Synthesis and Crystal Structure of Li⁺@Fluoreno[60]fullerene: Effect of Encapsulated Lithium Ion on Electrochemistry of Spiroannelated Fullerene

The reaction of [Li⁺@C₆₀]­TFSI^– (TFSI = bis­(trifluoromethanesulfonyl)­imide) with 9-diazofluorene directly produced a [6,6]-adduct of lithium-ion-containing fluoreno[60]­fullerene, [6,6]-[Li⁺@C₆₀(fluoreno)]­TFSI^–, which was crystallographically characterized. Cyclic voltammetry of the compound showed a reversible one-electron reduction wave at −0.51 V (vs Fc/Fc⁺) and an irreversible reduction wave for the second electron. The latter was attributed to opening of the three-membered ring due to strong stabilization of the resulting sp³-carbanion by the encapsulated Li⁺ and formation of a 14π-electron aromatic fluorenyl anion

Pentacyclic triterpene acids, rotungenic acid and barbinervic acid, from fresh leaves of <i>Diospyros kaki</i> Thunberg and their glutaminase inhibitory activities

Glutaminase is an important target that is often over-expressed in neurodegenerative and lifestyle-related diseases but few effective inhibitors of this enzyme have yet reached clinical trials. Three compounds isolated from fresh leaves of Diospyros kaki Thunberg, ursolic acid (1), rotungenic acid (2) and barbinervic acid (3), were identified by analyzing their NMR and MS spectral data and comparison of these with reported data. The IC50 values of 1-3 and 6-diazo-5-oxo-L-norleucine (DON) as control were 775, 13, 14, and 434 μM, respectively. Compounds 2 and 3 showed higher glutaminase inhibitory activities than DON. Compounds 2 and 3 may serve as potential lead compounds for the prevention and treatment of neurodegenerative and lifestyle-related diseases by targeting glutaminase. This is the first report on glutaminase inhibitory activities of 2 and 3.</p

Crystallographic information file of [Li+@C60−](NiOEP)∙CH2Cl2 at 400 K from Structure of [60]fullerene with mobile lithium cation inside

Crystallographic information file of [Li+@C60−](NiOEP)∙CH2Cl2 at 400

Crystallographic information file of [Li+@C60](TFPB−)∙C4H10O at 260 K from Structure of [60]fullerene with mobile lithium cation inside

Crystallographic information file of [Li+@C60](TFPB−)∙C4H10O at 260

Crystallographic information file of [Li+@C60](TFSI−)∙CH2Cl2 at 150 K from Structure of [60]fullerene with mobile lithium cation inside

Crystallographic information file of [Li+@C60](TFSI−)∙CH2Cl2 at 150

Kinetic Study of the Diels–Alder Reaction of Li⁺@C₆₀ with Cyclohexadiene: Greatly Increased Reaction Rate by Encapsulated Li⁺

We studied the kinetics of the Diels–Alder reaction of Li⁺-encapsulated [60]­fullerene with 1,3-cyclohexadiene and characterized the obtained product, [Li⁺@C₆₀(C₆H₈)]­(PF₆^–). Compared with empty C₆₀, Li⁺@C₆₀ reacted 2400-fold faster at 303 K, a rate enhancement that corresponds to lowering the activation energy by 24.2 kJ mol^–1. The enhanced Diels–Alder reaction rate was well explained by DFT calculation at the M06-2X/6-31G­(d) level of theory considering the reactant complex with dispersion corrections. The calculated activation energies for empty C₆₀ and Li⁺@C₆₀ (65.2 and 43.6 kJ mol^–1, respectively) agreed fairly well with the experimentally obtained values (67.4 and 44.0 kJ mol^–1, respectively). According to the calculation, the lowering of the transition state energy by Li⁺ encapsulation was associated with stabilization of the reactant complex (by 14.1 kJ mol^–1) and the [4 + 2] product (by 5.9 kJ mol^–1) through favorable frontier molecular orbital interactions. The encapsulated Li⁺ ion catalyzed the Diels–Alder reaction by lowering the LUMO of Li⁺@C₆₀. This is the first detailed report on the kinetics of a Diels–Alder reaction catalyzed by an encapsulated Lewis acid catalyst rather than one coordinated to a heteroatom in the dienophile

Molecular Mechanism of ATP Hydrolysis in F₁-ATPase Revealed by Molecular Simulations and Single-Molecule Observations

Enzymatic hydrolysis of nucleotide triphosphate (NTP) plays a pivotal role in protein functions. In spite of its biological significance, however, the chemistry of the hydrolysis catalysis remains obscure because of the complex nature of the reaction. Here we report a study of the molecular mechanism of hydrolysis of adenosine triphosphate (ATP) in F₁-ATPase, an ATP-driven rotary motor protein. Molecular simulations predicted and single-molecule observation experiments verified that the rate-determining step (RDS) is proton transfer (PT) from the lytic water molecule, which is strongly activated by a metaphosphate generated by a preceding P_γ–O_β bond dissociation (POD). Catalysis of the POD that triggers the chain activation of the PT is fulfilled by hydrogen bonds between Walker motif A and an arginine finger, which commonly exist in many NTPases. The reaction mechanism unveiled here indicates that the protein can regulate the enzymatic activity for the function in both the POD and PT steps despite the fact that the RDS is the PT step

Common Evolutionary Origin for the Rotor Domain of Rotary Atpases and Flagellar Protein Export Apparatus

<div><p>The V₁- and F₁- rotary ATPases contain a rotor that rotates against a catalytic A₃B₃ or α₃β₃ stator. The rotor F₁-γ or V₁-DF is composed of both anti-parallel coiled coil and globular-loop parts. The bacterial flagellar type III export apparatus contains a V₁/F₁-like ATPase ring structure composed of FliI₆ homo-hexamer and FliJ which adopts an anti-parallel coiled coil structure without the globular-loop part. Here we report that FliJ of <i>Salmonella enterica</i> serovar Typhimurium shows a rotor like function in <i>Thermus thermophilus</i> A₃B₃ based on both biochemical and structural analysis. Single molecular analysis indicates that an anti-parallel coiled-coil structure protein (FliJ structure protein) functions as a rotor in A₃B₃. A rotary ATPase possessing an F₁-γ-like protein generated by fusion of the D and F subunits of V₁ rotates, suggesting F₁-γ could be the result of a fusion of the genes encoding two separate rotor subunits. Together with sequence comparison among the globular part proteins, the data strongly suggest that the rotor domains of the rotary ATPases and the flagellar export apparatus share a common evolutionary origin.</p> </div