It is used to indicate the presence of unwanted organic contaminants such as Trizol, phenol, Guanidine HCL and guanidine thiocyanate. Expected 260/230 values are commonly in the range of 1.8-2.2. If the ratio is out of the general acceptable range, it may indicate the presence of contaminants which absorb at 230 nm.

A spectrophotometer is able to determine the average concentrations of the nucleic acids DNA or RNA present in a mixture, as well as their purity. Thus, an Absorbance (A) of 1 corresponds to a concentration of 50 μg/ml for double-stranded DNA. This method of calculation is valid for up to an A of at least 2.

Quantification of DNA is a very important step in many procedures where it is necessary to know the amount of DNA that is present when carrying out restriction digests or performing different techniques such as PCR and RAPDs.

The spectrophotometer measures these absorbances using UV-transparent cuvettes. Then you measure the absorbance of the DNA sample. These absorbance measures give you an idea of the concentration of your DNA prep and whether there are any other contaminants. Nucleic acids (DNA and RNA) absorb maximally at 260 nm.

DNA concentration is estimated by measuring the absorbance at 260nm, adjusting the A260 measurement for turbidity (measured by absorbance at 320nm), multiplying by the dilution factor, and using the relationship that an A260 of 1.0 = 50µg/ml pure dsDNA.

FAQ

1. Add 1/10 volume of 3 M Na-Acetate pH 5.2, and 2 to 2.5 volumes of ice-cold 100% ethanol to the DNA sample.
2. Mix, and store at -20°C for at least 1 hour to precipitate the DNA.
3. Recover the precipitated DNA by centrifugation at full speed in a microcentrifuge for 15-20 minutes.

The most widely used method for concentrating DNA is precipitation with ethanol. Adjust the concentration of monovalent cations either by dilution with TE (pH 8.0) if the DNA solution contains a high concentration of salts or by addition of one of the salt solutions shown in Table A.

Basically, you can purify your DNA samples by lysating your cell and/or tissue samples using the most appropriate procedure (mechanical disruption, chemical treatment or enzymatic digestion), isolating the nucleic acids from its contaminants and precipitating it in a suitable buffer solution.

DNA (Deoxyribonucleic Acid) is the genetic material that contains the “code of life.” Each person has a unique DNA code in each of their cells that can be used to identify them and their children. We get our unique DNA code from our biological parents in equal amounts.