4. At pH 7.0, in what order would the following three peptides (described by their amino acid composition) elute from an anion exchange resin? Each peptide is 100 amino acids long. Ala Gly Peptide A 4% Peptide B 12% Peptide C 7% Phe Asn Gln Ser Asp Glu Lys Arg 7% 5% 6% 4% 8% 19% 15% 20% 12% 36% 8% 11% 14% 17% 5% 0% 2% 14% 6% 21% 8% 11% 3% 10% 4% 8% 11% 1 of 2

K₁ = α [H+][A-] [HA] [A-] pH = pK+log [HA] 1-1 The Amino acid Arginine ionizes according to the scheme below. Calculate the isoelectric point of Arginine and the average charge on arginine when pH = 9.2. NH2 H C=N NH pka-2.17 -H' NH2 H C=N H NH PK-8.99 -H +H* H (CH2)3 H-N-C-COOH | H H +H* H (CH2)3 H-N-C-coo- H H Ans: 10.75; +0.38 NH2 NH2 H C=N C=N-H H NH PK-12.5 -H NH | +H* (CH2)3 H₂N-C-COO- | H III (CH2)3 H₂N-C COO- H IV

Given the amino acids below, what amino acid will elute first in a cation-exchange column. 1. Aspartate or Lysine using a buffer at pH 7 2. Arginine or Methionine using a buffer at pH 7 3. Lysine or Valine using a buffer at pH 7 4. Glycine or Valine using a buffer at pH 7 5. Serine or Alanine using a buffer at pH 7

What is the charge of this peptide at pH 1.5?

A HEPTAPEPTIDE that punctures the bacterial cell wall has just been recently isolated from the venom gland of a frog. Amino acid analysis of the peptide reveals the following information below: (NOTE: when the sequence is not known, a comma separates the amino acids) Hydrezine Acid Hydrolysis (6 N HC) at 10 C Heptapeptide (2) Arg. Pro, Phe, Tyr, Ala, Lys 2,4 dinitrafluerobenzene DNP-Phe Lys and modified free amino acids Peptide 1 (Ala, Lys) Cleovage with Trypsin, then chrometogrophy Peptide 2 (Pro, Arg, Tyr) Peptide 3 (Phe, Arg) Phe Peptide 4 (Arg. Tyr) Clevege with Chymetrypsin, then cromategrphy Peptide 5 (Lys, Pro, Ala, Arg)

At pH = 4, what is the net charge of the peptide GKPAD? +0.5 O-10 0 O-0.5

Please calculate and plot the charge on a peptide with the sequence of NEYK over the pH range from 1 to 13. Please use the pKa values from the table. You may calculate the charge at 1 pH unit intervals.

use one-letter code for the amino acid if needed   what is the sequence of peptide 4?

Refer to following peptide structure: H&N CH3 IZ CH3- CH₂OH IZ OH ZI CH3 CH3. OH IZ OH IZ CH2 CONH2 parce 0 IZ Calculate the net charge of this peptide at pH = 12. OH CH3 What is the identity of the second residue in the peptide shown below? Enter the capitalized single letter abbreviation. 0- Estimate the pl and round to the nearest whole number. Use pKa values provided in lecture.

Can you please help find the net charge?