The overall effect is a significant net dipole for the a helix that gives a partial positive charge at the amino end and a partial negative charge at the carboxy end of the a helix. 

TLS Online TPP Program

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#Unit 2. Cellular Organization

If Lk <Lk0 and DLk is <0 means negative, then the DNA is said to be “negatively supercoiled.”

TLS Online TPP Program

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#Unit 2. Cellular Organization

Conversely, if Lk >Lk0  and DLk >0 means positive, then the DNA is “positively supercoiled.”

TLS Online TPP Program

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#Unit 2. Cellular Organization

Superhelical Density 

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#Unit 2. Cellular Organization

Circular DNA molecules purified from both bacteria and eukaryotes are usually negatively supercoiled, having values of s of approximately –0.06.

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#Unit 2. Cellular Organization

How to calculate linking number?

TLS Online TPP Program

#Id: 377

#Unit 2. Cellular Organization

For negatively supercoiled circle W < 0 

For a positively coiled superhelix W > 0.