tailieunhanh - Thermodynamics Kinetics of Dynamic Systems Part 10

Tham khảo tài liệu 'thermodynamics kinetics of dynamic systems part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Calorimetric Investigations of Non-Viral DNA Transfection Systems 259 2005 . The importance of the cationic lipid is however not restricted solely to the charge of its head group. Cherezov et al. 2002 . Kreiss et al. believed that both the nature or structure of the cationic lipid as well as the DNA backbone exert a strong influence on lipid-DNA packing and complex morphology with the formation of the lipoplexes resulting from competitive interactions between electrostatic forces of lipid-DNA and elasticity forces driven by the lipid hydrophobic moiety Zuzzi et al. 2007 Ma et al. 2007 Kreiss et al. 1999 . It has been suggested that lipoplex formation is an endothermic process and the repulsion force between DNA molecules as well as the release of tightly bound counterions from DNA and the lipid mainly controls the formation of cationic lipid DNA complex Ma et al. 2007 . In the course of complex formation DNA acts as a polyanion molecule interacting with the cationic headgroups at the surface of liposomes. The neutralization of charges seems to affect both the DNA and the liposome structures. First DNA might adopt a more compact structure which is less accessible to intercalating dyes or nucleases. Second neutralization might induce lipid bilayer mixing and or aggregation resulting in fusion of liposomes and or multilamellar structure formation. The fact that different structures are observed in the same lipoplex preparation further complicates the interpretation Zabner et al. 1995 . Apart from the electrostatic interactions between positively charged lipid head groups and the negatively charged DNA phosphate backbone variations in lipid-lipid and DNA-DNA ionic repulsive forces attractive lipidlipid hydrophobic interactions hydration forces and other structural properties of the liposome and plasmid DNA can result in a wide variety of macromolecular structures that can vary not only with concentration s but also as a function of time. Hence upon mixing of cationic .