The Use of Fast Protein Liquid (Size Exclusion) Chromatography for the Fractionation of Crystallins and the Study of β-Crystallin Aggregation

Bovine lens crystallins do contain helical structure: a circular dichroism study

In order to settle a recent discussion on the secondary structure of lens crystallins, we have measured the circular dichroism (CD) spectra of alpha-, beta(H)-, and beta(L)-crystallin from 178 to 250 nm and of gamma-crystallin from 168 to 250 nm. The results were analysed by means of a newly developed algorithm that almost doubles the reliability of secondary structure prediction and that allows discrimination between alpha- and 3(10)-helical, and between extended and polyproline beta-type structure. The results indicate that the crystallins studied contain a non-negligible amount of alpha-helical structure, although at least 50% of it is in the form of single and/or distorted loops. In alpha-crystallin, which is related to the chaperones, the helical content is lower than in beta- and gamma-crystallin. In some cases, the helices may play a role in DNA binding by the crystallins.

Comparison of free solution capillary electrophoresis and size exclusion chromatography for quantitating non-covalent aggregation of an acylated peptide

There are few methods available for the rapid and precise quantitation of non-covalent aggregation. The very methods used to measure the aggregation can easily disrupt the weak forces holding an aggregate together. This paper describes the novel application of free solution capillary electrophoresis (CE) for the quantitation of a biologically inactive non-covalent aggregate of C8GLIP (Des-amino-histidine-7-arginine-26 N(epsilon)-octanoyl-lysine-34-human glucagon-like insulinotropic peptide), an acylated peptide. The CE results are compared to a more traditional approach using size exclusion chromatography (SEC). Under the conditions explored in this paper, SEC showed a significantly slower apparent rate of aggregation than CE. This is due to the disruption of the aggregate during the SEC process. The cause of the disruption is complex and is potentially related to the separation process itself, on-column dilution effects, and/or interactions of the aggregate with the column packing or SEC components. Analysis times and dilution are greatly reduced by CE, and, because there is no potentially interactive stationary phase and because both the protein and the walls of the capillary are negatively charged, potential disaggregation due to surface interactions is reduced. Thus, CE is shown to be superior to SEC for this peptide in that disruption of the aggregate is minimized.

Large-scale high-performance liquid chromatography of enzymes for food applications

Processes for the production of food-grade enzymes must be cost-effective. Fortunately, most enzymes manufactured for food applications are not required to be highly purified. However, enzymes are considered additives and thus the concentration of DNA and other extraneous materials must be within FDA guidelines. Developing efficient, low-cost, large-scale HPLC methods for food applications is becoming more feasible with the introduction of new HPLC tools and technologies. Enzymes can be successfully separated from cell extracts by size-exclusion and ion-exchange HPLC using optimal gradient elution programs for the latter. Large-scale HPLC methods developed for the purification of some significant food enzymes are discussed in this paper.