Addendum to "quantative measure of folding in two-dimensional polymers"

Recently, we introduced a measure of folding complexity for two-dimensional polymers, (N) over bar, the mean radial intersection number [Phys. Rev. E 59, 4209 (1999)]. In this addendum, we expand on three aspects of the previous work. First, we provide an analytical expression for (N) over bar that is valid for two-dimensional networks. Second, we show that the power-law scaling (N) over bar approximate to n(beta), with n the number of monomers. has a different critical exponent for random and self-avoiding walks. Finally, we find that the folding features in optimized projections of experimental three-dimensional (native) protein backbones fall between the latter limit models. [S1063-651X(99)08511-6].