✂
Version 1.3
λ  (nm)
A
260
280
A260=
0.000
A280=
0.000
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lab

Activity with the simulator of ultraviolet absorption spectra for proteins and nucleic acids

Please enter the percentage composition of the sample, or choose among the examples below:

% protein
% DNA
in colour

characterístic wavelengths
Examples:

The code corresponding to samples 1 and 2 in this particular experiment is
(Each time the page is loaded, samples are different as well as their code)

Activities to do with this simulator:

Let's suppose that the DNA in each sample has been extracted from 1 g of tissue, has been precipitated with cold ethanol and has been dissolved in 5 mL of distilled water (step "a"). After that, 1 mL has been added of a solution with 0.15 M NaCl and 0.01 M EDTA (step "b"). Then, 200 µL of this mixture ha been taken and diluted 20-fold with water (1/20 dilution) (step "c").

You may show or hide a diagram of this procedure.

To preparae the dilution from "b" to "c" we must add  mL of water.

Then we place the already dilued sample ("c") into a quartz cuvette for spectrophotometric measurements and we record its UV spectrum in the simulator, hence obtaining absorbance values at 260 nm and 280 nm.

Datum: The extinction coefficient of double-strand DNA at 260 nm is 0.020 L mg−1 cm−1

1. Describe the differeneces you observe between the spectra of both samples.

2. Which of the two samples has a better purified DNA?

3. Calculate DNA concentration in step "c" of each sample.
Sample 1:  mg/L
Sample 2:  mg/L

4. Calculate the amount of DNA obtained per 100 g of tissue (To do this, you must take into account the dilutions that have been successively performed with the DNA)
Sample A: mg / 100 g of tissue
Sample B: mg / 100 g of tissue