No abstract

A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.

Many protein crystals are distinguished by 3-D structures that contain well-ordered interpenetrating nanoporous and mesoporous solvent channels often 0.5-10 nm in diameter. [1] These channels provide a chemically heterogeneous and chiral environment that comprises 30-65 % of the total crystal volume with associated pore volumes and surface areas in the range of 0.9-3.6 mL g À1 and 800-3000 m 2 g À1 , respectively. [1][2][3] The use of protein crystals for materials applications has been traditionally restricted by their mechanical and chemical fragility; however the onset of simple cross-linking technology has significantly extended the scope for protein aggregates and crystals in catalysis and drug delivery, [4,5] separation science, [2,[6][7][8] and sensors. [9] In general, cross-linking is achieved by soaking the protein crystals in a 1-5 % aqueous glutaraldehyde solution containing a heterogeneous mixture of monomers and aldol-based oligomers of various lengths. [10] Reaction of these species with lysine residues results in a network of Schiff-base coupled intermolecular linkages to produce cross-linked protein crystals with high structural fidelity.[11] As a result, the glutaraldehyde-fixed crystals are physically robust, stable in organic solvents, and insoluble in water. Moreover, immersion of the cross-linked crystals in aqueous solutions of organic dyes, drugs, and antibiotics results in uptake of the guest molecules specifically within the solvent channels of the protein lattice. [12][13][14][15][16] Here, we extend the above strategies for the sequestration of metal ions and their reduction products within the solvent channels of glutaraldehyde cross-linked lysozyme single crystals. We note that a related approach, but involving cross-linked virus crystals, has been used recently to template the deposition of Pt/Pd nanoparticles. [17] Lysozyme is an enzyme with a single polypeptide chain consisting of 129 amino acids (M w = 14 600), and can be readily crystalized in various polymorphic forms. [18][19][20][21][22] Significantly, the tetragonal polymorph (space group P4 3 2 1 2) has discrete uni-directional solvent channels, 1 to 2.5 nm in diameter, which are aligned parallel to the crystallographic c axis.[23] Each channel is located in the centre of the unit cell, surrounded locally by four protein molecules, and constructed from an interlinked network of pores and cavities lined with aspartate and lysine residues.[24] Herein, we exploit this structural arrangement as an ordered 1-D intracrystalline reaction environment for the periodic organization and nanoscale confinement of plasmonic nanowires of Ag or Au. Arrays of metallic nanofilaments are produced within the protein crystals by in situ redox reactions involving photoreduction of sequestered Ag À by BH 4 À ions preorganized into the solvent channels. The resulting metalized protein crystals are physically robust, regular in external morphology, and uniform in size. Such materials represent a new class of hybrid monoliths with patterned nanostruc...

Nanoscale objects with advanced structure and function are of considerable interest in areas such as sensing, drug delivery and bioelectronics, [1,2] and have important implications for biotoxicity [3,4] and the emergence of life. [5] In many cases, the synthesis and structuration of hybrid nano-objects is achieved under equilibrium or non-equilibrium conditions through a range of strategies involving integrative, higher-order, or transformative self-assembly. [6,7] Often these approaches involve the confinement and templating of reactions on or within supramolecular assemblies such as dendrimers, [8] organogel nanofilaments, [9] peptide fibers, [10] helical micelles, [11] virus capsids, [12] and protein cages. [13] Recently, cross-linked lysozyme crystals, approximately 200 mm in size, have been used to prepare nanoplasmonic arrays by intracrystalline metallization, [14] suggesting that the high mesoporosity of protein crystals might be exploited in general for the template-directed assembly of organized inorganic nanostructures across a range of length scales. Whilst many common proteins readily form crystals with macroscopic dimensions, it is generally difficult to produce nanoscale counterparts that would be effective as templates for the preparation of discrete hybrid nanomaterials. In this regard, the iron storage protein, ferritin, which consists of a 12 nm diameter spherical polypeptide shell enclosing a 5-6 nm sized iron oxide core [15] is known to readily form two-dimensional (2D) superlattices on various substrates [16] and can be clustered into aggregates in solution using biotin-streptavidin linkages or inorganic nanoparticles.[17] It should therefore be possible to control the self-assembly of discrete nanometersized ferritin crystals, and as a consequence use these nanocrystals as porous templates for the fabrication of hybrid nanoparticles with ordered mesostructured interiors.Here, we use water-in-oil microemulsion droplets as a medium for controlling the aggregation of entrapped ferritin molecules to produce discrete protein nanocrystals that can be stabilized by in situ silicification of the intracrystalline voids to produce mesostructured silica-ferritin hybrids. Microemulsions are versatile reaction media for the confinement and synthesis of inorganic nanoparticles, [18] nanowires, [19] nanoparticle superlattices, [20] and complex hierarchical architectures.[21] In addition, microemulsion droplets have been used for the encapsulation of drugs, [22] exploration of organic chemical reactions, [23] entrapment of functional enzymes, [24] and for the separation of protein mixtures.[25]Although droplet instability can often be a problem in these applications, herein we demonstrate that protein-mediated aggregation of the water pools can be exploited to produce discrete ferritin nanocrystals and silicified counterparts with well-ordered close packed structures. As silicification of the interstitial pores occurs with high precision and without degradation of the protein, it should be possible to ex...

Research concerning child victims of sexual abuse in the judicial system cites largely negative experiences and outcomes. However, few investigations focus on parental experiences of the justice system. Using a grounded theory method this Canadian study explored parental experiences of legal and judicial processes for child sexual abuse victims. Nineteen in‐depth interviews with parents encountering the justice system, as well as interviews with professionals working in those systems were analyzed. Results show a wide range of experiences, with parents reporting predominantly negative outcomes that potentially impede healing for children, indicating earlier judicial reforms have not been realized. Recommendations call for structural changes in the judicial system and more provision of parent‐focused supports.