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    Adsorption Mechanism of Myelin Basic Protein on Model Substrates and Its Bridging Interaction between the Two Surfaces

    Year: 2015

    Journal: LANGMUIR, Vol. 31, p 3159-3166, 20150526

    Authors: Lee, Dong Woog; Banquy, Xavier; Kristiansen, Kai; Min, Younjin; Ramachandran, Arun; Boggs, Joan M.; Israelachvili, Jacob N.

    Organizations: Univ Calif Santa Barbara, Dept Chem Engn, Santa Barbara, CA 93106 USA; Univ Montreal, Fac Pharm, Canada Res Chair Bioinspired Mat & Interfaces, Montreal, PQ H3C 3J7, Canada; Univ Akron, Dept Polymer Engn, Akron, OH 44325 USA; Univ Toronto, Dept Chem Engn & Appl Chem, Toronto, ON M5S 3E5, Canada; Hosp Sick Children, Dept Mol Struct & Funct, Toronto, ON MSG 1X8, Canada; Univ Toronto, Dept Lab Med & Pathobiol, Toronto, ON M5G 1L5, Canada; Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA

    Myelin basic protein (MBP) is an intrinsically disordered (unstructured) protein known to play an important role in the stability of myelin's multilamellar membrane structure in the central nervous system. The adsorption of MBP and its capacity to interact with and bridge solid substrates has been studied using a surface forces apparatus (SFA) and a quartz crystal microbalance with dissipation (QCM-D). Adsorption experiments show that MBP molecules adsorb to the surfaces in a swollen state before undergoing a conformational change into a more compact structure with a thickness of similar to 3 nm. Moreover, this compact structure is able to interact with nearby mica surfaces to form adhesive bridges. The measured adhesion force (energy) between two bridged surfaces is 1.0 +/- 0.1 mN/m, (E-ad = 0.21 +/- 0.02 mJ/m(2)), which is slightly smaller than our previously reported adhesion force of 1.7 mN/m (E-ad = 0.36 mJ/m(2)) for MBP adsorbed on two supported lipid bilayers (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775). The saturated surface concentration of compact MBP on a single SiO2 surface reaches a stable value of 310 +/- 10 ng/cm(2) regardless of the bulk MBP concentration. A kinetic three-step adsorption model was developed that accurately fits the adsorption data. The developed model is a general model, not limited to intrinsically disordered proteins, that can be extended to the adsorption of various chemical compounds that undergo chemical reactions and/or conformational changes upon adsorbing to surfaces. Taken together with our previously published data (Lee et al., Proc. Natl. Acad. Sci. U.S.A. 2014, 111, E768-E775), the present results confirm that conformational changes of MBP upon adsorption are a key for strong adhesion, and that such conformational changes are strongly dependent on the nature of the surfaces.