In this Article we described a ruthenium-catalysed carbonyl addition method for alcohol production via simple unsubstituted hydra-zone intermediates, but we inadvertently omitted the citation of two papers that had previously reported a similar carbanion reactivity 1,2. In these papers, the authors illustrated a series of substituted hindered hydrazones (for example, tert-butyl-, trityl-and diphenyl-4-pyri-dylmethyl) for additions to carbonyl compounds; however, to yield the target alcohols under these circumstances, the lithium salts of these hydrazones had to be pre-formed, with subsequent CC bond formation and removal of bulky substituents on azo-intermediates via radical decomposition. References 1. Baldwin, J. E. et al. Azo anions in synthesis: use of trityl-and diphenyl-4-pyridylmethylhydrazones for reductive C−C bond formation. Tetrahedron 42, 4235−4246 (1986). 2. Baldwin, J. E., Bottaro, J. C., Kolhe, J. N. & Adlington, R. M. Azo anions in synthesis. Use of trityl-and diphenyl-4-pyridylmethyl-hydrazones for reductive CC bond formation from aldehydes and ketones. J. Chem. Soc. Chem. Commun. 22−23 (1984). Addendum: Aldehydes as alkyl carbanion equivalents for additions to carbonyl compounds © 2 0 1 7 M a c m i l l a n P u b l i s h e r s L i m i t e d , p a r t o f S p r i n g e r N a t u r e. A l l r i g h t s r e s e r v e d .

The performance of organic photovoltaic (OPV) material systems are hypothesized to depend strongly on the intermolecular arrangements at the donor:fullerene interfaces. A review of some of the most efficient polymers utilized in polymer:fullerene PV devices, combined with an analysis of reported polymer donor materials wherein the same conjugated backbone was used with varying alkyl substituents, supports this hypothesis. Specifically, the literature shows that higher-performing donor-acceptor type polymers generally have acceptor moieties that are sterically accessible for interactions with the fullerene derivative, whereas the corresponding donor moieties tend to have branched alkyl substituents that sterically hinder interactions with the fullerene. To further explore the idea that the most beneficial polymer:fullerene arrangement involves the fullerene docking with the acceptor moiety, a family of benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione polymers (PBDTTPD derivatives) was synthesized and tested in a variety of PV device types with vastly different aggregation states of the polymer. In agreement with our hypothesis, the PBDTTPD derivative with a more sterically accessible acceptor moiety and a more sterically hindered donor moiety shows the highest performance in bulk-heterojunction, bilayer, and low-polymer concentration PV devices where fullerene derivatives serve as the electron-accepting materials. Furthermore, external quantum efficiency measurements of the charge-transfer state and solid-state two-dimensional (2D) (13)C{(1)H} heteronuclear correlation (HETCOR) NMR analyses support that a specific polymer:fullerene arrangement is present for the highest performing PBDTTPD derivative, in which the fullerene is in closer proximity to the acceptor moiety of the polymer. This work demonstrates that the polymer:fullerene arrangement and resulting intermolecular interactions may be key factors in determining the performance of OPV material systems.

The structures and properties of membrane proteins in lipid bilayers are expected to closely resemble those in native cell-membrane environments, although they have been difficult to elucidate. By performing solid-state NMR measurements at very fast (100 kHz) magic-angle spinning rates and at high (23.5 T) magnetic field, severe sensitivity and resolution challenges are overcome, enabling the atomic-level characterization of membrane proteins in lipid environments. This is demonstrated by extensive 1H-based resonance assignments of the fully protonated heptahelical membrane protein proteorhodopsin, and the efficient identification of numerous 1H–1H dipolar interactions, which provide distance constraints, inter-residue proximities, relative orientations of secondary structural elements, and protein–cofactor interactions in the hydrophobic transmembrane regions. These results establish a general approach for high-resolution structural studies of membrane proteins in lipid environments via solid-state NMR.

The diverse functionalities of membrane proteins (MPs) have garnered much interest in leveraging these biomolecules for technological applications. One challenge of studying MPs in artificial micellar surfactant environments is that many factors modulate their structures and functionalities, including the surfactants that interact with the MP or their assembly into oligomers. As oligomerization offers a means by which MPs could selectively interact among the copious environmental factors in biological environments, we hypothesized that MP function is predominantly modified by oligomerization rather than interactions with local surfactants that, by comparison, largely interact with MPs nonspecifically. To test this, we study the light-activated proton pump proteorhodopsin (PR) in micellar surfactant solutions because it is functionally active in monomeric and oligomeric forms, the light-activated functionalities of which can be assessed in detail. The surfactant composition and oligomerization are correlated with PR function, as measured by the protonation behaviors of aspartic acid residue 97, which mediates light-activated proton transport, and the associated photocycle kinetics. The results demonstrate that oligomerization dominantly mediates PR function in different surfactant environments, whereas some surfactants can subtly modulate proton-pumping kinetics. This work underscores the importance of understanding and controlling oligomerization of MPs to study and exploit their function.

The local electric field distribution and the effect of surface-enhanced Raman spectroscopy (SERS) were investigated on the quasi-3D (Q3D) plasmonic nanostructures formed by gold nanohole and nanodisc array layers physically separated by a dielectric medium. The local electric fields at the top gold nanoholes and bottom gold nanodiscs as a function of the dielectric medium, substrate, and depth of Q3D plasmonic nanostructures upon the irradiation of a 785 nm laser were calculated using the three-dimensional finite-difference time-domain (3D-FDTD) method. The intensity of the maximum local electric fields was shown to oscillate with the depth and the stronger local electric fields occurring at the top or bottom gold layer strongly depend on the dielectric medium, substrate, and depth of the nanostructure. This phenomenon was determined to be related to the Fabry-Pérot interference effect and the interaction of localized surface plasmons (LSPs). The enhancement factors (EFs) of SERS obtained from the 3D-FDTD simulations were compared to those calculated from the SERS experiments conducted on the Q3D plasmonic nanostructures fabricated on silicon and ITO coated glass substrates with different depths. The same trend was obtained from both methods. The capabilities of tuning not only the intensity but also the location of the maximum local electric fields by varying the depth, dielectric medium, and substrate make Q3D plasmonic nanostructures well suited for highly sensitive and reproducible SERS detection and analysis.

The outer membrane of a bacterium is composed of chemical and biological components that carry specific molecular information related to strains, growth stages, expressions to stimulation, and maybe even geographic differences. In this work, we demonstrate that the biochemical information embedded in the outer membrane can be used for rapid detection and identification of pathogenic bacteria using surface-enhanced Raman spectroscopy (SERS). We used seven different strains of the marine pathogen Vibrio parahaemolyticus as a model system. The strains represent four genetically distinct clades isolated from clinical and environmental sources in Washington, U.S.A. The unique quasi-3D (Q3D) plasmonic nanostructure arrays, optimized using finite-difference time-domain (FDTD) calculations, were used as SERS-active substrates for sensitive and reproducible detection of these bacteria. SERS barcodes were generated on the basis of SERS spectra and were used to successfully detect individual strains in both blind samples and mixtures. The sensing and detection methods developed in this work could have broad applications in the areas of environmental monitoring, biomedical diagnostics, and homeland security.

A versatile synthetic protocol is reported that allows high concentrations of functionally active membrane proteins to be incorporated in mesostructured silica materials. Judicious selections of solvent, surfactant, silica precursor species, and synthesis conditions enable membrane proteins to be stabilized in solution and during subsequent co-assembly into silica-surfactant composites with nano- and mesoscale order. This was demonstrated by using a combination of non-ionic (n-dodecyl-β-D-maltoside or Pluronic P123), lipid-like (1,2-diheptanoyl-s,n-gycero-3-phosphocholine), and perfluoro-octanoate surfactants under mild acidic conditions to co-assemble the light-responsive transmembrane protein proteorhodopsin at concentrations up to 15 wt% into the hydrophobic regions of worm-like mesostructured silica materials in films. Small-angle X-ray scattering, electron paramagnetic resonance spectroscopy, and transient UV-visible spectroscopy analyses established that proteorhodopsin molecules in mesostructured silica films exhibited native-like function, as well as enhanced thermal stability compared to surfactant or lipid environments. The light absorbance properties and light-activated conformational changes of proteorhodopsin guests in mesostructured silica films are consistent with those associated with the native H+-pumping mechanism of these biomolecules. The synthetic protocol is expected to be general, as demonstrated also for the incorporation of functionally-active cytochrome c, a peripheral membrane protein enzyme involved in electron transport, into mesostructured silica-cationic surfactant films.

Protein-catalyzed capture agents (PCCs) are synthetic and modular peptide-based affinity agents that are developed through the use of single generation in situ click chemistry screens against large peptide libraries. In such screens, the target protein, or a synthetic epitope fragment of that protein, provides a template for selectively promoting the non-copper catalyzed azide-alkyne dipolar cycloaddition click reaction between either a library peptide and a known ligand, or a library peptide and the synthetic epitope. The development of epitope-targeted PCCs was motivated by the desire to fully generalize pioneering work from the Sharpless and Finn groups in which in situ click screens were used to develop potent, divalent enzymatic inhibitors. In fact, a large degree of generality has now been achieved. Various PCCs have demonstrated utility for selective protein detection, as allosteric or direct inhibitors, as modulators of protein folding, and as tools for in vivo tumor imaging. We provide a historical context for PCCs, and place them within the broader scope of biological and synthetic aptamers. The development of PCCs is presented as: (i) Generation I PCCs, which are branched ligands engineered through an iterative, non-epitope targeted process, and (ii) Generation II PCCs, which are typically developed from macrocyclic peptide libraries and are precisely epitope targeted. We provide statistical comparisons of Generation II PCCs relative to monoclonal antibodies in which the protein target is the same. Finally, we discuss current challenges and future opportunities of PCCs.