Question

1. Ultraviolet (UV) light can be used to estimate protein solution concentrations because

a.glycine absorbs at 260 nm

b.All the amino acids absorb UV light

c.Alanine amino acids absorb at 280 nm

d.Tryptophan and tyrosine absorb at 280 nm

e.All of the above

2. Which statement is not true about the peptide bond?

a.The peptide bond has partial double-bond character

b.The peptide bond is longer than the typical carbon-nitrogen bond

c.Rotation is restricted about the peptide bond

d.The carbonyl oxygen and the amide hydrogen are most often in a trans configuration with respect to one another

3. Iodoacetate is used to acetylate sulfhydryl groups to prevent their oxidation to disulfides.

a.TRUE

b.FALSE

4. Proteins are treated with substances such as 2-mercaptoethanol to remove disulfide bonds before being sequenced because the disulfide bonds will interfere with the sequencing procedure.

a.TRUE

b.FALSE

Answer 1

1.d

UV light is used to estimate protein concentrations because the amino acids like tyrosine and tryptophan absorbs light of wavelengths 280nm.

2.b

Except b all statements are true. The bond length of peptide bond is actually shorter than normal carbon nitrogen bond since it is double bond and there is presence of resonance.

3 a

Iodoacetate is used to prevent the oxidation of sulfhydryl group of protein. It adds acetyl group to the sulphur of the S-S bond and keep them in reduced state.

4.true

Edman degradation process involves the treatment of protein with beta mercaptoethanol so that the disulphide bond should break and not reoxidised.