HYDRO is a program for the calculation of sedimentation and diffusion coefficients, rotational relaxation times, and intrinsic viscosities of rigid macromolecules of arbitrary shape that are represented by bead models. Actually, HYDRO contains various FORTRAN callable subroutines that can be linked to the user's own programs to account for variability of shape or flexibility. Some hints are given for the use of HYDRO in various situations.

Hot water and cellulase hydrolysis extraction methods were used to obtain soluble and insoluble fractions of dietary fiber (DF). Concentrates of the DF fractions were used to study their structure, physical properties (particle size, density, porosity, and oil adsorption capacity), hydration properties (swelling, water binding capacity, and viscosity), and glucose dialysis retardation index. Hydrolysis with cellulase modified the physical and hydration properties of the different samples analyzed, since this enzyme reduced the particle size in soluble and insoluble dietary fiber (SDF and IDF, respectively), while increasing the water binding capacity of IDF and decreasing that of SDF. Correlation studies carried out between the different properties analysed, showed that the behavior of hydrated fiber and the delay in glucose diffusion are determined by the physical properties of fiber. Keywords: Dietary fiber; functional properties; fiber extraction and artichoke

Hydrodynamic properties (translational diffusion, sedimentation coefficients and correlation times) of short B-DNA oligonucleotides are calculated from the atomic-level structure using a bead modeling procedure in which each non-hydrogen atom is represented by a bead. Using available experimental data of hydrodynamic properties for several oligonucleotides, the best fit for the hydrodynamic radius of the atoms is found to be approximately 2.8 A. Using this value, the predictions for the properties corresponding to translational motion and end-over-end rotation are accurate to within a few percent error. Analysis of NMR correlation times requires accounting for the internal flexibility of the double helix, and allows an estimation of approximately 0.85 for the Lipari-Szabo generalized order parameter. Also, the degree of hydration can be determined from hydrodynamics, with a result of approximately 0.3 g (water)/g (DNA). These numerical results are quite similar to those found for globular proteins. If the hydrodynamic model for the short DNA is simply a cylindrical rod, the predictions for overall translation and rotation are slightly worse, but the NMR correlation times and the degree of hydration, which depend more on the cross-sectional structure, are more severely affected.

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The non-Newtonian behavior of dilute polymer solutions is investigated by computer simulation of a bead-and-spring model, using the Brownian dynamics technique to evaluate the shear rate dependence of the intrinsic viscosity. This behavior is a consequence of the combined effects of hydrodynamic interaction, excluded volume, and finite extensibility. The simulations allow the study of the influence of each effect separately. When all the effects are considered, the simulation results can be compared to experimental data of solution viscosities, which are available just in the region of moderately small shear rates. Data from molecular architecture and other solution properties are obtained to parametrize the bead-and-spring model, with emphasis in the description of the chain extensibility. Comparison of simulation and experimental results is presented for both highly flexible vinyl polymers and locally stiff cellulose chains.

The translational and rotational diffusion coefficients of very short DNA fragments have been calculated using a double-helical bead model in which each nucleotide is represented by one bead. The radius of the helix is regarded as an adjustable parameter. The translational coefficient and the perpendicular rotation coefficient agree very well with experimental values for oligonuclotides with 8, 12, and 20 base pairs, for a single value of the helical radius of about 10 A. We have also calculated a nuclear magnetic resonance relaxation time in which the coefficient for rotation about the main axis is involved. As found previously with cylindrical models, the results deviate from experimental values, indicating that the internal motion of the bases has a remarkable amplitude. An attempt to quantify the extent of internal motions is presented.

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