Q9. What would happen if the column was allowed to run dry?

Q8. Why would it be important to apply the protein sample very carefully to the column?

Q1. What is the fractionation range (MW) for proteins when using Sephadex G100?

Consider the following peptide sequence:

GSQANVMLTIHWEDCA

This peptide will be proteolytically cut by chymotrypsin, but not by trypsin.

What single amino acid substitution could you make that would prevent this peptide being cut by chymotrypsin but enable it to be cut by trypsin?

Consider the following peptide sequence:

ACDEGHIKLMGNPQST

This peptide will be proteolytically cut by trypsin, but not by chymotrypsin.

What single amino acid substitution could you make that would prevent this peptide being cut by trypsin but enable it to be cut by chymotrypsin?

Consider the following peptide sequence:

MVNNPQSTACDEGHIKL

This peptide will be proteolytically cut by trypsin, but not by chymotrypsin.

What single amino acid substitution could you make that would prevent this peptide being cut by trypsin but enable it to be cut by chymotrypsin?

An eager young biochemist was digesting the same protein in three different tubes. Each tube had a separate protease:

• trypsin
• chymotrypsin, which cleaves at the carboxyl side of the three large and bulky aromatic amino acids
• Glu-C, which cleaves C-terminally to Glu or Asp

After digestion, the samples were analysed by mass spectrometry but -- oh no! -- the biochemist forgot to label their tubes.

Luckily, they have you to help them.

Look at the sequences from each sample below to deduce (if possible) which enzyme had been used in which tube.

Shown below is a DNA duplex sequence, including both the coding (top) and non-coding (bottom) strands. 

Which one of the following pairs of oligonucleotide primers would be most suitable for amplifying (by PCR) the region of this duplex shaded in yellow?

[Note: You are not expected to estimate Tm values for these primers. If they have the correct sequence to anneal in the correct position, you should assume that they will.]

Shown below are three short DNA duplexes.

What is the correct order of stability of these duplexes (from most stable to least stable)

[Note: You do not need to calculate T_m values. You should be able to determine the order of stability “by eye”.]