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871.
Ooi WY Fujita M Pan P Tang HY Sudesh K Ito K Kanayama N Takarada T Maeda M 《Journal of colloid and interface science》2012,374(1):315-320
Poly(N-isopropylacrylamide) (PNIPAAm) grafted with single-stranded (ss) DNA conjugate (PNIPAAm-g-DNA) self-assembles above its lower critical solution temperature to form colloidal particles. When the ssDNA within the particle hybridizes with its complementary DNA, the particles aggregate above a certain threshold of salt concentration with drastically increased turbidity in solution. Detailed structural information of the particle was obtained mainly by small-angle X-ray scattering. The influence of copolymer composition on the morphology of particle and non-crosslinking aggregation was examined. The particle consists of hydrophobic PNIPAAm core surrounded by hydrophilic DNA strands. The increase in DNA fraction brought about a significant decrease in core size, whereas the shell thickness little changed and corresponded to the length of DNA. A structural model with a sticky potential was applied to the analysis of particle aggregate. This analysis provided that the particles aggregate while the coronal layers interpenetrate each other. The interaction between the particles was quantified in terms of the sticky potential and showed a trend to be influenced by the particle size rather than the graft density of DNA strands on the particle. 相似文献
872.
873.
Prof. Dr. Tsutomu Hoshino Akifumi Chiba Naomi Abe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13108-13116
Lanosterol synthase catalyzes the polycyclization reaction of (3S)‐2,3‐oxidosqualene ( 1 ) into tetracyclic lanosterol 2 by folding 1 in a chair‐boat‐chair‐chair conformation. 27‐Nor‐ and 29‐noroxidosqaulenes ( 7 and 8 , respectively) were incubated with this enzyme to investigate the role of the methyl groups on 1 for the polycyclization cascade. Compound 7 afforded two enzymatic products, namely, 30‐norlanosterol ( 12 ) and 26‐normalabaricatriene ( 13 ; 12 / 13 9:1), which were produced through the normal chair‐boat‐chair‐chair conformation and an atypical chair‐chair‐boat conformation, respectively. Compound 8 gave two products 14 and 15 ( 14 / 15 4:5), which were generated by the normal and the unusual polycyclization pathways through a chair‐chair‐boat‐chair conformation, respectively. It is remarkable that the twist‐boat structure for the B‐ring formation was changed to an energetically favored chair structure for the generation of 15 . Surprisingly, 14 and 15 consisted of a novel 6,6,6,6‐fused tetracyclic ring system, thus differing from the 6,6,6,5‐fused lanosterol skeleton. Together with previous results, we conclude that the methyl‐29 group is critical to the correct folding of 1 , with lesser contributions from the other branched methyl groups, such as methyl‐26, ‐27, and ‐28. Furthermore, we demonstrate that the methyl‐29 group has a crucial role in the formation of the five‐membered D ring of the lanosterol scaffold. 相似文献
874.
Akifumi?Kijima Keiko?Yokoyama Hiroyuki?ShimaEmail author Yuji?Yamamoto 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(2):41
The multiplayer dynamics of a football game is analyzed to unveil self-similarities in the time evolution of player and ball positioning. Temporal fluctuations in both the team-turf boundary and the ball location are uncovered to follow the rules of fractional Brownian motion with a Hurst exponent of H ~ 0.7. The persistence time below which self-similarity holds is found to be several tens of seconds, implying a characteristic time scale that governs far-from-equilibrium motion on a playing field. 相似文献
875.
Michito Yoshizawa Dr. Jeremy K. Klosterman Dr. Makoto Fujita Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(19):3418-3438
Insider dealing : Self‐assembled hosts applied as “molecular flasks” can alter and control the reactivity and properties of molecules encapsulated within their well‐defined, confined spaces. A variety of functional hosts of differing sizes, shapes, and utility have been prepared by using the facile and modular concepts of self‐assembly.
876.
Shinya Fujita 《Discrete Mathematics》2009,309(11):3534-3540
Let k,n be integers with 2≤k≤n, and let G be a graph of order n. We prove that if max{dG(x),dG(y)}≥(n−k+1)/2 for any x,y∈V(G) with x≠y and xy∉E(G), then G has k vertex-disjoint subgraphs H1,…,Hk such that V(H1)∪?∪V(Hk)=V(G) and Hi is a cycle or K1 or K2 for each 1≤i≤k, unless k=2 and G=C5, or k=3 and G=K1∪C5. 相似文献
877.
878.
Dr. Atsushi Hirano Prof. Dr. Yutaka Maeda Dr. Xiaofei Yuan Ryuuichi Ueki Yosuke Miyazawa Prof. Dr. Jun‐ichi Fujita Prof. Dr. Takeshi Akasaka Prof. Dr. Kentaro Shiraki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(40):12221-12228
For the development of biofunctional carbon nanotubes for biosensors, drug carriers, and nanobiocatalysts, their aggregation and biofouling in aqueous solutions are crucial problems because this behavior leads to a reduction of their excellent optical and electrical properties and nanoscale size effects. This paper presents a new method for enhancing the dispersibility of protein–carbon nanotube conjugates and for exfoliating the protein from the carbon nanotube sidewalls through controlling the concentration of guanidine hydrochloride (Gdn ? HCl) in the solution. In medium concentrations (2–3 M ) of Gdn ? HCl, the dispersibility of protein–carbon nanotube conjugates was found to be substantially increased without denaturation or aggregation of the proteins. At higher concentrations (>6 M ) of Gdn ? HCl, pristine carbon nanotubes were precipitated instantly as a result of dissociation of the protein. These phenomena indicate that Gdn ? HCl functions not only as a dispersion adjuvant for biofunctional protein–carbon nanotube conjugates, but also as a cleaning agent for the purification of biofouled carbon nanotubes. The dissociation concentrations of Gdn ? HCl were higher than the midpoint of protein denaturation, suggesting that protein adsorption on carbon nanotubes is more stable than protein folding toward Gdn ? HCl. 相似文献
879.
Novel water-soluble Cp*Ir-ammine complexes have been synthesized, and a new and highly atom-economical system for the synthesis of organic amines using aqueous ammonia as a nitrogen source has been developed. With a water-soluble and air-stable Cp*Ir-ammine catalyst, [Cp*Ir(NH(3))(3)][I](2), a variety of tertiary and secondary amines were synthesized by the multialkylation of aqueous ammonia with theoretical equivalents of primary and secondary alcohols. The catalyst could be recycled by a facile procedure maintaining high activity. A one-flask synthesis of quinolizidine starting with 1,5,9-nonanetriol was also demonstrated. This new catalytic system would provide a practical and environmentally benign methodology for the synthesis of various organic amines. 相似文献
880.
Perfectly monodisperse DNA nanoparticles were prepared via the self-assembly of 12 Pd(II) ions and 24 bidentate ligands functionalized with oligonucleotides of varying length (n = 1-3). The DNA nanoparticles formed hydrogen bonds with cDNA strands and an insoluble aggregate formed only with matching trimeric nucleotide strands (tri-A). 相似文献