Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immobilized serum albumin membranes at isoelectric points of the amino acids. The effective fixed charge density was estimated to decrease after the injection of alamine, phenylalanine, and tryptophan and to increase after the injection of serine. The change in the fixed charge density originated from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and amino acids in the membranes, since the conformational change of the immobilized albumin membranes induced by the binding of the amino acids to the serum albumin was observed from circular dichroism measurements. There was found, however, some discrepancy between the conformational change of the serum albumin in the albumin membranes detected by the membrane potential measurements and the circular dichroism measurements. This is explained by the fact that the circular dichroism measurements detect the increase or decrease in the α-helix, β sheet, and random coil contents; however, they do not always contribute to the detection of the change in the charge density due to the presence of the amino acid in the albumin membranes. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyanions with various charge densities with a solvatochromic acid-base indicator dye attached to the main chain were prepared by the terpolymerization of acrylic acid, acrylamide, and a small mole fraction of 1-(2-methacryloyloxyethyl)-4-(2-(4-hydroxyphenyl)ethenyl)pyridinium bromide. The apparent pK value for the polymer-bound indicator dye (pKabs) was determined by the spectroscopic pH titration. The interfacial electrostatic potential (ψ) was calculated from pKobs. Dielectric contribution to the acid-base equilibrium was taken into account for the calculation. The electrostatic potentials thus obtained were compared with those calculated from the nonlinearized Poisson-Boltzmann equation for a cylinder model. The indicator dye moieties are suggested to be reporting the mean field potential at a distance of about 10 Å from the axis of the polyion cylinder. The observed values as a function of the charge density were also discussed in connection with Manning's theory.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0887-624X
    Keywords: polyanions ; counterion condensation ; pH-sensitive merocyanine dye ; poly(acrylic acid-co-acrylamide) ; charge density parameters ; Manning's theory ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effects of monovalent and divalent counterions on the acid-base equilibrium of a pH-sensitive merocyanine dye covalently attached to copolymers of acrylic acid and acrylamide with varying charge densities (0.28 〈 ξ 〈 2.8) were investigated. Added chloride salts of Li+, Na+, K+, and NH+4 (〈 0.2 mM) had essentially no effect on pK observed (pKobs) for the equilibrium. By contrast, the salts of Mg2+, Ca2+, Sr2+, and Ba2+ caused a significant decrease in pKobs for the copolymers with larger ξ. With smaller ξ, most likely when ξ 〈 0.5, no decrease in pKobs was observed upon addition of the salts of divalent cations. A competitive effect of Ca2+ and Na2+ ions on pKobs in the presence of an excess of Na+ ions implied that Ca2+ ions at very low concentrations were preferentially, and therefore exhaustively, condensed on the polyanions with sufficiently large ξ probably until effective charge density was lowered to 0.5. The observed difference in the influence of the monovalent and divalent cations on pKobs was discussed in terms of the difference in the microscopic behavior of the condensed monovalent and divalent cations. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The shifts in membrane potential, caused by the injection of glucose into a permeation cell, were measured using immobilized (entrapped) glucose oxidase membranes. No, pH change in the permeation cell was observed upon injection of glucose, but the shift in membrane potential was definitely detected. The shift in membrane potential was observed under nitrogen bubbling (in the absence of oxygen) using initially used enzyme membranes. It was, therefore, suggested that the shifts in membrane potential were not caused by an enzyme-substrate reaction, but by binding of the substrate to the enzyme, which indues a conformational change in the enzyme and leads to a change in charge density in the enzyme membrane. This mechanism is also supported by the fact that the shifts in membrane potential were observed upon injection of not only D-glucose but also L-glucose as reported in our previous study [J. Chem. Soc. Faraday Trans., 87, 695 (1991)]. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0887-6266
    Keywords: membrane ; dual-mode sorption ; infrared spectroscopy ; carbon dioxide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of CO2 sorbed in rubbery and glassy polymers were measured to examine the relationships between the spectroscopic data and physical properties of the polymeric membranes. The “V-shape” tendency in the plot of W1 [i.e., half-width of CO2 peak sorbed in the membranes] vs glass-transition temperature (Tg) is observed, and has exactly the same tendency that is widely known from the plot of log D (diffusion coefficient) vs Tg. It is suggested that the membranes having a wider W1 give a faster diffusion coefficient, since W1 is inversely related to the moment of inertia of CO2 in the membranes. Two distinct peaks of CO2 were not observed in the infrared spectra of CO2 sorbed in the glassy polymers. This suggests that the states of CO2 in the Henry mode and Langmuir mode in the glassy polymers are similar in the spectroscopic measurements. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0887-6266
    Keywords: membrane ; diffusion ; dual-mode sorption ; permeation ; infrared spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of CO2 sorbed in rubbery and glassy polymeric membranes were measured to examine the relationships between the spectroscopic data and the physical properties of the membranes. The two peaks observed in the spectra of CO2 were attributed to the R branch and P branch of CO2 sorbed in the membranes based on the consideration that both peaks were observed at a temperature above the glass transition temperature of the membranes. Apparent diffusion coefficients of CO2 in the membranes were measured from the desorption kinetics of CO2 detected by FTIR spectroscopy. The solubility coefficients of CO2 were also estimated from absorbance spectra of CO2 sorbed in the membranes using Lambert-Beer's rule. The permeability, solubility, and diffusion coefficients estimated by the FTIR method were found to correlate well with the coefficients obtained by conventional methods such as vacuum-pressure or sorption isotherm methods. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0887-6266
    Keywords: polyimide membrane ; ultraviolet light irradiation ; crosslinking ; physical changes ; gas permeability ; sorption property ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two types of polyimide membranes; one crosslinkable and the other noncrosslinkable using ultraviolet light irradiation (UV irradiation), were prepared and investigated concerning the effect of UV irradiation on their gas permeabilities and selectivities. Permeability and diffusion coefficients for O2, N2, H2, and CO2 were determined using the vacuum pressure and time lag method. Sorption properties for carbon dioxide were carried out to evaluate the changes in the free volume in the membranes due to the irradiation. In both membranes, permeability coefficients for all gases used in this study decreased and permselectivity, particularly for H2 over N2, increased with increasing UV irradiation time without a significant decrease in the flux of H2. The coefficients depended on the membrane thickness, suggesting asymmetrical changes in both membranes due to UV irradiation. It was suggested by an attenuated total reflection (ATR) FTIR method and analysis of the gas sorption properties of the membranes that the physical changes due to UV irradiation at the irradiated side in both membranes significantly affected their gas permeation properties compared with the chemical changes, especially the crosslinking in the crosslinkable type. © 1997 John Wiley & Sons, Inc. J. Polym Sci B: Polym Phys 35: 2259-2269, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 7 (1969), S. 909-916 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The infrared absorption spectrum in the 4000-400 cm- region of an oriented film of a DNA-RNA hybrid in its undeuterated and deuterated states was observed with the polarized radiation. Most of the stronger bands found in the double-helical DNA's and double-helical RNA's are identified in the spectrum of the hybrid. The absorption band at 1225 cm-1 shows a perpendicular dichroism and that at 1085 cm-1 shows almost no dichroism. These facts indicate that the orientation of the group with respect to the helix axis in the hybrid structure is not entirely the same as that in the double-helical Na DNA at, 75% RH., although the x-ray diffraction pattern of the hybrid is quite similar to that of the DNA A form. The PO2- orientation is not the same as that in the double-helical RNA either. The observed dichroism is explained, however, by considering that the PO2- group in the RNA moiety takes nearly the same orientation as that in the double-helical RNA, and the PO2- group in the DNA moiety takes nearly the same as that in the double-helical DNA.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quinoxaline antibiotic triostin A has a bicyclic octadepsipeptide structure. Proton and carbon-13 nmr spectra showed the presence of two symmetrical conformations favoring polar and nonpolar solvents, respectively. They interconvert slowly on the nmr time scale, and this slow interconversion is due to the cooperative effects of the presence of the quinoxaline ring and the N-methyl peptide bonds. Reversal of the chirality of the disulfide bond as the origin of the slow exchange was excluded by the presence of two conformers for S-benzyltriostin A. Conformer 2, which favors the polar solvent, can form hydrogen-bonded complexes with purine nucleoside derivatives in organic solvents, but conformer 1 does not. The binding sites were elucidated and a mode of interaction with DNA proposed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...