[missUK11]

QUESTION:

The absorbance  in a cell with a 1 cm path length, of a solution containing
NAD+ and NADH is 0.21 at a wavelength of 340 nm and 0.85 at 260 nm. The
molar extinction coefficient of both NAD+ and NADH at 260 nm is
1.8 x10^4 mol-1 dm^3 cm-1 , while the value at 340 nm for NADH is
6.22 x103 mol-1 dm^3 Cm-1. NAD+ does not absorb radiation of wavelength 340
nm. Calculate the concentrations of NAD+ and NADH in the solution

So i understand that i have to apply the beer lambert law for this question but im not sure on how to do so, can anyone give me some tips please?. Thanks in advance

[dipesh747]

Right so you have 2 compounds in the cell. They both have chromophores that absorb light at 260 so that means that absorbance will be effected by both concentrations.

NAD+ does not absorb at 340nm, which means if you use the beer lambert law at that frequency you can calculate NADH concentration.

After you have done that you can work out the concentration of the absoprtion at 260 nm and take that away from your previous answer leaving you with NAD+ concentration

[missUK11]

Right so you have 2 compounds in the cell. They both have chromophores that absorb light at 260 so that means that absorbance will be effected by both concentrations.

NAD+ does not absorb at 340nm, which means if you use the beer lambert law at that frequency you can calculate NADH concentration.

After you have done that you can work out the concentration of the absoprtion at 260 nm and take that away from your previous answer leaving you with NAD+ concentration

Thanks so much for your help !!!!!!!!..when you said i should work out the concentration at 260nm, would that be for the NAD+ OR NADH :/ ?

[Borek]

Thanks so much for your help !!!!!!!!..when you said i should work out the concentration at 260nm, would that be for the NAD+ OR NADH :/ ?

Sum.