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6. A. List all of the ionizable functional groups that are found in insulin when in aqueous solution. List which amino acid residues have these ionizable groups and list all of the pK, and pK, values (including the R groups) that are on both polypeptide chains that make up insulin. (see the table at the end of this HW set; note that tyrosine and cysteine both have unusual pka's, since these side groups ionize above the pKR's given to have a negative charge). B. The isoelectric point of insulin is reported to be around 5.3-5.35. Using the method covered in class, estimate the isoelectric point of insulin and compare your answer to the values above. C. For a polypeptide to be soluble in an aqueous solution, is it good to be near the isoelectric point? Why or why not? Notes: a couple of unusual R group's that ionize (cysteine and tyrosine have R groups that have pka values; histidine has a pkb). The table at the end of this homework set (also in the lecture notes) lists the pka's and pkp's for each amino acid and the amino acid sequence for insulin is in the class notes. Also, any ionizable group that has a + charge in equilibrium with neutral has a pKb, and ionizable groups that are in equilibrium between- and neutral have a pka. Ignore disulfide bridges or any other weak interactions (that is, include CYS as an ionizable group).

6. A. List all of the ionizable functional groups that are found in insulin when in aqueous solution. List which amino acid residues have these ionizable groups and list all of the pK, and pK, values (including the R groups) that are on both polypeptide chains that make up insulin. (see the table at the end of this HW set; note that tyrosine and cysteine both have unusual pka's, since these side groups ionize above the pKR's given to have a negative charge). B. The isoelectric point of insulin is reported to be around 5.3-5.35. Using the method covered in class, estimate the isoelectric point of insulin and compare your answer to the values above. C. For a polypeptide to be soluble in an aqueous solution, is it good to be near the isoelectric point? Why or why not? Notes: a couple of unusual R group's that ionize (cysteine and tyrosine have R groups that have pka values; histidine has a pkb). The table at the end of this homework set (also in the lecture notes) lists the pka's and pkp's for each amino acid and the amino acid sequence for insulin is in the class notes. Also, any ionizable group that has a + charge in equilibrium with neutral has a pKb, and ionizable groups that are in equilibrium between- and neutral have a pka. Ignore disulfide bridges or any other weak interactions (that is, include CYS as an ionizable group).

Biochemistry
Biochemistry
6th Edition
ISBN:9781305577206
Author:Reginald H. Garrett, Charles M. Grisham
Publisher:Reginald H. Garrett, Charles M. Grisham
Chapter22: Gluconeogenesis, Glycogen Metabolism, And The Pentose Phosphate Pathway
Section: Chapter Questions
Problem 8P
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Amino Acid Alanine Amine+ Arginine 2.35 2.01 Asparagine 2.02 COO Aspartic Acid 2.10 SHS Cysteine 2.05 COO-Glutamic Acid 2.10 Glutamine 2.17 Glycine 2.35 Amine Histidine 1.77 Isoleucine 2.32 2.33 2.18 Methionine 2.28 Phenylalanine 2.58 2.00 2.21 Threonine 2.09 Tryptophan 2.38 2.20 2.29 Leucine Amine Lysine Proline Serine pk Values for amino acids pk, (a-COOH) a-carboxylic acid OH → 0 Tyrosine Valine pk. (a-NH₂) a-amine 9.87 9.04 8.80 9.82 10.25 9.47 9.13 9.78 9.18 9.76 9.74 8.95 9.21 9.24 10.60 9.15 9.10 9.39 9.11 9.72 pka (side) Side chain 12.48 3.86 8.00 4.07 6.10 10.53 10.07 Amino acids with ionizable R groups (pK's) carboxylic acid COOH PK 's other weak acids with pk's primary amine NH₂ pk's weak tertiary amine N pK,
Transcribed Image Text:Amino Acid Alanine Amine+ Arginine 2.35 2.01 Asparagine 2.02 COO Aspartic Acid 2.10 SHS Cysteine 2.05 COO-Glutamic Acid 2.10 Glutamine 2.17 Glycine 2.35 Amine Histidine 1.77 Isoleucine 2.32 2.33 2.18 Methionine 2.28 Phenylalanine 2.58 2.00 2.21 Threonine 2.09 Tryptophan 2.38 2.20 2.29 Leucine Amine Lysine Proline Serine pk Values for amino acids pk, (a-COOH) a-carboxylic acid OH → 0 Tyrosine Valine pk. (a-NH₂) a-amine 9.87 9.04 8.80 9.82 10.25 9.47 9.13 9.78 9.18 9.76 9.74 8.95 9.21 9.24 10.60 9.15 9.10 9.39 9.11 9.72 pka (side) Side chain 12.48 3.86 8.00 4.07 6.10 10.53 10.07 Amino acids with ionizable R groups (pK's) carboxylic acid COOH PK 's other weak acids with pk's primary amine NH₂ pk's weak tertiary amine N pK,
6. A. List all of the ionizable functional groups that are found in insulin when in aqueous solution. List which amino acid residues have these ionizable groups and list all of the pka and pKb values (including the R groups) that are on both polypeptide chains that make up insulin. (see the table at the end of this HW set; note that tyrosine and cysteine both have unusual pka's, since these side groups ionize above the pKR's given to have a negative charge). B. The isoelectric point of insulin is reported to be around 5.3-5.35. Using the method covered in class, estimate the isoelectric point of insulin and compare your answer to the values above. C. For a polypeptide to be soluble in an aqueous solution, is it good to be near the isoelectric point? Why or why not? Notes: a couple of unusual R group's that ionize (cysteine and tyrosine have R groups that have pka values; histidine has a pkb). The table at the end of this homework set (also in the lecture notes) lists the pka's and pKb's for each amino acid and the amino acid sequence for insulin is in the class notes. Also, any ionizable group that has a + charge in equilibrium with neutral has a pkb, and ionizable groups that are in equilibrium between - and neutral have a pka. Ignore disulfide bridges or any other weak interactions (that is, include CYS as an ionizable group).
Transcribed Image Text:6. A. List all of the ionizable functional groups that are found in insulin when in aqueous solution. List which amino acid residues have these ionizable groups and list all of the pka and pKb values (including the R groups) that are on both polypeptide chains that make up insulin. (see the table at the end of this HW set; note that tyrosine and cysteine both have unusual pka's, since these side groups ionize above the pKR's given to have a negative charge). B. The isoelectric point of insulin is reported to be around 5.3-5.35. Using the method covered in class, estimate the isoelectric point of insulin and compare your answer to the values above. C. For a polypeptide to be soluble in an aqueous solution, is it good to be near the isoelectric point? Why or why not? Notes: a couple of unusual R group's that ionize (cysteine and tyrosine have R groups that have pka values; histidine has a pkb). The table at the end of this homework set (also in the lecture notes) lists the pka's and pKb's for each amino acid and the amino acid sequence for insulin is in the class notes. Also, any ionizable group that has a + charge in equilibrium with neutral has a pkb, and ionizable groups that are in equilibrium between - and neutral have a pka. Ignore disulfide bridges or any other weak interactions (that is, include CYS as an ionizable group).
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