The button test: a small scale method using microdialysis cells for assessing protein solubility at concentrations suitable for NMR.

A simple method has been developed for screening solution conditions to determine conditions under which a protein is soluble at the high concentrations typically used for NMR spectroscopy. The method employs microdialysis cells or 'buttons'. The low sample volume (5 microliters) required for each microdialysis button permits testing of a wide range of solution conditions and temperatures with high protein concentrations, using a small amount of protein. Following precipitation of several NMR samples of the C-terminal core domain of human TFIIB, the microdialysis button screen facilitated identification of conditions in which precipitation of the TFIIB core domain was eliminated. The microdialysis button method for screening solution conditions is generally applicable and has been used to permit rapid identification of suitable NMR sample solution conditions for proteins involved in transcription and cell adhesion.