Consider the pentapeptide Ile-Lys-Asp-Phe-Gly and answer the following (use the pKa values in the table): 1. Draw the structure of the predominant form of the pentapeptide at pH = 12. 2. Draw the structure of the Zwitterion form of the pentapeptide. 3. What is the IpH of the peptide?

The R group of the amino acid Asp contains a carboxyl group with a pKa of 3.7. But the pka of the alpha-carboxyl group in Asp is 1.9. Which of the following. explanations could reasonably account for this difference? 3.7 is the isoelectric pH, which is estimated by averaging the pka of the alpha- carboxyl group with the much higher pKa of the alpha-amino group The R group of Asp also contains an NH2 group, which is less acidic than a carboxylic acid The conjugate base of the alpha-carboxyl could be stabilized by an attractive ionic interaction with the nearby alpha-amino group, which is protonated at low pH Water has better access to the R group than to the alpha-carboxyl group, so it more effectively solvates the charged form of the R group and stabilizes it

Peptides can be separated using an ion-exchange column based on their isoelectric (pl) values. At which pH values would two different peptides, one with a pl of 5.6 and the other with a pl of 9.1, bind to a cation- and anion-exchange column? Each peptide may be capable of binding to each column at more than one pH value. anion-exchange column at pH = 3.1 pH = 7.2 pH = 10.6 ****** cation-exchange column at pH = 3.1 pH = 7.2 PH =10.6 Answer Bank peptide B pl = 9.1 peptide A pl = 5.6

Draw a tetra peptide of Ser-His-Leu-Tyr at pH=1

The RGD peptide is critical for the establishment of the extracellular matrix of animal cells. a. Draw the structure of the RGD peptide at physiological pH (pH = 7). b. What is the charge of this peptide at physiological pH? At high pH (pH> 13)? Low pH (pH < 3)?

Report the isoelectric point of the peptide, Gly-Asp-Lys-Ile?

An unknown amino acid labeled KEMISTRI has an IpH value equal to 5.41. If its pKa1 is equal to 2.03, calculate the pKa2 of KEMISTRI. Show complete solutions. Based on the table below, what is the probable identity of KEMISTRI?