CMMB 411 Lecture 4: DNA Topology — Part 4
21 Sep 2018
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Negative supercoiling represents certain amount of energy that is stored. Reflects the amount of energy that is stored in biological systems. Reflects the negative or positive supercoiling you have in your dna molecule. For mesophilic organisms (bacteria to humans), they keep sigma value to be in the narrow range of -0. 06 to -0. 07. Reason for narrow range is that you need to have the negative supercoiling for transcription or translation. If the sigma value is too negative (lots of negative supercoiling), dna will become single stranded. In single stranded state, dna is not very stable, and many side reactions can occur, which have the potential to modify dna structure and chemistry. R = gas constant (1. 98 x 10-3 kcal/mol/deg) N = number of base pairs (n 2000 base pairs), or the length of dna you"re working with. For the equation to be accurate, you need a minimum of 2000 base pairs.
