Question

In: Biology

The amino acid sequence of human adrenocorticotropin, a polypeptide hormone, is: Ser-Tyr-Ser-Met-Glu-His-Glu-Arg-Trp-Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Glu-Pro-Leu-Glu-Phe a)What is the appr

The amino acid sequence of human adrenocorticotropin, a polypeptide hormone, is: Ser-Tyr-Ser-Met-Glu-His-Glu-Arg-Trp-Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Glu-Pro-Leu-Glu-Phe a)What is the approximate net charge of this molecule at pH 3? ph 7? ph 9? Assume that the pKs of the terminal -NH3+ and -COOH groups are 7.8 and 3.6, respectively.

Solutions

Expert Solution

pH < pKa : protonated form

pH > pKa :deprotonated form

Positively charged amino acids : Arginine , Histidine and Lysine have one extra NH3+ group

Side chain pKa value : Lys - 10.5, His - 6.0, Arg - 12.5

Negatively charged amino acids : Glutamic acid and Aspartic acid have one extra COO- group

Side chain pKa value : Glu -4.3, Asp - 3.9

At pH 3 :

pKs of the terminal -NH3+ and -COOH groups are 7.8 and 3.6, respectively.

Amino terminal pH (3) < pKa (7.8) - Protonated form +1 (NH3+)

Carboxy terminal pH (3) < pKa (3.6) - Protonated form 0 (COOH)

Lys side chain pH < pKa Protonated form +1 (NH3+)

Arg side chain pH < pKa Protonated form +1 (NH3+)

His side chain pH < pKa Protonated form +1 (NH3+)

Glu and Asp side chain pH < pKa Protonated form : 0 (COOH)

Hence, there are 5 Glutamic acid (0), 4 lysine (+4), 1 histidine (+1), 3 arginine (+3) and 1 aspartic acid (0)

Amino terminal (+1) + Lysine (+4) + Histidine (+1) + Arginine (+3) = 9

The net charge at pH 3 is +9

At pH 7 :

Amino terminal (+1) + Lysine (+ 4) + Histidine (0) + Arginine (+3) + glutamic acid (0) + aspartic acid (0) + Carboxy terminal (-1)

Net charge at pH 7 = 8 - 1 = +7

At pH 9 :

Amino terminal (0) + Lysine (+ 4) + Histidine (0) + Arginine (+3) + glutamic acid (0) + aspartic acid (0) + Carboxy terminal (-1)

Net charge at pH 9 = 7 - 1 = +6


Related Solutions

QUESTION 6 Which of the following peptides is most likely an alpha helix? Arg-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Asp Glu-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Lys Glu-Ala-Tyr-Phe-Met-Gln-Val-Leu-Ser-Lys...
QUESTION 6 Which of the following peptides is most likely an alpha helix? Arg-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Asp Glu-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Lys Glu-Ala-Tyr-Phe-Met-Gln-Val-Leu-Ser-Lys Arg-Ala-Tyr-Phe-Met-Gln-Val-Leu-Ser-Asp
For the peptide below Thr, Ser, Tyr, Met, Asp, Phe, His, Lys, Trp, Gly, Pro, Arg,...
For the peptide below Thr, Ser, Tyr, Met, Asp, Phe, His, Lys, Trp, Gly, Pro, Arg, Ile, Glu Calculate overall charge for pH=5 and pH=11 Calculate overall pI
Determine which of these four peptides is most likely to become a beta sheet. Met-Leu-Lys-Ala-Ser-Ala-Leu-Glu-Lys-Leu-Ser-Glu Ala-Glu-Met-Leu-Gln-Lys-Arg-Gly-Cys-Gly-Asp-Glu...
Determine which of these four peptides is most likely to become a beta sheet. Met-Leu-Lys-Ala-Ser-Ala-Leu-Glu-Lys-Leu-Ser-Glu Ala-Glu-Met-Leu-Gln-Lys-Arg-Gly-Cys-Gly-Asp-Glu Lys-Thr-Val-Ile-Trp-Pro-Phe-Tyr-Ile-Gln-Ile-Gly Arg-Ser-Tyr-Glu-Gly-Leu-Lys-Arg-Ile-Ala-Glu-Ser I would like help with the question but also I would like to know what makes a peptide more likely to form a beta sheet over and alpha helix and vice versa.
Examine the following peptide then answer parts a-c Lys-Asp-Pro-Leu-Trp-Ala-His-Met-Gln-Phe-Gly-Arg a.estimate the net charge at pH 7...
Examine the following peptide then answer parts a-c Lys-Asp-Pro-Leu-Trp-Ala-His-Met-Gln-Phe-Gly-Arg a.estimate the net charge at pH 7 B.estimate the net charge at pH 12
which rptoleyic enzye would cleave this peptide into the most fragments? Asn-Met-Thr-Gln-Gly-Arg-Cys-Lys-Val-Asn-Thr-Phe-Val-His-Glu-Leu-Val-Asp-Val-Cys-Phe-Lys-Glu A. Trypsin B.Chymotrypsin C.Thermolysint...
which rptoleyic enzye would cleave this peptide into the most fragments? Asn-Met-Thr-Gln-Gly-Arg-Cys-Lys-Val-Asn-Thr-Phe-Val-His-Glu-Leu-Val-Asp-Val-Cys-Phe-Lys-Glu A. Trypsin B.Chymotrypsin C.Thermolysint D.they would all given an equal amou
In the protein adenylate kinase, the C-terminal region is a helical, with the sequence Val-Asp-Asp-Val-Phe-Ser-Gln-Val-Cys-Thr-His-Leu-Asp-Thr-Leu-Lys. a)...
In the protein adenylate kinase, the C-terminal region is a helical, with the sequence Val-Asp-Asp-Val-Phe-Ser-Gln-Val-Cys-Thr-His-Leu-Asp-Thr-Leu-Lys. a) Underline the hydrophobic amino acids in the sequence. b) If you identified the correct amino acids you will notice that there is a periodicity of hydrophobic amino acids. What is this periodicity and why would this occur?
Look at this undecapeptide: Arg Asp Cys Glu Leu Lys Met Phe NH4+. What would each...
Look at this undecapeptide: Arg Asp Cys Glu Leu Lys Met Phe NH4+. What would each step do to the udecapeptide? Draw the final structure. a. treatement with iodoacetate that had no affect on the undecapeptide. b. treatment with 2 x 2-mercaptoethanol yielding a tripe-tide and octapeptide. c. treatment with carboxypeptidase A liberated leucine. d. treatment with cyanogen bromide yielding a methionine, a tripeptide and a heptapeptide. The question states that these amino acids are only some components of the...
Deduce the sequence of a heptapeptide that contains the amino acids Gly, His, Tyr, Ser, Ala, Met, and Arg, from the following experimental data
Deduce the sequence of a heptapeptide that contains the amino acids Gly, His, Tyr, Ser, Ala, Met, and Arg, from the following experimental data. Edman degradation cleaves Ala from the heptapeptide, and carboxypeptidase forms His and a hexapeptide. Treatment of the heptapeptide with chymotrypsin forms a hexapeptide and a single amino acid. Treatment of the heptapeptide with trypsin forms a pentapeptide and a dipeptide. Partial hydrolysis forms His, Ala, Tyr, and the tripeptides Ser-Gly-Met and Gly-Met-Arg. 7 amino acids total
Propose (3) three qualitative chemical tests that can differentiate the given peptides below: Trp-Ala-Arg-Met-Ser (1) Pro-Phe-Cys-Arg-Glu...
Propose (3) three qualitative chemical tests that can differentiate the given peptides below: Trp-Ala-Arg-Met-Ser (1) Pro-Phe-Cys-Arg-Glu (2)             Support your choice of tests with brief explanation
Consider the following peptide: Cys-Arg-Pro-Asp-Thr-Leu-His-Lys-Gln-Glu-His How is the peptide different at pH = 6 and pH...
Consider the following peptide: Cys-Arg-Pro-Asp-Thr-Leu-His-Lys-Gln-Glu-His How is the peptide different at pH = 6 and pH 8? Which of the two pHs would you use to run an ion exchange column, and would you choose anion or cation exchange?
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT