HHOHHOHHOHHOHHO. HO=C-O-HO=C-N-HH. HHOHHOHHOHHOHHOOH. SHO=C-N-HO=C-O-H
There are 20 kinds of common amino acids in the natural world. In this problem, we only consider 10 of them: Alanine, Asparagine, Aspartate, Cysteine, Glutamine, Glutamate, Glycine, Methionine, Serine and Threonine. By condensation reaction, nnn (n≥2nge 2n≥2) amino acids can be linked by n−1n-1n−1 peptide bonds into a peptide chain and produce n−1n-1n−1 water molecules at the same time. Recall that each water molecule has a molecular mass of 18. Figure: Idealized scheme showing condensation of two amino acids to give a peptide bond. Given a set of different amino acids and a number NNN, you are asked to print the structural formula of all possible peptide chains, with a molecular mass not greater than NNN, which can be formed by the given amino acids. Chains are considered different if the permutations of amino acids of the chain is different. Here are the structural formula of the 10 amino acids and the peptide bond. Ala: Asp: Asn: Cys: Gly: H H O H H O H H O H H O H H O | | || | | || | | || | | || | | || H-N-C-C-O-H H-N-C-C-O-H H-N-C-C-O-H H-N-C-C-O-H H-N-C-C-O-H | | | | | H-C-H H-C-H H-C-H H-C-S-H H | | | | H O=C-O-H O=C-N-H H | H Ser: Met: Thr: Gln: Glu: Peptide bond: H H O H H O H H O H H O H H O O H | | || | | || | | || | | || | | || || | H-N-C-C-O-H H-N-C-C-O-H H-N-C-C-O-H H-N-C-C-O-H H-N-C-C-O-H -C---N- | | | | | H-C-O-H H-C-H H-C-O-H H-C-H H-C-H | | | | | H H-C-H H-C-H H-C-H H-C-H | | | | S H O=C-N-H O=C-O-H | | H-C-H H | H See below for molecular mass of amino acids. Amino acid 3-letter symbol Molecular mass Alanine Ala 89 Asparagine Asn 132 Aspartate Asp 133 Cysteine Cys 121 Glutamine Gln 146 Glutamate Glu 147 Glycine Gly 75 Methionine Met 149 Serine Ser 105 Threonine Thr 119