SDS-PAGE is an essential technique for separating proteins. Separation occurs predominantly due to differences in protein:

The technique of Edman degradation is useful for sequencing a protein/peptide from:

The image below is a representation of an acid-base titration of a diprotic amino acid, labelled at specific points (i through v).

Which region corresponds to the pH being equal to the pKa of the protonated amino group?

In attempting to define the subunit composition of an unknown protein, you decide to subject the protein to SDS-PAGE in the presence or absence of the reducing agent DTT. The results of this analysis are shown below.

Lane 1: molecular weight marker ladder.

Lane 2: protein sample without DTT

Lane 3: protein sample with DTT.

From this analysis, what is the subunit composition of the original native protein?

A sample containing an unknown polypeptide of 20 amino acids was assessed through a combination of Edman degradation and tryptic digest with mass spectrometry.

The Edman degradation result showed a peptide sequence of: MMFSRVNMLKM

The tryptic digest and mass spectrometry result showed peptide/amino acid sequences of: 

VNMLK and MMFSR and A and MLLATVLLR 

What is the complete polypeptide sequence?

(Use the single letter amino acid code, with no spaces or non-amino acid characters)

The image below is a representation of an acid-base titration of a diprotic amino acid, labelled at specific points (i through v).

Which region(s) have maximum pH buffering capacity?

SDS-PAGE is an essential technique for separating proteins. Which ONE of the following statements is true?

Amino acids have characteristic titration curves. A plot of the titration of an amino acid (bearing a non-ionisable side chain) with a strong base will result in two distinct phases, corresponding to:

Consider that you wish to separate a mixture of arginine, glutamate and valine by ion exhange chromatography.

Using a cation exchange column at pH 6, which amino acid would you expect to elute first and which last?

pKa and pI values are as follows:

Arginine: pK₁ = 2.17, pK₂ = 9.04, pK_R = 12.48, pI = 10.76

Glutamate: pK₁ = 2.19, pK₂ = 9.67, pK_R = 4.25, pI = 3.22

Valine: pK₁ = 2.32, pK₂ = 9.62, pI = 5.97

Which ONE of the following statements applies to mass spectrometry?