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
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
Related questions
Question
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,
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).
Expert Solution
This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
This is a popular solution!
Trending now
This is a popular solution!
Step by step
Solved in 5 steps with 1 images
Recommended textbooks for you
Biochemistry
Biochemistry
ISBN:
9781319114671
Author:
Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:
W. H. Freeman
Lehninger Principles of Biochemistry
Biochemistry
ISBN:
9781464126116
Author:
David L. Nelson, Michael M. Cox
Publisher:
W. H. Freeman
Fundamentals of Biochemistry: Life at the Molecul…
Biochemistry
ISBN:
9781118918401
Author:
Donald Voet, Judith G. Voet, Charlotte W. Pratt
Publisher:
WILEY
Biochemistry
Biochemistry
ISBN:
9781319114671
Author:
Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:
W. H. Freeman
Lehninger Principles of Biochemistry
Biochemistry
ISBN:
9781464126116
Author:
David L. Nelson, Michael M. Cox
Publisher:
W. H. Freeman
Fundamentals of Biochemistry: Life at the Molecul…
Biochemistry
ISBN:
9781118918401
Author:
Donald Voet, Judith G. Voet, Charlotte W. Pratt
Publisher:
WILEY
Biochemistry
Biochemistry
ISBN:
9781305961135
Author:
Mary K. Campbell, Shawn O. Farrell, Owen M. McDougal
Publisher:
Cengage Learning
Biochemistry
Biochemistry
ISBN:
9781305577206
Author:
Reginald H. Garrett, Charles M. Grisham
Publisher:
Cengage Learning
Fundamentals of General, Organic, and Biological …
Biochemistry
ISBN:
9780134015187
Author:
John E. McMurry, David S. Ballantine, Carl A. Hoeger, Virginia E. Peterson
Publisher:
PEARSON