Biological molecular assemblies are excellent models for the development of nanoengineered systems with desirable biomedical properties. Here we report an approach for fabrication of spontaneous, biologically active molecular networks consisting of bacteriophage (phage) directly assembled with gold (Au) nanoparticles (termed Au-phage). We show that when the phage are engineered so that each phage particle displays a peptide, such networks preserve the cell surface receptor binding and internalization attributes of the displayed peptide. The spontaneous organization of these targeted networks can be manipulated further by incorporation of imidazole (Au-phage-imid), which induces changes in fractal structure and near-infrared optical properties. The networks can be used as labels for enhanced fluorescence and dark-field microscopy, surface-enhanced Raman scattering detection, and near-infrared photon-to-heat conversion. Together, the physical and biological features within these targeted networks offer convenient multifunctional integration within a single entity with potential for nanotechnology-based biomedical applications.target ͉ fractal ͉ hydrogel ͉ stem cell ͉ assembly I n nature, the assembly of molecules and particles is often directed by hydrophobic, van der Walls, and͞or electrostatic interactions (1, 2). Biological systems in particular are driven toward energetically favorable structures that have molecular selectivity and recognition and thus serve as models for nanoscale engineering-based molecular assembly. Given that filamentous bacteriophage (phage) (3-6) are resistant to harsh conditions such as high salt concentration, acidic pH, chaotropic agents, and prolonged storage (6), they are suitable candidate building blocks to meet the challenges of bottom-up nanofabrication (1, 2). Moreover, the pIII minor capsid protein of the phage can be easily engineered genetically to display ligand peptides that will bind to and modify the behavior of target cells in selected tissues (3,4,(6)(7)(8). Thus, the tactic of integrating phage display technology with tailored nanoparticle assembly processes offers opportunities for reaching specific nanoengineering and biomedical goals (1-4, 6, 8-10).In this work, we show that such networks are biocompatible and preserve the cell-targeting and internalization attributes mediated by a displayed peptide and that spontaneous organization (without genetic manipulation of the pVIII major capsid protein), and optical properties can be manipulated by changing assembly conditions. By taking advantage of gold (Au) optical properties (11-16), we generated Au-phage networks that, in addition to targeting cells, can function as signal reporters for fluorescence and dark-field microscopy and near-infrared (NIR) surface-enhanced Raman scattering (SERS) spectroscopy. Notably, this strategy maintains the low-cost, high-yield production of complex polymer units (phage) in host bacteria and bypasses many of the challenges in developing cell͞peptide detection tools, such as complex syn...

A new method to obtain improved structural parameters by supplementing gas-phase electron diffraction (GED) data with restraints based on the results of ab initio calculations is proposed. The procedure involves the use of ab initio parameters with estimated uncertainties as additional observations; this allows previously fixed parameters to refine, with all geometrical parameters included in the final refinement. The refinement of the molecular structure of 2,5-dichloropyrimidine is used as an example to illustrate the principle of this technique. In this simple case, the effects are not very great, but this new approach allowed refinement of all structural parameters. The nine independent structural parameters (r R structure) were found to be: 6)-H( 10)] ) 109.9(12) pm, ∠[N(1)C( 2)N(3)] ) 127.9(4)°, ∠[C(2)N(3)C( 4)] ) 116.3(7)°, and ∠[N(3)C(4)H( 8)] ) 117.2(5)°. All structural parameters were found to be in good agreement with both ab initio and crystallographic values, which are presented for comparison.

Calculations of intermolecular potentials are presented for homo-molecular and hetero-molecular clusters of 24 peri-condensed PAH spanning monomer masses ranging from 78 to 1830 Da. Binding energies of homo-molecular dimers rise rapidly with molecular size and asymptotically approach the experimentally established exfoliation energy for graphite of 5.0 kJ mol(-1) (carbon atom)(-1). Binding energies of hetero-molecular dimers correlate well with the reduced mass of the pair. From calculations of homo-molecular stacks, binding energies were observed to increase with each added molecule and rise asymptotically, approaching a limit which scales linearly with monomer molecular mass. These results are reviewed in the context of molecular growth in flames and in the context of astrophysical observations.