Conformational changes and spectroscopic study of polyethylene glycol and ctDNA biocomplexes in various environment conditions

Abstract

The electronic absorption spectroscopy in polymer molecule and DNA interaction is one of the most useful technique s for studying the biocomplex formation for bioengineering and gene therapy. The current study focuses onto potential conformational changes during the (PEG) and ctDNA biocomplex formation at different environment, using Ultraviolet Visible spectroscopy (UV-visible) NIR spectra analysis, Fourier-Transform Infrared (FTlR) spectroscopy and Transmission Electron Microscope (TEM). The influence of different PEG ratios, buffer, end pH environment on the PEG-ctDNA biocomplex has been studied mainly by using UV- visible at pH7.4 and 22 ''C for 10 minutes at the first stage. While the effect of interaction time duration was studied using FTlR at different incubation time using a ratio 1:1 of PEG-ctDNA. The UV visible spectroscopy showed a change of absorption effect. The result also showed that using pH medium effects on PEG ctDNA binding,. a little bathochromic peak shift in acidic medium, while blue peak shift (hypochromic) has been not iced in alkaline media. This provided a significant effect of pH medium sensitivity in the UV visible spectroscopy study of PEG-ctDNA biocomplex. FTlR characterization of the same biocomplexes showed the binding reaction of PEG and ctDNA proceeds rapidly at room temperature and complexation optimum stability reached a maximum peak in 1hr. On the other hand, microscopic characterization by TEM of biocomplex at ratio of 1:1 rep resented obvious biocomplex interactive structure and classical condensate structures. The biocomplex has be en obtained in form of regular morphology structure like toroidal and rod-~k e particles and irregular aggregate structures. Finally, the spectroscopic studies indicated that PEG forms biocomplex with ctDNA rapidly via out side groove binding or electrostatic binding modes. Moreover, the increase of PEG amount ratios to DNA was insignificant on UV visible spectra . FTlR demonstrated as a valuable tool for studying the biological properties of PEG with ctDNA an d has shown a rapid, good stability and significant effect of the pH sensitivity in the biocomplex formation. Moreover the microscopic characterization provided another dimension and represented through different condensate structures as a result of inter-potyelectotyter interactions between the biocomplexes.