I started studying Biology using EK recently and came across some confusing (mis)information. Anyway it essentially says "when heated or immersed in high concentration salt solution" DNA will denature.
Now I know that "high salt concentration" will decrease strand repulsion by shielding the negative charge of the phosphates thereby making denaturing more difficult, not less.
My confusion came later when I was reading about Southern Blotting, it states "the gel is made alkaline to denature the DNA fragments."
I don't know why, but I thought salt and alkaline were referencing the same thing?
My friend tried to explain it like this: a salt solution is essentially Na+Cl- where the Na+ can associate with the O- from the phosphate and shield the negative charge whereas an alkaline solution contains more OH- (basic) thus it will disrupt the H bonds holding the ds together.
If for example, NaOH is used to make the solution alkaline, wouldn't the Na+ in solution help decrease charge repulsion? Conversely, why would the Cl- in a salt solution not disrupt the H-bonds in a similar way to OH- for the alkaline solution?
The only thing that comes to mind for me is that the Cl- is a weak conjugate base of a strong acid (HCl) whereas OH- is a strong conjugate base of a weak acid (H2O).
This probably will not be tested directly on the mcat but I would like to be able to understand this without having to spend time trying to look up information or trying to piece together exactly how it works.
What I know to be true is that alkaline solutions are basic and have higher OH- concentrations than H+ and LOW salt concentration, not HIGH, denature DNA.
Can anyone simplify the difference between a salt solution and alkaline? I tried google but came up with nothing.
Now I know that "high salt concentration" will decrease strand repulsion by shielding the negative charge of the phosphates thereby making denaturing more difficult, not less.
My confusion came later when I was reading about Southern Blotting, it states "the gel is made alkaline to denature the DNA fragments."
I don't know why, but I thought salt and alkaline were referencing the same thing?
My friend tried to explain it like this: a salt solution is essentially Na+Cl- where the Na+ can associate with the O- from the phosphate and shield the negative charge whereas an alkaline solution contains more OH- (basic) thus it will disrupt the H bonds holding the ds together.
If for example, NaOH is used to make the solution alkaline, wouldn't the Na+ in solution help decrease charge repulsion? Conversely, why would the Cl- in a salt solution not disrupt the H-bonds in a similar way to OH- for the alkaline solution?
The only thing that comes to mind for me is that the Cl- is a weak conjugate base of a strong acid (HCl) whereas OH- is a strong conjugate base of a weak acid (H2O).
This probably will not be tested directly on the mcat but I would like to be able to understand this without having to spend time trying to look up information or trying to piece together exactly how it works.
What I know to be true is that alkaline solutions are basic and have higher OH- concentrations than H+ and LOW salt concentration, not HIGH, denature DNA.
Can anyone simplify the difference between a salt solution and alkaline? I tried google but came up with nothing.