Solubility-Weighted Index: fast and accurate prediction of protein solubility

Bikash K. Bhandari; Paul P. Gardner; Chun Shen Lim

Protein structural flexibility, in particular, the flexibility of local regions, is often associated with function (Craveur et al. 2015) . The calculation of flexibility is usually performed by assigning a set of 20 normalised B-factors-a measure of vibration of C-alpha atoms (see Supplementary Notes)-to a protein sequence and averaging the values by a sliding window approach (Ragone et al. 1989; Karplus and Schulz 1985; M. Vihinen, Torkkila, and Riikonen 1994; Smith et al. 2003) . We reasoned that such sliding window approach can be approximated by a more straightforward arithmetic mean for calculating global structural flexibility (see Supplementary Notes). We determined the correlation between flexibility (Vihinen et al. 's sliding window approach as implemented in Biopython) and solubility scores calculated as follows: