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排序方式: 共有1149条查询结果,搜索用时 15 毫秒
931.
Hyung Soon Park Joo Hee Cho Junghun Suh 《Journal of polymer science. Part A, Polymer chemistry》1997,35(14):2935-2942
Three molecules of 5-(bromoacetyl)salicylate ( 1 ) complexed to uranyl UO ion were crosslinked with branchy poly(ethylenimine) (PEI) in DMSO by alkylation of amino groups of PEI with 1, leading to the formation of UO2(Sal) PEI. Upon demetalation of UO2(Sal) PEI with HCl, apo(Sal) PEI was obtained. Based on the pH dependence of log Kf for UO2(Sal) PEI, it was concluded that each uranyl binding site in UO2(Sal) PEI or apo(Sal) PEI contains three salicylate moieties. In terms of the equilibrium constant for formation of the uranyl complex, apo(Sal) PEI was found to be comparable to or better than the previously reported effective uranophiles. In terms of the rates for the formation of the uranyl complex, however, apo(Sal) PEI was far superior to those other uranophiles. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2935–2942, 1997 相似文献
932.
Indrajit Bandyopadhyay Kyung Hui Oh Sik Lee Seung Joo Cho Seung Bin Kim 《Journal of Molecular Structure》2004,680(1-3):211-217
The s-cis and s-trans isomers resulting from the rotation about the acyl–oxygen bond of two envelope conformations with C5 (neighbour to substituted carbon C4) and C4 as apical atoms in the five-membered ring and vibrational spectra of cyclopentyl acetate are studied with density functional molecular orbital theory at the B3LYP/6-311++G** level. In the case of C5 at the flap and –OAc group in the axial position, it is found that the s-cis isomer (1:s-cis) is more stable than the s-trans isomer (1:s-trans) by 7.46 kcal/mol. The s-cis–s-trans rotational barrier is 15 kcal/mol. The other two conformers with C4 at the flap and –OAc group in the equatorial position, the relative energies of the s-cis and s-trans isomers (2:s-cis and 2:s-trans) with respect to 1:s-cis are found to be 0.45 and 8.21 kcal/mol, respectively. The infrared spectra (200–3200 cm−1) in gas and liquid phase and Raman spectra (3200–150 cm−1) in liquid phase for cyclopentyl acetate and 10 of its isotopomers are recorded. The calculated spectra of all conformers along with the observed spectra has helped study the effect of rotational isomerism on the vibrational spectra. The normal coordinate analysis in terms of non-redundant local coordinates is done for vibrational assignments of the 57 normal modes. The experimental and theoretical results are compared to the corresponding quantities of some similar molecules. 相似文献
933.
Byung Joo Lee Kimberly S. DeGlopper Prof. Tehshik P. Yoon 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):203-208
Methods that enable the direct C−H alkoxylation of complex organic molecules are significantly underdeveloped, particularly in comparison to analogous strategies for C−N and C−C bond formation. In particular, almost all methods for the incorporation of alcohols by C−H oxidation require the use of the alcohol component as a solvent or co-solvent. This condition limits the practical scope of these reactions to simple, inexpensive alcohols. Reported here is a photocatalytic protocol for the functionalization of benzylic C−H bonds with a wide range of oxygen nucleophiles. This strategy merges the photoredox activation of arenes with copper(II)-mediated oxidation of the resulting benzylic radicals, which enables the introduction of benzylic C−O bonds with high site selectivity, chemoselectivity, and functional-group tolerance using only two equivalents of the alcohol coupling partner. This method enables the late-stage introduction of complex alkoxy groups into bioactive molecules, providing a practical new tool with potential applications in synthesis and medicinal chemistry. 相似文献
934.
935.
Won-Woo Park Kyung Min Lee Dr. Byeong Sung Lee Young Jae Kim Se Hun Joo Prof. Dr. Sang Kyu Kwak Prof. Dr. Tae Hyeon Yoo Prof. Dr. Oh-Hoon Kwon 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7155-7162
Here, we propose an experimental methodology based on femtosecond-resolved fluorescence spectroscopy to measure the hydrogen (H)-bond free energy of water at protein surfaces under isothermal conditions. A demonstration was conducted by installing a non-canonical isostere of tryptophan (7-azatryptophan) at the surface of a coiled-coil protein to exploit the photoinduced proton transfer of its chromophoric moiety, 7-azaindole. The H-bond free energy of this biological water was evaluated by comparing the rates of proton transfer, sensitive to the hydration environment, at the protein surface and in bulk water, and it was found to be higher than that of bulk water by 0.4 kcal mol−1. The free-energy difference is dominated by the entropic cost in the H-bond network among water molecules at the hydrophilic and charged protein surface. Our study opens a door to accessing the energetics and dynamics of local biological water to give insight into its roles in protein structure and function. 相似文献
936.
Xiang Ji Teng Zhou Yongbo Deng Liuyong Shi Xianman Zhang Sang Woo Joo 《Electrophoresis》2020,41(10-11):758-760
A completely new droplet breakup phenomenon is reported for droplets passing through a constriction in an electrokinetic flow. The breakup occurs during the droplet shape recovery process past the constriction throat by the interplay of the dielectrophoretic stress release and the interface energy for droplets with smaller permittivity than that of the ambient fluid. There are conditions for constriction ratios and droplet size that the droplet breakup occurs. The numerical predictions provided here require experimental verification, and then can give rise to a novel microfluidic device design with novel droplet manipulations. 相似文献
937.
938.
Dr. Hyo-Jung Park Dr. Eun-Kyoung Bang Dr. Jung Joo Hong Prof. Dr. Sang-Myeong Lee Hae Li Ko Hye Won Kwak Dr. Hyelim Park Kyung Won Kang Rhoon-Ho Kim Seung Rok Ryu Green Kim Dr. Hanseul Oh Hye-Jung Kim Dr. Kyuri Lee Minjeong Kim Soo Young Kim Dr. Jae-Ouk Kim Karim El-Baz Prof. Dr. Hyukjin Lee Dr. Manki Song Dr. Dae Gwin Jeong Dr. Gyochang Keum Prof. Dr. Jae-Hwan Nam 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11637-11646
As agonists of TLR7/8, single-stranded RNAs (ssRNAs) are safe and promising adjuvants that do not cause off-target effects or innate immune overactivation. However, low stability prevents them from mounting sufficient immune responses. This study evaluates the adjuvant effects of ssRNA derived from the cricket paralysis virus intergenic region internal ribosome entry site, formulated as nanoparticles with a coordinative amphiphile, containing a zinc/dipicolylamine complex moiety as a coordinative phosphate binder, as a stabilizer for RNA-based adjuvants. The nanoformulated ssRNA adjuvant was resistant to enzymatic degradation in vitro and in vivo, and that with a coordinative amphiphile bearing an oleyl group ( CA-O ) was approximately 100 nm, promoted effective recognition, and improved activation of antigen-presenting cells, leading to better induction of neutralizing antibodies following single immunization. Hence, CA-O may increase the efficacy of ssRNA-based adjuvants, proving useful to meet the urgent need for vaccines during pathogen outbreaks. 相似文献
939.
Malina Bilo Maximilian Münzner Christian Küster Prof. Dirk Enke Dr. Young Joo Lee Prof. Michael Fröba 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11220-11230
Herein, it is reported how pseudomorphic transformation of divinylbenzene (DVB)-bridged organosilica@controlled pore glasses (CPG) offers the possibility to generate hierarchically porous organosilica/silica hybrid materials. CPG is utilized to provide granular shape/size and macroporosity and the macropores of the CPG is impregnated with organosilica phase, forming hybrid system. By subsequent pseudomorphic transformation, an ordered mesopore phase is generated while maintaining the granular shape and macroporosity of the CPG. Surface areas and mesopore sizes in the hierarchical structure are tunable by the choice of the surfactant and transformation time. Two-dimensional magic angle spinning (MAS) NMR spectroscopy demonstrated that micellar-templating affects both organosilica and silica phases and pseudomorphic transformation induces phase transition. A double-layer structure of separate organosilica and silica layers is established for the impregnated material, while a single monophase consisting of randomly distributed T and Q silicon species at the molecular level is identified for the pseudomorphic transformed materials. 相似文献
940.
Native mass spectrometry (nMS) is a rapidly growing method for the characterization of large proteins and protein complexes, preserving “native” non-covalent inter- and intramolecular interactions. Direct infusion of purified analytes into a mass spectrometer represents the standard approach for conducting nMS experiments. Alternatively, CZE can be performed under native conditions, providing high separation performance while consuming trace amounts of sample material. Here, we provide standard operating procedures for acquiring high-quality data using CZE in native mode coupled online to various Orbitrap mass spectrometers via a commercial sheathless interface, covering a wide range of analytes from 30–800 kDa. Using a standard protein mix, the influence of various CZE method parameters were evaluated, such as BGE/conductive liquid composition and separation voltage. Additionally, a universal approach for the optimization of fragmentation settings in the context of protein subunit and metalloenzyme characterization is discussed in detail for model analytes. A short section is dedicated to troubleshooting of the nCZE-MS setup. This study is aimed to help normalize nCZE-MS practices to enhance the CE community and provide a resource for the production of reproducible and high-quality data. 相似文献