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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
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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
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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
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Considerable attention is being directed toward defining a binding site in the central region of calmodulin that forms a high affinity interaction with certain enzymes and amphiphilic peptides. However, other regions of calmodulin are also known to be involved in the activation of enzymes such as myosin light chain kinase, regions which may not be directly involved in the binding of small peptides, e.g. mastoparan X. We investigated the properties of wheat calmodulin fluorescent derivatives, which were modified chemically in the first calcium binding site at Cys-27, in the activation of rabbit fast skeletal muscle myosin light chain kinase. Unmodified wheat calmodulin stimulated myosin light chain kinase to a greater maximal velocity than wheat calmodulin that was modified at Cys-27 by any of four fluorescent compounds, IAANS (2-[4'-iodoacetamidoanilino]naphthalene-6-sulfonic acid), 5-[2'-[[iodoacetyl]amino]ethyl]aminonaphthalene]-1-sulfonic acid, 5-iodoacetamidofluorescein, and 7-diethylamino-3-[4'-maleimidylphenyl]-4-methylcoumarin; the midpoints for activation of myosin light chain kinase were not significantly different for unmodified wheat calmodulin and three of the four wheat calmodulin derivatives. Myosin light chain kinase, but not mastoparan X, enhanced the fluorescence emission intensity of wheat calmodulin-IAANS. Mastoparan X reversed, in a dose-dependent manner, the changes in fluorescence intensity of a preformed complex of myosin light chain kinase and wheat calmodulin-IANNS. Thus, we propose that the region vicinal to Cys-27 participates in the activation but not the high affinity association of myosin light chain kinase. Lastly, a comparison of mammalian and plant calmodulin showed that the Vmax for the stimulation of myosin light chain kinase was 1.6-fold greater for bovine than wheat calmodulin. The difference between the two calmodulins was more pronounced at lower Ca2+ because less Ca2+ was needed to saturate the kinase rate when stimulated by bovine calmodulin. 相似文献
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The localization of soluble endoplasmic reticulum (ER) chaperones in the cell organelle is mediated by the C‐terminal KDEL (lysine, aspartic acid, glutamic acid and leucine) motif. This motif is recognized by the KDEL receptor, a seven‐transmembrane protein that cycles between the ER and cis‐Golgi to capture missorted KDEL chaperones from post‐ER compartments in a pH‐dependent manner. The KDEL receptor's target chaperones have a substantial role in protein folding and assembly. In this study, the gene expression level of KDEL receptor 1 shows a moderate upregulation during either ER stress or growth of Chinese hamster ovary (CHO) cells in batch culture, while the ER chaperones show higher upregulation. This might indicate the possibility of saturation of the ER retention machinery or at least hindered retention during late stage batch culture in recombinant CHO cells. KDELR1 is overexpressed in a monoclonal antibody‐producing CHO cell line to improve the intracellular chaperone retention rate in the ER. An increase in the specific productivity of IgG1 by 13.2% during the exponential phase, and 23.8% in the deceleration phase of batch culture is observed. This is the first study to focus on the ER retention system as a cell engineering target for enhancing recombinant protein production. 相似文献
10.
Hannah L. Owens Vivian Ribeiro Erin E. Saupe Marlon E. Cobos Peter A. Hosner Jacob C. Cooper Abdallah M. Samy Vijay Barve Narayani Barve Carlos J. Muoz‐R. A. Townsend Peterson 《Ecology and evolution》2020,10(14):6967-6977
Reconstructing ecological niche evolution can provide insight into the biogeography and diversification of evolving lineages. However, comparative phylogenetic methods may infer the history of ecological niche evolution inaccurately because (a) species' niches are often poorly characterized; and (b) phylogenetic comparative methods rely on niche summary statistics rather than full estimates of species' environmental tolerances. Here, we propose a new framework for coding ecological niches and reconstructing their evolution that explicitly acknowledges and incorporates the uncertainty introduced by incomplete niche characterization. Then, we modify existing ancestral state inference methods to leverage full estimates of environmental tolerances. We provide a worked empirical example of our method, investigating ecological niche evolution in the New World orioles (Aves: Passeriformes: Icterus spp.). Temperature and precipitation tolerances were generally broad and conserved among orioles, with niche reduction and specialization limited to a few terminal branches. Tools for performing these reconstructions are available in a new R package called nichevol. 相似文献