Dynamic Light Scattering in Protein Studies

Protein

If you have been reading some of the other posts on this blog you will know by now that dynamic light scattering offers a quick and accurate method of obtaining information on size, and size distribution, of particles held in suspension or solution. The variety of particle types to which it can be applied is enormous, ranging from 0.6 nm to 7 µm in size and from simple solutions and suspensions to polymers in very complex fluids.

Particles don’t come much more complex than proteins. Sometimes known as polypeptides, these compounds are composed of long chains of amino acids, held together by peptide bonds. The chains are, in turn, folded into complex shapes.

These chains are very sensitive to such factors as the chemical conditions in which they find themselves and the temperatures to which they are exposed. Variation in those factors can make the protein unstable.

This can be a major problem in the field of medicine. A new pharmaceutical product may hold great potential but if it is unstable it may not prove not to be usable. In particular, many proteins will, under certain conditions, clump together to form aggregates. As well as affecting the effectiveness of the product, aggregates may actually be harmful to the patient.

For this reason, it is important that therapeutic products and the proteins they contain should be studied very closely to see whether their characteristics change under particular circumstances and whether aggregates are formed.

Dynamic light scattering, or photon correlation spectroscopy as it is otherwise known, provides a readily applicable and non-invasive technique for use in such studies. It can be used for accurate characterisation of the proteins, in terms of particle size, and for detection of even the smallest quantity of aggregate.

It is worth mentioning that a number of dynamic light scattering instruments on the market are also able to apply electrophoretic light scattering to determine zeta potential, which is a useful indicator of a suspension’s likelihood to remain stable. Meritics will be happy to advise on the range of equipment available.