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991.
Kohji Yoshinaga Suguru Motokucho Ken Kojio Akemi Nakai 《Colloid and polymer science》2012,290(12):1221-1226
Dispersion of fullerene, C60, by addition of polymethacrylate dispersant in methyl methacrylate (MMA) and incorporation of C60 into poly(methyl methacrylate) (PMMA) were investigated. Copolymers synthesized by radical copolymerization of MMA and 2-naphthyl methacrylate (NMA), poly(MMA-co-NMA), effectively dispersed C60 in MMA to form clusters of 20?nm. In these cases, addition of minimal 110 naphthyl groups per unit C60 molecule afforded to give clusters with minimum of 20?nm sizes. Furthermore, block copolymers, poly(MMA-b-NMA) with MMA/NMA mole ratio from 12:1 to 20:1, also efficiently dispersed C60 to give formation of clusters of 20?nm size by addition of minimal 40 naphthyl groups per unit C60 molecule, which was corresponding to approximate nine layers of naphthyl group in block copolymer adsorbed on the surface of the cluster. Hybrid films of C60/PMMA, prepared by casting of C60-dispersed solution containing PMMA, exhibited absorbance at 400?nm linearly increased with C60 content. 相似文献
992.
Leung KC Xuan S Zhu X Wang D Chak CP Lee SF Ho WK Chung BC 《Chemical Society reviews》2012,41(5):1911-1928
This critical review provides an overview of current research activities that focused on the synthesis and application of multi-functional gold and iron oxide (Au-Fe(x)O(y)) hybrid nanoparticles and nanocomposites. An introduction of synthetic strategies that have been developed for generating Au-Fe(x)O(y) nanocomposites with different nanostructures is presented. Surface functionalisation and bioconjugation of these hybrid nanoparticles and nanocomposites are also reviewed. A variety of applications such as theranostics, gene delivery, biosensing, cell sorting, bio-separation, and catalysis is discussed and highlighted. Finally, future trends and perspectives of these sophisticated nanocomposites are outlined. Underpinning the fundamental requirements for effectively forming Au-Fe(x)O(y) hybrid nanocomposite materials would shed light on future development of nanotheranostics, nanomedicines, and chemical technologies. It would be interesting to investigate such multi-component composite nanomaterials with different novel morphologies in the near future to advance chemistry, biology, medicine, and engineering multi-disciplinary research (120 references). 相似文献
993.
Chan CH Chen FJ Huang YJ Chen SY Liu KL Wang ZC Peng HL Yew TR Liu CH Liou GG Hsu KY Chang HY Hsu L 《Langmuir : the ACS journal of surfaces and colloids》2012,28(19):7428-7435
The Klebsiella pneumoniae type 3 fimbriae are mainly composed of MrkA pilins that assemble into a helixlike filament. This study determined the biomechanical properties of the fimbriae and analyzed 11 site-directed MrkA mutants to identify domains that are critical for the properties. Escherichia coli strains expressing type 3 fimbriae with an Ala substitution at either F34, V45, C87, G189, T196, or Y197 resulted in a significant reduction in biofilm formation. The E. coli strain expressing MrkAG189A remained capable of producing a normal number of fimbriae. Although F34A, V45A, T196A, and Y197A substitutions expressed on E. coli strains produced sparse quantities of fimbriae, no fimbriae were observed on the cells expressing MrkAC87A. Further investigations of the mechanical properties of the MrkAG189A fimbriae with optical tweezers revealed that, unlike the wild-type fimbriae, the uncoiling force for MrkAG189A fimbriae was not constant. The MrkAG189A fimbriae also exhibited a lower enthalpy in the differential scanning calorimetry analysis. Together, these findings indicate that the mutant fimbriae are less stable than the wild-type. This study has demonstrated that the C-terminal β strands of MrkA are required for the assembly and structural stability of fimbriae. 相似文献
994.
We report here a test of the Semi-Explicit Assembly (SEA) model in the solvation free energy category of the SAMPL3 blind prediction event (summer 2011). We tested how dependent the SEA results are on the chosen force field by performing calculations with both the General Amber and OPLS force fields. We compared our SEA results with full molecular dynamics simulations in explicit solvent. Of the 20 submissions, our SEA/OPLS results gave the second smallest RMS errors in free energies compared to experiments. SEA gives results that are very similar to those of its underlying force field and explicit solvent model. Hence, while the SEA water modeling approach is much faster than explicit solvent simulations, its predictions appear to be just as accurate. 相似文献
995.
Steve Po‐Yam Li Tommy Siu‐Ming Tang Dr. Ken Shek‐Man Yiu Prof. Kenneth Kam‐Wing Lo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(42):13342-13354
A new class of phosphorescent cyclometalated iridium(III)–polyamine complexes [{Ir(N^C)2}n(bPEI)](PF6)n (bPEI=branched poly(ethyleneimine), average Mw=25 kDa, n=15.6–27.4; HN^C=2‐phenylpyridine Hppy ( 1 a ), 2‐((1,1′‐biphenyl)‐4‐yl)pyridine Hpppy ( 2 a ), 2‐phenylquinoline Hpq ( 3 a ), 2‐phenylbenzothiazole Hbt ( 4 a ), 2‐(1‐naphthyl)benzothiazole Hbsn ( 5 a )) and [Ir(N^C)2(en)](PF6) (en=ethylenediamine; HN^C=Hppy ( 1 b ), Hpppy ( 2 b ), Hpq ( 3 b ), Hbt ( 4 b ), Hbsn ( 5 b )) have been synthesized and characterized. The X‐ray crystal structure of complex 5 b was also determined. All of these complexes showed a reversible iridium(IV/III) oxidation couple at +1.01 to +1.26 V and a quasi‐reversible ligand‐based reduction couple at ?1.54 to ?2.08 V (versus SCE). Upon photoexcitation, the complexes displayed intense and long‐lived green to orange–red emission in fluid solutions at room temperature and in low‐temperature glass. Lipophilicity measurements indicated that bPEI played a dominant role in the polar nature of complexes 1 a – 5 a , thus rendering them very soluble in aqueous solutions. Inductively coupled plasma–mass spectrometry (ICP‐MS) and confocal laser scanning microscopy (CLSM) data indicated that an energy‐requiring process, such as endocytosis, was involved in the cellular uptake of all of the complexes. In addition, the cytotoxicity of the complexes toward human cervix epithelioid carcinoma (HeLa) and human embryonic kidney 293T (HEK293T) cell‐lines has been evaluated by the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. The DNA‐binding properties of complex 5 a have been investigated by gel‐retardation assays and the polyplexes that were formed from this complex with plasmid DNA (pDNA) were studied by zeta‐potential measurements and particle‐size estimation. Furthermore, complex 5 a was grafted with poly(ethylene glycol) (PEG, average Mw=2 kDa) to different extents, thereby yielding the phosphorescent copolymers PEG12.3‐g‐5 a , PEG25.4‐g‐5 a , and PEG62.1‐g‐5 a . Interestingly, these copolymers showed enhanced transfection activity, as revealed by in vitro transfection experiments with tissue‐culture‐based luciferase assays. 相似文献
996.
Agnieszka Bartoszewicz Dr. Rocío Marcos Dr. Suman Sahoo Dr. A. Ken Inge Prof. Xiaodong Zou Dr. Belén Martín‐Matute 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(45):14510-14519
A series of new iridium(III) complexes containing bidentate N‐heterocyclic carbenes (NHC) functionalized with an alcohol or ether group (NHC? OR, R=H, Me) were prepared. The complexes catalyzed the alkylation of anilines with alcohols as latent electrophiles. In particular, biscationic IrIII complexes of the type [Cp*(NHC‐OH)Ir(MeCN)]2+2[BF4?] afforded higher‐order amine products with very high efficiency; up to >99 % yield using a 1:1 ratio of reactants and 1–2.5 mol % of Ir, in short reaction times (2–16 h) and under base‐free conditions. Quantitative yields were also obtained at 50 °C, although longer reaction times (48–60 h) were needed. A large variety of aromatic amines have been alkylated with primary and secondary alcohols. The reactivity of structurally related iridium(III) complexes was also compared to obtain insights into the mechanism and into the structure of possible catalytic intermediates. The IrIII complexes were stable towards oxygen and moisture, and were characterized by NMR, HRMS, single‐crystal X‐ray diffraction, and elemental analyses. 相似文献
997.
User influence is generally considered as one of the most critical factors that affect information cascading spreading. Based on this common assumption, this paper proposes a theoretical model to examine user influence on the information multi-step communication in a micro-biog. The multi-steps of information communication are divided into first-step and non-first-step, and user influence is classified into five dimensions. Actual data from the Sina micro-blog is collected to construct the model by means of an approach based on structural equations that uses the Partial Least Squares (PLS) technique. Our experimental results indicate that the dimensions of the number of fans and their authority significantly impact the information of first-step conxrnunication. Leader rank has a positive impact on both first-step and non-first-step communication. Moreover, global centrality and weight of friends are positively related to the information non-first-step communication, but authority is found to have much less relation to it. 相似文献
998.
Louis Nadelson Cheryl Jorcyk Dazhi Yang Mary Jarratt Smith Sam Matson Ken Cornell Virginia Husting 《School science and mathematics》2014,114(2):76-86
Trust in science and scientists can greatly influence consideration of scientific developments and activities. Yet, trust is a nebulous construct based on emotions, knowledge, beliefs, and relationships. As we explored the literature regarding trust in science and scientists we discovered that no instruments were available to assess the construct, and therefore, we developed one. Using a process of data collection from science faculty members and undergraduate students, field testing, expert feedback, and an iterative process of design, we developed, validated, and established the reliability of the Trust in Science and Scientist Inventory. Our 21‐item instrument has a reliability of Cronbach's alpha of .86, and we have successfully field‐tested it with a range of undergraduate college students. We discuss implications and possible applications of the instrument, and include it in the appendix. 相似文献
999.
Robert R. Milburn Ken McRae Johann Chan Jason Tedrow Robert Larsen Margaret Faul 《Tetrahedron letters》2009,50(8):870-9099
The condensation of alkyl phosphonates with aryl esters to give β-ketophosphonates may be carried out at elevated temperatures mediated by LiHMDS under Barbier type conditions. The reaction is scalable, does not require specialized cryogenic equipment, and is general for all aryl and heteroaryl esters examined. 相似文献
1000.
Ken Kamikawa Takayuki Shiromoto Jun Yamaguchi Shin Takemoto Hiroyuki Matsuzaka 《Research on Chemical Intermediates》2009,35(8-9):931-937
Peptide-based organocatalysts with a helical structure induced by a terminal l-histidine derivative were synthesized. These organocatalysts were applied to the kinetic resolution of secondary alcohol. 相似文献