Microwave-assisted preparation of affinity medium

Microwave assisted solubilization of inclusion bodies

Background

Production of recombinant proteins in bacterial hosts often produces insoluble intracellular particles called inclusion bodies. Recovery of active protein from inclusion bodies generally requires their solubilization in chemical denaturants followed by a refolding strategy. The solubilization is carried out with shaking/stirring and takes several hours.

Results

Using inclusion bodies of seven diverse kinds of recombinant proteins [mutants of controller of cell division or death protein B (CcdB), human CD4D12, thioredoxin fusion protein (malETrx), mutants of maltose binding protein (MBP), single chain variable fragment (ScFv) b12 and single chain antigen binding fragment (ScFab) b12 (anti-HIV-1)], it is shown that exposure to microwave irradiation (200 W) for 2 min, solubilized these inclusion bodies completely. This was confirmed by data based upon turbidity measurements at 400 nm and dynamic light scattering studies. These solubilized inclusion bodies could be refolded correctly in all the cases by known methods. The refolding was confirmed by fluorescence emission spectra and biological activity studies.

Conclusion

Solubilization of the inclusion bodies before refolding is a part of protein production processes for several recombinant proteins which are overexpressed in the bacterial host systems. Our results show that microwave assistance can considerably shorten the process time.

Sample preparation and fractionation for proteome analysis and cancer biomarker discovery by mass spectrometry

Sample preparation and fractionation technologies are one of the most crucial processes in proteomic analysis and biomarker discovery in solubilized samples. Chromatographic or electrophoretic proteomic technologies are also available for separation of cellular protein components. There are, however, considerable limitations in currently available proteomic technologies as none of them allows for the analysis of the entire proteome in a simple step because of the large number of peptides, and because of the wide concentration dynamic range of the proteome in clinical blood samples. The results of any undertaken experiment depend on the condition of the starting material. Therefore, proper experimental design and pertinent sample preparation is essential to obtain meaningful results, particularly in comparative clinical proteomics in which one is looking for minor differences between experimental (diseased) and control (nondiseased) samples. This review discusses problems associated with general and specialized strategies of sample preparation and fractionation, dealing with samples that are solution or suspension, in a frozen tissue state, or formalin-preserved tissue archival samples, and illustrates how sample processing might influence detection with mass spectrometric techniques. Strategies that dramatically improve the potential for cancer biomarker discovery in minimally invasive, blood-collected human samples are also presented.

Leveraging protein purification strategies in proteomics

The proteomic studies, although, tend to be analytical in nature, yet many strategies of preparative protein purification can be usefully employed in such studies. This review points out the importance of purification techniques which are capable of dealing with samples which are suspensions rather than clear solution, e.g. aqueous two phase partitioning, three phase partitioning, expanded bed chromatography, etc. The review also outlines the potential of non-chromatographic techniques in dealing with fractionation of proteomes. Separation protocols which can deal with post-translationally modified (PTM) proteins are also considered.