Abstract
The interaction of polycation-DNA can form complexes with DNA resulting in the coil–globule conformational transition in the DNA molecules and DNA condensation. It was proposed that polycation-DNA complex formation is entropy driven and electrostatic force due to the ion pairs formed between positively charged groups of polycation molecule and the phosphate groups of DNA. In our studies, we try to use cationic diblock copolymer and homopolymer as polycations, and complex with DNA to investigate the actual internal structure. This is more one parameter in cationic diblock copolymer than homo-polycation to control the structure of complexes. The level of aggregation is related to the properties of the components as well as to the medium and external conditions of the polyplexes formation, so that we carried out studies that effect of ionic strength, temperature on polyplexes. The internal structure of DNA polyplexes formed with P4VP(CH3I) and PS-P4VP(CH3I) are investigated by POM, SAXS and TEM. The results were hexagonal packing of DNA in both complexes in aqueous solution. This salt-induced phase behavior was found for P4VP(CH3I)/DNA. The surprising studies are temperature-induced ordering packing for DNA and PS sphere in the complexes and the processes were irreversible. According to our results, we proposed simple models for both complexes to reveal the structures.