Fig. 2.

Binary bit string representation of genome-wide drug-protein interaction profiles of individual drugs and drug combinations. In the bit strings, the drug interaction with each protein is encoded by four bits representing binding (B), inhibition (I), activation (A), and catalysis (C). For any drug, if information for an interaction is present in the STITCH database with at least a medium confidence level, the corresponding bit in the string is turned on (assigned a value of 1); otherwise, it is turned off (assigned a value of 0). To generate a drug pair-protein interaction profile ĝ(d _i d _j) from the constituent drug-protein interaction profiles ĝ(d _i) and ĝ(d _j), we implemented the logical OR operation. Thus, we turned the bit off when neither drug interacts with a protein; otherwise, we turned it on when interactions for either or both drugs are present