A photoenhanced oxidation of amino acids and the cross-linking of lysozyme mediated by tetrazolium salts

A Spidroin-Inspired Hierarchical-Structure Binder Achieves Highly Integrated Silicon-Based Electrodes

As a promising component for next-generation high-energy lithium-ion batteries, silicon-based electrodes have attracted increasing attention by virtue of their ultrahigh theoretical specific capacities. Nevertheless, fast capacity fading posed by tremendous silicon-based electrode volume changes during cycling remains a huge challenge before large-scale applications. In this work, an aqueous-oil binary solution based blend (AOB) binder characterized by a spidroin-like hierarchical structure for tolerating the huge volume changes of silicon-based electrodes is developed. In the AOB binder, the polymer, containing hydrophobic tetrazole groups, denoted as PPB, and the water-soluble amorphous poly(acrylic acid), mimick the β-sheet and α-helix structure of spidroin, respectively. Benefitting from such biomimetic design, the AOB binder enables both high tensile strength and elasticity, and strong electrode adhesion, therefore apparently stabilizing the silicon-based electrode structure and rendering prolonged electrode cycle life. Such a strategy endows 3.3 Ah soft package cells assembled with Si/C composite anode and NCM811 cathode with a discharge specific capacity of 2.92 Ah after 700 cycles. This work marks a milestone in developing state-of-the-art silicon-based electrodes toward high-energy-density lithium-battery applications.

Sensitivity of Isomerization Kinetics of 1,3,5-Triphenylformazan on Cosolvents Added to Toluene

Formazan molecules exhibit photochromism because isomerization processes following excitation may occur in both the azo group and the hydrazone group; thus, each formazan may be present in various forms with different colors. The ratio of these forms depends on the illumination conditions and the environment of the formazan with a most incisive sensibility of the thermal anti-syn relaxation of the C═N toward slight traces of impurities in toluene solutions, as reported most prominently for 1,3,5-triphenylformazan. Here, we study the latter compound with transient absorption spectroscopy to investigate the role of these traces by adding small amounts of both protic and aprotic cosolvents. Whereas the activation barrier decreases if the binary solvent mixture has a higher polarity, the role of hydrogen bonding can have a reverse impact on the thermal isomerization rate. Both the addition of an aprotic cosolvent and the addition of a protic cosolvent can slow the reaction due to their hydrogen-bond accepting and hydrogen-bond donating properties, respectively. In the case of methanol as a cosolvent, this effect outweighed that of the polarity increase for small concentrations, which was not observed for the fluorinated alcohol hexafluoroisopropanol. The results are explained in the context of a competition between solute-cosolvent and cosolvent-cosolvent hydrogen bonding.

Picosecond excited-state lifetimes of protonated indazole and benzimidazole: The role of the N-N bond

Certain chemical groups give rise to characteristic excited-state deactivation mechanisms. Here, we target the role of a protonated N-N chemical group in the excited-state deactivation of protonated indazole by comparison to its isomer that lacks this group, protonated benzimidazole. Gas-phase protonated indazole and protonated benzimidazole ions are investigated at room temperature using picosecond laser pump-probe photodissociation experiments in a linear ion-trap. Excited state lifetimes are measured across a range of pump energies (4.0-5.4 eV). The ¹ππ* lifetimes of protonated indazole range from 390 ± 70 ps using 4.0 eV pump energy to ≤18 ps using 4.6 eV pump energy. The ¹ππ* lifetimes of protonated benzimidazole are systematically longer, ranging from 3700 ± 1100 ps at 4.6 eV pump energy to 400 ± 200 ps at 5.4 eV. Based on these experimental results and accompanying quantum chemical calculations and potential energy surfaces, the shorter lifetimes of protonated indazole are attributed to πσ* state mediated elongation of the protonated N-N bond.

Integration of Mass Spectrometry Data for Structural Biology

Mass spectrometry (MS) is increasingly being used to probe the structure and dynamics of proteins and the complexes they form with other macromolecules. There are now several specialized MS methods, each with unique sample preparation, data acquisition, and data processing protocols. Collectively, these methods are referred to as structural MS and include cross-linking, hydrogen-deuterium exchange, hydroxyl radical footprinting, native, ion mobility, and top-down MS. Each of these provides a unique type of structural information, ranging from composition and stoichiometry through to residue level proximity and solvent accessibility. Structural MS has proved particularly beneficial in studying protein classes for which analysis by classic structural biology techniques proves challenging such as glycosylated or intrinsically disordered proteins. To capture the structural details for a particular system, especially larger multiprotein complexes, more than one structural MS method with other structural and biophysical techniques is often required. Key to integrating these diverse data are computational strategies and software solutions to facilitate this process. We provide a background to the structural MS methods and briefly summarize other structural methods and how these are combined with MS. We then describe current state of the art approaches for the integration of structural MS data for structural biology. We quantify how often these methods are used together and provide examples where such combinations have been fruitful. To illustrate the power of integrative approaches, we discuss progress in solving the structures of the proteasome and the nuclear pore complex. We also discuss how information from structural MS, particularly pertaining to protein dynamics, is not currently utilized in integrative workflows and how such information can provide a more accurate picture of the systems studied. We conclude by discussing new developments in the MS and computational fields that will further enable in-cell structural studies.