A new correlation is proposed for the prediction of protein diffusion coefficients in free solution. Molecular weight and radius of gyration of proteins are employed as correlation parameters in this method. Both parameters can be easily found in the literature. The correlation works well for diverse proteins with different shapes and extensive molecular weight. Furthermore, this method does not require a preassumption regarding the protein shape while it offers a rapid and convenient calculation with a high accuracy. Also, the proposed correlation can elucidate the estimation deviation of previous correlation methods in the literature.

Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) experiments were performed to investigate the micelle structure of n-octyl-β-maltopyranoside (OM). Density measurements were carried out to obtain the volumetric characteristics of OM for micelle structure analysis. Both temperature and concentration were varied in scattering experiments to study their effects on micelle size. The scattering data were analyzed by the indirect Fourier transformation method (IFT) and model fitting. The IFT method gave the radius of gyration of the micelles and their pair distance distribution function. It was found that the radii of gyration from SANS data were much smaller than those from SAXS data at similar solution conditions. Moreover, pair distance distribution functions from SANS and SAXS data were also different. Model fitting indicated that a spherical shell model can be used to describe both SANS and SAXS data using similar structure parameters. Comparison of SAXS data in D 2 O and H 2 O shows that the OM micelle has a similar structure in both solvents. The size of the micelle does not increase with increasing concentration up to 188 mM. From 10 to 50 °C, the structure of the micelle is not sensitive to temperature changes. Comparison of the micelle structures of OM with those of its two closely related glycolipids, n-octyl-β-glucopyranoside (OG) and n-dodecyl-β-maltopyranoside (DM), suggests that the hydrophilic force plays an important role in the micelle structure of glycolipids.

Thin films are usually obtained by depositing atoms with a continuous flux.We show that using a chopped flux changes the growth and the morphology of the film. A simple scaling analysis predicts how the island densities change as a function of the frequency of the chopped flux in simple cases where aggregation is irreversible. These predictions are confirmed by computer simulations.We show that the model can be used to obtain information on the diffusion or the evaporation of the adatoms. The model is also useful to understand the growth of thin films prepared by pulsed sources.Typeset using REVT E X 1 One of the main interests of usual deposition techniques such as Molecular Beam Epitaxy [1] is that the structure of the deposited films is to a large extent determined by kinetic factors, as opposed to thermodynamic equilibrium. This allows to "play games" [2] with the different growth parameters (incident flux of particles, diffusion coefficient of an adatom . . . ) in order to obtain different film morphologies. A simple example is given by the quantity of islands grown on a substrate at low enough temperatures : it is known that the number of islands at saturation is given by (F/D) 1/3 [3][4][5] where F is the incident flux and D the diffusion coefficient. Then, by increasing the flux or decreasing the diffusion constant (by lowering the substrate temperature), one can adjust the saturation number of islands grown on the substrate. In this sense, each kinetic factor is a "handle" on the system, allowing to control the morphology of the films. We introduce in this Letter a new kinetic handle, which should enable a larger control over film growth : the chopping of the incident flux. We note that this flux modulation is intrinsic to other deposition techniques such as cluster laser vaporization (the laser is pulsed [6]). It is therefore important to understand how growth proceeds in the presence of a modulated flux if one is to be able to interpret experiments performed in these conditions. For example, one may wonder whether the usual growth theories [3][4][5] can be used by replacing the continuous flux by the average value of the chopped flux over a cycle. In the following, we will show that this is not the case, and that the growth of the film is profoundly changed by the modulation of the incident flux for the case of growth with irreversible aggregation (critical island size 1, see [3][4][5][7][8][9]. Conversely, we show what kind of information can be derived from experiments carried under these conditions.The basic idea of our method is that if instead of using a continuous flux we use a chopped flux to grow a film, the number of islands formed on a substrate will depend on the chopping frequency f and on d, the fraction of the period the flux is "on" (see Fig. 1).This dependence is due to the fact that the free particle concentration on the surface does not reach its steady state concentration instantaneously, but only after a time which we will call τ m . Then, if the timescale of the chopping (...