Adsorption characteristics of Cytochrome c/DNA complex Langmuir molecular assemblies at the air–water interface: a surface area-normalized isotherm study

Abstract

We present the formation of a complex molecular network consisting of highly water soluble λ-DNA and a redox protein, Cytochrome c (Cyt c), at the air–water interface by Langmuir–Blodgett technique. Time dependent adsorption of these materials and the formation of a Cyt c/λ-DNA complex interfacial layer in the Langmuir trough were systematically studied by recording surface pressure versus trough area isotherms after various subphase incubation times. We have succeeded in separating two effects: one is the phase change of the monolayers and the other is the number of molecules participating in the monolayer formation with the change in incubation time using a normalized isotherm in units of critical surface area. The interaction in the complex monolayer was found to be same as that of single component λ-DNA during 3 h of subphase incubation. However, it was also similar to that of a single component Cyt c monolayer after 5 h incubation. The morphology and electrical polarizations of these interfacial films deposited onto a mica substrate were analyzed by Atomic Force Microscopy and electrostatic force microscopy respectively. It was found that Cyt c and λ-DNA immediately form the complex network at the air–water interface, and change to rod-like large aggregates with prolonged incubation.