10 mol of Ca2+/mol and this binding produces a conformational change. S-100 protein also has 25 binding sites for Mn2+, but this binding does not alter fluorescence and does not appear to affect conformation. Competitive binding experiments demonstrate that the binding sites of S-100 protein for Ca2+ and Mn2+ are independent. The alteration of electrophoretic migration in gels of S-100 protein produced by Ca2+ and of MBP produced by Mn2+ are in accord with the observations based on fluorescence. Mn2+ does not affect the electrophoretic mobility of S-100. These results indicate that the formation of the complex between MBP and S-100 protein in the presence of either Ca2+ or Mn2+ is due to the conformational change induced by these ions in S-100 protein, MBP, or both. 相似文献
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