Question

A pentapeptide has the sequence$\mathbf{NNKNN}$(using one-letter symbols for amino acids). Calculate the mass of this peptide, as determined by mass spectrometry, to three significant figures.

Short answer

The mass of this peptide, as determined by mass spectrometry, to three significant figures is $602gmo{l}^{-1}$.

Step-by-step solution

Definition of peptide

A molecule is made up of at least two amino acids. Proteins, which are also chains of amino acids, are larger than peptides.

Step 2: Calculate the mass of this peptide

Mass: Here are 4 N residues, so,$4\times 114=456$

ASPARAGINE (N): $114\text{g}{\text{mol}}^{-1}$N and K are connected by peptide bondsso an additional $O$atom and$H$ atoms are counted.

$O:16\text{g\hspace{0.17em}}{\text{mol}}^{-1}$and$H2\text{g\hspace{0.17em}}{\text{mol}}^{-1}$

$456+128+6+2=602gmo{l}^{-1}$

Therefore, the mass is$602gmo{l}^{-1}$ .