Crown‐Shaped Tungstogermanates as Solvent‐Controlled Dual Systems in the Formation of Vesicle‐Like Assemblies

Reaction of early lanthanides, GeO₂, and Na₂WO₄ in a NaOAc buffer results in large crown‐shaped polyoxometalates based on [Ln₂GeW₁₀O₃₈]^6? subunits. By using Ni²⁺ as a crystallizing agent, [Na?Ln₁₂Ge₆W₆₀O₂₂₈(H₂O)₂₄]^35? ( Na?Ln₁₂ ) hexamers formed by alternating β(1,5)/β(1,8) subunits were obtained for Ln=Pr, Nd. The addition of K⁺ led to a similar anion for Ln=Sm, namely, [K?Sm₁₂Ge₆W₆₀O₂₂₈(H₂O)₂₂]^35? ( K?Sm₁₂ ) and [K?K₇Ln₂₄Ge₁₂W₁₂₀O₄₄₄(OH)₁₂(H₂O)₆₄]^52? ( K?Ln₂₄ ) dodecamers that consist of a central core identical to K?Sm₁₂ decorated with six external γ(3,4) subunits for Ln=Pr, Nd. These anions dissociate in water into hexameric cores and monomeric entities, as shown by ESI mass spectrometry. The former self‐assemble into spherical, hollow, and single‐layered blackberry‐type structures with radii of approximately 75 nm, as monitored by laser light scattering (LLS) and TEM techniques. Analogous studies performed for K?Nd₂₄ in water/acetone mixtures show that the dodecamers remain stable and form in turn their own type of blackberries with sizes that increase from approximately 20 to 50 nm with increasing acetone content. This control over both the composition and size of the vesicle‐like assemblies is achieved for the first time by modifying the architecture of the species that undergoes supramolecular association through the solvent polarity.     

Glucose Oxidase and Glucose for Redox‐Initiating the Free Radical Copolymerization of N‐(ferrocenoylmethyl)acrylamide in Aqueous Cyclodextrin Solution

The glucose oxidase and glucose mediated formation of amphipilic copolymers of N‐(ferrocenoylmethyl)acrylamide (NFMA) and N,N‐diethylacrylamide (DEA) in aqueous cyclodextrin solution is presented. Thereby, NFMA is not only a comonomer but also part of the redox initiation system. The obtained copolymers contain NFMA units between 1 and 10 mol%. The molecular masses of the copolymers are dependent on the ferrocene content, whereupon molecular weights between 38 000 and 71 000 g mol⁻¹ are achieved.

     

Syntheses and Molecular Structures of [(thf)4Li] [{(thf)Li}M(C4H8)3] (M = Zr,Hf) and Their Solution Behavior

The reaction of MCl₄(thf)₂ (M = Zr, Hf) with 1,4-dilitiobutane in diethyl ether at –25 °C or at 0 °C with a molar ratio of 1 : 3 yields the homoleptic “ate” complexes [(thf)₄Li] [{(thf)Li}M(C₄H₈)₃] 1 - Zr (M = Zr) and 1 - Hf (M = Hf). The crystalline compounds form ion lattices with solvent-separated [(thf)₄Li]⁺ cations and [{(thf)Li}M(C₄H₈)₃]^– anions. The NMR spectra at –20 °C show magnetic equivalence of the M–CH₂ and of the β-CH₂ groups of the butane-1,4-diide ligands on the NMR time scale. Analogous reactions of MCl₄(thf)₂ with 1,4-dilithiobutane with a molar ratio of 1 : 2 proceed unclear. However, single crystals of [Li(thf)₄] [HfCl₅(thf)] ( 2 ) can be isolated with the hafnium atom in a distorted octahedral coordination sphere of five chloro and one thf ligand. NMR spectra allow to elucidate the time-dependent degradation of 1-Hf and 1-Zr in THF and toluene at 25 °C via THF cleavage. Addition of tmeda to a solution of 1-Zr allows the isolation of intermediately formed [{(tmeda)Li}₂Zr(nBu)₂(C₄H₈)₂] ( 3 ).     

Exciton correlations and input–output relations in non-equilibrium exciton superfluids

The photoluminescence (PL) measurements on photons and the transport measurements on excitons are the two types of independent and complementary detection tools to search for possible exciton superfluids in electron–hole semi-conductor bilayer systems. In fact, it was believed that the transport measurements can provide more direct evidences on superfluids than the spectroscopic measurements. It is important to establish the relations between the two kinds of measurements. In this paper, using quantum Heisenberg–Langevin equations, we establish such a connection by calculating various exciton correlation functions in the putative exciton superfluids. These correlation functions include both normal and anomalous greater, lesser, advanced, retarded, and time-ordered exciton Green functions and also various two exciton correlation functions. We also evaluate the corresponding normal and anomalous spectral weights and the Keldysh distribution functions. We stress the violations of the fluctuation and dissipation theorem among these various exciton correlation functions in the non-equilibrium exciton superfluids. We also explore the input–output relations between various exciton correlation functions and those of emitted photons such as the angle resolved photon power spectrum, phase sensitive two mode squeezing spectrum and two photon correlations. Applications to possible superfluids in the exciton–polariton systems are also mentioned. For a comparison, using conventional imaginary time formalism, we also calculate all the exciton correlation functions in an equilibrium dissipative exciton superfluid in the electron–electron coupled semi-conductor bilayers at the quantum Hall regime at the total filling factor ν_T=1${\nu }_T=1$. We stress the analogies and also important differences between the correlations functions in the two exciton superfluid systems.     

Self‐Recognition Between Two Almost Identical Macroions During Their Assembly: The Effects of pH and Temperature

Two Keplerate‐type macroions, [Mo^VI₇₂Fe^III₃₀O₂₅₂‐ (CH₃COO)₁₂{Mo₂O₇(H₂O)}₂{H₂Mo₂O₈(H₂O)}(H₂O)₉₁]?ca. 150 H₂O= {Mo₇₂Fe₃₀} and [{Na(H₂O)₁₂}?{Mo^VI₇₂Cr^III₃₀O₂₅₂(CH₃COO)₁₉‐ (H₂O)₉₄}]?ca. 120 H₂O= {Mo₇₂Cr₃₀} , with identical size and shape but different charge density, can self‐assemble into spherical “blackberry”‐like structures in aqueous solution by means of electrostatic interactions. These two macroanions can self‐recognize each other and self‐assemble into two separate types of homogeneous blackberries in their mixed dilute aqueous solution, in which they carry ?7 and ?5 net charges, respectively. Either adjusting the solution pH or raising temperature is expected to make the self‐recognition more difficult, by making the charge densities of the two clusters closer, or by decreasing the activation energy barrier for the blackberry formation, respectively. Amazingly, the self‐recognition behavior remains, as confirmed by dynamic and static light scattering, TEM, and energy dispersive spectroscopy techniques. The results prove that the self‐recognition behavior of the macroions due to the long‐range electrostatic interaction is universal and can be achieved when only minimum differences exist between two types of macroanions.     

Photodecarboxylative additions of phenoxyacetates to N-methylphthalimide

Photoaddition of various phenoxyacetates to N-methylphthalimide affords the corresponding hydroxyphthalimidines in yields of 21-93%. The diastereoselectivity of the intermolecular addition is studied for a series of 2-substituted phenoxyacetates with low diastereoselectivities being observed. Comparison experiments with anisole and ether-containing phthalimide confirm that the crucial electron-transfer step occurs from the carboxylate functionality.     

The determination of protein phosphorylation on electrophoresis gel blots by laser ablation inductively coupled plasma-mass spectrometry

Laser ablation interfaced with inductively coupled plasma-mass spectrometry is described as a new method to determine the presence of phosphorylated proteins on electrophoresis gel blots. The method was applied to the phosphoprotein beta-casein with good detection levels being observed at 16 pmole. Attempts at using the technique to detect beta-casein on electrophoresis gels are also described.     

Photodecarboxylative cyclizations of ω-phthalimido-ortho-phenoxy carboxylates

ω-Phthalimido-ortho-phenoxy carboxylates efficiently undergo photodecarboxylative cyclizations in reasonable to good yields of 12-75%. Although the photocyclization efficiency decreases with increasing carbon chain lengths, target ring sizes up to 15 are successfully realized. Likewise, intermolecular photodecarboxylative additions of ω-phenoxy carboxylates to N-methyl phthalimide give hydroxyphthalimidines in yields of 45-73%.     

Origin of the unusual kinetics of iron deposition in human H-chain ferritin

From microorganisms to humans, ferritin plays a central role in the biological management of iron. The ferritins function as iron storage and detoxification proteins by oxidatively depositing iron as a hydrous ferric hydroxide mineral core within their shell-like structures. The mechanism by which the mineral core is formed has been the subject of intense investigation for many years. A diiron ferroxidase site located on the H-chain subunit of vertebrate ferritins catalyzes the oxidation of Fe(II) to Fe(III) by molecular oxygen. A previous stopped-flow kinetics study of a transient mu-peroxodiFe(III) intermediate formed at this site revealed very unusual kinetics curves, the shape of which depended markedly on the amount of iron presented to the protein. In the present work, a mathematical model for catalysis is developed that explains the observed kinetics. The model consists of two sequential mechanisms. In the first mechanism, turnover of iron at the ferroxidase site is rapid, resulting in steady-state production of the peroxo intermediate with continual formation of the mineral core until the available Fe(II) in solution is consumed. At this point, the second mechanism comes into play whereby the peroxo intermediate decays and the ferroxidase site is postulated to vacate its complement of iron. The kinetic data reveal for the first time that Fe(II) in excess of that required to saturate the ferroxidase site promotes rapid turnover of Fe(III) at this site and that the ferroxidase site plays a role in catalysis at all levels of iron loading of the protein (48-800 Fe/protein). The data also provide evidence for a second intermediate, a putative hydroperoxodiFe(III) complex, that is a decay product of the peroxo intermediate.