Protein Molecular Weight

Intermediate Bioinformatics Protein Mass Spectrometry Molecular Weight

Significance:

Mass spectrometry identifies proteins by matching observed masses against predicted ones, so
computing a peptide's monoisotopic mass is the bridge between a sequence database and a real
spectrum. The water term matters: forming each peptide bond releases a water molecule, so the
whole peptide weighs one water more than the sum of its residues.

Statement

Given a protein string, compute its monoisotopic molecular weight in daltons.

Sum the monoisotopic residue mass of each amino acid, then add the mass of one water molecule
(18.01056) for the intact peptide.

Use these residue masses:

A 71.03711   C 103.00919   D 115.02694   E 129.04259   F 147.06841
G 57.02146   H 137.05891   I 113.08406   K 128.09496   L 113.08406
M 131.04049  N 114.04293   P 97.05276    Q 128.05858   R 156.10111
S 87.03203   T 101.04768   V 99.06841    W 186.07931   Y 163.06333

Print the total rounded to three decimal places. Your answer is compared numerically with a
tolerance of 0.01.

Input — read from standard input

Variable	Type	Description
`protein` line 1	str	The protein sequence in single-letter amino acid codes 1 <= length <= 1000, uppercase standard amino acid letters

These variables are already read for you in the starter code on the right.

Output

float the monoisotopic peptide mass, rounded to 3 decimal places

Sample Cases

Sample 1

Input

SKADYEK

Expected Output

839.402

The seven residues sum to 821.392, plus one water (18.011) gives 839.402.

Sample 2

Input

Expected Output

89.048

A single alanine residue plus water.

Submit also runs your code against 4 hidden test cases. Hidden inputs are never shown — if one fails you'll get its number and a description of the mismatch, not the data.

Constraints

1 <= length(protein) <= 1000
Only the 20 standard amino acid letters appear
Remember to add one water mass (18.01056) to the residue total