Structural characteristics of lysozyme Langmuir layers grown on a liquid surface from an oligomeric mixture formed during the early stages of lysozyme crystallization

• Published in: Thin solid films 2019-05, Vol.677, p.13-21
• Main Authors: Kovalchuk, Mikhail V., Boikova, Anastasiia S., Dyakova, Yulia A., Ilina, Kseniia B., Konarev, Petr V., Marchenkova, Margarita A., Pisarevskiy, Yury V., Prosekov, Pavel A., Rogachev, Alexander V., Seregin, Alexey Yu
• Format: Article
• Language: English
• Subjects: grazing-incidence X-ray standing waves; Langmuir monolayers; lysozyme films; Small-angle X-ray scattering; X-ray standing waves method under total external reflection
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2019.02.051

An approach for forming Langmuir monolayers of proteins is described, with lysozyme serving as an example. The essence of this approach is the deposition of a lysozyme solution containing a precipitant, KCl, onto the water surface in a Langmuir trough. The results of small-angle X-ray scattering indicate that the precipitant in the protein solution causes a significant fraction (>10%) of the protein molecules to assemble into dimers and octamers. Studying the formation of these monolayers by grazing-incidence X-ray standing waves (or X-ray standing waves under total external reflection conditions) showed that the thickness of the resulting protein layer was twice the diameter of an individual lysozyme molecule and matched the diameter of the octamer. Thin layers of precipitant ions (K and Cl) formed directly under the protein monolayer. Our results indicate that adding precipitant to the solution caused the formation of octamers with a retained structure that participated in Langmuir monolayer formation when the solution was applied to the water-subphase surface. Thus, the precipitant ions interacted with the protein monolayer. The proposed approach could facilitate the formation of ordered protein films in hybrid system design and in developing transition methods for nature-like technologies. •Here, we describe an approach for forming Langmuir monolayers with lysozyme.•A lysozyme–precipitant (KCl) solution was deposited in a Langmuir trough.•SAXS data point to the formation of dimers and octamers upon addition of KCl.•The precipitant ions interact with the protein monolayer.•Our approach may enable ordered protein film formation during hybrid system design.