Draw a schematic of the chemical structure of the Leu-Tyr-Met-Lys tetrapeptide, with thecorrect ionization at neutral pH (pH 7). Also, give an estimate the pl of this tetrapeptide (youare given that the pKa of any acidic R group is 4, the pKa of any basic R group is 11.5, and thepKa of the α-COOH is 2, and the a-NH3 is 9.5). Provide rationale!

Structure of Leu-Tyr-Met-Lys at neutral pH (7) : At neutral pH (around 7), the ionization state of…

Answered: Draw a schematic of the chemical…

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

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Consider a protein in which a negatively charged glutamic acid side chain (pKa=4.2) makes a salt bridge (ion-ion interaction) with a positively charged histidine side chain (pKa=6.5). Part C: Justify your answer with calculations of partial charges on these amino acid side chains at pH=7.9.(Hint: Consider lessons from Coulomb's law, and the Henderson-Hasselbalch equation.)
Phosphate buffers are commonly used to mimic biological systems. Given that phosophoric acid is a triprotic acid with three pKas (2.12, 7.21, and 12.32), why do you think this is? What are the dominant buffering compounds present in a phosphate buffer near physiological pH?
The amino acid glycine is often used as an ingredient in buffers for biochemistry experiments. The amino group of glycine has a pKa of 9.6. Glycine exists in either a protonated form (-NH3+) or a free base (-NH₂). a) In what pH range can glycine be used as an effective buffer? b) In a 0.1M solution of glycine at pH 9.0, what fraction has its amino group in the protonated form? c) When 99% of the glycine is in the protonated from, what is the numerical relation between the pH of the solution and the pKa of the amino group?
Glucose-1-phosphate has a ΔG°′ value of −20.9 kJ/mol, whereas that for glucose-6-phosphate is −12.5 kJ/mol. After reviewing the molecular structures of these compounds, explain why there is such a difference in these values.
The amino acid arginine ionizes according to the following scheme: (a) Calculate the isoelectric point of arginine. You can neglect contributions from form I. Why? (b) Calculate the average charge on arginine when pH = 9.20. (c) Is the value of average charge you calculated in part b reasonable, given the pI you calculated in part a? Explain your answer
Hemoglobin is considered to be a tetrameric complex with a 64 kDa (α β)2. When attempting to purify hemoglobin, we must first purify the α and β monomers (about 16 kDa each) to prepare the tetramer. This is formed from the dimer intermediate: 2 α + 2 β -> 2 αβ -> (α β)2. The graph given represents a size-exclusion chromatogram after the refolding of the hemoglobin tetramer Using the size-exclusion chromatogram given, 1. Draw an SDS-Page Gel with a reducing agent such as BME using the three peaks listed on the graph.
After staining an SDS-PAGE gel with Coomassie Blue G-250, the protein bands are visualized by de-staining the gel in a Coomassie Blue G-250 de-staining solution. This solution is made up of 10% acetic acid, 50% methanol, and 40% distilled water. How much of each of these components do you need to prepare 5 liters of Coomassie Blue G-250 de-staining solution?
Identify the structure of the predominant form of the pentapeptide at pH = 12 if there is a pentapeptide Ile-Lys-Asp-Phe-Gly
if the tetrapeptide shown in the binding site above (Gly-Ser-His-lle) were in an aqueous solution at pH=6.2, what fraction of peptide molecules would have a +1 charge?
Consider an amino acid (A) with no ionizable side chains, and call the three species involved in the acid/base equilibria H2A+, HA, and A- (see scheme below). Assume that pKa(1) = 2.0 and that pKa(2) = 9.0. Suppose that the total concentration of the amino acid is 1.0 mM. Report to two significant digits. pH [H2A+] (mM) [HA] (mM) [A-] (mM) 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0
Draw the Fischer projections representing the L forms of the following amino acids at pH higher than their isoelectric point. a) cysteine b) alanine

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