Molecular Biology Answers

Immortalized, easily transduced human cell lines will be transfected either with full length and truncation mutants of the cell adhesion molecule X and protein Y.

What is the structure and function of features of transcription factor domains such as DND binding domains, dimerization domains,transcription activation domains,transcription repressor domains,etc?

Q:A purified protein fraction containing buffer with salt can be desalted by one of the following techniques:

(1) Gel filtration chromatography

(2) Paper chromatography

(3) Affinity chromatography

(4) Thin layer chromatography

My attempt at a solution:

Well, the analyte contains salt (possible inorganic so the particles, ions will be small enough as compared to a protein) and protein (a large one) so SEC or gel filtration looks perfect.

But there's affinity chromatography too. Two things come to my mind: 1.having an antibody or enzyme in the stationary phase will definitely work at holding back the proteins 2. but there may be some non specific polar interactions between the protein and the ions, so... (1) 's the right one?

Two proteins of similar molecular weight (<900 Da), same net charge in the solution but with different amino acid composition is to be separated. Which one should be used?

a. Cation exchange b. Anion exchange c. gel filtration d. Reverse phase

My attempt:

Since the net charge is the same so there's no point using ion-exchange.

Gel filtration or Size exclusion rules out as the sizes are the same.

So the only thing left to be exploited is the hydrophobicity of the side-chain of amino acids.

I have a feeling that hydrophobic interactions are least in proteins, less no. of hydrophobic groups are to be found in one as compared to polar groups. So using reverse will be best because...

Well I think I'm missing out something. Aren't we suppose to decide the combination of stationary and mobile phases based on the component of analyte we want to elude at the end?