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101.
[reaction: see text] Molecular modeling was used to design mimetics of the HIV-1 matrix protein nuclear localization signal (NLS) in which a scaffold of two resorcinol units joined by a diamide linker presents 3-aminopropyl ethers in place of lysine side chains. Prospective mimetics with linkers of 6, 8, 10, or 12 atoms were synthesized and compared in a competition assay for binding to the nuclear import receptor subunit karyopherin alpha, showing the 10-atom linker to be best and shorter ones ineffective. 相似文献
102.
Highly ordered mesoporous silica can be regenerated from a mesoporous carbon CMK-3 that is a negative replica of mesoporous silica SBA-15, indicating reversible replication between carbon and inorganic materials. 相似文献
103.
We present a new set of V–V rate coefficients for vibrational levels 0–5 in H2 at 300 K, measured using a stimulated Raman–spontaneous Raman pump/probe apparatus. The measured rate of the non-resonant process, H2(v = 1) + H2(v = 1) → H2(v = 0) + H2(v = 2), is consistent with the previously reported experimental value of Kreutz et al. However, semi-classical predictions of such non-resonant processes, using the identical inter-molecular potential and methodology to that given by Cacciatore and Billing, results in rates which are too slow, by a factor of approximately 3. For the “resonant” V–V process, H2(v = 1) + H2(v = 0) → H2(v = 0) + H2(v = 1), the semi-classical rate is found to be too slow by an even larger factor, of approximately 30, compared to the experimental rate, but consistent with the previously reported experimental result of Farrow and Chandler. Further, unlike the semi-classical model prediction in which the (1, 1 → 2, 0) process rate is predicted to exceed that of the (1, 0 → 0, 1) process, the experimental data shows it to be a factor of approximately 2.5 less, suggesting that semi-classical methods that treat the rotational motion classically are unsuitable for the highly anharmonic H2 molecule. The ratio of pure rotation and rotation–vibration Raman cross sections for scattering from levels 0 and 1 is also determined, with results which agree with calculations of Schwartz and LeRoy, but are somewhat larger than previous experimental results of Cureton. 相似文献
104.
Dong Hyun KimHyun Il Cho Taehyoung ZyungLee-Mi Do Ki-Min BarkGap Chul Shin Sung Chul Shin 《European Polymer Journal》2002,38(1):133-137
New tetradentate Schiff-base polymers, in which phenylene units alternate with salicylideneiminato units, have been prepared by condensation of 2,5-(didodecyloxy)-1,4-bis(3-formyl-4-hydroxyphenyl)benzene (DFHB) with appropriate diamines in a mixed solution of CHCl3/toluene/acetic acid with 31-79% yields. DFHB as the key building block was prepared by the Suzuki reaction of 2,5-(didodecyloxy)benzene-1,4-diboronic acid with 5-bromosalicylaldehyde in a two-phase solution of tetrahydrofuran/water in the presence of NaHCO3/Pd(PPh3)4 in 45% yield. The molecular structures of the prepared compounds were identified by spectroscopy. Their absorption spectroscopic profiles have been analyzed. 相似文献
105.
Abstract— The Stern-Volmer constants for fluorescence quenching by tetramethylethylene decrease in the order DMC ≫ DHP > F-2 > 8-MOP. The same order was observed for the quantum yields of [2+2] cycloaddition reaction with tetramethylethylene on direct irradiation. In [2+2] photocycloaddition of F-2 with tetramethylethylene in ethanol, the ratio of quantum yields deduced from singlet and triplet states of F-2; φ3 0 /φ1 0 , is about 5. The excited triplet state is the reactive state for the [2+2] photocycloaddition of F-2 with tetramethylethylene in solution but the excited singlet state of F-2 becomes very important in biological conditions. 相似文献
106.
Chan Sik Cho Na Young Lee Tae‐Jeong Kim Sang Chul Shim 《Journal of heterocyclic chemistry》2004,41(3):423-429
Nitroarenes are reductively cyclized with an array of tetraalkylammonium halides and trialkylarnmonium chlorides in the presence of a catalytic amount of a ruthenium catalyst along with tin(II) chloride dihydrate at 180° to afford the corresponding quinolines in moderate to good yields. The addition of tin(II) chloride dihydrate is necessary for the effective formation of quinolines and toluene is the solvent of choice. A reaction pathway involving initial reduction of nitroarenes to anilines and conversion of alkylammonium halides to alkylamines, alkyl group transfer from alkylamines to anilines to form an imine, dimerization of imine, and heteroannulation is proposed for this catalytic process. 相似文献
107.
The preparation of an 1,3-alternate calix[4]arene tetraphosphane ligand, 25,26,27,28-tetrakis{2-(diphenylphosphino)ethoxy}calix[4]arene (4), is described. Ligand 4 is obtained in four steps in 17% overall yield. Reaction of 4 with AgBF4 produced the encapsulated two silver complex [Ag2{(P,P,P,P)-tetraphencalix[4]arene}](BF4)2. The solid-state structure shows that the encapsulated silver undergoes a substantial pi-interaction by two opposite arene rings. Rhodation of 4 employing [Rh(cot)2]BF4 yielded the encapsulated complex with a bent coordination mode. Two organometallic fragments inclusioned inside a 1,3-alternate calix[4]arene tetraphosphane was also achieved by the reaction of 4 with [PtH(PPh3)2 (thf)]+. Full characterization includes X-ray structural studies of compounds 4-6. 相似文献
108.
109.
Temperature-dependent intermolecular force measurement of poly(N-isopropylacrylamide) grafted surface with protein 总被引:1,自引:0,他引:1
We have investigated the temperature dependence of the intermolecular force between poly(N-isopropylacrylamide) (PNiPAM) grafted surface and bovine serum albumin (BSA) in phosphate buffer (pH 7.4) using atomic force microscopy at the nanonewton scale. These observations show that the interaction force is nearly zero below the phase transition temperature of PNiPAM and that it increases steeply during the phase transition. Since the PNiPAM chains are grafted onto the aminosilane (gamma-aminopropyltriethoxysilane)-treated silicon wafer, we measured the force-distance curve of BSA-immobilized tips for the bare and the aminosilane-treated silicon wafer. These surfaces show no temperature dependence and their values are different from those of the PNiPAM-grafted surfaces at 30 degrees C. The results indicate that the measured adhesion force is between the PNiPAM-grafted surface and the BSA-immobilized tip. Our studies on the intermolecular force between other surfaces (CH(3)- and COOH-terminated self-assembled monolayers) and the BSA-immobilized tip indicate that the variation in the intermolecular force between the PNiPAM surface and BSA with temperature can be attributed to the changes in the properties of the PNiPAM chains. From consideration of the PNiPAM phase transition mechanism, it is speculated that the intermolecular force between the PNiPAM-grafted surface and BSA would be affected by changes in the arrangement of the bound water molecules around the PNiPAM chain and by changes in the conformation (i.e., in the chain mobility) of the PNiPAM chain during the phase transition. 相似文献
110.
Mixing enhancement has drawn great attention from designers of micromixers, since the flow in a microchannel is usually characterized by a low Reynolds number (Re) which makes the mixing quite a difficult task to accomplish. In this paper, a novel integrated efficient micromixer named serpentine laminating micromixer (SLM) has been designed, simulated, fabricated and fully characterized. In the SLM, a high level of efficient mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other terms, lamination) mechanism is obtained by the successive arrangement of "F"-shape mixing units in two layers. The advection is induced by the overall three-dimensional serpentine path of the microchannel. The SLM was realized by SU-8 photolithography, nickel electroplating, injection molding and thermal bonding. Mixing performance of the SLM was fully characterized numerically and experimentally. The numerical mixing simulations show that the advection acts favorably to realize the ideal vertical lamination of fluid flow. The mixing experiments based on an average mixing color intensity change of phenolphthalein show a high level of mixing performance was obtained with the SLM. Numerical and experimental results confirm that efficient mixing is successfully achieved from the SLM over the wide range of Re. Due to the simple and mass producible geometry of the efficient micromixer, SLM proposed in this study, the SLM can be easily applied to integrated microfluidic systems, such as micro-total-analysis-systems or lab-on-a-chip systems. 相似文献