Single Chain Observation on Collapse Transition in Giant DNA Induced by Negatively-Charged Polymer

Poly-glutamic acid, a polyanion, has been shown to induce the all-or-none collapse transition in individual duplex DNAs from an elongated coil into a collapsed compact state, through the observation of single chains by fluorescence microscopy. This experimental finding is discussed in relation to the change in the higher-order structure of DNAs in the cytoplasmic space induced by a change in the concentration of polyanions, such as mRNA, as a possible route for feedback in gene expression.