Solution to PS 3 #3

1)  Backbone -bonds involving the C=O and N-H groups of the polypeptide chain.
2)  Side chain -bonds involving any possible H-bond donor (N-H of R group in His, Arg, Lys, etc.;  OH's in Asp, Ser, etc.) or acceptors on the side chain (O's on side chains:  C=O in Asp, Glu; OH in Tyr, etc.;  Some N's in Side chains)
3)  Hydrophobic interactions involving non-polar groups in a protein (many possiilities).
4)  Electrostatic interactions involving charged groups; Example: at pH 7 Asp carries a neg.  charge and Lys carries a pos.  charge so a salt brige can form between the two side Chains at pH 7.
5)  Metal ligation involving coordination between side chains atoms (often S, O, or N) and a metal ion.  [Asp, Glu, Cys, Tyr, His, Met, Lys are commonly found as ligands to metal ions.]



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