Fig. 4. Dependence of secondary structure formability indexes (alpha-helix (A), beta-sheet (B) and beta-turn(C)) upon GC content of a gene. Total indexes, which were calculated from structure index of each amino acid and amino acid composition of a hypothetical protein encoded by an antisense sequence of a gene from 7 microbial genome data, are plotted against GC content of a gene. Two horizontal lines in the figure show the position of the average values (A.V) plus and minus the standard deviations (S.D.) of actual proteins. The average values and the standard deviations are given in Table 1. It can be seen that over about 50% GC content, index values enter the regions of A.V. plus and minus of S.D. of globular proteins.