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71.
Helical poly(3-methyl-4-vinylpyridine) (P3M4VP)/amino acid complexes have been prepared via acid-base reaction of the achiral polymer with D and L amino acids: alanine, leucine, valine, serine and phenylalanine. The circular dichroism (CD) spectra of P3M4VP/D- and L-alanine complexes in CH(3)OH/H(2)O show opposing (near mirror image) Cotton effect signals at 278.4, 274.8 and 270.8 nm, indicating the formation of enantiomeric secondary structures. The formation of the enantiomeric structures is supported by observed [alpha](D)(25) values of -3.0 and +3.0 for the P3M4VP/D-alanine and P3M4VP/L-alanine complexes, respectively. The preparation of helical P3M4VP/amino acid complexes has been carried out in CH(3)OH and H(2)O at pH 1.8 and 2.7. The intensities of the Cotton effect signals were good. For example, for the P3M4VP/L-alanine complexes in CH(3)OH/H(2)O and H(2)O (pH 1.8), the second Cotton effect signal around 275-277 nm show [theta;] values of 49 980 and 79 210 deg . cm(2) . dmol(-1), respectively. The formation of the helical secondary structure is rapid. The acid-base reaction between P3M4VP and L-alanine in CH(3)OH/H(2)O, in 10 min, show a CD spectrum with Cotton effect signals at 274 and 272 nm with [theta] values of 27,000 deg . cm(2) . dmol(-1) and -36,000 deg . cm(2) . dmol(-1), respectively. P3M4VP permits ready conformational reorientation on complexation with amino acids, but once the helical P3M4VP/amino acid complexes are formed, it is stable at room temperature. P3M4VP is not compatible with HeLa ovarian cancer cells, but the helical P3M4VP/amino acid complexes are compatible with HeLa cells. The complexes minimally interfere with the adhesion and growth of HeLa cells on complex surfaces. Helical poly(3-methyl-4-vinylpyridine)/D- and L-alanine complexes support the attachment and growth of HeLa cells. The micrographs shows HeLa cells after three days: left panel: on P3M4VP/L-alanine complex; right panel: on P3M4VP/D-alanine complex. 相似文献
72.
The chiroptical properties and transient rheological behavior of (acetyl)(ethyl)cellulose (AEC) m-cresol liquid crystalline solutions have been investigated. Chiroptical properties were manipulated through (i) increasing degree of acetylation of ethyl cellulose (EC), and (ii) blending AEC with EC. At the same average degree of acetylation (DA), the chiroptical properties of pure AEC were different from those of the EC/AEC mixtures. However, at the same DA, the AEC and mixed AEC/EC solutions showed similar steady state flow and oscillatory behaviors, but the transient behaviors were different. At high flow rates the mixed AEC/EC solutions exhibited double recoil after cessation of steady-state flow, whereas the AEC solutions showed double recoil only in the high DA AEC solutions. All solutions, pure and mixed, had the same stress relaxation behavior. Both pitch and handedness affected the transient behavior. After cessation of high shear rate flow, the rate of modulus evolution decreased with increasing pitch, and was faster in right-handed mesophases than in left-handed ones at a similar pitch. 相似文献
73.
Shleev SV Khan IG Gazaryan IG Morozova OV Yaropolov AI 《Applied biochemistry and biotechnology》2003,111(3):167-184
The screening of potential redox mediators for laccase was performed using homogeneous enzyme preparations from Coriolus hirsutus and Coriolus zonatus. It was discovered that derivatives of 1-phenyl-3-methyl-pyrazolones were efficient substrates for the laccases. The characterization of two representatives of the 1-phenyl-pyrazolone class, sodium 1-phenyl-3-methyl-4- methylamino-pyrazolone-5-N(4)-methanesulfonate and 1-(3'-sulfophenyl)-3- methylpyrazolone-5, in the reaction catalyzed by laccase was carried out using spectral, electrochemical, and enzyme kinetics methods. The kinetic parameters for the oxidation of the newly discovered substrates were comparable with those for 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) oxidation by laccase. Electrochemical experiments demonstrated that oxidation of these compounds yielded two high-potential intermediates capable of oxidizing veratryl alcohol, which was used as a lignin model substrate, to the corresponding aldehyde and acid. 1-(3'-Sulfophenyl)-3- methylpyrazolone-5 was about 30-40% as effective in degrading veratryl alcohol compared to ABTS as judged from high-performance liquid chromatography kinetic studies. 1-Phenyl-3-methyl-pyrazolones may be of commercial interest for oxidoreductase-catalyzed biodegradation of organic compounds. 相似文献
74.
Effects of cetyltrimethylammonium bromide (CTABr) micelles on second-order rate constants (k(n)(obs)) for nucleophilic reactions of amines (piperidine and n-butylamine) with ionized phenyl salicylate (PS(-)) reveal a nonlinear decrease with the increase in [D(n)] (where [D(n)] = [CTABr](T) - cmc) at a constant [NaBr] and 35 degrees C. The observed data, at a constant [NaBr], fit reasonably well to a pseudophase model of micelles, and such a data fit gives kinetic parameters such as CTABr micellar binding canstant (K(S)) of PS(-). The effect of [NaBr] upon K(S) is explained with the empirical relationship K(S) = K(S)(0)/(1 + psi[NaBr]), where psi is an empirical parameter. 相似文献
75.
M. S. Rahman Khan 《Applied Physics A: Materials Science & Processing》1984,35(4):263-265
The resistivity of thin films (80–200 Å) of ErH2 increases sharply when heated for 2 h at 300 °C in vacuum in the presence of hydrogen gas at 10–2 Torr. This confirms that the films, originally metallic conductor, have become converted to semiconducting ErH3 which is in conformity with the structural studies. The negative values of TCR also indicate the semiconducting nature of the hydrogen treated films. Activation energies of the films have been evaluated. 相似文献
76.
K. Sistemich W. -D. Lauppe T. A. Khan H. Lawin H. A. Selič J. P. Bocquet E. Monnand F. Schussler 《Zeitschrift für Physik A Hadrons and Nuclei》1978,285(3):305-313
Nuclear spectroscopy studies of 51 133 Sb82 have been performed at the recoil fission product separators JOSEF and LOHENGRIN. A tentative level scheme has been established for this nucleus with one proton in addition to the doubly closed shell core132Sn. Two isomeric states with half-lives of 3 and 16 μs have been found at excitation energies of >4300 keV and 4526 keV, respectively. Lower limits of 15/2 are deduced for the spins of these levels. The h11/2 proton state is suggested at 2792 keV in agreement with the systematics of the lighter Z=51 isotopes and the heavier N=82 isotones. Several states have been observed between 4300 and 4600 keV which are probably due to the coupling of the single proton to core-excited states which have energies between 4000 and 4800 keV. 相似文献
77.
Ali Raza Hala A. Hejazi Sami Ullah Khan M. Ijaz Khan Kamel Smida Iskander Tlili 《印度化学会志》2022,99(7):100568
In this investigation, a mixed convective nanoparticles fluid flow over an inclined plate is deliberated. The effects of slip boundary wall and magnetic field are also considered. The dimensionless governing system for the considered problem is attained by implementing recent definitions of fractional derivatives (FD). The generalized solution is obtained through the Laplace Transformation Scheme (LTS) for the momentum and thermal expressions. To improve the novelty and to demonstrate some more physical perception of the stated research work, some remarkable special cases of velocity distribution through CF and AB-fractional derivative concept are addressed, whose daily life implication is well known in the existing literature. Moreover, to evaluate the physical interest of the stated problem, the outcomes of the obtained system graphical illustrations are made by utilizing MATHEMATICA. As a result, we concluded that the aluminium oxide nanoparticles show more decaying behavior as compared to titanium oxide nanoparticles for temperature and velocity profile. Furthermore, both fields i.e., momentum and thermal distributions are increased with the help of rising estimations parameter. Current results report novel applications in enhancement of heat transfer, thermal engineering, chemical processes, engineering and electronics devices, solar systems, extrusion processes, fission reactions etc. 相似文献
78.
Kabir-ud-DinEmail author S.?M.?Shakeel?Iqubal Zaheer?Khan 《Colloid and polymer science》2005,283(5):504-511
Kinetics of oxidation of DL-malic acid by water soluble colloidal MnO2 (prepared from potassium permanganate and sodium thiosulfate solutions) have been studied spectrophotometrically in the absence and presence of nonionic Triton X-100 surfactant. The reaction is autocatalytic and manganese(II) (reduction product of the colloidal MnO2) may be the autocatalyst. The order of the reaction is first in colloidal [MnO2] as well as in [malic acid] both in the absence and presence of the surfactant. The reaction has acid-dependent and acid-independent paths and, in the former case, the order is fractional in [H+]. The effect of externally added manganese(II) is complex. The results show that the rate constant increases as the manganese(II) concentration is increased. It is not possible to predict the exact dependence of the rate constants on manganese(II) concentration, which has a series of reactions with other reactants. In the presence of TX-100, the observed effect on k is catalytic up to a certain [TX-100]; thereafter, an inhibitory effect follows. The catalytic effect is explained in terms of the mathematical model proposed by Tuncay et al. (in Colloids Surf A Physicochem Eng Aspects 149:279 3). Activation parameters associated with the observed rate constants (kobs/k) have also been evaluated and discussed. 相似文献
79.
7-Ethyl-10-hydroxycamptothecin (SN-38) is an active metabolite of Irinotecan (CPT-11), an anticancer pro-drug. To support clinical pharmacokinetic studies for liposome based formulation of SN-38 (LE-SN38) in cancer patients, a rapid, simple and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the quantification of total SN-38 in human plasma. Sample preparation was carried out by one-step protein precipitation using cold acetonitrile with 0.5% acetic acid (v/v). Camptothecin was used as an internal standard (IS). Chromatographic separation of SN-38 and IS was achieved using a Synergi Hydro-RP column (C(18), 50 x 2 mm, 4 micro m), with a gradient elution of acetonitrile and 0.1% acetic acid. After ionization in electrospray source (positive ions), the acquisition was performed in the multiple reactions monitoring mode. Quantitation was accomplished using the precursor-->product ion combinations of m/z 393.1-->349.2 for SN-38 and 349.1-->305.1 for IS. The quantification limit of 0.05 ng/mL was achieved by using much lower volume (0.2 mL) of plasma and in the presence of LE-SN38. The method was validated over the concentration range of 0.05-400 ng/mL. Accuracy was within +/-12% of nominal at all concentration levels. Inter-day and intra-day precisions expressed as percentage coefficient of variation (%CVs) for quality control (QC) samples were less than 14 and 5%, respectively. 相似文献
80.