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  • 1
    Electronic Resource
    Electronic Resource
    Interpretation of the effect of an oscillating electric field on membrane enzymes (1992)
    s.l. : American Chemical Society
    Biochemistry 31 (1992), S. 138-141 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00116a020
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  • 2
    Electronic Resource
    Electronic Resource
    Imposed oscillations of kinetic barriers can cause an enzyme to drive a chemical reaction away from equilibrium (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 11063-11068 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00077a001
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  • 3
    Electronic Resource
    Electronic Resource
    Nonlinear effect of an oscillating electric field on membrane proteins (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4891-4901 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nonlinear response of a two-state chemical transition to an oscillating electric field is examined. A reaction for which this analysis is particularly relevant is a conformational transition of a membrane protein exposed to an ac electric field. Even a modest externally applied field leads to a very large local field within the membrane. This gives rise to nonlinear behavior. The applied ac field causes harmonics in the polarization and can cause a dc shift in the state occupancy, both of which can be observed and used to determine kinetic parameters. Fourier coefficients are calculated for the enzyme state probability in the ac field, exactly for infinite frequency, and in powers of the field for finite frequency. Kramers–Kronig relations are proved and response functions are given for the leading terms of the harmonics. The results are extended to the spherical symmetry relevant to suspensions of spherical cells, vesicles, or colloidal particles. If the protein catalyzes a reaction, free energy is transduced from the electric field to the output reaction, even if that reaction is electrically silent. Many transport enzymes are ideal examples. The ac field can cause the enzyme to pump ions or molecules through the membrane against an (electro)chemical potential. The efficiency of this energy transduction can be as high as 25%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456728
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  • 4
    Electronic Resource
    Electronic Resource
    Frequency dependence of catalyzed reactions in a weak oscillating field (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7414-7419 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The frequency dependence of the average rates of reactions catalyzed by one or more catalysts in a weak oscillating field is derived. The average rates are sums of Lorentzian curves whose characteristic frequencies are the inverse relaxation times of the normal modes of the kinetic system and whose amplitudes are quadratic in the field. The signs of the Lorentz amplitudes can be either positive or negative, so the rates versus frequency can have a variety of shapes, including frequency windows. One can get relaxation times and amplitudes by measuring steady-state rates as a function of the frequency of the field. The theory is applied to determine the Lorentz amplitudes and characteristic frequencies of ion transport rates catalyzed by Na+–K+–ATPase in erythrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460173
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  • 5
    Electronic Resource
    Electronic Resource
    Energy transduction between a concentration gradient and an alternating electric field (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5062-5066 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A four-state transport protein that has electric charges that move concomitantly with conformational changes can transduce energy in either direction between an alternating membrane potential and a concentration gradient. An alternating electric potential of very large amplitude is considered, and the rapid-equilibrium approximation is used for the conformational changes. This permits deriving simple expressions for the transport flux, the power supplied by the alternating potential, and the power applied to the concentration gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458644
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  • 6
    Electronic Resource
    Electronic Resource
    Comment on "Remarks on the information entropy maximization method and extended thermodynamics" [J. Chem. Phys. 108, 5834 (1998)] (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6144-6145 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By making the short-correlation-time and short-correlation-distance approximations, we show how the Liouville equation can be used to produce a theory that describes ireversible processes even though the equation is invariant under time reversal. Thus B. C. Eu's claims about the consistency of the equations of motion formalism in nonequilibrium statistical mechanics are not well supported. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479910
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  • 7
    Electronic Resource
    Electronic Resource
    Mobility variance determined from ac electrophoretic light scattering (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3873-3876 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The homodyne correlation function for light scattered from an aqueous suspension of particles in a uniform oscillating electric field is calculated assuming the mobility varies from particle to particle. The correlation function has an exponential decay that is modulated at frequency ω/2π with amplitude (q⋅E/ω)2 〈Δμ2〉, where q is the scattering vector, E and ω/2π are the amplitude and frequency of the oscillating field, and 〈Δμ2〉 is the variance of the mobility of the particles. The variance can be determined by fitting the theoretical correlation function to homodyne photon autocorrelation measurements. This technique has the advantage of insensitivity to convection of the particles from heating by the applied electric field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460794
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  • 8
    Electronic Resource
    Electronic Resource
    Quadratic response of a chemical reaction to external oscillations (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6536-6542 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a second-order response theory to investigate the effects of external periodic perturbations on a chemical reaction at a stable steady state in an open reactor. We apply the theory to the quadratic Schlögl model, a single-variable nonlinear reaction. In the presence of oscillating reactant or product concentrations or oscillating rate coefficients, the average intermediate concentration, the fluxes, and the dissipation are each a Lorentzian function of frequency with midpoint at the inverse relaxation time of the system. Thus even very short relaxation times can be determined by measuring average rates as a function of frequency of the perturbation. The amplitude of the Lorentzian depends on the chemical mechanism of the reaction and is proportional to the square of the amplitude of the applied perturbation. We also show that energy from the perturbation can be used to drive the reaction in a direction opposite of that predicted by the Gibb's free energy difference of reactants and products, even under circumstances where the overall affinity is independent of the perturbation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462592
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  • 9
    Electronic Resource
    Electronic Resource
    Time dependence of pressure in a bubbler tube (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 922-929 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental and theoretical study is presented of the time dependence of air pressure in a bubbler tube used to measure the liquid level in a tank. The observed time dependence of the air pressure is a superposition of two components. The first component is a repeated slow rise and sudden fall in the air pressure that is associated with bubble growth and breakoff. It is the sudden breakoff that generates the second component consisting of damped oscillations associated with sound waves in the air interacting with an oscillating flow of the liquid. The air pressure during bubble growth is described theoretically. This result is combined with the gas law to predict the functional form of the slow pressure rise; this prediction agrees with experiment. An equation for the oscillation frequencies is derived, solved, and compared with experiment; agreement is within the measurement accuracy of 5%.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690280606
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  • 10
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    Imposed oscillations of kinetic barriers can cause an enzyme to drive a chemical reaction away from equilibrium (1993)
    American Chemical Society
    Details
    Publication Date: 1993-12-01
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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