The electron density difference mapfig. 3 clearly indicates that there is substantial re-arrangement of the electron density at the interface due to formation of hydrogen-bond between Cys52 and Arg266. The interfacial electron redistri-bution extends from the porphyrin macrocycle to guanidino group of the Arg266. On the other hand, at the PLP α-helix 8 interface, the phosphate group of PLP forms several hydrogen bonds (fig. ) with its neighbouring residues present within the α-helix 8. A large amount of electron density of the PLP moiety redistribute over those hydrogen bonding interactions. The accumulated electron density was observed to be extended up to few residues apart from the hydrogen bonding site. The intra-molecular hydrogen bonds present between different peptide bonds facilitates the conjuncture of the fractional electron transfers at the interfaces. Thus, the hydrogen bond network, constituted of the hydrogen bond at Heme-α-helix 8 and PLP-α-helix 8 interfaces and the intramolecular hydrogen bonds inside α-helix 8, form through-bond (hydrogen bond) electronic communication channels in hCBS.