Question

Which technique to use?

Give reasons for and against as appropriate.

- If you have a sample of a zinc protein to study, would you use UV-vis and/or CD.

Answer 1

We will use UV- visible . Because  as most proteins absorb strongly at 280 nm. UV-Visible is also used as a standard technique to quantify the amount of DNA   in a sample, as all the bases absorb strongly at 260 nm. RNA and  proteins also absorb at 260 nm, so absorbance at other wavelengths can be measured to check for interferences. Specifically, proteins absorb strongly at 280 nm, so the ratio of absorbance at 280/260 can give a measure of the ratio of protein to DNA in a sample.

Most simple analyses measure the absorbance one wavelength at a time. However, more chemical information is present if measurements are made at many wavelengths simultaneously. CD instrument capture all the light that is transmitted, split the light into different colors using a prism or holographic grating, and then absorbance at different wavelengths is captured on a linear array of photodiodes. The advantage of this method is that it is useful for measuring many different molecules simultaneously.