In contrast, differences in cavity volumes for O-and N-targeting MTases are not statistically significant. Cavity volumes only differ by 70.8 Å 3 on average (Figure ), which is considerably smaller than the standard deviations of 262.0 Å 3 and 185.0 Å 3 for O-and N-targeting targeting MTases, respectively. Using student's t-test, the cavity volume distributions are not considered to be statistically significant with a p-value of 0.20. The upper and lower limits of cavity volumes for both heteroatom targeting enzymes are also comparable (i.e., ~550 Å 3 to ~1425