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451.
Syuji Fujii Tatsushi Isojima Naoki Sasaki Kenji Kubota Mitsuo Nakata 《Colloid and polymer science》2003,281(5):439-446
The viscoelastic behavior of the shear-induced structural transformation from the lamellar phase to multilamellar vesicles (MLVs) of a mixed-surfactant system was investigated. The transformation was divided into two processes on the basis of the strain dependence of the apparent viscosity. The first stage is a lamellar-to-intermediate structure transformation. It was found that a strain, not an applied shear rate, governed this process. The second stage is an intermediate-to-MLV phase transformation, which was not controlled by the strain. These structure developments were found in the shear-thickening viscosity regime. The MLV phase formed by applying shear flow exhibited shear-thinning viscosity behavior and reversible response to shear flow. The viscoelastic properties of the MLV phase were investigated by dynamic viscoelastic measurements. Under oscillating shear deformation, the amplitude dependence of the dynamic modulus indicated that the viscoelasticity of the MLV depended on the initial structure, such as the number of vesicle shells and the size of the MLV, which is governed by the preshear rate. 相似文献
452.
An efficient convergent strategy for the construction of a trans-fused 6-6-6-6-membered tetracyclic ether ring system was developed. The key steps involve coupling of two cyclic ethers by esterification, SmI2-promoted intramolecular reductive cyclization of iodo ester to hemiacetal, dehydration to dihydropyran, hydroboration, oxidation, intramolecular acetalization, and Lewis-acid catalyzed silane reduction. 相似文献
453.
A drastic innovation has been achieved in the time-resolved far-infrared magnetooptics by introducing multichannellisation of the delay time. The key section of the new system utilises a digital boxcar unit connected with a common personal computer. Making use of a test pattern signal by magneto-plasma absorption of electron-hole drops in Ge, an eight channel performance over the time window of 100 s is demonstrated. 相似文献
454.
Fukuzawa K Kitaura K Uebayasi M Nakata K Kaminuma T Nakano T 《Journal of computational chemistry》2005,26(1):1-10
We have theoretically examined the relative binding affinities (RBA) of typical ligands, 17beta-estradiol (EST), 17alpha-estradiol (ESTA), genistein (GEN), raloxifene (RAL), 4-hydroxytamoxifen (OHT), tamoxifen (TAM), clomifene (CLO), 4-hydroxyclomifene (OHC), diethylstilbestrol (DES), bisphenol A (BISA), and bisphenol F (BISF), to the alpha-subtype of the human estrogen receptor ligand-binding domain (hERalpha LBD), by calculating their binding energies. The ab initio fragment molecular orbital (FMO) method, which we have recently proposed for the calculations of macromolecules such as proteins, was applied at the HF/STO-3G level. The receptor protein was primarily modeled by 50 amino acid residues surrounding the ligand. The number of atoms in these model complexes is about 850, including hydrogen atoms. For the complexes with EST, RAL, OHT, and DES, the binding energies were calculated again with the entire ERalphaLBD consisting of 241 residues or about 4000 atoms. No significant difference was found in the calculated binding energies between the model and the real protein complexes. This indicates that the binding between the protein and its ligands is well characterized by the model protein with the 50 residues. The calculated binding energies relative to EST were very well correlated with the experimental RBA (the correlation coefficient r=0.837) for the ligands studied in this work. We also found that the charge transfer between ER and ligands is significant on ER-ligand binding. To our knowledge, this is the first achievement of ab initio quantum mechanical calculations of large molecules such as the entire ERalphaLBD protein. 相似文献
455.
Hisashi Miyafuji Toshiki Nakata Katsunobu Ehara Shiro Saka 《Applied biochemistry and biotechnology》2005,124(1-3):963-971
The water-soluble (WS) portion obtained by supercritical water treatment of lignocellulosics was studied for its fermentability
to ethanol. A fermentation test of the WS portion showed it was not fermented to ethanol. Therefore, a wood characoal treatment
was applied to the WS portion to remove furan and phenolic compounds, which are thought to be the inhibitors to sugar fermentability.
It was found that treatment with wood charcoal can be effective at removing these inhibitors and improving the fermentability
of the WS portion without reducing the levels of fermentable sugars. 相似文献
456.
Mituhiro Fukuda Bastiaan J. Braams Maho Nakata Michael L. Overton Jerome K. Percus Makoto Yamashita Zhengji Zhao 《Mathematical Programming》2007,109(2-3):553-580
It has been a long-time dream in electronic structure theory in physical chemistry/chemical physics to compute ground state
energies of atomic and molecular systems by employing a variational approach in which the two-body reduced density matrix
(RDM) is the unknown variable. Realization of the RDM approach has benefited greatly from recent developments in semidefinite
programming (SDP). We present the actual state of this new application of SDP as well as the formulation of these SDPs, which
can be arbitrarily large. Numerical results using parallel computation on high performance computers are given. The RDM method
has several advantages including robustness and provision of high accuracy compared to traditional electronic structure methods,
although its computational time and memory consumption are still extremely large.
The work of Mituhiro Fukuda was primarily conducted at the Courant Institute of Mathematical Sciences, New York University. 相似文献
457.
Photoinduced electron‐transfer reactions of tris(2,2′‐bipyridine)ruthenium(II)‐based carbonic anhydrase inhibitors tethering plural binding sites
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Mikiko Suwa Narumi Imamura Pirika Awano Eiji Nakata Hiroshi Takashima 《Journal of Physical Organic Chemistry》2018,31(9)
Tris(2,2′‐bipyridine)ruthenium(II) complex‐based carbonic anhydrase (CA) inhibitors, [Ru(bpy)2(bpydbs)]2+ {bpy = 2,2′‐bipyridine and bpydbs = 2,2′‐bipyridinyl‐4,4′‐dicarboxilic acid bis[(2‐{2‐[2‐(4‐sulfamoylbenzoylamino)ethoxy]ethoxy}ethyl)amide]} and [Ru(bpydbs)3]2+, tethering plural benzenesulfonamide groups have been prepared. The CA catalytic activity was effectively suppressed by these synthetic [Ru(bpy)2(bpydbs)]2+ and [Ru(bpydbs)3]2+ inhibitors, and their dissociation constants at pH = 7.2 and at 25°C were determined to be KI = 0.93 ± 0.02 μM and KI = 0.24 ± 0.03 μM, respectively. Next, 2 photoinduced electron‐transfer (ET) systems comprising a Ru2+‐CA complex and an electron acceptor, such as chloropentaamminecobalt(III) ([CoCl(NH3)5]2+) or methylviologen (MV2+) were studied. In the presence of CA and a sacrificial electron acceptor, such as pentaamminechlorocobalt(III) complex, the photoexcited triplet state of 3([Ru(II)]2+)* was quenched through an intermolecular photoinduced ET mechanism. In case of the [Ru(bpydbs)3]2+‐CA‐MV2+ system, the photoexcited triplet state of 3([Ru(bpydbs)3]2+)* was quenched by sacrificial quencher through an intermolecular photoinduced ET mechanism, giving the oxidized [Ru(bpydbs)3]3+. Then the following intramolecular ET from the amino acid residue, Tyr6, near the active site of CA proceeded. We observed a transient absorption around at 410 nm, arising from the formation of a Tyr?+ in the [Ru(bpydbs)3]2+‐CA‐MV2+ system. These artificial Ru(II)‐CA systems may clearly demonstrate both intermolecular and intramolecular photoinduced ET reactions of protein and could be one of the interesting models of the ET proteins. Their photophysical properties and the detailed ET mechanisms are discussed in order to clarify the multistep ET reactions. 相似文献
458.
The dynamics of isolated high molecular weight (MH) polymer chains dissolved in a nonentangled semidilute solution of a low molecular weight (ML) polymer were investigated by monitoring the elongational flow birefringence. Because of its nonentangled nature, a low molecular weight matrix polymer solution is regarded as a pure solvent (a binary pseudo-solvent). A ternary solution consisting of a small amount of a high molecular weight probe polymer and the binary pseudo-solvent is effectively a dilute solution of the probe polymer. It was observed that the birefringence from the orientation and/or stretching of the probe polymer chains starts to increase rather abruptly at a certain critical strain rate,
, and the spatial birefringence pattern is localized along the elongation axis, characteristics that are reminiscent of the coil-stretch transition of flexible polymer chains in a simple dilute solution. The relaxation time for the chain extension, el, defined as the reciprocal of the critical strain rate
, was determined at various temperatures, matrix polymer concentrations cL, and test chain molecular weights MH. It was found that el varied with molecular weight as el~MHa , with a ranging from 1.3 to 1.8, which is roughly consistent with the molecular weight dependence of the non-free-draining Zimm relaxation time. A scaled relaxation time elkT/, which can be used to estimate the radius of gyration Rg of the probe polymer, decreased with increasing cL, indicating contraction of the high molecular weight polymer due to a screening of the excluded volume effect caused by the matrix polymer in the pseudo-solvent. 相似文献
459.
o-Nitrobenzyl photochemistry as induced by UV-A irradiation was applied to a photoactivated drug releasing system based on a molecular beacon strategy. A stem-and-loop structured oligodeoxynucleotide (ODN) possessing a photoreactive o-nitrobenzyl chromophore at the 3'-end and 1-aminonaphthalene quencher at the 5'-end underwent conformational change into a conventional double strand structure by hybridization with a specified target DNA. The intrinsic stem-and-loop structure suppressed photoactivated release of benzoic acid as a phantom drug from the o-nitrobenzyl chromophore because of intramolecular quenching by the 1-aminonaphthalene unit in close proximity to the chromophore. Formation of the double strand structure in the presence of perfectly matched target DNA minimized occurrence of intramolecular quenching and thereby enhanced the photoactivated drug release. 相似文献
460.