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831.
Chitta RK Rempel DL Gross ML 《Journal of the American Society for Mass Spectrometry》2005,16(7):1031-1038
The dimerization of gramicidin, a 15-residue membrane peptide, in solution can be viewed as a model for protein-protein interactions. We reported previously that the dimer can be observed when electrosprayed from organic solvents and that the abundances of the dimer depends on the dielectric constant of the solvent. Here, we report an effort to determine an affinity constant for the dimerization of gramicidin by using gas-phase abundance. Two issues affecting the determination are the electrospray-induced dissociation of the dimer and discrimination in the electrospray of the dimer compared with the monomer. Other methods developed for the purpose of determining affinity from mass spectral abundance do not address the dissociation of the complex in the gas phase or can not be applied for cases of low affinity constant, K(a). We present a mathematical model that uses the ratio of the signal intensities of the dimer and the monomer during a titration. The model also incorporates the dissociation and an electrospray ionization-response factor of the dimer for extracting the affinity constant for the dimerization of gramicidin. The dimerization constants from the new method agree within a factor of two with values reported in the literature. 相似文献
832.
The dependent relation between temperature and pressure of supercritical CO2+ ethanol binary system under the pressure range from 5 to 10 MPa with the variety of densities and mole fractions of ethanol
that range from 0 to 2% was investigated by the static visual method in a constant volume. The critical temperature and pressure
were experimentally determined simultaneously. The PTρ figures at different ethanol contents were described based on the determined pressure and temperature data, from which pressure
of supercritical CO2 + ethanol binary system was found to increase linearly with the increasing temperature. P-T lines show certain convergent feature in a specific concentration of ethanol and the convergent points shift to the region
of higher temperature and pressure with the increasing ethanol compositions. Furthermore, the effect of density and ethanol
concentration on the critical point of CO2 + ethanol binary system was discussed in details. Critical points increase linearly with the increasing mole fraction of
ethanol in specific density and critical points change at different densities. The critical compressibility factors Zc of supercritical CO2 + ethanol binary systems at different compositions of ethanol were calculated and Z
c
-ρ figure was obtained accordingly. It was found from Z
c
-ρ figure that critical compressibility factors of supercritical CO2 unitary or binary systems decline linearly with the increasing density, by which the critical point can be predicted precisely. 相似文献
833.
Alternative mobile phases for the reversed-phase high-performance liquid chromatography of peptides and proteins 总被引:2,自引:0,他引:2
The use of a high content of acetic acid as mobile phase additive for the reversed-phase high-performance liquid chromatography (RP-HPLC) of several proteins and extracts of biological tissues was evaluated for a divinylbenzene (DVB)-based stationary phase, and the separations obtained with acetic acid gradients in acetonitrile, isopropanol or water were compared with classical polypeptide RP-HPLC on silica C4 with trifluoroacetic acid (TFA)-acetonitrile. The separation patterns for recombinant derived interleukin-1 beta (IL-1 beta) on the C4 column eluted with TFA-acetonitrile and the DVB column eluted with acetic acid-acetonitrile were similar, but only the polymeric column was able to separate the components present in an iodinated IL-1 beta preparation. Neither eluent had any harmful effect on the biological activity of IL-1 beta isolated after RP-HPLC. Several standard proteins could be separated when the polymeric column was eluted with acetic acid gradients in acetonitrile, isopropanol or water and, although the separation efficiency with acetic acid in water was lower than that in combination with classical organic modifiers, insulin, glucagon and human growth hormone (hGH) were eluted as sharp, symmetrical peaks. The recoveries of insulin and hGH were comparable for all three mobile phases (80-90%). The separation patterns obtained from a crude acetic acid extract of a normal and a diabetic, human pancreas analysed using acetic acid gradients with or without organic modifiers were found to be similar and comparable to those obtained on a silica C4 column eluted with an acetonitrile gradient in TFA. The principal differences resulted from the use of different UV wavelengths (215 nm for TFA-acetonitrile, 280 nm for acetic acid). Acetic acid extracts of recombinant derived hGH-producing Escherichia coli were separated on the DVB column eluted with an acetic acid gradient in water. Although the starting material was a highly complex mixture, the hGH isolated after this single-step purification was surprisingly pure (as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis). Consequently several (pure) polypeptides and complex biological samples were separated on a polymeric stationary phase eluted with acetic acid gradients in water without the use of organic modifiers. 相似文献
834.
Vesna Radulovi? Alessia Bacchi Giancarlo Pelizzi Du?an Sladi? Ilija Br?eski Katarina Andjelkovi? 《Monatshefte für Chemie / Chemical Monthly》2006,23(3):681-691
Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide
were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized
by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure
was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex
is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation. 相似文献
835.
Jaime?WisniakEmail author René?D.?Peralta Ramiro?Infante Gladis?Cortez 《Journal of solution chemistry》2005,34(2):171-183
Densities of the ternary system 1,4-dioxane + butyl acrylate + ethyl acrylate and its binary butyl acrylate + ethyl acrylate have been measured in the whole composition range, at 298.15 K and atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The calculated excess molar volumes of the binary system are positive and were correlated with the Redlich–Kister equation and with a series of Legendre polynomials. Several models were used to correlate the ternary behavior from the excess molar volume data of their constituent binaries and were found equally good to fit the data. The best fit was based on a direct approach, without information on the component binary systems. 相似文献
836.
Agnieszka G?dek 《Journal of organometallic chemistry》2005,690(3):685-690
Photolysis of W(CO)6 in the presence of Ph3SiH in n-heptane leads to the formation of the first tricarbonyl(η6-triphenylhydrosilane)tungsten complex W(CO)3(η6-PhSiHPh2) (1) in good yield (ca. 70%). The molecular structure of the new tungsten-silane compound was established by single-crystal X-ray diffraction studies and characterized by IR, UV-Vis, 1H, 13C{1H}, and 29Si{1H} NMR spectroscopy. 相似文献
837.
Oren?Regev Jean-Fran?ois?Gohy Bas?G.?G.?Lohmeijer Sunil?K.?Varshney Dominique?H.?W.?Hubert Peter?M.?Frederik Ulrich?S.?SchubertEmail author 《Colloid and polymer science》2004,282(4):407-411
Metallo-supramolecular diblock copolymers consisting of a polystyrene (PS) block connected to a poly(ethylene oxide) (PEO) block by a bis(terpyridine)ruthenium complex (PS20-[Ru]-PEO
y
) were used to prepare aqueous micelles. The length of the PS block was kept constant, while two PEOs of different molecular weight were used. The resulting hydrated micelles and aggregates were characterized by a combination of cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering measurements. The results were compared to those obtained for a covalent counterpart (PS22-b-PEO70). Cryogenic transmission electron microscopy allowed visualization of the PS core of the micelles. Moreover, the aggregates result from clustering of individual micelles. 相似文献
838.
Spevácková V Korunová V Cejchanová M Vobecký M 《Analytical and bioanalytical chemistry》2004,380(2):346-350
A sampling procedure appropriate for the determination of mercury in whole blood was tested by using both inactive controls and a 197Hg mercury radio-indicator. To exclude the influence of the instrumental device (an AMA 254 single-purpose mercury atomic absorption spectrometer) on the determination of mercury in whole blood, the function of the instrument was checked by using rat blood with metabolised 197Hg. The measurement procedure was found to be free of errors. However, the study showed that the material used for the sampling vessels is a crucial parameter for obtaining accurate analytical results. The stability of solutions and samples was tested towards polyethylene (PE) and polypropylene (PP) vessels. PE displayed a time-dependent increase in the mercury content both in the samples and in the blood control material. The probable cause of this increase was direct contamination from the material of the vessel and/or diffusion of mercury from the environment through the vessel walls related to a strong complexing affinity of the sample matrix. This assumption was confirmed by supplying the vessels with the complexing agent Na2EDTA (0.05 mol L–1). Commercial PP vessels for blood sampling (Sarstedt S-Monovette Metall Analytik) did not give rise to statistically significant variations in mercury content in the samples and blood control material over a 30-day period. 相似文献
839.
A new 2D (two-dimensional) coordination polymer, [Fe(μ4-bta)o.5(phen)(OH)]n (1), has been hydrothermally synthesized with FeCl3 6H2, Na4bta (h4bta = 1,2,4,5-benzentetracarboxylic acid), 1,10-phen (1,10-phenanthroline) and H2O as raw materials. The crystals of the compound belong to monoclinic P21/n space group, a = 1.0129(2) nm, b = 0.9265(2) nm, c = 1.5696(3) nm, β=91.37(3)°V=1.4721(5) nm3,Z=3, final R1=0.0292, wR
2=0.0798 for 2572 [/>2σ(/)] observed reflections. The result of structure determination shows that in the compound each bta
ligand is connected with four Fe3, forming a new μ4-coordination mode. Four deprotonated carboxylic groups of bta link to Fe3 ions alternatively through monodentate and bidentate coordination fashion, constructing 2D layer network. The measurement
of variable temperature magnetic susceptibility indicates that there exist antiferromagnetic interactions between Fe3 ions in the compound. The TGA spectrum displays relatively fine thermal stability of the compound. In addition, IR and UV-Vis
spectra of compound 1 have also been measured. 相似文献
840.
Zohreh Habibi Peyman Salehi Maryam Yousefi Yahya Hejazi Ahmad Laleh Valiollah Mozaffarian Shiva Masoudi Abdolhossein Rustaiyan 《Chemistry of Natural Compounds》2006,42(6):689-692
The hydrodistilled oils from the aerial parts of Ferula latisecta and Mozaffariania insignis, which is endemic to Iran, were analyzed by GC and GC/MS. (Z)-Ocimenone (32.4%), (E)-ocimenone (20.3%), and cis-pinocarvone (11.4%) were the main components among the 22 constituents characterized in the oil of F. latisecta, representing 87.7% of the total components detected. Twenty-five compounds were identified in the oil of M. insignis, representing 99.0% of the total oil, with octyl acetate (41.1%), β-pinene (30.3%), and α-pinene (23.9%) as the main constituents. The essential oils were examined for their potential antimicrobial activities.
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 561–563, November–December, 2006. 相似文献