A self-assembling protein template for constrained synthesis and patterning of nanoparticle arrays

Self-assembling biomolecules that form highly ordered structures have attracted interest as potential alternatives to conventional lithographic processes for patterning materials. Here, we introduce a general technique for patterning nanoparticle arrays using two-dimensional crystals of genetically modified hollow protein structures called chaperonins. Constrained chemical synthesis of transition metal nanoparticles is initiated using templates functionalized with polyhistidine sequences. These nanoparticles are ordered into arrays because the template-driven synthesis is constrained by the nanoscale structure of the crystallized protein. We anticipate that this system may be used to pattern different classes of nanoparticles based on the growing library of sequences shown to specifically bind or direct the growth of materials.     

Crystal structures and phase transition in the system SrTiO3-La2/3TiO3

The distribution of A-site cations in the perovskite system La_xSr_1−3x/2TiO₃ depends on the concentration of La³⁺ ions and associated vacancies. For small x (x?0.2), the substitutions are expected to be random. For x?0.55, the cations are ordered in such a way that successive layers of A-sites are occupied to greater and lesser degree, and this ordering drives a tetragonal distortion. For x from about 0.3 to 0.5, the X-ray patterns show diffuse peaks indicative of similar ordering, but this is not long-range order and no tetragonal distortion results. The lower temperature structures also exhibit out-of-phase tilting of the TiO₆ octahedra, setting in at temperatures varying linearly with composition from 105 K for x=0, to about 650 K at x=2/3.     

pH-sensitive modulation of the second hydration sphere in lanthanide(III) tetraamide-DOTA complexes: a novel approach to smart MR contrast media

The lanthanide(III) complexes of three tetraamide DOTA bearing pyridyl, phenolic and hydroxypyridyl substituents have been studied by NMR, luminescence and cyclic voltammetry. The relaxivity profiles of the gadolinium complexes of the pyridyl and phenolic ligands were flat and essentially the same between pH 2 and 8. The hydroxypyridyl ligand, however, exhibited two regions of enhanced relaxivity. The small relaxivity enhancement (25 %) at lower pH (pH 2-4) has been attributed to an increase in the prototropic exchange of the coordinated water molecule while the slightly larger enhancement (84 %) at higher pH (pH 6-9) reflects deprotonation of the ligand amide protons. Deprotonation of the amides results in the formation of an intramolecular acid-base pair interaction with the phenolic protons and this, in turn, causes a highly organized second hydration sphere to come into effect, thereby increasing the relaxivity. The water relaxivity of the Gd(3+)-hydroxypyridyl complex is further enhanced upon binding to serum albumin.     

Bond energy, aromatic stabilization energy and strain in IPR fullerenes

Various models applied to DFT structures and energies of 2-D and 3-D aromatic molecules shed new light on the effects of strain and aromaticity in these systems. The cyclic pi electron delocalisation does not stabilize the fullerene C60 formation; and 5-6 and 6-6 CC bonds have near-identical bond stretch potentials.     

Synthesis and characterisation of the platinum complexes [PtCl(CClPAr)(PPh3)2] and [PtCl(CClPAr′)(PPh3)2] as potential intermediates in the preparation of phosphaalkynes

Oxidative addition reactions of Cl₂CPR (R = 2,4,6-tris(trifluoromethyl)phenyl (Ar) or 2,6-bis(trifluoromethyl)phenyl (Ar′) with Pt(PPh₃)₄ yield the cis and trans (at platinum) complexes [PtCl(ClCPAr)(PPh₃)₂] and [PtCl(ClCPAr′)(PPh₃)₂]. All starting materials and intermediates have been characterised by NMR spectroscopy. The crystal and molecular structures of the trans-platinum complexes have been determined by single-crystal X-ray diffraction at low temperature.     

Polymerization by oxidation coupling. I. A study of the oxidation of 2,6-diphenylphenol to poly(2,6-diphenyl-1,4-phenylene ether)

The synthesis of poly(2,6-diphenyl-1,4-phenylene ether), by the oxidative coupling of 2,6-diphenylphenol has been studied. Procedures were found which demonstrated that polymers of very high molecular weight \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\overline M _n > 200{\rm 000; }\left[ \eta \right]_{{\rm CHCl}_{\rm 3} }^{25^\circ {\rm C}} > 1.1{\rm }{{{\rm dl}} \mathord{\left/ {\vphantom {{{\rm dl}} g}} \right. \kern-\nulldelimiterspace} g}} \right) $\end{document} could be made with a copper-amine catalyst system. A low nitrogen-to-copper ratio (1 N atom/Cu atom) was necessary to obtain the very high molecular weights under the conditions of these reactions. A variety of amines formed active catalysts; the effectiveness of mono- and bis- primary, secondary, and tertiary amines were compared. Effects of the type of copper halide, reaction temperature, desiccants, addition rates of 2,6-di-phenylphenol, and solvents were also examined. Samples of polymer were isolated at different times during the polymerization. Measurements of viscosity, osmotic pressure, light scattering, gel permeation, phenolic hydroxyl groups, and nitrogen content were made on various samples over a range of intrinsic viscosities of 0.05–0.59 dl/g. A very narrow molecular weight distribution was found for all samples. Hydroxyl endgroup analyses indicated that the concentration of phenolic endgroups per mole of polymer does not change during the polymerization. The presence of some side reactions is indicated by nitrogen analyses. The relationships between the intrinsic viscosity in chloroform at 25°C and M?_n and M?_w are: log [η] = ?3.97 + 0.72₇ log M?_n and log [n] = ?3.56 + 0.62₄ log M?_w.     

The molecular and ionic solubility of nickel dimethylglyoximate

Values are reported for the solubility product constant and the ionization constant of nickel(II) dimethylglyoximate in aqueous solution. The solubility of nickel dimethylglyoximate in the investigated pH range from 2 to 9 is accounted for by the species Ni⁺² and Ni(HDx)₂; there is no evidence for the existence of a significant amount of NiHDx⁺.The extraction constant

has been calculated from the ionization constants of Ni(HDx)₂ and H₂Dx and the molecular solubilities of the former in water and chloroform.     

Hyperoxygenation enhances the tumor cell killing of photofrin-mediated photodynamic therapy

Tumor hypoxia, either preexisting or as a result of oxygen depletion during photodynamic therapy (PDT) light irradiation, can significantly reduce the effectiveness of PDT-induced cell killing. To overcome tumor hypoxia and improve tumor cell killing, we propose using supplemental hyperoxygenation during Photofrin-PDT. The mechanism for the tumor cure enhancement of the hyperoxygenation-PDT combination is investigated using an in vivo-in vitro technique. A hypoxic tumor model was established by implanting mammary adenocarcinoma in the hind legs of mice. Light irradiation (200 J/cm2 at either 75 or 150 mW/cm2), under various oxygen supplemental conditions (room air, carbogen, 100% normobaric or hyperbaric oxygen), was delivered to animals that received 12.5 mg/kg Photofrin 24 h before light irradiation. Tumors were harvested at various time points after PDT and grown in vitro for colony formation analysis. Treated tumors were also analyzed histologically. The results show that when PDT is combined with hyperoxygenation, the hypoxic condition could be improved and the cell killing rate at various time points after PDT could be significantly enhanced over that without hyperoxygenation, suggesting an enhanced direct and indirect cell killing associated with high-concentration oxygen breathing. This study further confirms our earlier observation that when a PDT treatment is combined with hyperoxygenation it can be more effective in controlling hypoxic tumors.     

Participation of Bao2* in chemiluminescence from low-pressure Ba(g) + O2 flames

New spectioscopic and vibronic population data support the essential correctness of BaO₂^* as the nascent polyatomic emitter and as the precursor to BaO (A ¹Σ⁺ → X¹Σ⁺) and (A' ¹Π → X¹Σ⁺) visible chemiluminescence from metal-rich Ba(g) + O₂ (+ Ar) diffusion flames at 2–350 mTorr- Absolute visible photon yields are reported over this pressure regime.     

SV40 INDUCTION FROM A MAMMALIAN CELL LINE BY ULTRAVIOLET RADIATION and THE PHOTOSENSITIZERS 8-METHOXYPSORALEN and ANGELICIN

Abstract SV40-transformed weanling Syrian hamster kidney cells were exposed to long wavelength ultraviolet radiation in the presence of 8-methoxypsoralen or angelicin. The number of viruses induced as a result of this treatment was quantitated on CV-1P cells. The results indicate that angelicin, which is generally believed to form only monoadducts, is a potent viral inducing agent even when compared with 8-methoxypsoralen (8-MOP), which forms both monoadducts and crosslinks. At low radiation exposures 8-MOP is more effective than angelicin; as the radiation exposure is increased angelicin is capable of inducing the same peak level of virus expression as was 8-MOP. It appears that the induction of SV40 is a phenomenon possibly related to the repair of monoadducts.