BIOC 2580 Lecture Notes - Lecture 3: Silica Gel, Lysine, Protein Structure

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9 Jan 2017

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In order to be completely deprotonated the pka needs to be one below. Answer: histidine since it has the same pka value. Calculate the charge of the side chain of lys at ph 9. 8. Use henderson hasselbach equation: ph = pka + log[dep]/[pro] Amino acid analysis helps to determine protein structure. Can be qualitative (tells you what is present) Can be quantitative (tells you how much is present) Can be preparative (separated components can be recovered for further experiments. Partition chromatography is an important method for separating components of a mixture. Particles of solid are chosen with a specific property, eg. silica gel has ho-si-oh groups that can hydrogen-bond to polar amino acids. Liquid solvent or buffer flows pas the particles and is non-polar. Polar amino acids p spend more of their time hydrogen bonded to silica and move slowly. Non-polar amino acids n spend more time in solvent, and move almost as fast as solvent.

Related Questions

CHEM 451 Homework 2 Date: August 28, 2014 Due 9/2/2014, 9:30 amHomework must be stapled to receive full credit.

1. What is the absolute difference in [H+] between 2 aqueoussolutions, one of pH 2.0 and one of pH 3.0? What is the [OH-]concentration of the solution of pH 2.0?

2. Draw three amino acid with the following properties(6 pts) a)A sulfur containing amino acid at pH 5. What is its pI? b) Anaromatic amino acid at pH7. What is the single letter code for thisamino acid? c) An acidic amino acid at pH 11. What is its pI?

3. The Henderson-Hasselbach equation is pH = pKa + log [protonacceptor]/[proton donor]. Show how it proves that the pKa of a weakacid is equal to the pH of the solution at the midpoint of itstitration.

4. Calculate the pH of a mixture of 0.10 M acetic acid and 0.20M sodium acetate. The pKa of acetic acid is 4.76.

Lactic acid, given that when the concentration of lactic acid is0.01M and the concentration of lactate is 0.087M, the pH is4.80.

6. Show your school pride and draw the hexapeptide that has thesingle letter code âAGGIESâ at pH 7. Circle the peptide bonds. (6pts)

7. The amino acid histidine has three ionizable groups, with pKavalues of 1.8, 6.0, and 9.2. (a) Which pKa corresponds to thehistidine side chain? (b) In a solution at pH 5.4, what percentageof the histidine side chains will carry a positive charge? (5pts)

Amino acid side chain charge calculation (approximation)
1. Write out ionic forms of the amino acids and determine acid and base charge forms. 2. Use the Henderson-Hasselbach equation to calculate ratio
3. Assigncharge(approximation):

If 10%, assign plus/minus 0.9 or 0.10 values. If 99% assign whole number (or 1% of whole and 99% of whole). If at pKa assign half value 0.5 (plus/minus)

a) The amino acid sequence of sea lamprey adrenocorticotropic hormone is given below. Given the sequence, identify each ionizing amino acid residue and indicate its charge (-1, 0, or +1) in the completely protonated amino acid form of the polypeptide hormone.

S-V-S-S-P-K-Y-A-M-G-H-F-R-W-G-S-P-D-K-A-T-I

Given the same sequence above, indicate the charge (-1, 0, or +1) on each amino acid residue in

the completely proton dissociated form of the polypeptide hormone.

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BIOC 2580 Lecture Notes - Lecture 3: Silica Gel, Lysine, Protein Structure

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