Terminal supraparticle assemblies from similarly charged protein molecules and nanoparticles

Abstract

Self-assembly of proteins and inorganic nanoparticles into terminal assemblies makes possible a large family of uniformly sized hybrid colloids. These particles can be compared in terms of utility, versatility and multifunctionality to other known types of terminal assemblies. They are simple to make and offer theoretical tools for designing their structure and function. To demonstrate such assemblies, we combine cadmium telluride nanoparticles with cytochrome C protein and observe spontaneous formation of spherical supraparticles with a narrow size distribution. Such self-limiting behaviour originates from the competition between electrostatic repulsion and non-covalent attractive interactions. Experimental variation of supraparticle diameters for several assembly conditions matches predictions obtained in simulations. Similar to micelles, supraparticles can incorporate other biological components as exemplified by incorporation of nitrate reductase. Tight packing of nanoscale components enables effective charge and exciton transport in supraparticles as demonstrated by enzymatic nitrate reduction initiated by light absorption in the nanoparticle.

Generic, phenomenological, on-the-fly renormalized repulsion model for self-limited organization of terminal supraparticle assemblies

“…The repulsion renormalization in our model is designed to capture the many-body effects associated with the interaction between the primary particles upon aggregation, which are not present in ordinary pairwise potentials. Such many-body effects are highly relevant for systems where, e.g., the primary particles are similarly charged, yet able to aggregate because of short-ranged attraction (12,13).…”

“…self-assembly | terminal assemblies | self-limited aggregation T he spontaneous formation of uniformly sized aggregates observed in inorganic, biological, and colloidal systems (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) is of both fundamental and practical interest. Their formation suggests that a generic mechanism is applicable to those chemically distinct systems, whereas their ability to serve as building blocks for engineering nanostructures at larger length scales is of practical interest.…”

“…In a recent study, we observed the assembly of positively charged polydisperse CdSe, PbS, and PbSe nanoparticles (NPs) into monodisperse supraparticles (SPs), which form colloidal crystals at sufficiently high density (12). Spherical SPs with uniform size were also obtained from the assembly of similarly charged protein molecules (cytochrome C) and CdTe nanoparticles (13). It was also demonstrated that SPs can serve as a versatile tool to make nanoscale assemblies with unusual spiky shapes and form several constitutive blocks (14).…”

Nanoparticle Assembly:A Perspective and some Unanswered Questions

“…Therefore, the preparation of functional materials based on DNAbridged NP assemblies for use in practical applications does not currently leverage the advances in understanding from these model studies. In a different vein, the spontaneous assemblies of many thousands of anisotropic NPs modified driven by often subtle differences in their interaction reached a level of sophistication comparable to biological systems in respect to geometrical complexities and functions 26,27 . These strides can be made when we partially relax the requirements for structural determinism and rely on dynamic collective interactions of NPs that we have only begun to understand 28 .…”

The self assembly of proteins; probing patchy protein interactions

“…8,9 The degree to which self assembly can be controlled is greatly improved by using anisotropic particles. These anisotropic, or ''patchy'' particles, may be anisotropic in shape, [10][11][12][13] surface charge density, 14 size ratio 15 or have surface functionality. 4,8 Anisotropy is central to protein self assembly.…”