Electron Transfer between Genetically Modified Hansenula polymorpha Yeast Cells and Electrode Surfaces via Os‐complex modified Redox Polymers

Graphite electrodes modified with redox‐polymer‐entrapped yeast cells were investigated with respect to possible electron‐transfer pathways between cytosolic redox enzymes and the electrode surface. Either wild‐type or genetically modified Hansenula polymorpha yeast cells over‐expressing flavocytochrome b2 (FC b₂) were integrated into Os‐complex modified electrodeposition polymers. Upon increasing the L ‐lactate concentration, an increase in the current was only detected in the case of the genetically modified cells. The overexpression of FC b₂ and the related amplification of the FC b₂/L ‐lactate reaction cycle was found to be necessary to provide sufficient charge to the electron‐exchange network in order to facilitate sufficient electrochemical coupling between the cells, via the redox polymer, to the electrode. The close contact of the Os‐complex modified polymer to the cell wall appeared to be a prerequisite for electrically wiring the cytosolic FC b₂/L ‐lactate redox activity and suggests the critical involvement of a plasma membrane redox system. Insights in the functioning of whole‐cell‐based bioelectrochemical systems have to be considered for the successful design of whole‐cell biosensors or microbial biofuel cells.     

Fabrication of a Highly Sensitive Glucose Biosensor Based on Immobilization of Osmium Complex and Glucose Oxidase onto Carbon Nanotubes Modified Electrode

In this research a novel osmium complex was used as electrocatalyst for electroreduction of oxygen and H₂O₂ in physiological pH solutions. Electroless deposition at a short period of time (60 s), was used for strong and irreversible adsorption of 1,4,8,12‐tetraazacyclotetradecane osmium(III) chloride (Os(III)LCl₂) ClO₄ onto single‐walled carbon nanotubes (SWCNTs) modified GC electrode. The modified electrode shows a pair of well defined and reversible redox couple, Os(IV)/Os(III) at wide pH range (1–8). The glucose biosensor was fabricated by covering a thin film of glucose oxidase onto CNTs/Os‐complex modified electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The fabricated biosensor shows high sensitivity, 826.3 nA μM^?1cm^?2, low detection limit, 56 nM, fast response time <3 s and wide calibration range 1.0 μM–1.0 mM. The biosensor has been successfully applied to determination of glucose in human plasma. Because of relative low applied potential, the interference from electroactive existing species was minimized, which improved the selectivity of the biosensor. The apparent Michaelis‐Menten constant of GOx on the nanocomposite, 0.91 mM, exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this glucose biosensor.     

Electrophilic Arene Hydroxylation and Phenol O?H Oxidations Performed by an Unsymmetric μ‐η1:η1‐O2‐Peroxo Dicopper(II) Complex

Reactions of the unsymmetric dicopper(II) peroxide complex [Cu^II₂(μ‐η¹:η¹‐O₂)(m‐XYL^N3N4)]²⁺ ( 1 O₂ , where m‐XYL is a heptadentate N‐based ligand), with phenolates and phenols are described. Complex 1 O₂ reacts with p‐X‐PhONa (X=MeO, Cl, H, or Me) at ?90 °C performing tyrosinase‐like ortho‐hydroxylation of the aromatic ring to afford the corresponding catechol products. Mechanistic studies demonstrate that reactions occur through initial reversible formation of metastable association complexes [Cu^II₂(μ‐η¹:η¹‐O₂)(p‐X‐PhO)(m‐XYL^N3N4)]⁺ ( 1 O₂ ?X‐PhO) that then undergo ortho‐hydroxylation of the aromatic ring by the peroxide moiety. Complex 1 O₂ also reacts with 4‐X‐substituted phenols p‐X‐PhOH (X=MeO, Me, F, H, or Cl) and with 2,4‐di‐tert‐butylphenol at ?90 °C causing rapid decay of 1 O₂ and affording biphenol coupling products, which is indicative that reactions occur through formation of phenoxyl radicals that then undergo radical C? C coupling. Spectroscopic UV/Vis monitoring and kinetic analysis show that reactions take place through reversible formation of ground‐state association complexes [Cu^II₂(μ‐η¹:η¹‐O₂)(X‐PhOH)(m‐XYL^N3N4)]²⁺ ( 1 O₂ ?X‐PhOH) that then evolve through an irreversible rate‐determining step. Mechanistic studies indicate that 1 O₂ reacts with phenols through initial phenol binding to the Cu₂O₂ core, followed by a proton‐coupled electron transfer (PCET) at the rate‐determining step. Results disclosed in this work provide experimental evidence that the unsymmetric 1 O₂ complex can mediate electrophilic arene hydroxylation and PCET reactions commonly associated with electrophilic Cu₂O₂ cores, and strongly suggest that the ability to form substrate?Cu₂O₂ association complexes may provide paths to overcome the inherent reactivity of the O₂‐binding mode. This work provides experimental evidence that the presence of a H⁺ completely determines the fate of the association complex [Cu^II₂(μ‐η¹:η¹‐O₂)(X‐PhO(H))(m‐XYL^N3N4)]ⁿ⁺ between a PCET and an arene hydroxylation reaction, and may provide clues to help understand enzymatic reactions at dicopper sites.     

Theoretical Study on Reactivity of Electron Transfer in Model—System of Oxidation of α—Amino Carbon—centered Radical by O2

Electron transfer reaction between a simplified model model molecule of α－amino carbon-centered radical and O2 has studied with ab initio calculations at the MP2/6-31 G^**//UHF/6-31 G^** level,The reactant complex and the ion pair complex have been optimized and employed to perform calculation of the reaction heat and the reorganization energy,Solvent effects have been considered by applyning the conductor-like screening model,Theoretical results show that the highly endothermic charge separation process ,in which one electron transfers from the α－amino carbon-centered radical to O2,so as to form an ion pair complex,is difficult to occur in gas-phase,By apply-ing an external electronic field to prepare the charge-locallized molecular orbitals,the charge-separated state has been obtained using the initial-guess-induced self-consistent field technique,The theoretical investigations indicate that the solvent effect in the process of the oxidation of α-animo carbon-centered radical by O2 is remarkable.From the rate constant estima-tion ,it can be predicted that the oxidation of the model donor molecule by O2 can proceed,but not very fast.A peroxyl radi-cal compound has been found to be a competitive intermediate in the oxidation process.     

Direct Electrochemistry of Multi‐Copper Oxidases at Carbon Nanotubes Noncovalently Functionalized with Cellulose Derivatives

This study describes the direct electron transfer of multi‐copper oxidases, i.e., laccase (from Trametes versicolor) and bilirubin oxidase (BOD, from Myrothecium verrucaria) at multiwalled carbon nanotubes (MWNTs) noncovalently functionalized with biopolymers of cellulose derivatives, i.e., hydroxyethyl cellulose (HEC), methyl cellulose (MC), and carboxymethyl cellulose (CMC). The functionalization of the MWNTs with the cellulose derivatives is found to substantially solubilize the MWNTs into aqueous media and to avoid their aggregation on electrode surface. Under anaerobic conditions, the redox properties of laccase and BOD are difficult to be defined with cyclic voltammetry at either laccase/MWNT‐modified or BOD/MWNT‐modified electrodes. The direct electron transfer properties of laccase and BOD are thus studied in terms of the bioelectrocatalytic activities of the laccase/MWNT‐modified and BOD/MWNT‐modified electrodes toward the reduction of oxygen and found to be facilitated at the functionalized MWNTs. The possible application of the laccase‐catalyzed O₂ reduction at the laccase/MWNT‐modified electrode is illustrated by constructing a CNT‐based ascorbate/O₂ biofuel cell with the MWNT‐modified electrode as the anode for the oxidation of ascorbate biofuel.     

A New Organic‐Inorganic Charge‐transfer Salt [C15H17N4]4[Mo8O26] — Synthesis,Properties and Crystal Structure

A new organic donor 3‐amino‐6‐dimethylamino‐2‐methyl‐phenazine was introduced to charge‐transfer complex with polyoxometalate. The complex [C₁₅H₁₇N₄]₄[Mo₈O₂₆] ( 1 ) was synthesized by hydrothermal reaction of neutral red chloride (3‐amino‐6‐dimethylamino‐2‐methyl‐phenazine hydrochloride) and (NH₄)₆[Mo₇O₂₄] · 4H₂O and was characterized by EPR, element analysis and single crystal x‐ray diffraction.     

A New Approach for the Photosynthetic Antenna–Reaction Center Complex with a Model Organized Around an s‐Triazine Linker

Two new artificial mimics of the photosynthetic antenna‐reaction center complex have been designed and synthesized (BDP‐H₂P‐C₆₀ and BDP‐ZnP‐C₆₀). The resulting electron‐donor/acceptor conjugates contain a porphyrin (either in its free‐base form (H₂P) or as Zn‐metalated complex (ZnP)), a boron dipyrrin (BDP), and a fulleropyrrolidine possessing, as substituent of the pyrrolidine nitrogen, an ethylene glycol chain terminating in an amino group C₆₀‐X‐NH₂ (X=spacer). In both cases, the three different components were connected by s‐triazine through stepwise substitution reactions of cyanuric chloride. In addition to the facile synthesis, the star‐type arrangement of the three photo‐ and redox‐active components around the central s‐triazine unit permits direct interaction between one another, in contrast to reported examples in which the three components are arranged in a linear fashion. The energy‐ and electron‐transfer properties of the resulting electron‐donor/acceptor conjugates were investigated by using UV/Vis absorption and emission spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. Comparison of the absorption spectra and cyclic voltammograms of BDP‐H₂P‐C₆₀ and BDP‐ZnP‐C₆₀ with those of BDP‐H₂P, BDP‐ZnP and BDP‐C₆₀, which were used as references, showed that the spectroscopic and electrochemical properties of the individual constituents are basically retained, although some appreciable shifts in terms of absorption indicate some interactions in the ground state. Fluorescence lifetime measurements and transient absorption experiments helped to elucidate the antenna function of BDP, which upon selective excitation undergoes a rapid and efficient energy transfer from BDP to H₂P or ZnP. This is then followed by an electron transfer to C₆₀, yielding the formation of the singlet charge‐separated states, namely BDP‐H₂P ^.+‐ C₆₀ ^.? and BDP‐ZnP ^.+‐ C₆₀ ^{. ?}. As such, the sequence of energy transfer and electron transfer in the present models mimics the events of natural photosynthesis.     

Acceleration of the single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride in water at 25 °C

The accelerated single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) in H₂O/tetrahydrofuran (THF) at 25 °C is reported. This process is catalyzed by sodium dithionite (Na₂S₂O₄)‐sodium bicarbonate (NaHCO₃). Electron transfer cocatalysts (ETC) 1,1′‐dialkyl‐4,4′‐bipyridinum dihalides or alkyl viologens were also employed in this polymerization. The resulting poly(vinyl chloride) (PVC) has a number‐average molecular weight (M_n) = 2,000–12,000, no detectable amounts of structural defects, and both active chloroiodomethyl and inactive chloromethyl chain ends. The molecular weight distribution of PVC obtained is M_w/M_n = 1.5. The surface active agents afford the final polymers as a powder and provide an acceleration of the rate of polymerization. The role of ETC is to accelerate the single electron transfer (SET) step, whereas THF enhances the degenerative chain transfer (DT) step. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6364–6374, 2004     

A Z‐Scheme‐Inspired Photobioelectrochemical H2O/O2 Cell with a 1 V Open‐Circuit Voltage Combining Photosystem II and PbS Quantum Dots

A biohybrid photobioanode mimicking the Z‐scheme has been developed by functional integration of photosystem II (PSII) and PbS quantum dots (QDs) within an inverse opal TiO₂ architecture giving rise to a rather negative water oxidation potential of about ?0.55 V vs. Ag/AgCl, 1 m KCl at neutral pH. The electrical linkage between both light‐sensitive entities has been established through an Os‐complex‐modified redox polymer (P_Os), which allows the formation of a multi‐step electron‐transfer chain under illumination starting with the photo‐activated water oxidation at PSII followed by an electron transfer from PSII through P_Os to the photo‐excited QDs and finally to the TiO₂ electrode. The photobioanode was coupled to a novel, transparent, inverse‐opal ATO cathode modified with an O₂‐reducing bilirubin oxidase for the construction of a H₂O/O₂ photobioelectrochemical cell reaching a high open‐circuit voltage of about 1 V under illumination.     

Direct Electron Transfer and Electrocatalysis of Myoglobin Based on its Direct Immobilization on Carbon Ionic Liquid Electrode

Direct electron transfer of myoglobin (Mb) was achieved by its direct immobilization on carbon ionic liquid electrode (CILE) with a conductive hydrophobic ionic liquid, 1‐butyl pyridinium hexaflourophosphate ([BuPy][PF₆]) as binder for the first time. A pair of well‐defined, quasi‐reversible redox peaks was observed for Mb/CILE resulting from Mb redox of heme Fe(III)/Fe(II) redox couple in 0.1 M phosphate buffer solution (pH 7.0) with oxidation potential of ?0.277 V, reduction potential of ?0.388 V, the formal potential E°′ (E°′=(E_pa+E_pc)/2) at ?0.332 V and the peak‐to‐peak potential separation of 0.111 V at 0.5 V/s. The average surface coverage of the electroactive Mb immobilized on the electrode surface was calculated as 1.06±0.03×10^?9 mol cm^?2. Mb retained its bioactivity on modified electrode and showed excellent electrocatalytic activity towards the reduction of H₂O₂. The cathodic peak current of Mb was linear to H₂O₂ concentration in the range from 6.0 μM to 160 μM with a detection limit of 2.0 μM (S/N=3). The apparent Michaelis–Menten constant (K and the electron transfer rate constant (k_s) were estimated to be 140±1 μM and 2.8±0.1 s^?1, respectively. The biosensor achieved the direct electrochemistry of Mb on CILE without the help of any supporting film or any electron mediator.     

Oxygen‐Atom Transfer Chemistry and Thermolytic Properties of a Di‐tert‐Butylphosphate‐Ligated Mn4O4 Cubane

[Mn₄O₄{O₂P(OtBu)₂}₆] ( 1 ), an Mn₄O₄ cubane complex combining the structural inspiration of the photosystem II oxygen‐evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen‐atom acceptor (PEt₃), to give the butterfly complex [Mn₄O₂{O₂P(OtBu)₂}₆(OPEt₃)₂]. The cubane structure is restored by reaction of the latter complex with the O‐atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X‐ray absorption spectroscopy to determine the fate of the Mn₄O₄ unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn^II species. Finally, the related butterfly complex [Mn₄O₂{O₂P(pin)}₆(bpy)₂] (pin=pinacolate) is described.     

Direct electrochemistry and spectroelectrochemistry of osmium substituted horseradish peroxidase

In this contribution the substitution of the central protoporphyrin IX iron complex of horseradish peroxidase by the respective osmium porphyrin complex is described. The direct electrochemical reduction of the Os containing horseradish peroxidase (OsHRP) was achieved at ITO and modified glassy carbon electrodes and in combination with spectroscopy revealed the three redox couples Os^IIIHRP/Os^IVHRP, Os^IVHRP/Os^VHRP and Os^VHRP/Os^VIHRP. The midpoint potentials differ dependent on the electrode material used with E_1/2 (Os^III/IV) of − 0.4 V (ITO) and − 0.25 V (GC), E_1/2 (Os^IV/^V) of − 0.16 V (ITO) and + 0.10 V (GC), and E_1/2 (Os^V/VI)of + 0.18 V (ITO), respectively. Moreover, with immobilised OsHRP the direct electrocatalytic reduction of hydrogen peroxide and tert-butyl hydroperoxide was observed. In comparison to electrodes modified with native HRP the sensitivity of the OsHRP-electrode for tert-butyl hydroperoxide is higher.     

Theoretical Study on Electron Transfer Matrix Element in Oxidation of α—Amino Carbon—Centered Radical by O2

As a successive work of our previous paper,^1the electron transfer matrix element(Vrp)in the oxidation of the simplified model molecule of α-amino carbon-centered radical by O2 has been investigated with ab initio calculation at the level of UHF/6-31 G**.Based on the optimized geometries of the reactgant and the ion-pair complex obtained previously,the reaction heat and the iuner reorganization energy have been obtained by constructing the potential energy curves of reactant and product states considering the solvent effect with the conductor-like screening model(COSMO).The solvent reorganization energy has been estimated using Lippert-Mataga relationship.The calculated results show that the value of Vrp is several times larger than that of RT,which means that the model reaction is an adiabatic one.Theoretical investigation indicates that the solvent effect on the direct electron transfer (ET) process of oxidation of α-amino carbon-centered radical by oxygen is remarkable.     

The Effect of Metal‐Ligand Affinity on Fe3O4_Supported Co–Rh Catalysts for Dicyclopentadiene Hydroformylation

The catalytic performances of Co‐Rh/Fe₃O₄ catalysts modified with phosphine ligands (PPh₃) and its analogues on dicyclopentadiene hydroformylation were evaluated. Among these catalysts, Co‐Rh/Fe₃O₄ modified with tris(p‐trifluoromethylphenyl)phosphine was determined to be effective for monoformyltricyclodecanes production, whereas Co‐Rh/Fe₃O₄ modified with PPh₃ or tri‐p‐tolylphosphine was effective for the diformyltricyclodecanes production. To investigate the ligand effects, the complex catalyst system (Co‐Rh/Fe₃O₄ and phosphine ligand) was subjected to pretreatment with syngas and then characterized by thermogravimetry and differential thermal analysis (TG‐DTA). It was determined that the threshold decomposition temperature reflected the corresponding Rh‐phosphine interaction strength, affecting the catalytic selectivity toward different products. A weak Rh‐phosphine interaction was desirable to produce monoformyltricyclodecanes with fast reaction kinetics, whereas a strong Rh‐phosphine complex was required for the synthesis of diformyltricyclodecanes. In addition to the selectivity rule shown in the PPh₃ series, experiments with other ligands also demonstrated similar selectivity trends.     

η1‐Allypalladium Complexes with Tridentate PNP’ Ligand for the Assembly of Modified Screen Printed Electrodes: an Electrochemical Study

Specific Pd‐based organometallic complex, in particular the [Pd(η¹‐CH₂? CH=CH₂)(P? N? P’)]BF₄ was used for the assembly of chemically modified Screen Printed Electrodes (SPEs) and their electrochemical reactivity was also investigated. For this purpose potassium ferricyanide, hexaammineruthenium(III) chloride, sodium hexachloroiridate‐(III) hydrate, ascorbic acid (AA), uric acid (UA), acetaminophen (Ac), guanine (G) and adenine (A) were used to study the electron‐transfer processes, which occurred at modified SPEs, fabricated by using the [Pd(η¹‐CH₂? CH=CH₂)(P? N? P’)]BF₄, applying the drop casting procedure. Interesting results were obtained in the case of the guanine (G) quantitative detection, especially in terms of a wide range of concentration (2.5–40 nM), an high sensitivity (of 49.0 A M^?1 cm^?2), a low detection limit (LOD=1.0 nM) and a fast response time (of t=2 s). The intra‐electrode reproducibility (RSD%) was <1 % for the same SPE used for each point of the calibration plot. The inter‐electrode reproducibility (RSD%), estimated by using different SPEs for each single point of the quantitative calibration graph, ranging from 5 to 10 %, better than that exhibited by other different chemical sensors, described in literature, and reported in this work for comparison. In addition, the high selectivity of the chemically modified sensors toward the oxidation of guanine, exhibited in presence of a mixture of G+A, in the same electrochemical bath solution, could be related to the different electro‐catalytic mechanisms, as demonstrated by the XPS study. This chemical sensor prototype could be very promising for bio‐medicine applications.     

A two‐dimensional CdII coordination polymer based on naphthalenediimide: synthesis,crystal structure and photochromic properties

Naphthalenediimides, a class of organic dyes with an expanded π‐electron‐deficient plane, have attracted considerable interest because of their photoinduced electron transfer from neutral organic moieties to stable anionic radicals. This makes them excellent candidates for organic linkers in the construction of photochromic coordination polymers. Such a photochromic two‐dimensional coordination polymer has been prepared using N,N′‐bis(pyridin‐4‐ylmethyl)naphthalene‐1,8:4,5‐bis(dicarboximide) (DPMNI). In crystallization tubes, upon slow diffusion of an MeOH solution of cadmium perchlorate into a CHCl₃ solution of DPMNI, the complex poly[[bis[μ₂‐2,7‐bis(pyridin‐4‐ylmethyl)benzo[imn][3,8]phenanthroline‐1,3,6,8(2H,7H)‐tetrone‐κ²N:N′]bis(perchlorato‐κO)cadmium(II)] chloroform tetrasolvate], {[Cd(C₂₆H₁₆N₄O₄)₂(ClO₄)₂]·4CHCl₃}_n, (I), was obtained. The asymmetric unit contains one Cd²⁺ cation, two DPMNI ligands, two coordinated ClO₄⁻ anions and four CHCl₃ solvent molecules. Each Cd²⁺ cation is interconnected by four DPMNI linkers to generate a neutral two‐dimensional naphthalenediimide coordination network with all the ClO₄⁻ anions above or below this plane. Strong interlaminar anion–π interactions between the coordinated ClO₄⁻ anions and the imide rings of an adjacent layer lead to a three‐dimensional supramolecular structure. Compound (I) exhibits reversible photochromic behaviour and photocontrolled tunable luminescence properties, which may originate from the photoinduced electron‐transfer generation of radicals in the DPMNI ligand.     

Deciphering a 20‐Year‐Old Conundrum: The Mechanisms of Reduction by the Water/Amine/SmI2 Mixture

The reaction of SmI₂ with the substrates 3‐methyl‐2‐butanone, benzyl chloride, p‐cyanobenzyl chloride, and anthracene were studied in the presence of water and an amine. In all cases, the water content versus rate profile shows a maximum at around 0.2 M H₂O. The rate versus amine content profile shows in all cases, except for benzyl chloride, saturation behavior, which is typical of a change in the identity of the rate‐determining step. The mechanism that is in agreement with the observed data is that electron transfer occurs in the first step. With substrates that are not very electrophilic, the intermediate radical anions lose the added electron back to samarium(III) relatively quickly and the reaction cannot progress efficiently. However, in a mixture of water/amine, the amine deprotonates a molecule of water coordinated to samarium(III). The negatively charged hydroxide, which is coordinated to samarium(III), reduces its electrophilicity, and therefore, lowers the rate of back electron transfer, which allows the reaction to progress. In the case of benzyl chloride, in which electron transfer is rate determining, deprotonation by the amine is coupled to the electron‐transfer step.     

Direct Electrochemistry of Hemoglobin Based on Fe3O4@SiO2 Nanoparticles Modified Electrode

A biosensor based on hemoglobin‐Fe₃O₄@SiO₂ nanoparticle bioconjunctions modified indium‐tin‐oxide (Hb/Fe₃O₄@SiO₂/ITO) electrode was fabricated to determine the concentration of H₂O₂. UV‐vis absorption spectra, fourier transform infrared (FT‐IR) spectroscopy, cyclic voltammetry (CV) and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the bioconjunction of Fe₃O₄@SiO₂ with Hb. Experimental results demonstrate that the immobilized Hb on the Fe₃O₄@SiO₂ matrix retained its native structure well. In addition, Fe₃O₄@SiO₂ nanoparticles (NPs) are very effective in facilitating electron transfer of the immobilized enzyme, which can be attributed to the unique nanostructure and larger surface area of the Fe₃O₄@SiO₂ NPs. The biosensor displayed good performance for the detection of H₂O₂ with a wide linear range from 2.03×10^?6 to 4.05×10^?3 mol/L and a detection limit of 0.32 µmol/L. The resulting biosensor exhibited fast amperometric response, good stability, reproducibility, and selectivity to H₂O₂.     

Regulation of Glucose Oxidase Activity through Interaction with Fullerene Derivatives

The 2‐(hydroxymethyl)pyridine modified C₆₀ (PY‐C₆₀) and methoxydiglycol modified C₆₀ (MDG‐C₆₀) are synthesized using Bingel‐Hirsch reaction and characterized by nuclear magnetic resonance (NMR) and mass spectra. PY‐C₆₀ and MDG‐C₆₀ can bind to glucose oxidase (GOx) and quench the fluorescence of tryptophan (Trp) residue in GOx through static mechanism. The conformation of GOx is disturbed after formation of complex with these fullerene derivatives. Kinetic analysis indicates that PY‐C₆₀ and MDG‐C₆₀ may affect the catalytic activity of GOx with a partial mixed‐type inhibition mechanism. In the plasma glucose concentration range (3.6–5.2 mmol·L^?1), PY‐C₆₀ may significantly accelerate the catalytic velocity of GOx, however, MDG‐C₆₀ exerts almost no obvious change to the initial velocity of GOx, suggesting that elaborate design of molecular structure of fullerene derivative is very important for regulating the biological activity of fullerene‐enzyme complex.     

Barium(II)–2,4‐dinitrophenolate–18‐crown‐6 at 183 K

The title compound, bis(2,4‐dinitrophenolato‐κ²O,O′)(1,4,7,10,13,16‐hexaoxadecane‐κ⁶O)barium(II), [Ba(C₆H₃N₂O₅)₂(C₁₂H₂₄O₆)], is a 1:1 complex of barium(II)–2,4‐di­nitro­phenolate and 1,4,7,10,13,16‐hexaoxa­cyclo­octa­decane (18‐crown‐6). Its structure is located on a crystallographic inversion centre. The temperature dependence of the crystal structure has been studied. The monoclinic β angle of the P2₁/­n space group increases with increasing temperature. The packing structure of the complex is stabilized by intermolecular C—H?O interactions.