DNA stability

[ahkian82]

In the studies of the DNA binding with inorganic complexes, NaCl was used to keep the DNA in the helix form. Instead of using NaCl, is it possible to use other sodium salts, such as sodium acetate, for the same purpose? What is the individual role playing by Na+ and Cl- in this context? In the process of determining the purity of the calf thymus DNA, the ratio A260/A280 was calculated. However, i'm doubt of its purity because the ratio exceeded 2 (it gave 2.0213 by using the equation Ratio=(A260-A320)/(A280-A320) ). For ratio below 1.6, the DNA is contaminated with protein. What does the figure 2.0213 tells? Thanks

ahkian82

[gandalfthegrey]

the ratio A260 / A280 is basically a ratio of

___DNA____
PROTEIN

a higher amount of DNA and lower Protein means you get a ratio greater than 1

A ratio of A260/A280 is good for nucleic acid preps, > 1.8 becuase it suggests there is little protein contamination in a DNA/RNA sample.

usually expected to be around 2.0 however highly pure nucleic acid (in vitro synthesis) can get a ratio even to 2.5..

so your ratio of about 2.13 is very good!

Hope that helps

[gandalfthegrey]

In terms of NaCl or salt,

it is very important to have your DNA in a salt or buffer in order to keep it in its proper form

see
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

[ahkian82]

Thanks Gandalfthegrey for the reply . It's such a big good news for a freshman in biological research. I was so worried initially for having the ratio out of the value. Besides that, absorption spectrum of this calf thymus DNA that gave a small absorption from 305-366 nm with absorbance 0.04, with respect to 0.7 absorbance at 260 nm, make me confuse about the purity of the DNA. Is it true that with such a high A260/A280 ratio, there is no need to further purify the DNA from non-nucleic acid component in the matrix? Hahahaa... question again? A person in a new field always have too much to ask... sorry bout that. And thanks for helping...

[gandalfthegrey]

No problem.

What will you do with the DNA? it depends on what you are doing. but I think most things are great with that purity.

[ahkian82]

Thanks again. Yup, agree. Higher purity will be just great for most of the work. Actually, we are trying to look into the binding properties of some inorganic complexes with the DNA here. Thank you so much for clearing my doubts. Wish me good luck... and all the best to you...^_^

with best regards,
ahkian82