Influence of Backbone Regioregularity on the Optoelectronic and Mechanical Response of Conjugated Polyelectrolyte-Based Hydrogels.

The ability to form robust, optoelectronically responsive, and mechanically tunable hydrogels using facile processing is desirable for sensing, biomedical, and light-harvesting applications. We demonstrate that such a hydrogel can be formed using aqueous complexation between one conjugated and one nonconjugated polyelectrolyte. We show that the rheological properties of the hydrogel can be tuned using the regioregularity of the conjugated polyelectrolyte (CPE) backbone, leading to significantly different mesoscale gel morphologies. We also find that the exciton dynamics in the long-time limit reflect differences in the underlying electronic connectivity of the hydrogels as a function CPE regioregularity. The influence of excess small ions on the hydrogel structure and the exciton dynamics similarly depends on the regioregularity in a significant way. Finally, electrical impedance measurements lead us to infer that these hydrogels can act as mixed ionic/electronic conductors. We believe that such gels possess an attractive combination of physical-chemical properties that can be leveraged in multiple applications.

A practice-based evidence investigation of God representations in spiritually integrated psychotherapies.

OBJECTIVE: This practice-based evidence study examined trajectories of God representations and psychological distress among Christians participating in spiritually integrated psychotherapies (SIPs). METHODS: In total, 17 clinicians practicing SIPs in a mid-sized city on the US Gulf Coast implemented session-to-session assessments of these outcomes with 158 clients over a 4-month period and also reported their use of specific spiritual interventions after each session (e.g., affirmed client's divine worth). RESULTS: Multivariate growth modeling revealed clients' psychological distress decreased over the study period whereas authoritarian God representations increased and benevolent God representations remained stable. In addition, clients who increased in benevolent representations of God had a greater likelihood of experiencing alleviation of psychological distress. CONCLUSION: These findings affirm the potential efficacy of SIPs and cultural importance of belief in a benevolent deity as a source of strength, identity, and potential healing among Christians clients who prefer a spiritually integrated approach in psychotherapy.

Antimicrobial activity of graphene oxide quantum dots: impacts of chemical reduction.

Design and engineering of graphene-based functional nanomaterials for effective antimicrobial applications has been attracting extensive interest. In the present study, graphene oxide quantum dots (GOQDs) were prepared by chemical exfoliation of carbon fibers and exhibited apparent antimicrobial activity. Transmission electron microscopic measurements showed that the lateral length ranged from a few tens to a few hundred nanometers. Upon reduction by sodium borohydride, whereas the UV-vis absorption profile remained largely unchanged, steady-state photoluminescence measurements exhibited a marked blue-shift and increase in intensity of the emission, due to (partial) removal of phenanthroline-like structural defects within the carbon skeletons. Consistent results were obtained in Raman and time-resolved photoluminescence measurements. Interestingly, the samples exhibited apparent, but clearly different, antimicrobial activity against Staphylococcus epidermidis cells. In the dark and under photoirradiation (400 nm), the as-produced GOQDs exhibited markedly higher cytotoxicity than the chemically reduced counterparts, likely because of (i) effective removal by NaBH4 reduction of redox-active phenanthroline-like moieties that interacted with the electron-transport chain of the bacterial cells, and (ii) diminished production of hydroxyl radicals that were potent bactericidal agents after chemical reduction as a result of increased conjugation within the carbon skeletons.

Tuning from Quantum Dots to Magic Sized Clusters of CsPbBr3 Using Novel Planar Ligands Based on the Trivalent Nitrate Coordination Complex.

We report the first demonstration of using trivalent metal hydrated nitrate coordination complexes (TMHNCCs) as novel passivation ligands to control the synthesis of magic sized clusters (MSCs) and quantum dots (QDs) of CsPbBr3 perovskite at room temperature. We can easily tune from QDs to MSCs or produce a mixture of the two by changing the amount of TMHNCC ligands used, with more ligands favoring MSCs. The original TMHNCC introduced, aluminum nitrate nonahydrate [ANN, Al(NO3)3·9H2O], led to the production of aluminum dihydroxide nitrate tetrahydrate {ADNT, [Al(OH)2(NO3)]·4H2O}, with the assistance of oleic acid (OA) and oleylamine (OAm). Through several control experiments, we determined that ADNT is the primary ligand for effectively passivating the MSCs and QDs, with OAm being essential for deprotonating ANN and OA for adjusting the pH of the reaction system. We suggest that ADNT is planar on the surface of the MSCs or QDs with its NO3- and OH- groups binding to the Cs+ and Pb2+ defect sites and Al3+ binding to the Br- defect sites of the MSCs or QDs.

Heparin Binding to an Engineered Virus-like Nanoparticle Antagonist.

The anticoagulant activity of heparin administered during medical interventions must be reversed to restore normal clotting, typically by titrating with protamine. Given the acute toxicity associated with protamine, we endeavored to generate safer heparin antagonists by engineering bacteriophage Qß virus-like particles (VLPs) to display motifs that bind heparin. A particle bearing a single amino acid change from wild-type (T18R) was identified as a promising candidate for heparin antagonism. Surface potential maps generated through molecular modeling reveal that the T18R mutation adds synergistically to adjacent positive charges on the particle surface, resulting in a large solvent-accessible cationic region that is replicated 180 times over the capsid. Chromatography using a heparin-sepharose column confirmed a strong interaction between heparin and the T18R particle. Binding studies using fluorescein-labeled heparin (HepFL) resulted in a concentration-dependent change in fluorescence intensity, which could be perturbed by the addition of unlabeled heparin. Analysis of the fluorescence data yielded a dissociation constant of approximately 1 nM and a 1:1 binding stoichiometry for HepFL:VLP. Dynamic light scattering (DLS) experiments suggested that T18R forms discrete complexes with heparin when the VLP:heparin molar ratios are equivalent, and in vitro clotting assays confirmed the 1:1 binding stoichiometry as full antagonism of heparin is achieved. Biolayer interferometry and backscattering interferometry corroborated the strong interaction of T18R with heparin, yielding Kd ∼ 1-10 nM. These biophysical measurements further validated T18R, and VLPs in general, for potential clinical use as effective, nontoxic heparin antagonists.

Exciton Transfer and Emergent Excitonic States in Oppositely-Charged Conjugated Polyelectrolyte Complexes.

Photosynthetic organisms have mastered the use of "soft" macromolecular assemblies for light absorption and concentration of electronic excitation energy. Nature's design centers on an optically inactive protein-based backbone that acts as a host matrix for an array of light-harvesting pigment molecules. The pigments are organized in space such that excited states can migrate between molecules, ultimately delivering the energy to the reaction center. Here we report our investigation of an artificial light-harvesting energy transfer antenna based on complexes of oppositely charged conjugated polyelectrolytes (CPEs). The conjugated backbone and the charged side chains of the CPE lead to an architecture that simultaneously functions as a structural scaffold and an electronic energy "highway". We find that the process of ionic complex formation leads to a remarkable change in the excitonic wavefunction of the energy acceptor, which manifests in a dramatic increase in the fluorescence quantum yield. We argue that the extended backbone of the donor CPE effectively templates a planarized acceptor polymer, leading to excited states that are highly delocalized along the polymer backbone.

Directed polyvalent display of sulfated ligands on virus nanoparticles elicits heparin-like anticoagulant activity.

Heparin is a sulfated glycosaminoglycan that is widely used as an anticoagulant. It is typically extracted from porcine or bovine sources to yield a heterogeneous mixture that varies both in molecular weight and in degree of sulfation. This heterogeneity, coupled with concern for contamination, has led to widespread interest in developing safer alternatives. Described herein are sulfated bacteriophage Qß virus-like particles (VLPs) that elicit heparin-like anticoagulant activity. Sulfate groups were appended to the VLP by synthesis of single- and triple-sulfated ligands that also contained azide groups. Following conversion of VLP surface lysine groups to alkynes, the sulfated ligands were attached to the VLP via copper-catalyzed azide-alkyne cycloaddition (CuAAC). MALDI-MS analysis of the intermediate alkyne VLP indicated that the majority of the coat proteins contained 5-7 of the alkyne linkers; similar analysis of the intermediate alkyne particles conjugated to a fluorescein azide suggest that nearly the same number of attachment points (3-6) are modified via CuAAC. Analysis by SDS-PAGE with fluorescent staining indicated altered migration patterns for the various constructs: compared to the wild-type nanoparticle, the modified coat proteins appeared to migrate farther toward the positive pole in the gel, with coat proteins displaying the triple-sulfated ligand migrating significantly farther. Clotting activity analyzed by activated partial thrombin time (APTT) assay showed that the sulfated particles were able to perturb coagulation, with VLPs displaying the triple-sulfated ligand approximately as effective as heparin on a per mole basis; this activity could be partially reversed by protamine. ELISA experiments to assess the response of the complement system to the VLPs indicate that sulfating the particles may reduce complement activation.

Metal- and metallocycle-binding sites engineered into polyvalent virus-like scaffolds.

Metal-binding motifs appear on protein scaffolds throughout nature and are critical for a vast array of functions that span structure, electron transfer, and catalysis. In an effort to reproduce and exploit this activity in vitro, described herein are versatile bacteriophage Qbeta particles bearing metal-binding motifs polyvalently. The three motifs, His(6), His(6)-His(6), and Cys-His(6), were incorporated into the capsid via a coexpression methodology at ratios of 1.1:1, 1.1:1, and 2.3:1 for wild-type to modified coat protein. Size-exclusion chromatography yielded elution profiles identical to wild-type particles, while Ni-NTA affinity chromatography resulted in retention times that increase according to Qbeta-His(6) < Qbeta-Cys-His(6) < Qbeta-His(6)-His(6). In addition to interacting with metal-derivatized surfaces, Qbeta-Cys-His(6) and Qbeta-His(6)-His(6) bind heme as evidenced by the appearance of new absorbances at 416 and 418 nm, respectively, upon addition of hemin-Cl. The heme-bearing particles were also found to be electrochemically active as a surface-confined system. While both constructs yield similar E(1/2) values anaerobically and with carbon monoxide present, and both display similar pH dependences, a standard rate constant k degrees could only be measured for Qbeta-Cys-His(6) (83 s(-1)), as electron transfer for Qbeta-His(6)-His(6) was too rapid to estimate. Experiments with rotated-disk electrodes yielded significant activity of the constructs toward dioxygen reduction. The versatility of the particles is further underscored by their multivalent nature, permitting simultaneously a range of activities for applications demanding polyfunctionality.