Comparison 3D-BLAST with PSI-BLAST. Evaluation of the 3D-BLAST and PSI-BLAST in database search and family/superfamily assignments by SCOP-516 based on (a) receiver operating characteristic (ROC) curves and (b) percentages of correct classification assignments. 3D-BLAST (black lines) outperforms PSI-BLAST (gray lines) in the ROC curve. The dashed and solid lines denote the ROC curves for the SCOP superfamily and SCOP family assignments, respectively. 3D-BLAST (black bars) is much better than PSI-BLAST (gray bars) when the sequence identity is under 20%.