Redox Shuttles with Axisymmetric Scaffold for Overcharge Protection of Lithium‐Ion Batteries

The derivatives of 1,4‐dimethoxybenzene are thus far the best performing redox shuttle additives for overcharge protection of Li‐ion batteries. The most durable molecules of this kind typically possess two in‐plane methoxy groups that are equivalent by inversion symmetry. However, such geometry leads to a vanishing average dipole moment that causes poor solubility of these molecules in carbonate‐based electrolytes. In this study, a novel redox shuttle additive, 1,2,3,4‐tetrahydro‐6,7‐dimethoxy‐1,1,4,4‐tetramethyl‐naphthalene (TDTN), is introduced. It has been demonstrated that reversible oxidation at 4.05 V versus Li⁺/Li, high polarity, high solubility (around 0.4 m ), and excellent electrochemical stability (150 overcharge cycles at C/2 rate with 100% overcharge) can all be achieved simultaneously by the imposition of axial symmetry in the corresponding radical cation that is generated by electrochemical oxidation of TDTN in the battery. The intricate interplay between the symmetry and the chemical stability of the radical cation is scrutinized using magnetic resonance spectroscopy and electron structure modeling.     

Corolla chirality does not contribute to directed pollen movement in Hypericum perforatum (Hypericaceae): mirror image pinwheel flowers function as radially symmetric flowers in pollination

Corolla chirality, the pinwheel arrangement of petals within a flower, is found throughout the core eudicots. In 15 families, different chiral type flowers (i.e., right or left rotated corolla) exist on the same plant, and this condition is referred to as unfixed/enantiomorphic corolla chirality. There are no investigations on the significance of unfixed floral chirality on directed pollen movement even though analogous mirror image floral designs, for example, enantiostyly, has evolved in response to selection to direct pollinator and pollen movement. Here, we examine the role of corolla chirality on directing pollen transfer, pollinator behavior, and its potential influence on disassortative mating. We quantified pollen transfer and pollinator behavior and movement for both right and left rotated flowers in two populations of Hypericum perforatum. In addition, we quantified the number of right and left rotated flowers at the individual level. Pollinators were indifferent to corolla chirality resulting in no difference in pollen deposition between right and left flowers. Corolla chirality had no effect on pollinator and pollen movement between and within chiral morphs. Unlike other mirror image floral designs, corolla chirality appears to play no role in promoting disassortative mating in this species.     

Predicting the functional motions of p97 using symmetric normal modes

p97 is a protein complex of the AAA+ family. Although functions of p97 are well understood, the mechanism by which p97 performs its unfolding activities remains unclear. In this work, we present a novel way of applying normal mode analysis to study this six‐fold symmetric molecular machine. By selecting normal modes that are axial symmetric and give the largest movements at D1 or D2 pore residues, we are able to predict the functional motions of p97, which are then validated by experimentally observed conformational changes. Our results shed light and provide new understandings on several key steps of the p97 functional process that were previously unclear or controversial, and thus are able to reconcile multiple previous findings. Specifically, our results reveal that (i) a venous valve‐like mechanism is used at D2 pore to ensure a one‐way exit‐only traffic of substrates; (ii) D1 pore remains shut during the functional process; (iii) the “swing‐up” motion of the N domain is closely coupled with the vertical motion of the D1 pore along the pore axis; (iv) because of the shut D1 pore and the one‐way traffic at D2 pore, it is highly likely that substrates enter the chamber through the gaps at the D1/D2 interface. The limited chamber volume inside p97 suggests that a substrate may be pulling out from D2 while at the same time being pulling in at the interface; (v) lastly, p97 uses a series of actions that alternate between twisting and pulling to remove the substrate. Proteins 2016; 84:1823–1835. © 2016 Wiley Periodicals, Inc.     

Synthesis and Application of C2 and C3 Symmetric (R)‐Phenylglycinol‐Derived Chiral Stationary Phases

A C3 symmetric (R)‐phenylglycinol N‐1,3,5‐benzenetricarboxylic acid‐derived chiral stationary phase (CSP) and three C2 symmetric (R)‐phenylglycinol CSPs were newly synthesized using o‐, m‐, and p‐phthaloyl dichlorides. © 2016 Wiley Periodicals, Inc. These CSPs were used to compare the resolution of 25 chiral samples using a previously reported 3,5‐dinitrobenzoyl (R)‐phenylglycinol‐derived CSP. Even though all CSPs have the same chiral moiety, the C3 symmetric CSP showed the best resolution. Chirality 28:186–191, 2016.© 2016 Wiley Periodicals, Inc.     

Regulated Activation of the PAR Polarity Network Ensures a Timely and Specific Response to Spatial Cues

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Enhancement of tomogram interpretability using the locked self-rotation function

The interpretation of cryo-electron tomograms of macromolecular complexes can be difficult because of the large amount of noise and because of the missing wedge effect. Here it is shown how the presence of rotational symmetry in a sample can be utilized to enhance the quality of a tomographic analysis. The orientation of symmetry axes in a sub-tomogram can be determined using a locked self-rotation function. Given this knowledge, the sub-tomogram density can then be averaged to improve its interpretability. Sub-tomograms of the icosahedral bacteriophage phiX174 are used to demonstrate the procedure.     

An easy NMR method to study the formation of parallel β-sheets in peptide aggregates

There is currently great interest in the study of peptide aggregation by -sheet formation because of its relevance in pathological states or in the design of self-assembling systems of technological interest. NMR studies of -sheet aggregates are difficult because of their long correlation times and spectral degeneracy. In this communication we demonstrate the combination of a semiselective TOCSY-NOESY experiment with partial deuterium exchange of labile protons to assign inter-molecular NOE cross peaks and prove the presence of a soluble parallel -sheet in fast exchange with monomeric Ac-ASTTTNYT-NH₂ (Ac-T-NH₂) in solution.     

Challenges in structure prediction of oligomeric proteins at the united-residue level: searching the multiple-chain energy landscape with CSA and CFMC

A revised version of the Conformational Space Annealing (CSA) global optimization method is developed, with three separate measures of structural similarity, in order to overcome the inability of a single distance measure to evaluate multiple-chain protein structures adequately. A second search method, Conformational Family Monte Carlo (CFMC), involving genetic-type moves, Monte Carlo-with-minimization perturbations, and explicit clustering of the population into conformational families, is adapted to treat multiple-chain proteins. These two methods are applied to two oligomeric proteins, the retro-GCN4 leucine zipper and the synthetic domain-swapped dimer. CFMC proves superior to CSA in its search for low-energy representatives of its conformational families, but both methods encounter difficulty in finding the native packing arrangements in the absence of native-like symmetry constraints, even when native monomers are present in the population.