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1.
2.
Summary Molecular surface areas accessible to a 4 ? diameter spherical probe were calculated from crystallographic data for five proteins:
α-chymotrypsinogen A, lysozyme, trypsinogen, ribonuclease A and ribonuclease S. The retention factors of various proteins
were measured on stationary phases having polyether- and phenylligates and with aqueous eluents containing (NH4)2SO4, Na2SO4 or NaCl at pH 7.0. The logarithmic retention factors were plotted against the salt molality and the hydrophobic interaction
parameters evaluated from the limiting slopes of the plots at high salt concentrations for the proteins in the chromatographic
systems investigated. The hydrophobic interaction parameters thus obtained were linear in both the molecular surface areas
of the proteins and the molal surface tension increments of the salts. The experimental results obtained with these relatively
simple proteins of known molecular structure, which were available in high purity, support earlier theoretical predictions
for the dependence of the hydrophobic interaction parameter on the surface area of the protein and the surface tension raising
effect of the salt. 相似文献
3.
Use of a novel coupling reagent, N,N-bis[2-oxo-3-oxazolidinyl]phosphorodiamidic chloride (BOPDC) in the synthesis of oligodeoxyribonucleotides is described. This reagent allows the synthesis of phosphotriesters in high yields (70–80%) without detectable side reactions. Synthesis of a hexanucleotide, d(A-A-C-C-C-G) is presented as an example. 相似文献
4.
Biomaterials in total joint replacement 总被引:9,自引:0,他引:9
Katti KS 《Colloids and surfaces. B, Biointerfaces》2004,39(3):133-142
The current state of materials systems used in total hip replacement is presented in this paper. An overview of the various material systems used in total hip replacement reported in literature is presented in this paper. Metals, polymers, ceramics and composites are used in the design of the different components of hip replacement implants. The merits and demerits of these material systems are evaluated in the context of mechanical properties most suitable for total joint replacement such as a hip implant. Current research on advanced polymeric nanocomposites and biomimetic composites as novel materials systems for bone replacement is also discussed. This paper examines the current research in the materials science and the critical issues and challenges in these materials systems that require further research before application in biomedical industry. 相似文献
5.
Raghuraman K Katti KK Barbour LJ Pillarsetty N Barnes CL Katti KV 《Journal of the American Chemical Society》2003,125(23):6955-6961
Phosphorus functionalized trimeric alanine compounds (l)- and (d)-P(CH(2)NHCH(CH(3))COOH)(3) 2 are prepared in 90% yields by the Mannich reaction of Tris(hydroxymethyl)phosphine 1 with (l)- or (d)- Alanine in aqueous media. The hydration properties of (l)-2 and (d)-2 in water and water-methanol mixtures are described. The crystal structure analysis of (l)-2.4H(2)O, reveals that the alanine molecules pack to form two-dimensional bilayers running parallel to (001). The layered structural motif depicts two closely packed monolayers of 2 each oriented with its phosphorus atoms projected at the center of the bilayer and adjacent monolayers are held together by hydrogen bonds between amine and carboxylate groups. The water bilayers are juxtaposed with the H-bonded alanine trimers leading to 18-membered (H(2)O)(18) water rings. Exposure of aqueous solution of (l)-2 and (d)-2 to methanol vapors resulted in closely packed (l)-2 and (d)-2 solvated with mixed water-methanol (H(2)O)(15)(CH(3)OH)(3) clusters. The O-O distances in the mixed methanol-water clusters of (l)-2.3H(2)O.CH(3)OH and (d)-2.3H(2)O.CH(3)OH (O-O(average) = 2.857 A) are nearly identical to the O-O distance observed in the supramolecular (H(2)O)(18) water structure (O-O(average) = 2.859 A) implying the retention of the hydrogen bonded structure in water despite the accommodation of hydrophobic methanol groups within the supramolecular (H(2)O)(15)(CH(3)OH)(3) framework. The O-O distances in (l)-2.3H(2)O.CH(3)OH and (d)-2.3H(2)O.CH(3)OH and in (H(2)O)(18) are very close to the O-O distance reported for liquid water (2.85 A). 相似文献
6.
Seturam Bandacharaya Katti Peter Rüedi Conrad Hans Eugster 《Helvetica chimica acta》1982,65(7):2189-2197
Diterpenoids from Leaf Glands of Plectranthus purpuratus: p-Quinomethanes, Extended Quinones, p-Acylcatechols and a Novel Phyllocladanon Derivative From the complex mixture of terpenoids from the title plant, the following novel diterpenoids have been isolated: 11-hydroxy-19-(3-methyl-2-butenoyloxy)- and 11-hydroxy-19-(3-methylbutanoyloxy)-5,7,9 (11), 13-abietatetraen-12-one ( 1a / 1b ), 11-hydroxy-19-(3-methyl-2-butenoyloxy)- and 11-hydroxy-19-(3-methylbutanoyl-oxy)-7,9(11), 13-abietatrien-6,12-dione ( 2a / 2b ), 6α, 11-dihydroxy-19-(3-methyl-2-butenoyloxy)- and 6α, 11 -dihydroxy-19-(3-methylbutanoyloxy)-7,9 (11), 13-abieta-trien-12-one ( 3a / 3b ), 11,12-dihydroxy-19-(3-methyl-2-butenoyloxy)- and 11,12-di-hydroxy-19-(3-methylbutanoyloxy)-8,11,13-abietatrien-7-one ( 4a / 4b ), and (16R)-17,19-diacetoxy-16-hydroxy-13β-kauran-3-one (=(16R)-17,19-diacetoxy-16-hydro-xyphyllocladan-3-one; 10 ). Compounds 2 and 3 are derivates of taxodione and taxodone, respectively, 4 is a derivative of cryptojaponol. The structure of 10 is Wised on a single-crystal- X -ray analysis and CD . data. 相似文献
7.
Mohamed Habibullah S. K. Katti 《Annals of the Institute of Statistical Mathematics》1991,43(2):391-404
In maximizing a non-linear function G(), it is well known that the steepest descent method has a slow convergence rate. Here we propose a systematic procedure to obtain a 1–1 transformation on the variables , so that in the space of the transformed variables, the steepest descent method produces the solution faster. The final solution in the original space is obtained by taking the inverse transformation. We apply the procedure in maximizing the likelihood functions of some generalized distributions which are widely used in modeling count data. It was shown that for these distributions, the steepest descent method via transformations produced the solutions very fast. It is also observed that the proposed procedure can be used to expedite the convergence rate of the first derivative based algorithms, such as Polak-Ribiere, Fletcher and Reeves conjugate gradient methods as well. 相似文献
8.
A reversed-phase high-performance liquid chromatographic method with electrochemical detection has been adapted for the determination of picogram concentrations of norepinephrine and epinephrine in bovine plasma and milk. This method has been used to monitor the levels of these catecholamines when lactating cows are exposed to heat stress under controlled conditions. In response to heat stress, epinephrine concentrations in milk and plasma were similar. However, norepinephrine concentrations in milk were one tenth of that in plasma. 相似文献
9.
10.
Raghuraman K Pillarsetty N Volkert WA Barnes C Jurisson S Katti KV 《Journal of the American Chemical Society》2002,124(25):7276-7277
The reactions of (HOCH2)2P(C6H4)P(CH2OH)2 (HMPB) and P(CH2OH)3 (THP) with RhCl3.xH2O in aqueous media gave water-soluble complexes cis-[RhCl2{eta2-(HOCH2)2P(C6H4)P(CH2OH)2}2]Cl (3) and fac-[RhCl3(P(CH2OH)3)3] (4) respectively in good yields, X-ray crystal structures of 3 and 4 confirmed their molecular constitution. These reactions provide the first examples demonstrating the kinetic propensity of hydroxymethyl phosphanes to stabilize Rh in +3 oxidation state in water. 相似文献