To optimize biodevice assembly and cholesterol sensing, recombinant and wild type P450scc cytochromes are extensively characterized both in solution and in thin solid films, using X-ray scattering, Brewster angle microscopy, quartz crystal nanobalance, ellipsdmetry, cyclic voltammetry, and circular dichroism. Efficient expression systems are implemented in microbial cells for the production of recombinant P450scc proteins, which are then purified. Modeling of the cholesterol interaction was also studied for the given application. Both types of P450 form monolayers at the air/water interface which can be transferred onto solid substrates, but only in the case of recombinant protein does the engineered monolayer turn out to be more dense and regular, and its thickness corresponds better to the native protein size. By surface pressure and surface potential measurements it is shown that at the air/water interface P450scc molecules orient themselves at the initial stage of the monolayer compression by self-assembly; increasing surface pressure yields high homogeneity, as confirmed by Brewster angle microscopy. CD measurements confirmed a significant increase in the stability of the protein secondary structure in the recombinant monolayers whose regular structure appears by X-ray measurements. The cyclic voltammetric study on LB films of cytochrome P450scc as a function of number of monolayers and of cholesterol concentration pointed to a possible electron transfer from the electrochemical process to cytochrome P450scc that in turn reacted with cholesterol, compatibly with the modeling showing that the nearest cholesterol atoms belonging to the main chain are only 4-5 Angstrom from the heme.