structure
double strand helical structure having a respective closure, with the result that the entire DNA molecule further bent to form a tertiary structure spin. It is those that are negative supercoiling. If otherwise produce a fracture or a chain of two different parts, the curvature becomes irrotational open loop DNA molecule. Extracted from cells containing plasmid or viral DNA both closed and open these two molecules. According to the different binding capacity of both the dye, and the two separated.
information
in the double helix structure, containing 10 per rotation of base pairs in the lowest energy state, less than 10 will form a right-handed supercoiled (cis hour), and vice versa for supercoiled left (counterclockwise). The former is called negatively supercoiled, which is referred to as positive supercoiling. This is a three stage construction. Prokaryotic cells is DNA supercoiling in DNA gyrase action, formed circular DNA energy provided by ATP negatively supercoiled, nucleosome DNA of eukaryotic cells with histones to form a positive supercoiled exist. DNA supercoiling exist in two forms: a spin with twisted wire and solenoid supercoiled supercoiled. Spin line having a twist occurs when the DNA supercoiling in the cell formed from independent, and when the solenoid is in DNA supercoiling chromatin maintained. Wherein in solenoid wound tighter, and the accessory proteins required in order to form - histone chromatin.
twist number (T; twisting number) number of windings (W; writhing number) with a chain ring (L; Linking number) can be written as the relationship between:
L = T + W
wherein, L (chain ring) is defined as when a DNA double helix molecule annular tile in the plane, the number of a chain across the other strand, T (number of twist), refers to a number of turns about a chain double spiral wound virtual axis, W (winding number) it is also referred to as a supercoiled number (number of turns of Superhelix)