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184 results on '"Yu, Hai‐Zhu"'

12. Upper Bound for the Exponential of a Class of Bicolor Directed Graphs

Author

Si Jin, Deng Hua, and Yu Hai-Zhu

Subjects
Discrete mathematics, Class (set theory), 020206 networking & telecommunications, Graph theory, Digraph, 02 engineering and technology, Directed graph, Upper and lower bounds, Exponential function, Combinatorics, 0202 electrical engineering, electronic engineering, information engineering, Exponent, 020201 artificial intelligence & image processing, Mathematics
Abstract

In recent years, the researches on primitive exponent of two-colored digraph have gained some achievements. This paper studies a kind of two-colored digraph, matrix theory and graph theory are used to research a two-colored digraph, which indicates color-patch map has only two circles, respectively n-cycle and (mn-1)-cycle, and these two cycles only have two public arcs. It gives the primitive condition of two-circled and two-colored digraph, and upper bound of its primitive exponent, as well as depicts the pole figure of upper bound of its primitive exponent.

Published
2016

16. Orbital Interactions in Native Chemical Ligation Reaction of Proline Thioesters

Author

YU Hai-Zhu, Zhang Qi, and Shi Jing

Subjects
Stereochemistry, Aryl, Interaction energy, Native chemical ligation, Rate-determining step, Specific orbital energy, chemistry.chemical_compound, chemistry, Computational chemistry, Intramolecular force, lipids (amino acids, peptides, and proteins), Reactivity (chemistry), Physical and Theoretical Chemistry, HOMO/LUMO
Abstract

A systematic theoretical study was carried out to investigate the origin of the relatively low reactivity of peptide-prolyl-thioesters in the native chemical ligation(NCL) reaction. Mechanistic calculations were performed on the two NCL reactions of peptide-prolyl-thioester(Path-Pro) and peptidealanyl-thioester(Path-Ala). The results show that both include three steps: intermolecular thiol-thioester exchange, transthioesterification, and a final intramolecular S→N acyl migration. The calculations indicate that the first step is the rate determining step of both pathways. Path-Pro is kinetically disfavored, so the peptide-prolyl-thioester is found to be less reactive in NCL reaction. This conclusion is consistent with the experimental observations. Further examination of the rate determining steps of these two pathways shows that the n→π* interaction of prolineαN carbonyl increases the LUMO orbital energy of peptidyl- prolylthioester, decreases the interaction energy between proline carbonyl and the sulphur atom in aryl thiol, and finally increases the total energy barrier.

Published
2013

40. Corrigendum

Author

Sun, Xiao-Hui, primary, Yu, Hai-Zhu, additional, Yang, Meng-Meng, additional, Yang, Yi-Meng, additional, and Dang, Zhi-Min, additional

Published
2015
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46. Mechanism of Nickel-Catalyzed Suzuki-Miyaura Coupling of Amides.

Author

Xu, Zheng ‐ Yang, Yu, Hai ‐ Zhu, and Fu, Yao

Subjects
*NICKEL catalysts, *SUZUKI reaction, *AMIDES, *CARBONYL compounds, *DENSITY functional theory
Abstract

The Ni-catalyzed Suzuki-Miyaura coupling of N-tert-butoxycarbonyl ( N-Boc)-protected amides provides a versatile strategy for the construction of C−C bonds. In this study, density functional theory (DFT) methods have been used to elucidate the mechanism of this reaction, with particular emphasis on the roles of N-Boc, K3PO4 and H2O. Our results corroborated those of previous reports, indicating that the overall catalytic cycle consists of three steps, including oxidative addition, transmetalation, and reductive elimination. Three of the possible transmetalation mechanisms were examined to interpret the effects of K3PO4 and H2O. According to the most feasible of these transmetalation mechanisms, K3PO4 (acting as a Lewis base) would initially interact with the Lewis acid PhBpin to give a K3PO4-PhBpin complex, which would readily undergo a hydrogen transfer step with H2O. The H transfer in the transmetalation step was determined to be the rate-determining step. Notably, the theoretical results showed good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Published
2017
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