Characterization by sedimentation analysis of kinetoplast DNA from Trypanosoma cruzi at different stage of culture

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Abstract
The kinetoplast DNA networks of Trypanosoms cruzi exist under two forums which have been studied by equilibritin density centrift in CsC1 gradients containing ethiditrn bruitide and by band sedin analysis. The relative pr orticwi of the two forum has been neasured and varies significantly between the exponential and stationary phase of growth, s that one of these forum is a replicative intersediate. Both forum exhibit very high sedirrentation coefficients. The sedinentat ion velocity ethidiun titration was used to measure the superhelix density of the kiretoplast DNA after haviog established the validity of the metbad with in vitro closed DNA networks. The superhelix density of the native form of the kinetoplast DNA rnmnicircles is very low and varies accordiog to the physiological state of the tryparosates. Furthermore, we observed a significant increase of the superhelix density of the kinetoplast DNA of trypanosortes grown in the presence of ethidium.