Post-lab Questions/Answer:
1. What does the λmax of the protein samples tell you about their amino acid composition/chromophores? Did the λmax change in presence of guanidine hydrocholride?
Ans. The value of λmax is 277nm for the protein in sodium phosphate-EDTA buffer whereas, the value is 276nm for the protein in guanidine hydrocholride buffer. These values are indicative of the fact that the solution bears aromatic rings and hence, most likely, the protein has tyrosine and tryptophan residues.
Yes, the value of λmax did change in the presence of guanidine chloride but just by 1 nm.
2. Is there a difference in the experimental molar extinction coefficients in neutral buffer and in 6M guanidine hydrochloride? Why or why not?
Ans. Yes, there was indeed a difference in the experimental molar extinction coefficients in neutral buffer and in 6M GuHCl.
The possible explanation to support this observation would be by the difference in the concentration of chromophores released, after the Ellman's reaction had occurred, in the two different buffer solutions. While unfolded, the protein is expected to perform the reaction more, whereas, the folded protein won't react much as it is expected to form disulfide bonds with residues within itself.