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921.
922.
Wei H Cheng C Chang C Chen WQ Cheng SX Zhang XZ Zhuo RX 《Langmuir : the ACS journal of surfaces and colloids》2008,24(9):4564-4570
Shell cross-linked (SCL) thermoresponsive hybrid micelles consisting of a cross-linked thermoresponsive hybrid hydrophilic shell and a hydrophobic core domain were synthesized from poly(N-isopropylacrylamide-co-3- (trimethoxysilyl)propyl methacrylate)-b-polymethyl methacrylate (P(NIPAAm-co-MPMA)-b-PMMA) amphiphilic block copolymers. Transmission electron microscopy (TEM) images showed that the SCL micelles formed regularly globular nanoparticles. The SCL micelles showed reversible dispersion/aggregation in response to temperature cycles through an outer polymer shell lower critical solution temperature (LCST) for PNIPAAm at around 33 degrees C, observed by turbidity measurements and dynamic light scattering (DLS). The drug loading and in vitro drug release properties of the SCL micelles bearing a silica-reinforced PNIPAAm shell were further studied, which showed that the SCL micelles exhibited a much improved entrapment efficiency (EE) as well as a slower release rate which allowed the entrapped molecules to be slowly released over a much longer period of time as compared with pure PNIPAAm-b-PMMA micelles. 相似文献
923.
By using the positive linear functional and the monotone subhomogeneous functional, including the general means and Riccati technique, some new oscillation criteria are established for the second order linear matrix differential system
(P(t)X'(t))' + R(t)X'(t) + Q(t)X(t) =0, t ≥ to 〉 0
where P(t), R(t), Q(t) are n × n real continuous matrix functions, P(t) and R(t) are commutative. Theresults improve and generalize those given in some previous papers, which can be seen by the examples given at the end of this paper. 相似文献
(P(t)X'(t))' + R(t)X'(t) + Q(t)X(t) =0, t ≥ to 〉 0
where P(t), R(t), Q(t) are n × n real continuous matrix functions, P(t) and R(t) are commutative. Theresults improve and generalize those given in some previous papers, which can be seen by the examples given at the end of this paper. 相似文献
924.
An electrochemically deposited poly3-methylthiophene (P3MT) thin film has been used as the primary electrochromic element
in a solid two-electrode electrochromic device (ECD) with a viscous polymeric electrolyte (PE) of polymethyl methacrylate
and lithium perchlorate co-dissolved in ethylene and propylene carbonates. The counter-electrode of the ECD was a transparent
conductive (indium-tin oxide, ITO) glass (single ECD) or a polyaniline (PANI)-coated ITO glass (dual ECD). Dual P3MT-PANI-based
ECDs exhibit a lower optical switch potential (less than 0.5 V) and a faster color change speed (around 1 s) compared with
the single devices, independent on the lithium salt concentration and the viscosity of the polymeric electrolyte. Electrochemical
impedance spectra of both types of ECDs were analyzed at zero bias. It indicates that the use of the secondary electroactive
element leads to a lower counter-ion diffusion resistance as well as to a larger counter-ion storage capacity in the electrochromic
element/polymeric electrolyte interfaces. Consequently, the oxidation–reduction potential is lower, and the charge transfer
process is faster in the dual devices than those in the single ones. 相似文献
925.
Zhao Y Ruan JL Wang JH Cong Y Song S Cai YL Fang W Zhou DN 《Natural product research》2008,22(3):233-240
3 Beta-acetoxy-(20S, 22E)-dammaran-22-en-25-ol, a new triterpene, was isolated along with five known triterpenes (ursolic acid, oleanolic acid, betulinic acid, 3-epiocotillol acetate, and dimmarenediol II acetate), and alpha-D-glc and sucrose from Radix Ranunculus ternati All of them, except oleanolic acid and alpha-D-glc, were isolated from the family of Ranunculaceae for the very first time, and the NMR data of sucrose was first described. In addition, the absolute configurations of alpha-D-glc and the glucose component of sucrose were determined. 相似文献
926.
Poly(ethylene glycol) (PEG) is a hydrophilic nonionic polymer used in many biochemical and pharmaceutical applications. We report the four diffusion coefficients for the PEG-KCl-water ternary system at 25 degrees C using precision Rayleigh interferometry. Here, the molecular weight of PEG is 20 kg mol(-1), which is comparable to that of proteins. The four diffusion coefficients are examined and used to determine thermodynamic preferential interaction coefficients. We find that the PEG preferential hydration in the presence of KCl is 1 order of magnitude larger than that previously obtained under the same conditions for lysozyme, a protein of similar molecular weight. In correspondence, the coupled diffusion in the PEG case was greater than that observed in the lysozyme case. We attribute this difference to the greater exposure of polymer coils to the surrounding fluid compared to that of globular compact proteins. Moreover, we observe that the PEG preferential hydration significantly decreases as salt concentration increases and attribute this behavior to the polymer collapse. Finally, we have also employed the equilibrium isopiestic method to validate the accuracy of the preferential interaction coefficients extracted from the diffusion coefficients. This experimental comparison represents an important contribution to the relation between diffusion and equilibrium thermodynamics. 相似文献
927.
A two-dimensional capillary electrophoresis platform, combining isoelectric focusing (IEF) and capillary zone electrophoresis (CZE), was established on a microchip with the channel width and depth as 100 mum and 40 mum, respectively. With polyacrylamide as permanent coating, EOF in the microchannel, which could impair the separation, was decreased to 3.4x10(-9)m(2).V(-1).s(-1), about 1/10 of that obtained in the uncoated set-up. During the separation, peptides were first focused by IEF in the first dimensional channel, and then directly driven into the perpendicular channel by controlling the applied voltages, and separated by CZE. Effects of various experimental parameters, including the electric field strength, channel length, and injection frequency from the first to the second dimensional separation channel, were studied. Under optimized condition, the digests of BSA and proteins extracted from E. coli were separated, and a peak capacity of 540 was obtained, which was far greater than that obtained by each single dimensional separation. All these results showed the promise of multidimensional separation on a microchip for the high-throughput and high-resolution analysis of complex samples. 相似文献
928.
Jian-An Li Letian Zhang Dr. Chunlei Wu Zihao Huang Shufeng Li Huaqing Zhang Qingchen Yang Dr. Zhu Mao Prof. Suilian Luo Prof. Cong Liu Prof. Guang Shi Prof. Bingjia Xu 《Angewandte Chemie (International ed. in English)》2023,62(7):e202217284
In this work, an efficient polymer-based organic afterglow system, which shows reversible photochromism, switchable ultralong organic phosphorescence (UOP), and prominent water and chemical resistance simultaneously, has been developed for the first time. By doping phenoxazine (PXZ) and 10-ethyl-10H-phenoxazine (PXZEt) into epoxy polymers, the resulting PXZ@EP-0.25 % and PXZEt@EP-0.25 % films show unique photoactivated UOP properties, with phosphorescence quantum yields and lifetimes up to 10.8 % and 845 ms, respectively. It is found that the steady-state luminescence and UOP of PXZ@EP-0.25 % are switchable by light irradiation and thermal annealing. Moreover, the doped films can still produce conspicuous UOP after soaking in water, strong acid and base, and organic solvents for more than two weeks, exhibiting outstanding water and chemical resistance. Inspired by these exciting results, the PXZ@EP-0.25 % has been successfully exploited as an erasable transparent film for light printing. 相似文献
929.
Xiangquan Qin Dr. Yiping Jiang Fuquan Yao Dr. Jie Chen Dr. Fanhui Kong Panxia Zhao Prof. Dr. Longyi Jin Prof. Dr. Zhiqi Cong 《Angewandte Chemie (International ed. in English)》2023,62(51):e202311259
A recent novel strategy for constructing artificial metalloenzymes (ArMs) that target new-to-nature functions uses dual-functional small molecules (DFSMs) with catalytic and anchoring groups for converting P450BM3 monooxygenase into a peroxygenase. However, this process requires excess DFSMs (1000 equivalent of P450) owing to their low binding affinity for P450, thus severely limiting its practical application. Herein, structural optimization of the DFSM-anchoring group considerably enhanced their binding affinity by three orders of magnitude (Kd≈10−8 M), thus approximating native cofactors, such as FMN or FAD in flavoenzymes. An artificial cofactor-driven peroxygenase was thus constructed. The co-crystal structure of P450BM3 bound to a DFSM clearly revealed a precatalytic state in which the DFSM participates in H2O2 activation, thus facilitating peroxygenase activity. Moreover, the increased binding affinity substantially decreases the DFSM load to as low as 2 equivalents of P450, while maintaining increased activity. Furthermore, replacement of catalytic groups showed disparate selectivity and activity for various substrates. This study provides an unprecedented approach for assembling ArMs by binding editable organic cofactors as a co-catalytic center, thereby increasing the catalytic promiscuity of P450 enzymes. 相似文献
930.
Bouslimani N Clément N Rogez G Turek P Bernard M Dagorne S Martel D Cong HN Welter R 《Inorganic chemistry》2008,47(17):7623-7630
We report here experimental evidence for the formation in the solid state of a new binuclear Fe (III) 2(mu-OMe) 2(HL) 4 complex (H 2L is 2-salicyloylhydrazono-1,3-dithiolane). The isostructural Mn (III) 2(mu-OMe) 2(HL) 4 complex has provided the strongest ferromagnetic interaction value (J approximately 20 cm (-1)) between Mn (III) ions to date. The new iron binuclear compound presented in this study shows antiferromagnetic intramolecular coupling, which agrees with the theoretical study that we previously proposed. During our synthetic work, we also observed an unexpected spontaneous reduction of the new Fe (III)(HL) 2Cl,S complex to the new Fe (II)(H 2L) 2Cl 2 high-spin mononuclear complex. This process has been checked by cyclo-voltammetry as well as pseudosteady voltammetry. 相似文献