Structural Hierarchy in DNA Hydrogels

Abstract

Sol gel transition in aqueous DNA solutions was probed to determine the gelation time tgel and temperature Tgel It was remarkable to observe that Tgel linearly increased from to deg C and tgellinearly decreased from to s with increase in DNA concentration The hydrogels were studied by using small angle neutron scattering SANS DNA le w v to determine the underlying hierarchy of length scales From structure factor profile analysis three distinct signatures were obtained a nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp Radius of gyration Rg asymp plusmn nm which assigned a length of nm to DNA strand b nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp Geometry of scattering moiety defined by the value of alpha asymp plusmn indicating Gaussian chain behavior c nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp nbsp Correlation length xi increased from to nm and the inter chain spacing d decreased from to nm with increase in DNA concentration Physical networks were formed for concentration c ge w v and the system involved at least five identifiable length scales A revisit has shown that hierarchical structure of DNA hydrogel owes its origin to considerable self organization at the molecular level dependent on biopolymer concentration