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排序方式: 共有1120条查询结果,搜索用时 414 毫秒
901.
902.
Dr. Mitchell R. Silk Dr. Jason R. Price Dr. Biswaranjan Mohanty Prof. Dr. Hanna-Kirsti S. Leiros Dr. Bjarte A. Lund Prof. Dr. Philip E. Thompson Dr. David K. Chalmers 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14489-14500
Our understanding of the factors affecting the stability of cyclic d/l peptide (CP) nanotubes remains underdeveloped. In this work, we investigate the impact of side chain alignment, hydrophobicity and charge on CP nanotube stability through X-ray crystallography, NMR spectroscopy and molecular dynamics (MD) simulations. We characterise the distinct CP-CP alignments that can form and identify stable and unstable dimers by MD simulation. We measure H-bond half-lives of synthesised CPs by 1H−D exchange experiments and find good correlation with predicted CP-CP stabilities. We find that hydrophobic amino acids improve CP dimer stability but experimentally reduce solubility. Charged amino acids either increase or decrease CP dimer stability depending on the relative orientation and composition of charged groups. X-ray crystal structures are solved for two CPs, revealing non-tubular folded conformations. Ultimately, this work will assist the educated design of stable tubular structures for potential applications in biomedicine. 相似文献
903.
Frederick C. Prehn Jr Brian D. Etz Daniel Price Amanda Trainor Caleb J. Reese Shubham Vyas Stephen G. Boyes 《Journal of polymer science. Part A, Polymer chemistry》2020,58(17):2407-2422
A detailed investigation into the role of initiator structure, the presence of an initiator, and basicity of the non-nucleophilic base in the chain-growth condensation (CGC) synthesis of poly(N-octyl benzamide) was conducted. A series of phenyl ester dimethyl amide initiators with different leaving groups were synthesized and used in the CGC preparation of poly(N-octyl benzamide). Additional polymerizations were conducted without the presence of an initiator and with different non-nucleophilic bases. Kinetic studies, along with nuclear magnetic resonance spectroscopy and gel-permeation chromatography, were used to determine progress of the reaction, molecular weights, and molecular weight distributions. The experimental and computational results demonstrated that initiators containing electron-withdrawing substituent phenyl esters, such as the p-nitrophenyl ester, and electron-withdrawing carbonyl character on the parent benzoate produce polymers with controllable molecular weights and narrow molecular weight distributions. Whereas, initiating species that contain electron-donating character on the benzoate backbone, such as dimethylamino and methyl ester groups, produce polymers that resemble the results from reactions involving no initiators at all, indicating poor polymerization control. 相似文献
904.
905.
The structures and energies of 1,2,7-thiadiazepane 1,1-dioxide and the axial and equatorial conformers of 1,2,7-thiadiazepane 1-oxide were calculated using the hybrid density functional B3LYP with the cc-pVDZ basis set. The results obtained explain the lower stabilities of equatorial conformers compared to the axial analogs and the lower stabilities of sulfones compared to sulfoxides.
相似文献906.
Rabindra N. Roy Lakshmi N. Roy Darin R. Gregory Stephanie A. Kiefer Bijan Das Kenneth S. Pitzer 《Journal of solution chemistry》1999,28(7):933-947
Activity coefficients for HCl in HCl + GaCl3 + H2O at eleven different temperatures from 5 to 55°C have been determined at total experimental ionic strengths from 0.01 to 3.0 mol-kg–1 using a cell of the type: Pt; H2(g, 1 atm)|HCl (mA) + GaCl3(mB)|AgCl, Ag (A) The results for the 770 experimental emf data points have been used to determine the variation of the activity coefficients of HCl with the change in molality of GaCl3 in the solution. It is found that the linear form of Harned's rule is not obeyed for this system. 相似文献
907.
Qi Duan Botang Li K. Djidjeli W. G. Price E. H. Twizell 《Journal of Applied Mathematics and Computing》1999,6(3):537-547
Controlling the convexity and the strain energy of the interpolating curve can be carried out by controlling the second-order derivative of the interpolating function. In [1], the rational cubic spline with linear denominator has been used to constrain the convexity and the strain energy of the interpolating curves, but it does not work in some case. This paper deals with the weighted rational cubic spline with linear denominator for this kind of constraint, the sufficient and necessary condition for controlling the convexity and strain energy of the interpolating curves are derived, and a numerical example is given. 相似文献
908.
Global optimization by controlled random search 总被引:5,自引:0,他引:5
W. L. Price 《Journal of Optimization Theory and Applications》1983,40(3):333-348
The paper describes a new version, known as CRS2, of the author's controlled random search procedure for global optimization (CRS). The new procedure is simpler and requires less computer storage than the original version, yet it has a comparable performance. The results of comparative trials of the two procedures, using a set of standard test problems, are given. These test problems are examples of unconstrained optimization. The controlled random search procedure can also be effective in the presence of constraints. The technique of constrained optimization using CRS is illustrated by means of examples taken from the field of electrical engineering. 相似文献
909.
910.