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Migration of circular DNA vs circular/crosslinked peptide in gels - (Aug/11/2015 )

As I understand it:

 

1. Relaxed circular DNA migrates slower on a gel than linearized DNA (e.g. here)

 

2. Circular peptides (or intra-crosslinked peptides) run faster on a gel than linearized peptide

 

--> So circular DNA runs slower and circular peptides run faster than their linear counterparts.

 

 

Why the difference? 

-labtastic-

I do not see any relationship between DNA and peptides from your condition, how did you get such conclusion?

-Andrea Fortina-

Circular, or internally crosslinked peptides run faster on an acrylamide (sieving) gel than its linearized counterpart. I have seen this many times and is pretty common knowledge. This makes sense because circular (e.g. disulfide intra-chain crosslinked) peptides are more compact than their linear (e.g. fully reduced) counterparts, and thus travel through the acrylamide matrix faster.

 

On the other hand, relaxed circular (e.g. nicked non-supercoiled) DNA travels slower than than its linearized (e.g. digested) counterpart in an agarose (sieving) gel. For example, see this gel

 

Same principles, same concept, yet two different migration patterns. 

-labtastic-