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71.
The exact residues within severe acute respiratory syndrome coronavirus (SARS-CoV) S1 protein and its receptor, human ACE2, involved in their interaction still remain largely undetermined. Identification of exact amino acid residues that are crucial for the interaction of S1 with ACE2 could provide working hypotheses for experimental studies and might be helpful for the development of antiviral inhibitor. In this paper, a molecular docking model of SARS-CoV S1 protein in complex with human ACE2 was constructed. The interacting residue pairs within this complex model and their contact types were also identified. Our model, supported by significant biochemical evidence, suggested receptor-binding residues were concentrated in two segments of S1 protein. In contrast, the interfacial residues in ACE2, though close to each other in tertiary structure, were found to be widely scattered in the primary sequence. In particular, the S1 residue ARG453 and ACE2 residue LYS341 might be the key residues in the complex formation. 相似文献
72.
73.
Mi-Young Song En-Young Kim Kyung Il Kim Hong-Seok Kim Chang-Hee Lee 《Tetrahedron letters》2004,45(2):299-301
Furans, thiazoles, fluorene or thiophene incorporated calix[4]pyrrole analogues were synthesized and characterized. The synthesis was achieved by utilization of various building blocks such as 7, 13, 14, 18 and 21. Acid catalyzed condensation of those building blocks with acetone or meso-disubstituted dipyrromethanes afforded desired macrocycles. 相似文献
74.
Surface plasmon resonance (SPR) has been successfully applied for the simple, rapid, and label-free assay of various biomolecules. This assay evaluates a novel wavelength modulation SPR biosensor for the detection of tetanus toxin. The wavelength modulation SPR biosensor is designed based on fixing the incident angle of light and measuring the reflected intensities in the resonance wavelength range spanning 400-800 nm simultaneously. Tetanus toxin (TeNT), one of the most potent toxins known, is synthesized as a 150 kDa single polypeptide chain. The SPR biosensor has been shown to be capable of directly detecting concentration of tetanus toxin as low as 0.028 Lf ml−1. Under selected experimental conditions, the SPR biosensor has a good reproducibility, sensitivity and reversibility. The results illustrate how wavelength modulation SPR biosensor can be used to detect biomolecular interactions. 相似文献
75.
Heat divided by ligand concentration vs. heat, similar to the Scatchard plot, was introduced to obtain the equilibrium constant
(K) and the enthalpy of binding (DH) using isothermal titration calorimetry data. Values of K and DH obtained by this linear
pseudo-Scatchard plot for a system with a set of independent binding sites (such as binding fluoride ions on urease and monosaccharide
methyl a-D-mannopyranoside on concavalin A) were remarkably like that obtained from a normal fitting Wiseman method and other
our technical methods. On applying this graphical method to study the binding of copper ion on myelin basic protein (MBP),
a concave downward curve obtained was consistent with the positive cooperativity in the binding. A graphical fitting by simple
method for determination of thermodynamic parameters was also introduced. This method is general, without any assumption and
restriction made in previous method. This general method was applied to the product inhibition study of adenosine deaminase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
对合肥市16671名1-12个月幼儿的发锌,钙含量进行了测定,并对测定值进行了统计分析。结果表明,锌,钙的含量随着月龄的增加呈直线递减。并给出了发锌,钙含量的趋势线方程,丰富了目前文献给出的发锌,钙的标准值,为及时准确判断周岁内幼儿微量元素锌,钙缺乏程度提出依据。 相似文献
77.
Apparent molar heat capacities and volumes of amylamine (PentNH2) 0.02m, capronitrile (PentCN) 0.02m and nitropentane (PentNO2) 0.009m in decyltrimethylammonium bromide (DeTAB) micellar solutions, in water and in octane were measured at 25°C. By assuming that their concentration approaches the standard infinite dilution state, heat capacities and volumes were rationalized by means of previously reported equations following which the distribution constant between the aqueous and the micellar phase and heat capacity and volume of the additives in both phases are simultaneously derived. The present results are compared to those we have previously obtained for pentanol (PentOH). The thermodynamic properties of PentNH2 in water and in micellar phase are substantially identical to those of PentOH but different from those of PentCN and PentNO2 whereas the opposite behavior was observed in their pure liquid state and in octane. The nature of the solvent medium seems to affect the thermodynamic behavior of PentNH2. Also, the study of the apparent molar heat capacities of the amyl compounds investigated here in micellar solutions as a function of surfactant concentration shows evidence of a maximum at about 0.4m DeTAB, which can be attributed to a micellar structural transition. Accordingly, the solubilities of PentCN and PentNO2 as a function of the DeTAB concentration drop in the neighborhood of the concentration where heat capacities display the maximum. 相似文献
78.
79.
CaO和NaCl焙烧混合稀土精矿过程中的分解反应 总被引:5,自引:0,他引:5
用XRD和TG-DTA热分析技术, 研究了含独居石和氟碳铈镧矿的混合稀土精矿在100~1000 ℃焙烧过程中, 添加CaO, NaCl时, REPO4和REFCO3的分解反应. 研究结果表明: 不添加CaO和NaCl时, 仅在377~450 ℃范围内存在REFCO3的分解反应, 其产物是REOF, RE2O3, 以及Ce2O3进一步的氧化产物CeO2, 而REPO4不分解; 添加CaO后在660~750 ℃之间, CaO有3种分解作用: (1) CaO分解REPO4, 其产物是RE2O3和Ca3(PO4)2. (2) CaO分解REOF, 其产物是RE2O3和CaF2. (3) CaO和REOF的分解产物CaF2共同作用分解REPO4, 其分解产物为RE2O3, Ca5F(PO4)3; 添加CaO, NaCl后, 混合精矿的分解率明显提高, NaCl的作用是为反应体系提供了液相, 促进了固相反应物间的传质过程, 加快了反应速度. 与此同时NaCl还可能参加了CaO分解REPO4的反应. 相似文献
80.
Grell E. Lewitzki E. Schacht A. Stolz M. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):471-481
Microcalorimetric titrations allow to recognize and investigate high-affinity ligand binding to Na,K-ATPase. Titrations with
the cardiac glycoside Ouabain, which acts as a specific inhibitor of the enzyme, have provided not only the thermodynamic
parameters of high-affinity binding with a stoichiometric coefficient of about 0.6 but also evidence for low-affinity binding
to the lipid. The marked enthalpic contribution of -95 kJ mol-1 at 298.2 K is partially compensated by a large negative entropy change, attributed to an increased interaction between water
and the protein. The calorimetric ADP and ATP titrations at 298.2 K are indicative of high-affinity nucleotide binding either
in 3 mM NaCl, 3 mM MgCl2 or at high ionic strength such as 120 mM choline chloride. However, no binding is detected in the buffer solution alone at
low ionic strength. The affinities for ADP and ATP are similar, around 106 M-1 and the stoichiometric coefficients are close to that of Ouabain binding. The exothermic binding of ADP is characterized
by a ΔH and ΔS value of -65 kJ mol-1 and -100 J mol-1 K-1, respectively. TheΔH value for ATP binding is larger than for ADP and is compensated by a larger, unfavorable ΔS value. This
leads to an enthalpy/entropy compensation, which could express that H-bond formation represents the major type of interaction.
As for Ouabain, the negative ΔS values that are also characteristic of nucleotide binding can indicate an increase of solvate
interaction with the protein due to a conformational transition occurring subsequent to the binding process. The resulting
binding constants are discussed with regard to the results of other studies employing different techniques. A molecular interaction
model for nucleotide binding is suggested.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献