Table 4.

Number of fully masked/unmasked TCDB entries and the corresponding average number of TM helices at various z-score thresholds of f = 0.840, 1.000, 1.282, 1.645 and 1.980

Mask ratio, m	f = 0.840		f = 1.000		f = 1.282		f = 1.645		f = 1.980
	No. of entries	Avg no. of TMs	No. of entries	Avg no. of TMs	No. of entries	Avg no. of TMs	No. of entries	Avg no. of TMs	No. of entries	Avg no. of TMs
0.0	246	4.4	326	4.8	546	5.8	1050	6.9	1470	7.3
1.0	208	1.8	170	1.5	123	1.2	79	1.1	49	1.1

The two mask ratios of m = 0 and m = 1 correspond to the extreme situation where the TM segments in a TCDB entry is fully unmasked or fully masked respectively (column 1). The column pairs (2,3), (4,5), (6,7), (8,9) and (10,11) denotes the number of TCDB entries and the average number of TM helices (total number of TM helices in the entries/total number of entries) given the associated mask ratio and the z-score thresholds of f = 0.840, 1.000, 1.282, 1.645 and 1.980 (corresponding to false-negative rates of 20%, 16%, 10%, 5% and 2.5%). The average number of masked helices ranges from 1.1 to 1.8 while the average number of unmasked helices is between 4.4 and 7.3. This means that the fully masked TCDB entries are almost exclusively the single-spanning ones while the fully unmasked entries are often the multi-spanning ones.