The absorption of ultraviolet light by RNA in the near UV (250-300nm) is due to electronic transitions within the bases. Absorption at 260 (E260= 10 nM^-1cm^-1) is approximately twice as intense as absorption at 280nm and increases by about 10% (at both wavelengths) when the secondary structure within an RNA molecule is disrupted. A certain RNA molecule has 100 nucleotides, of which approximately 50 residues are involved in regular double helices that define its secondary structure.

1. If the concentration of RNA in a solution is 0.01mg/mL, calculate its absorbance at 260nm. Assume a path length of 1 cm and each base to have an average molecular weight of 330.

2. What will the absorbance be at 260nM at a temperature of 90C when all the secondary structure has been disrupted?

3. To the same RNA solution, we added an equimolar amount of an RNA binding protein that binds to that RNA specifically. The protein has

a molecular weight of 100,000 and contains 10 Trp and 10 Tyrosine residues. THe absorption of ultraviolet light by proteins at wavelength= 280nm is largely due to tryptophan (?=5000M^-1cm^-1) residues. What would the absorption of the complex be at 280nm?

4. As the RNA structure unfolds, the protein does not bind anymore. What would the absorption of the complex be at 280nm and at 90C?