The role of molecular chaperones in protein folding has been expensively studied. In E. coli, the two primary chaperone networks are DnaK-DnaJ-GrpE and GroEL- GroES. There are several minor chaperones the expression of which are induced when the cells are under heat, chemical and oxidateive stress. The chap- erone proteins have been proposed to interact with nascent polypetides and to facilitate the correct folding. When DnaK-DnaJ-GrpE or GroEL-GroES complexes are overexpressed, the solubility of a number of aggregation- prone proteins is improved. Not all insoluble proteins exhibit improved solubility with overexpression of DnaK- DnaJ-GrpE or GroEL-GroES. It has been shown that the solubility of some proteins is increased when the ells are subjected to chemical, thermal and oxidative stresses before expression of the insoluble protein. Other chap- erones may be necessary for some proteins. The mechanism by which a given protein is recognizes by any given chaperone protein is not known. Augmedium was this designed to induce the expression of several different chaperone proteins thereby allowing for an improvement in the solubility of aggregate-prone proteins without the need for identifying a specific chaperone effector.

pEX™ Protein Expression Media P9102-40 Media Optimization Kit™ P9102-40A Turbo Broth™ P9102-40B Superior Broth™ P9102-40C Power Broth™ P9102-40D Hyper Broth™ P9102-40E M9Y (Glucose) Broth™ P9102-40F Glucose-Nutrient Mix P9102-40G LB Broth (Miller)

Not sure which media expression system to choose? United States Biological has developed a unique research tool for protein expression media selection: Media Optimization Kit™

Our experiences with the expression of recombinant proteins have shown that the level of expression is very much dependent on the medium used. Some proteins are expressed well in one medium, but are not expressed in the same host strain in another medium or protein may be expressed in one medium while another protein is not expressed in the same medium.

This demonstrates why for each recombinant protein a medium screen becomes a crucial part of the optimization process. To facilitate the researchers’ efforts to develop the best systems for their proteins, we have developed a Media Optimization Kit.™. The kit is composed of six media formulations (including four that are unique and proprietary) which we have found over the years to be the most reliable for the increased production of recombinant proteins in Escherichia coli. The kit is used to quickly and easily identify the most suitable medium for the expression of a particular recombinant protein. Included are suggested approaches for improving the production of recombinant proteins, thus passing along the knowledge our staff scientists have acquired while working to produce a wide variety of proteins.

1. Dissolve the contents of the container in the appropriate volume of dH2O (i.e 100ml container in 100ml dH2O; 500ml container in 500ml dH2O). 2. Sterile fiter.

Store powdered media at RT. Opened bottles should be capped tightly and kept in a dark, low humidity environment. Prepared media may be kept at 4°C for 2 months. For longer storage, aliquot and store at -20°C. Stable for 6 months.