Solvent‐Free Protein Liquids and Liquid Crystals

Abstract

Nanostructures such as functionalized nanoparticles and superlattices have wide-ranging applications in diverse areas. [1][2][3][4] Although these materials are invariably used in the form of aqueous/organic dispersions, ultrathin films, or bulk powders, Giannellis and co-workers have recently pioneered an approach to preparing functionalized inorganic nanostructures with liquidlike behavior. [5,6] These are produced by electrostatically grafting an organic canopy layer onto the surface of charged nanoparticles of silica, [7] iron oxides, [7] and titania [8] for example, to provide a fluidization medium for the preparation of solvent-free nanoparticle ionic fluids. Like nanoscale objects in general, proteins exhibit persistent structures with dimensions that exceed the range of their intermolecular forces, such that liquid-vapor co-existence is unattainable.[9] As a consequence, solid-state proteins sublime at low pressures or thermally degrade under ambient conditions: thus, there are no known liquid proteins in the absence of solvent.Herein, we report, to our knowledge, the first example of a solvent-free liquid protein. Specifically, we report the preparation and properties of a protein melt based on a stoichiometric ferritin-polymer nanoscale construct with surface modifications that extend the range of intermolecular interactions to a length scale that is commensurate with fluidity in the absence of water. Moreover, we show that these spherically shaped nano-constructs undergo anisotropic ordering during melting at 30 8C to produce a viscoelastic protein liquid that exhibits thermotropic liquid-crystalline behavior, and which subsequently transforms to a Newtonian fluid at temperatures above 40 8C and is stable up to a temperature of 405 8C. The method, which utilizes the sitespecificity of surface amino acid residues and high degree of uniformity in ferritin molecular architecture to produce discrete single-component ferritin-polymer constructs (Supporting Information, Figure S1), should be readily accessible to exploitation as a facile route to solvent-free liquid proteins and enzymes in general.Electrostatically induced complexation of cationized ferritin (C-Fn), comprising approximately 240 covalently coupled N,N-dimethyl-1,3-propanediamine (DMPA) groups per molecule (10 DMPA per subunit; Supporting Information, Figure S2 Protein melts were prepared in the absence of water by lyophilization of the aqueous [C-Fn][S] solutions to produce a low-density solid that was subsequently annealed at 50 8C to produce a transparent, viscous, red liquid that remained fluid when cooled to room temperature, but re-solidified at À50 8C (Figure 1). TEM studies of the melt revealed discrete electron-dense nanoparticles, approximately 8 nm in diameter, indicating that the protein nanostructure remained structurally intact in the liquid state (Supporting Information, Figure S4). The melts were readily soluble in water or dichloromethane. Thermogravimetric analysis of the melt gave a water content of less than 2 % and a resid...

Thermotropic liquid crystals from biomacromolecules

“…3B), the broad peak at q = 1.45 Å −1 corresponds to repeat distance of 4.3 Å, which is attributed to the intralayer packing of the alkyl chains of the surfactant (20). Regarding the X-ray results, no peak from the DNA intralayer packing was observed, which suggests that the oligonucleotide chains of ssDNA are randomly packed within the sublayer, without any positional or orientational order (34).…”

“…Water exhibits a high dielectric constant and has the ability to form hydrogen bonds, greatly influencing the structure and functions of biomacromolecules or compromising electronic properties such as charge transport (12)(13)(14)(15). Indeed, anhydrous TLC systems containing glycolipids (16)(17)(18)(19), ferritin (20), and polylysine have been reported (21)(22)(23). However, a general approach to fabricating TLCs based on nucleic acids, polypeptides, proteins, and protein assemblies of large molecular weights such as virus particles remains elusive.…”

Controlled freezing and freeze drying: a versatile route for porous and micro-/nano-structured materials

“…126 They further demonstrated the preparation of room-temperature 127 This review has focused on the use of freezing and freeze drying for the preparation of porous and micro-/nano-structured materials. Solutions, emulsions, and colloidal suspensions can be processed to obtain a wide range of porous structures and particulate materials.…”

Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells

“…This excess of reagent over protein resulted in high cationization efficiencies, comparable also to previously reported results for the cationization of ferritin. 35 For MALDI-TOF analysis, apoferritin and cationized apoferritin were used because of the excessive molecular mass of the magnetoferritin core. To yield high cationization efficiencies, optimal pH is also crucial.…”