Intracellular Assembly of Interacting Enzymes Yields Highly‐Active Nanoparticles for Flow Biocatalysis

All-enzyme hydrogel (AEH) particles with a hydrodynamic diameter of up to 120 nm were produced intracellularly with an Escherichia coli-based in vivo system. The inCell-AEH nanoparticles were generated from polycistronic vectors enabling simultaneous expression of two interacting enzymes, the Lactobacillus brevis alcohol dehydrogenase (ADH) and the Bacillus subtilis glucose-1-dehydrogenase (GDH), fused with a SpyCatcher or SpyTag, respectively. Formation of inCell-AEH was analyzed by dynamic light scattering and atomic force microscopy. Using the stereoselective two-step reduction of a prochiral diketone substrate, we show that the inCell-AEH approach can be advantageously used in whole-cell flow biocatalysis, by which flow reactors could be operated for >4 days under constant substrate perfusion. More importantly, the inCell-AEH concept enables the recovery of efficient catalyst materials for stable flow bioreactors in a simple and economical one-step procedure from crude bacterial lysates. We believe that our method will contribute to further optimization of sustainable biocatalytic processes

Superdeformation in Asymmetric N>>Z Nucleus 40^{40}Ar

A rotational band with five $\gamma$-ray transitions ranging from 2$^{+}$ to 12$^{+}$ states was identified in $^{40}$Ar. This band is linked through $\gamma$ transitions from the excited 2$^{+}$, 4$^{+}$ and 6$^{+}$ levels to the low-lying states; this determines the excitation energy and the spin-parity of the band. The deduced transition quadrupole moment of 1.45$^{+0.49}_{-0.31} eb$ indicates that the band has a superdeformed shape. The nature of the band is revealed by cranked Hartree--Fock--Bogoliubov calculations and a multiparticle--multihole configuration is assigned to the band

Synthesis and structure of tricarbonylchromium mono-, bis- and tris-complexes of 10-methyltribenzotriquinacene

Ceccon A, Gambaro A, Manoli F, et al. Synthesis and structure of tricarbonylchromium mono-, bis- and tris-complexes of 10-methyltribenzotriquinacene. Journal of the Chemical Society, Perkin Transactions 2, Physical Organic Chemistry. 1991;2(2):233-241.Complexation of 10-methyltribenzotriquinacene (MTBT) a bent triarene of C3v symmetry afforded six mono-, bis- and tris-Cr(CO)3complexed isomers which have been isolated and identified. The results of various synthetic experiments indicate that complexation at the convex side of a free benzene ring is favoured, probably for steric reasons. As compared with the isomer complexed at the convex face (anti), that complexed at the concave one (syn) is less stable. The 1H and 13C NMR spectral data together with the X-ray structures of the two bis- and one tris-complexes account for the lower stability of the syn isomers

Photochemistry of the Permanganate Ion in Low-Temperature Frozen Matrices

Photolysis of the permanganate anion, MnO₄^–, in tetralkylammonium tetrafluoroborate matrices at 85 K results in formation of a single product, the metastable manganese­(V) peroxo complex MnO₂(η²-O₂)⁻. Although previously unobserved, this peroxo species has been postulated to be an intermediate in the photodecomposition of permanganate, yielding O₂ and MnO₂^–. Results from variable-temperature and intensity-dependence photolysis experiments in solution, however, suggest that MnO₂(η²-O₂)⁻ does not lose O₂ thermally or photochemically and is not an intermediate in the photodecomposition reaction. A mechanism is proposed in which MnO₂(η²-O₂)⁻ is formed through vibrational relaxation of an excited [MnO₄^–]* species, which may also follow an alternative relaxation pathway that results in the formation of MnO₂^– and O₂ photodecomposition products

Role of a Metal–Metal Bonded Dimer Dication in the One-Electron Oxidation of Rh(η⁵‑C₅H₅)(CO)(PPh₃) and Related Compounds

The anodic oxidation mechanism of RhCp­(CO)­(PPh₃), <b>1</b>, has been studied in CH₂Cl₂/0.1 M [NBu₄]­[PF₆]. This complex and its analogue RhCp­(PPh₃)₂ had been previously shown to form the fulvalenyl dirhodium complexes [Rh₂FvL₂(PPh₃)₂]²⁺ (Fv = (η⁵,η⁵-C₁₀H₈), L = CO (<b>2</b>²⁺) or PPh₃) upon chemical oxidation. The present work investigated the reaction of <b>1</b> by variable-temperature electrochemistry and IR spectroelectrochemistry. The radical cation <b>1</b>⁺ initially undergoes a radical–radical coupling reaction, giving the metal–metal bonded dimer dication [Rh₂Cp₂(CO)₂(PPh₃)₂]²⁺ (<b>5</b>²⁺), which dominates at low temperatures. The room-temperature products are best accounted for by hydrogen atom transfer reactions of the dimer dication, affording <b>2</b>²⁺ and the metal hydride [RhCp­(CO)­(PPh₃)­H]⁺. The dimetalate complex [Rh₂(σ:η⁵-C₅H₄)₂(CO)₂(PPh₃)₂]²⁺ (<b>7</b>) may also be formed. The radical cation of the analogue RhCp­(CO)­(PPh₂Me) (<b>3</b>) undergoes very rapid formation of a similar metal–metal bonded dimer. A derivative with a large cone angle phosphine, RhCp­(CO)­(PⁱPr₃) (<b>4</b>), does not show the same tendency toward oxidative dimerization. The monomer/dimer equilibrium [RhCp­(CO)­L]⁺ ⇌ 1/2 [Rh₂Cp₂(CO)₂L₂]²⁺ increasingly favors the dimer in the sequence L = PⁱPr₃ < PPh₃ < PPh₂Me < PMe₃, P­(OPh)₃, the latter two being based on earlier work. The implied dinuclear hydrogen atom transfer reactions are not mechanistically well understood, but find analogies in the chemistry of second- and third-row early transition metal complexes