DNA fragmentation based combinatorial approaches to soluble protein expression Part II: library expression, screening and scale-up.

In this second of a two-part review encompassing random, combinatorial methods for soluble protein 'domain hunting', we focus upon the expression screening from DNA fragment libraries. Given a library of domain length-encoding DNA fragments assembled in expression vectors, it is necessary to devise reliable means to screen the sample DNA fragment population to find those that express stable, soluble target protein fragments, suitable for the required downstream aims. This review summarizes a variety of alternative strategies that have been employed to identify such stable truncates of full-length proteins. In addition, we review measures that can determine the quality of the expressed protein, the likely reliability of these measures, and the apparent extent of their application within the featured studies.