Diffusion coefficients protein

Kofinas et al. (1996) have prepared PEO hydrogels by a similar technique. In this work, they studied the diffusional behavior of two macromolecules, cytochrome C and hemoglobin, in these gels. They noted an interesting, yet previously unreported dependence between the crosslink density and protein diffusion coefficient and the initial molecular weight of the linear PEGs. 

A fundamental study was performed to demonstrate that flow FFF is a good alternative technique for the rapid measurement of protein diffusion coefficients [10]. The results obtained for 15 proteins were in good agreement (within 4%) with the literature data based on classical methods and a group of modern methods such as photon correlation spectrometry (PCS), laminar flow analysis, a chromatographic relaxation method, and analytical split-flow thin-cell (SPLITT) fractionation. The advantages of flow FFF are the high-speed separations and the calculation of D values directly from retention data. 

NMR measurement of solvent self-diffusion coefficients in polymer solutions NMR measurement of protein diffusion coefficients in solution and in synthetic membranes... 

Protein diffusion coefficients depend on the pH and ionic composition of the medium. For example, in a 1% bovine serum albumin (BSA) solution, the diffusion coefficient of BSA increased by a factor of 4 when KCl concentration in the solution was decreased below 0.01 M[54]. 

Molecular weight (Da), number of amino acids (A aa)> number of polypeptide chains (A c), diffusion coefficients in water 25 °C (D ). Protein diffusion coefficients from [11], unless otherwise indicated. Half-life in the plasma following i.v. injection, f[/2. 

The irreversibility of adsorption of some proteins also emphasizes the importance of understanding the kinetics of the adsorption process. Given a situation where transport of the protein to the material surface is diffusion controlled, Eq. (2) can be used during initial stages of adsorption, where the amount of protein on the surface (A) is proportional to the product of the protein concentration in solution (C) and the square roots of protein diffusion coefficient ( )) and time (t) ... 

Brune, D. and Kim, S., Predicting protein diffusion coefficients, Proc. Natl. Acad. Sci. USA, 90, 3835, 1993. 

The protein diffusion coefficient in hydrophilic polymers can be measured by a variety of experimental techniques. Since the type of diffusion coefficient measured by each technique can be different, the method of choice will depend on the desired information and variable. A summary of the advantages and disadvantages of techniques available for diffusivity measurements is presented in Table I. 

Many Immunological and enzymatic reactions have been studied by surface film technique. In addition, various aspects of protein structure can be deduced by investigation of spread protein films, for example, the study of compressibility of a protein film permits the determination of the molecular weight of the protein molecules forming the film. Tumit in 1954 has described a method for obftiining protein diffusion coefficient (D) by monolayer technique which is less cumbersome and is speedy too. Lastly, surface films have also been used to study the effect of irradiation of proteins and the results supplement the infonnatlon obtained by more conventional methods. 

The Stokes-Einstein equation has already been presented. It was noted that its vahdity was restricted to large solutes, such as spherical macromolecules and particles in a continuum solvent. The equation has also been found to predict accurately the diffusion coefficient of spherical latex particles and globular proteins. Corrections to Stokes-Einstein for molecules approximating spheroids is given by Tanford. Since solute-solute interactions are ignored in this theory, it applies in the dilute range only. 

The translational diffusion coefficient in Eq. 11 can in principle be measured from boimdary spreading as manifested for example in the width of the g (s) profiles although for monodisperse proteins this works well, for polysaccharides interpretation is seriously complicated by broadening through polydispersity. Instead special cells can be used which allow for the formation of an artificial boundary whose diffusion can be recorded with time at low speed ( 3000 rev/min). This procedure has been successfully employed for example in a recent study on heparin fractions [5]. Dynamic fight scattering has been used as a popular alternative, and a good demonstra-... 

Capillary zone electrophoresis, an up-to-date high resolution separation method useful for proteins and peptides, has been shown to be a useful method for determining electrophoretic mobilities and diffusion coefficients of proteins [3], Diffusion coefficients can be measured from peak widths of analyte bands. The validity of the method was demonstrated by measuring the diffusion coefficients for dansylated amino acids and myoglobin. 

Table 1 summarizes several of the experimental methods discussed in this chapter. A need exists for new or revised methods for transport experimentation, particularly for therapeutic proteins or peptides in polymeric systems. An important criterion for the new or revised methods includes in situ sampling using micro techniques which simultaneously sample, separate, and analyze the sample. For example, capillary zone electrophoresis provides a micro technique with high separation resolution and the potential to measure the mobilities and diffusion coefficients of the diffusant in the presence of a polymer. Combining the separation and analytical components adds considerable power and versatility to the method. In addition, up-to-date separation instrumentation is computer-driven, so that methods development is optimized, data are acquired according to a predetermined program, and data analysis is facilitated. 

Fluorescence correlation spectroscopy (FCS) measures rates of diffusion, chemical reaction, and other dynamic processes of fluorescent molecules. These rates are deduced from measurements of fluorescence fluctuations that arise as molecules with specific fluorescence properties enter or leave an open sample volume by diffusion, by undergoing a chemical reaction, or by other transport or reaction processes. Studies of unfolded proteins benefit from the fact that FCS can provide information about rates of protein conformational change both by a direct readout from conformation-dependent fluorescence changes and by changes in diffusion coefficient. 

Fig. 8. Dependence of (A) corrected diffusion coefficient (D), (B) steady-state fluorescence intensity, and (C) corrected number of particles in the observation volume (N) of Alexa488-coupled IFABP with urea concentration. The diffusion coefficient and number of particles data shown here are corrected for the effect of viscosity and refractive indices of the urea solutions as described in text. For steady-state fluorescence data the protein was excited at 488 nm using a PTI Alphascan fluorometer (Photon Technology International, South Brunswick, New Jersey). Emission spectra at different urea concentrations were recorded between 500 and 600 nm. A baseline control containing only buffer was subtracted from each spectrum. The area of the corrected spectrum was then plotted against denaturant concentrations to obtain the unfolding transition of the protein. Urea data monitored by steady-state fluorescence were fitted to a simple two-state model. Other experimental conditions are the same as in Figure 6.

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