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1.     Cysteine has a pKa of 8.18. Considering the R group only, will cysteine favor its protonated or

deprotonated state at pH 7? Use the Henderson Hasselbalch equation to calculate the ratio of protonated to deprotonated cysteine.


1.    In a Bradford assay, a 1:20 dilution of the protein of interest has an absorbance of 0.722. The absorbance of the highest standard is 0.643. The protein is too ____________ and you should try a _______ dilution instead.

a.    Concentrated 1:10

b.    Concentrated 1:40

c.    Dilute, 1:10

d.    Dilute, 1:40


1.    Beginning at low pH, draw tyrosine in all of its ionization states. Be sure to draw low pH on the left and high pH on the right.


How many grams of potassium permanganate would I need to prepare 600 mL of a 2.5 M solution?


1.    What would be the overall charge of the peptide below at pH 10?

Glu-Ala-His-Phe-Arg-Thr-Asp


How many grams of potassium permanganate would I need to prepare 600 mL of a 2.5 M solution?



1.    I am purifying a protein that precipitates at 72% ammonium sulfate. Which would be the best percent saturation for my FIRST ammonium sulfate fractionation?

a.    15%

b.    35%

c.    55%

d.    75%

e.    95%


1.    Calculate how much ammonium sulfate I would need to add (in g/mL) to achieve a 25% saturation. Assume you are starting with no salt in your solution.



1.    During anion exchange chromatography, explain the benefit of using a 100‑1000 mM salt to elute the protein of interest instead of using 1M salt without a gradient.



1.    . If the pH of the solution is less than the pI of your protein, the protein will have a __________ charge and will stick to ____________ exchange column.

a.    Negative, Anion

b.    Negative, Cation

c.    Positive, Anion

d.    Positive, Cation

e.    Neutral, neither a cation nor anion

Can you help me with these?

Top Answer

1.While considering only the alkyl group of cysteine molecule, at the neutral pH, it will favour protonation. The... View the full answer

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