Single Molecular Study of interaction between DNA and re-petitive peptides

The interaction between cationic polypeptides and deoxyribonucleic acid (DNA) is of great importance for basic research in biology and in the pathogenesis of numerous diseases.In this paper, we focus on the complexation of a series of peptides with repeating proline and arginine (poly PR) sequences with DNA in aqueous solution using magnetic tweezers (MT), dynamic light scattering (DLS), and optical inverted microscopy.Through the study of magnetic tweezers, we found that the critical condensing force (Fc) of poly PR would increase with the increase of concentration.However, after the concentration reaches a certain level, the critical condensing force begins to decline.The electrophoretic mobility of poly PR was measured by dynamic light scattering.Poly PR induces charge reversal of DNA and is very effective in neutralizing the positive charge of DNA.Related studies have found that poly PR is a positively charged polypeptide that binds to RNA to undergo liquid-liquid phase separation (LLPS) and further coagulation of the polypeptide, there by inducing the development of related diseases.We hypothesize that the high efficiency of charge neutralization is due to poly PR being positively charged.