Most common in molecular biology laboratory

1) SIze exclusion chromatography: This will tell you oligomeric state of your recombinant protein

2) Thermofluor assay using an RT PCR: This will tell you if the recombinant protein unfolds cooperatively

Further advanced needing specialized equipment but still very common:

1) Circular Dichroism: This will help you determine if the protein is folded (secondary and tertiary structures).

SAXS and Analytical Ultracentrifugation help you determine the particle size (radius of gyration) and oligomeric state of the recombinant protein. These techniques will need special equipment, that are not very common in many laboratories.

How much protein is required for these techniques?

One possibility is illustrated in the paper "Protein-Protein Interaction in the light of the Maximum Ordinality Principle" (May 2015)2015)