Binding models of reversible inhibitors to type-B monoamine oxidase

Interest in the inhibitors of type-B monoamine oxidase has grown in recent years, due to the evidence for multiple roles of one such agent (selegiline) in the pharmacological management of neurodegenerative disorders. A set of 130 reversible and selective inhibitors of MAO-B (including tetrazole, oxadiazolone, and oxadiazinone derivatives) were taken from the literature and subjected to a three-dimensional quantitative structure–activity relationship (3D-QSAR) study, using CoMFA and GOLPE procedures. The steric and lipophilic fields, alone and in combination, provided us with informative models and satisfactory predictions (q²=0.73). The validity of these models was checked against the 3D X-ray structure of human MAO-B. Flexible docking calculations, performed by using a new approach which took advantage from QXP and GRID computational tools, showed the diverse inhibitors to interact with MAO-B in a similar binding mode, irrespective of the heterocycle characterizing them. A significant trend of correlation was observed between estimated energies of the complexes and the experimental inhibition data.     

Some concepts of positive dependence for bivariate interchangeable distributions

In this work we consider some familiar and some new concepts of positive dependence for interchangeable bivariate distributions. By characterizing distributions which are positively dependent according to some of these concepts, we indicate real situations in which these concepts arise naturally. For the various families of positively dependent distributions we prove some closure properties and demonstrate all the possible logical relations. Some inequalities are shown and applied to determine whether under- (or over-) estimates, of various probabilistic quantities, occur when a positively dependent distribution is assumed (falsely) to be the product of its marginals (that is, when two positively dependent random variables are assumed, falsely, to be independent). Specific applications in reliability theory, statistical mechanics and reversible Markov processes are discussed. This work was partially supported by National Science Foundation GP-30707X1. It is part of the author's Ph.D. dissertation prepared at the University of Rochester and supervised by A. W. Marshall. Now at Indiana University.     

Migration Effects in Reversible System [Fe(CN)6]3–/4– on a Microelectrode

Migration factors Y are determined for an [Fe(CN)₆]^3–/4– reversible system at a platinum microelectrode 10 m in radius by measuring anodic and cathodic limiting currents at different concentrations of the redox forms in solution, from which Y _a and Y _c are calculated. The obtained results agree with theory. The experimental error for the Y _a/Y _c ratio is smaller than for each factor taken separately.     

Boundedness of solutions for semilinear reversible systems

In this paper we will study the boundedness of all solutions for second-order differential equations

where and satisfies the sublinear growth condition. Since the system in general is non-Hamiltonian, we have to introduce reversibility assumptions to apply the twist theorem for reversible mappings. Under some suitable conditions we then obtain the existence of invariant tori and thus the boundedness of all solutions.

     

大学物理实验的简化与深化

以复摆实验、地磁实验和衍射光栅实验为例,说明在大学物理实验中,通过提供简单的实验器材,就可以将实验内容延伸扩展,将原来内容单一的实验扩展为多层次、多目的的实验项目,实现大学物理实验的简化与深化.     

Synthesis of low grafting density molecular brush from a poly(N‐alkyl urea peptoid) backbone

The synthesis of a molecular brush was accomplished by combining step‐growth polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization in a “grafting from” methodology. A symmetrical N‐alkyl urea peptoid sixmer containing alkyne functional groups was prepared using a divergent strategy, and the structure of the product was confirmed using NMR spectroscopy and mass spectrometry. A step‐growth process was used to prepare a linear poly(N‐alkyl urea peptoid) by reacting the diamine‐functionalized N‐alkyl urea peptoid sixmer with a diisocyanate. RAFT chain transfer agents were coupled to the poly(N‐alkyl urea peptoid) backbone through a copper‐catalyzed azide/alkyne cycloaddition reaction. The afforded macro‐RAFT agent was used to sequentially polymerize styrene and tert‐butyl acrylate block copolymer arms from the poly(N‐alkyl urea peptoid) backbone. The tert‐butyl groups were removed using dilute trifluoroacetic acid affording hydrophilic polyacrylic acid segments. The molecular brushes were observed to generate micelles in aqueous solution. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Influence of the stirring speed and CaCl2 concentration on the nano‐object morphologies obtained via RAFT‐mediated aqueous emulsion polymerization in the presence of a water‐soluble macroRAFT agent

Aqueous emulsion polymerizations of styrene were performed in the presence of a macromolecular reversible addition‐fragmentation chain transfer (RAFT) agent (macroRAFT) composed of acrylic acid (AA) and poly(ethylene oxide) methyl ether acrylate (PEOA), end‐capped by a reactive dodecyl trithiocarbonate group (P(AA‐co‐PEOA)‐TTC). The influence of the stirring speed or the presence of different amounts of a divalent salt, CaCl₂, were investigated in this polymerization‐induced self‐assembly process, in which spherical and nonspherical nano‐objects were formed upon the synthesis of amphiphilic diblock copolymers in situ. It appeared that the addition of CaCl₂ led to the controlled formation of different nano‐objects such as spheres, fibers or vesicles, whereas an appropriate stirring speed was required for the formation of nanofibers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Block copolymer containing poly(3‐hexylthiophene) and poly(4‐vinylpyridine): Synthesis and its interaction with CdSe quantum dots for hybrid organic applications

Poly(3‐hexylthiophene)‐b‐poly(4‐vinylpyridine) diblock copolymer was synthesized by RAFT polymerization of 4‐vinyl pyridine using a trithiocarbonate‐terminated poly(3‐hexylthiophene) macro‐RAFT agent. The optoelectronic properties and the morphology of the block copolymer blends with CdSe quantum dots were investigated. UV‐vis and fluorescence experiments were performed to prove the charge transfer between CdSe and poly(3‐hexylthiophene)‐b‐poly(4‐vinylpyridine) diblock copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly(ascorbyl acrylate)s: Synthesis and evaluation of their redox polymerization ability in the presence of hydrogen peroxide

In this work, a strategy for chemical synthesis of ascorbic acid functionalized polyacrylates (PAAA) was accomplished in a two‐step process, first a reversible addition fragmentation chain‐transfer (RAFT) polymerization on a benzyl‐protected ascorbyl acrylate monomer, followed by a deprotection (debenzylation) reaction. The polymers were characterized by ¹H NMR, ¹³C NMR and gel permeation chromatograph. The polymerization ability of redox pair including PAAA and H₂O₂ were conducted through the measurement of 2‐hydroxyethyl acrylate (HEA) conversion against time via real‐time FT‐NIR. It was found that PAAA in the presence of H₂O₂, independent on itself chain length, exhibited much faster polymerization than small molecule ascorbic acid (smAA) as reductant at identical condition. Interestingly, when the concentration of ascorbate repeating unit was over some critical value, the polymerization kinetics of HEA could be tunable by simply adjusting the initial molar ratio of reductant to oxidant and environmental pH. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A Microgel Construction Kit for Bioorthogonal Encapsulation and pH‐Controlled Release of Living Cells

pH‐Cleavable cell‐laden microgels with excellent long‐term viabilities were fabricated by combining bioorthogonal strain‐promoted azide–alkyne cycloaddition (SPAAC) and droplet‐based microfluidics. Poly(ethylene glycol)dicyclooctyne and dendritic poly(glycerol azide) served as bioinert hydrogel precursors. Azide conjugation was performed using different substituted acid‐labile benzacetal linkers that allowed precise control of the microgel degradation kinetics in the interesting pH range between 4.5 and 7.4. By this means, a pH‐controlled release of the encapsulated cells was achieved upon demand with no effect on cell viability and spreading. As a result, the microgel particles can be used for temporary cell encapsulation, allowing the cells to be studied and manipulated during the encapsulation and then be isolated and harvested by decomposition of the microgel scaffolds.