Question

The chemical structures of the 20 standard amino acids at pH 7, along with their 3 and 1 letter codes, are givern in alphabetical order below. While the oxygen and nitrogen atoms of the peptide bonds may serve as a donor atom to complex a metal ion, very often the ligands for the metal come from the amino acid side chains. Takea few moments to examine the chemical structures of the different side chains. Circle the side chains that you expect to be able to serve as a ligand for a transition metal ion. H2N NH2 SH coo. Alanine (Ala, A) Arginine (Arg, R) Asparagine (Asn, N) Aspartic Acid (Asp, D) Cysteine (Cys, C) NH3 H3N Leucine (Leu, L) Lysine (Lys, K) Methionine (Met, M) Phenylalanine (Phe, F) Proline (Pro, P) COO HN соо H,N Glutamic Acid (Glu, E) Glutamine (Gln, Q) Glycine (Gly, G) Histidine (His, H) Isoleucine (Ile, ID) он он он H3N Serine (Ser, S) Threonine (Thr, T Tryptophan (Trp, W) Tyrosine (Tyr, Y) Valine (Val, V)

Answer 1

Find to the metal to form a complex usually by a coordination bond. A pair of electrons is generally present on a ligand. A ligand is an electron rich species so, in the given question if a side chain will out as ligand, it must have electron pair with it. Ala side chain has no electron density to donate Arg since N is present in side chain, this can act as ligand Asn both, O & N atoms can help in complexing with metal