The isoelectric point (pl) of a peptide is the pH at which the Group pK peptide ceases to migrate in an electric field. Since a peptide is aspartate 3.7 zwitterionic, there are the same number of positive charges as glutamate 4.3 negative charges on the peptide population. The pl can be histidine 6.0 estimated within 0.1 or 0.2 pH units from the pK values of all cysteine 8.2 the proton dissociable groups in the peptide. tyrosine 10.1 Determine the total positive charge on the peptide HANSEN lysine 10.5 when all acidic and basic groups are fully protonated. Enter arginine 12.5 your answer without the sign. peptide amino group 8.0 peptide carboxyl group 3.4 charge: Select the pK values used to estimate the pl. O 3.4 O 4.3 O 6.0 O 8.0 Estimate the pl value of the HANSEN peptide. pl =

The isoelectric point (pl) of a peptide is the pH at which the Group pK peptide ceases to migrate in an electric field. Since a peptide is aspartate 3.7 zwitterionic, there are the same number of positive charges as glutamate 4.3 negative charges on the peptide population. The pl can be histidine 6.0 estimated within 0.1 or 0.2 pH units from the pK values of all cysteine 8.2 the proton dissociable groups in the peptide. tyrosine 10.1 Determine the total positive charge on the peptide HANSEN lysine 10.5 when all acidic and basic groups are fully protonated. Enter arginine 12.5 your answer without the sign. peptide amino group 8.0 peptide carboxyl group 3.4 charge: Select the pK values used to estimate the pl. O 3.4 O 4.3 O 6.0 O 8.0 Estimate the pl value of the HANSEN peptide. pl =

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter27: Amino Acids And Proteins

Section: Chapter Questions

Problem 27.45P

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His-Met-Asp-Tyr-Phe-Ser Calculate an approximate pI (isoelectric point) for this peptide.
A tetradecapeptide (14 amino acid residues) gives the following peptide fragments on partial hydrolysis. (i) From this information, deduce the primary structure of this polypeptide. Fragments are are grouped according to size. Pentapeptide Fragments TetrapeptideFfragments Phe-Val-Asn-Gln-His His-Leu-Cys-Gly-Ser Gly-Ser-His-Leu-Val Gln-His-Leu-Cys His-Leu-Val-Glu Leu-Val-Glu-Ala Predict the products formed if the tetradecapeptide is acted upon by trypsin and elastse.
Chemistry Given TETRAPEPTIDE: Prolinyl-Argininyl-Cysteinyl-Tryptophan Predict the direction of the peptide in electrophoresis at pH 7 and pH11.5. (Use table on the upper right for the estimated pK values of some functional groups).
Hemoglobin A has a pI value of 5.6 whereas the variant hemoglobin M has an aspartate residue in place of the normal valine at position 85 of the alpha chain. What effect will this substitution have on the electrophoretic behavior of the protein at pH 7.0. (explain clearly the reason for your answer)
Calculate the isoelectric pH of this peptide: His-Tyr
Why is glycine the only amino acid commonly observed in peptides inconformations with phi and psi values which are not restricted to the values in the Ramachandran plot below?
1. A tetradecapeptide (14 amino acid residues) gives the following peptide fragments on partial hydrolysis.(i) From this information, deduce the primary structure of this polypeptide. Fragments are grouped according to size. Pentapeptide fragments Tetrapeptide fragments Phe-Val-Asn-Gln-His His-Leu-Cys-Gly-Ser Gly-Ser-His-Leu-Val Gln-His-Leu-Cys His-Leu-Val-Glu Leu-Val-Glu-Ala
Give the numbers of peptide bond present in given structure, structure is given at pH 10.5, find the error in if pH is 7.4
Finally, you want to make completely certain that you purified the correct protein and not some other protein (like biochemisnotfunase). To confirm the identity of your protein, you run a Western blot. When doing a Western, one typically needs a solution of phosphate-buffered saline, which is comprised of 10 mM phosphate buffer(pH 8.0) and 0.9% (w/v) NaCl. Describe how you would make 500 mL of this solution including the grams of sodium phosphate, monobasic and sodium phosphate, dibasic that you would need. Making the phosphate buffer is a little tricky. Be sure to use the correct ratio of monobasic and dibasic sodium phosphate to get the correct pH. The Henderson- Hasselbalch equation might come in handy here. Finally, the molecular weight of sodium phosphate, monobasic (NaH2PO4) is 119.98 g/mol and the molecular weight of sodium phosphate, dibasic (Na2HPO4) is 141.96 g/mol.
Using the information below, determine the amino acid sequence of the peptide, and explain how your structure is consistent with each piece of information. Complete hydrolysis by 6 M HCl at 110°C followed by amino acid analysis indicated the presence of Gly, Leu, Phe, and Tyr in a 2:1:1:1 molar ratio. Treatment of the peptide with1-fluoro-2,4-dinitrobenzene followed by complete hydrolysis and chromatography indicated the presence of the 2,4-dinitrophenyl derivative of tyrosine. No free tyrosine could be found. Complete digestion of he peptide with pepsin (which cleaves on the amino side of aromatic residues) followed by chromatography yielded a dipeptide containing Phe and Leu and a tripeptide containing Tyr and Gly in a 1:2 ratio.
For the determination of Pb in blood, a 5.00 mL sample was treated with trichloroacetic acid to precipitate the proteins. After centrifugation, the resulting solution was brought to pH 3 and extracted with two 5 mL portions of methyl isobutyl ketone containing the lead complexing agent APCD (ammonium 1-pyrrolidine carbodithiolate). The extract was drawn directly into an air-acetylene flame which produced an absorbance of 0.444 at 283.3 nm. Two 5.00 mL aliquots of solutions containing 0.250 and 0.450 ppm of Pb were subjected to the same sample treatment and the absorbance that occurred was 0.396 and 0.599 respectively. Calculate the concentration of Pb in µg/dL in the blood.
A typical amino acid with one amino group and one carboxylicacid group, such as serine, can exist in water in several ionic forms. (a) Suggest the forms of the amino acidat low pH and at high pH. (b) Amino acids generally havetwo pKa values, one in the range of 2 to 3 and the other inthe range of 9 to 10. Serine, for example, has pKa values of2.19 and 9.21. Using species such as acetic acid and ammoniaas models, suggest the origin of the two pKa values.(c) Glutamic acid is an amino acid that has threepKa's: 2.10, 4.07, and 9.47. Draw the structure of glutamicacid, and assign each pKa to the appropriate part of themolecule. (d) An unknown amino acid is titrated withstrong base, producing the following titration curve.Which amino acids are likely candidates for the unknown?