Question

Examine the peptide. Thr-Glu-Pro-Ile-Val-Ala-Pro-Met-Glu-Tyr-Gly-Lys Write the sequence using one-letter abbreviations. sequence: TKPIVAPMEYGK Estimate the net charge on the peptide at pH 7. charge at pH 7: Estimate the net charge on the peptide at pH 12.

help with these please

Answer 1

- Thr-Glu-Pro-Ile-Val-Ala-Pro-Met-Glu-Tyr-Gly-Lys

(Thr : Threonine - T, Glu: Glutamic acid -E, Pro: Proline -P, Ile: Isoleucine - I, Val: Valine - V, Ala: Alanine -A, Met: Methionine - M, Tyr: Tyrosine -Y, Gly: Glycine -G, Lys : Lysine -K)

So the abbreviation will be TEPIVAPMEYGK

The charge on the amino acid side chain depends on the pK of the amino acid and the pH of the solution.

- Net charge : -1 at pH 7.

- Net charge: -4 at pH 12

Given, Mass of single stranded alpha helical protein segment = 23.0 kDa = 23000 Da , Mean residue mass = 110 Da

- Number of residues = 23000 Da/ 110 Da = 209 residues

Rise per residue in an α helix is 1.5 Å,

So, the length of single stranded alpha helical protein segment = 209 residues x 1.5 Å = 313.5  Å

- Given, length = 1.30 x 102 Å

Rise per residue in a beta sheet conformation is 3.5 Å

So, the number of residues = 1.30 x 102 Å/ 3.5 Å = 37 residues