|MadSci Network: Biochemistry|
A hydrogen bond is the interaction between an electron-deficient hydrogen atom and an electronegative atom. The only thing that truly needs to have the partial charge is the hydrogen (hence the fact that hydrogen can only H-bond when it is connected to an O or N and not a C). The hydrogen bond involves the sharing of an electron between this partial positive hydrogen and an electronegatve atom that can share one of its electrons in a weak bond. So, in the case of oxyhemoglobin, the hydrogen in His has a partial positive charge due to its covalent bond with the nitrogen on the side chain, and it can readily H-bond with an oxygen molecule.
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