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Dilute solutions of DNA plasmid pUC18 (2687 base pairs) have been studied by polarized photon correlation spectroscopy. The autocorrelation functions of the scattered light have been measured and fitted to a sum of exponentials. When a two exponential fit of the autocorrelation functions is performed, the slower relaxation rate corresponds to the expected translational diffusion coefficient of the plasmid while the faster one shows a linear behavior below K2[bar_over_tilde:_approx._equal_to]5×1014 m-2, being superlinear at larger K2 values. The translational diffusion coefficient at T=25° is Dt=5.4±0.25×10-12 m2/s while the extrapolation of the fast relaxation rate to K2=0 yields the tumbling rotational coefficient R⊥=1.5±0.2 kHz. Monte Carlo simulations of the plasmid conformation have been performed with different sets of dynamical parameters (bending and torsional rigidities, Debye length), and the hydrodynamic coefficients have been computed according to known algorithms. The translational diffusion coefficient determined experimentally shows good agreement with the results of Monte Carlo simulations, while the simulated rotational tumbling coefficient is slightly larger than that found experimentally. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The conformation and slow internal motions of a DNA plasmid molecule pUC18 (2687 base pairs) are studied by means of depolarized photon correlation spectroscopy. The autocorrelation functions are measured at different scattering angles between 6.7° and 90° and analyzed as heterodyne autocorrelation functions. One obtains both a relaxation time of [bar_over_tilde:_approx._equal_to]140 μs, which is interpreted as the tumbling rotational diffusion coefficient of the plasmid, and some faster component with relaxation time around 15 μs. The value of the rotational diffusion relaxation time is in good agreement with the results of Monte Carlo simulations, while the faster decay has a nonsingle exponential decay behavior. The results of measurements made in the depolarized scattering configuration are compared to those obtained from polarized configuration and critically discussed. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on experimental and theoretical analysis of the effect of intermolecular interactions and dissociation on diffusional properties of carbon monoxide bovine hemoglobin in solution. Cumulant diffusion coefficient of the macromolecule; Simple theoretical expansion of the first cumulant diffusion coefficient; Protein interactions and dissociation.