Proteins Quasi-elastic light scattering

To determine the shape of ribosomal proteins in solution, ultracentrifugation, digital densimetry, viscosity, gel filtration, quasi-elastic light scattering, and small-angle X-ray or neutron scattering have all been used. With each technique it is possible to obtain a physical characteristic of the protein. Combining these techniques should allow the size and shape of the protein to be characterized quite well. However, the values determined in various laboratories for the same ribosomal proteins differ considerably. To help understand some of the reasons we will initially discuss each method briefly as it relates to proteins and then review the size and shape of the ribosomal proteins that have been so characterized. 

A major question in protein chemistry is why does one salt (or salt concentration) induce Ctystallization while most other conations lead to precipitation of a concentrated protein solution A quasi-elastic light scattering study of the effect of salts on lysozyme and concanavalin A precipitation concluded that salts that encourage precipitation lead to an increase in macromolecule polydispersity and size... 

Xia J., Dubin P. L., Kim Y., Muhoberac B. B., Klimkowski V. J. Electrophoretic and quasi-elastic light scattering of soluble protein-polyelectrolyte complexes. J. Phys. Chem. 1993 97 4528-4534. 

This is also known as photon correlation spectroscopy (PCS) or quasi-elastic light scattering (QELS). It uses scattered light to measure the rate of diffusion of protein particles in a sample. The data on molecular motion are digitally processed to yield a size distribution of particles in the sample, where the size is given by the mean Stokes radius or hydrodynamic radius of the protein particles this is the effective radius of a particle in its hydrated state. Clearly, the hydrodynamic radius depends on both mass and shape. 

Quasi-elastic light scattering (QELS) Measures translational, rotational, self, and mutual diffusion coefficients Experimental artifacts observed at low concentration Protein interactions can interfere at high concentratian... 

This method allowed to establish, that besides adsoption layer buildup at the interface the protein solution-organic phase, the distribution of the protein between hquid phases takes place. BSA and a-chymotrypsin at aqueous the protein solution-toluene were investigated in detail [155,156]. Transfer of the protein from the solution into interface layer as well as into organic phase was shown. In [157] the average hydrodynamic radius (r) of associates of BSA with non polar molecules in the adjacent phases of aqueous solution and hydrocarbon were determined by the quasi-elastic light scattering method. Results are given in Table 9. 

The adsorption of DNA films assembled from oligonucleotides composed of two homopolymeric diblocks (polyA G and polyTnCn) were studied in the presence of salt. The growth of fihn increased with salt concentration [22]. The studies on polyelectrolyte complexation have offered wide applications such as water treatment, surface modification, dmg delivery system, tissue engineering. To understand the formation of protein-polyelectrolyte complex is important due to the interaction between polyanions or polycations with protein macromolecules or polyelectrolytes. Soluble complexes can be formed and amphorous can be precipitated with the interaction of molecules. Complex formation is generally performed in the bulk solutions. Potentiometry, conductometry, viscosimetry, turbidimetry, or electrophoretic and quasi-elastic light scattering are used to follow... 

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