Surface charge- and space-dependent transport of proteins in crowded environments of nanotailored posts.
The reaction and diffusion of molecules across barriers and through crowded environments is integral to biological system function and to separation technologies. Ordered, microfabricated post arrays are a promising route to creating synthetic barriers with controlled chemical and physical characteristics. They can be used to create crowded environments, to mimic aspects of cellular membranes, and to serve as engineered replacements of polymer-based separation media. Here, the translational diffusion of fluorescein isothiocyante and various forms of green fluorescent protein (GFP), including "supercharged" variants, are examined in a silicon-based post array environment. The technique of fluorescence recovery after photobleaching (FRAP) is combined with analytical approximations and numerical simulations to assess the relative effects of reaction and diffusion on molecular transport, respectively. FRAP experiments were conducted for 64 different cases where the molecular species, the density of the posts, and the chemical surface charge of the posts were varied. In all cases, the dense packing of the posts hindered the diffusive transport of the fluorescent species. The supercharged GFPs strongly interacted with oppositely charged surfaces. With similar molecular and surface charges, transport is primarily limited by hindered diffusion. For conventional, enhanced GFP in a positively charged surface environment, transport was limited by the coupled action of hindered diffusion and surface interaction with the posts. Quantification of the size-, space-, time-, and charge-dependent translational diffusion in the post array environments can provide insight into natural processes and guide the design and development of selective membrane systems.
Choi
Chang Kyoung
CK
Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, Michigan 49931-1295, USA.
Fowlkes
Jason D
JD
Retterer
Scott T
ST
Siuti
Piro
P
Iyer
Sukanya
S
Doktycz
Mitchel J
MJ
D003460:Crystallization / Q000379:methods*; D036681:Fluorescence Recovery After Photobleaching / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D009038:Motion; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000648:ultrastructure*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D011485:Protein Binding; D055672:Static Electricity; D013499:Surface Properties
D046911:Macromolecular Substances; D046912:Multiprotein Complexes