Consider the peptide: (New info provided) (The residue # from left to right 1-4)

ID: 197586 • Letter: C

Question

Consider the peptide: (New info provided)

(The residue # from left to right 1-4)

H2N - (1) - (2) - (3) - (4) - COOH

H2N - Asp – Thr – Phe - Lys – COOH

(1) (2) (3) (4)

H2N – D -T – F – K – COOH

1. Determine the PI (isoelectric point) of the peptide. (Round to 2 decimal points)

The residue #3 is not Thr. The #2 is Thr

The pI value is from the textbook Table 3-1

Lehninger’s Principle of Biochemistry, 5th Edition Table 3-1

Properties and Conventions Associated with the Common Amino Acids Found Proteins

https://www.dropbox.com/s/g3fjghh71oeac5c/Lehninger 5th Edition.pdf?dl=0

2. Which type of noncovalent interaction would the indicated residue sidechain make at the given PH?

Please pay attention to the residue order (#) and select the best answer (only 1 correct answer)

1. H-bond. 2, Hydrophobic effect or Van der Waals. 3. Ionic bond or Salt bridge 4. No bond

Residue 1 @ pH 5.0

Residue 2 @ pH 6.0

Residue 3 @ pH 11.0

Residue 4 @ pH 10.0

Ans1)So we have to take two isoionic group.

Asparate have pka value-3.9

Lysine have pka value.-10.54

COOH -2.4

NH2 -9.4

So we take 9.4+3.90/2 =6.65

So Pi =6.65

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