Before revision:  Here we analyze 110 non redundant domain-swapped dimers filtered from the 3Dswap and Proswap databases, by keeping only structures not affected by the presence of holes along the main backbone chain. The linking number G' determined by Gauss integrals on the C_\alpha backbones is shown to be a solid and efficient tool for quantifying the mutual entanglement, also due to its strong correlation with the topological linking averaged over many closures of the chains. Our analysis evidences a quite high fraction of chains with a significant linking , that is with |G'| > 1. We report that Nature promotes configurations with G'<0 and surprisingly, it seems to suppress linking of long proteins.
After revision:  Here we analyze 110 non redundant domain-swapped dimers, our analysis evidences a quite high fraction of chains with a significant linking , that is with |G'| > 1. We report that Nature promotes configurations with G'<0 and surprisingly, it seems to suppress linking of long proteins.