What absorbance would you expect if the concentration of a p

What absorbance would you expect if the concentration of a protein was 5 uM, and it has 8 tryptophans and 10 tyrosines?

You analyze a DNA sample which gives an A260 of 1.74 and A280 of 0.64. What is the concentration of this DNA sample? Is it sufficiently pure?

Solution

2) Ideally, when a DNA sample is put for purity checking, the A₂₆₀ and A₂₈₀ ratios and their absorbance at these two wavelenghts are considered. The A₂₆₀ value for a pure DNA sample lies between 0.1-1.0 within the instruments linear range. Also, the A₂₆₀ / A₂₈₀ ratios are considered to estimate the purity of a DNA sample whose ratio ranges between 1.7-2.0.

Here, A₂₆₀ / A₂₈₀ = 1.74/0.64
= 2.718

The ratio is way over the ideal range. Thus, it can be safely said that the given DNA sample is not sufficiently pure. Moreover, depending on the ratio, the type og contaminant can also be identified. There might be an RNA contamination , which might be the residual from nucliec acid extraction.