NADH Photosynthesis System with Affordable Electron Supply and Inhibited NADH Oxidation

Photosynthesis offers a green approach for the recycling of nicotinamide cofactors primarily NADH in bio-redox reactions. Herein, we report an NADH photosynthesis system where the oxidation of biomass derivatives is designed as an electron supply module (ESM) to afford electrons and superoxide dismutase/catalase (SOD/CAT) cascade catalysis is designed as a reactive oxygen species (ROS) elimination module (REM) to inhibit NADH degradation. Glucose as the electron donor guarantees the reaction sustainability accompanied with oxidative products of gluconic acid and formic acid. Meanwhile, enzyme cascades of SOD/CAT greatly eliminate ROS, leading to a ≈2.00-fold elevation of NADH yield (61.1 % vs. 30.7 %). The initial reaction rate and turnover frequency (TOF) increased by 2.50 times and 2.54 times, respectively, compared with those systems without REM. Our study establishes a novel and efficient platform for NADH photosynthesis coupled to biomass-to-chemical conversion.     

Reagentless Bioluminescent Sensor for NADH

Abstract

A reagentless fiber optic biosensor specific for NADH, associated with flow injection analysis and based on bacterial bioluminescence is described. Only a buffer solution as flowing stream is required for the probe which works without supply of its coreactants (FMN and N-decyl-aldehyde). These are coentrapped in a poly(vinyl)alcohol (PVA) matrix which allows their internal release in the vicinity of the immobilized enzymes. Two PVA matrices differing by the reticulation process have been tested : first, by polymerization with glutaraldehyde and secondly, by a cyclic freezing-thawing process. The self-containment working time was estimated at 1 and 1.5 h of continuous measurements, respectively. NADH was determined using flow injection analysis. The sensor gave excellent reproducibility (RSD ≤ 3%) in the linear dynamic range 5 — 500 pmol with an average cycle-time of 2.5 min.     

Gold nanoparticles: catalyst for the oxidation of NADH to NAD(+)

Nicotinamide adenine dinucleotide is an important coenzyme involved in the production of ATP, the fuel of energy, in every cell. It alternates between the oxidized form NAD(+) and the reduced form dihydronicotinamide adenine dinucleotide (NADH) and serves as a hydrogen and electron carrier in the cellular respiratory processes. In the present work, the catalytic effect of gold nanoparticles on the oxidization of NADH to NAD(+) was investigated. The addition of gold nanoparticles was found to quench the NADH fluorescence intensities but had no effect on the fluorescence lifetime. This suggested that the fluorescence quenching was not due to coupling with the excited state, but due to changing the ground state of NADH. The intensity of the 340 nm absorption band of NADH was found to decrease while that of the 260 nm band of NAD(+) was found to increase as the concentration of gold nanoparticles increased. This conversion reaction was further supported by nuclear magnetic resonance and mass spectroscopy. The effect of the addition of NADH was found to slightly red shift and increase the intensity of the surface plasmon absorption band of gold nanoparticles at 520 nm. This gives a strong support that the conversion of NADH to NAD(+) is occurring on the surface of the gold nanoparticles, i.e. NADH is surface catalyzed by the gold nanoparticles. The catalytic property of this important reaction might have important future applications in biological and medical fields.     

Catalytic Hydroxylation of Benzene to Phenol by Dioxygen with an NADH Analogue

Hydroxylation of benzene by molecular oxygen (O₂) occurs efficiently with 10‐methyl‐9,10‐dihydroacridine (AcrH₂) as an NADH analogue in the presence of a catalytic amount of Fe(ClO₄)₃ or Fe(ClO₄)₂ with excess trifluoroacetic acid in a solvent mixture of benzene and acetonitrile (1:1 v/v) to produce phenol, 10‐methylacridinium ion and hydrogen peroxide (H₂O₂) at 298 K. The catalytic oxidation of benzene by O₂ with AcrH₂ in the presence of a catalytic amount of Fe(ClO₄)₃ is started by the formation of H₂O₂ from AcrH₂, O₂, and H⁺. Hydroperoxyl radical (HO₂^.) is produced from H₂O₂ with the redox pair of Fe³⁺/Fe²⁺ by a Fenton type reaction. The rate‐determining step in the initiation is the proton‐coupled electron transfer from Fe²⁺ to H₂O₂ to produce HO^. and H₂O. HO^. abstracts hydrogen rapidly from H₂O₂ to produce HO₂^. and H₂O. The Fe³⁺ produced was reduced back to Fe²⁺ by H₂O₂. HO₂^. reacts with benzene to produce the radical adduct, which abstracts hydrogen from AcrH₂ to give the corresponding hydroperoxide, accompanied by generation of acridinyl radical (AcrH^.) to constitute the radical chain reaction. Hydroperoxyl radical (HO₂^.), which was detected by using the spin trap method with EPR analysis, acts as a chain carrier for the two radical chain pathways: one is the benzene hydroxylation with O₂ and the second is oxidation of an NADH analogue with O₂ to produce H₂O₂.     

Platinum nanoparticles have an activity similar to mitochondrial NADH:ubiquinone oxidoreductase

This study was designed to examine if platinum nanoparticles have an activity similar to mitochondrial complex I, NADH:ubiquinone oxidoreductase. Platinum nanoparticles were prepared by a citrate reduction of H(2)PtCl(6) and protected by citrate itself and pectin (CP-Pt). Time- and dose-dependent decreases in NADH and a time-dependent increase in NAD(+) were observed in the presence of 50muM CP-Pt; these observations were made using a spectrophotometric method in which the maximum absorption spectra at 340 and 260nm were used for NADH and NAD(+), respectively. The required platinum concentration in CP-Pt to achieve a 50% oxidation of NADH for 3h was approximately 20muM, and this NADH oxidation did not require oxygen as an electron acceptor. We also verified NAD(+) formation using an NAD(+)/NADH quantification kit. The absorption peak shift from 278 to 284nm of 2,3-dimethoxy-5-methyl-6-(3-methyl-2-butenyl)-1,4-benzoquinone (CoQ(1)) was observed by incubating CoQ(1) with CP-Pt in an aqueous buffer. A further analysis with HPLC revealed the reduction of CoQ(1) to CoQ(1)H(2) by CP-Pt. As a whole, platinum nanoparticles have an NADH:ubiquinone oxidoreductase-like activity. This suggests that platinum nanoparticles are a potential medicinal substance for oxidative stress diseases with suppressed mitochondrial complex I.     

Fabrication of Thionin-Toluene Diisocyanate Modified Electrode and Its Electrocatalytic Oxidation to NADH

The chemically modified electrode constructed by chemically cross-linking of redox mediator thionin with toluene diisocyanate(TDI) directly at the surface of a spectrographic graphite electrode shows a significant electrocatalytic activity to the oxidation of reduced nicotinamide adenine dinucleotide(NADH) with oxidation overpotential reduced by 310mV.In the potential range from-0.1 to 0.3V,the adsorbed thionin -TDI behaves as a one electron and one proton reversible redox process. The modified electrode achieves a steady-state current of NADH within 20s and the detection limit is about 1.5μm.     

Stereoselective reductions with macrocyclic NADH models

Macrocyclic NADH models with two (C₂ symmetry) or four (D₂ symmetry) nicotinamide units comprised in a ring have been prepared and found to reduce activated carbonyl compounds in good yields and high enantiomeric excess. The roles of magnesium ions as a cocatalyst and the temperature have also been investigated. The smaller, C₂-symmetric macrocycle gave 96% ee upon reduction of ethyl benzoylformate whereas the best result with the larger D₂-symmetric model was 81% ee for the reduction of methyl benzoylformate.     

DMF-exfoliated graphene for electrochemical NADH detection

The electrochemical detection of NADH is of considerable interest because it is required as a cofactor in a large number of dehydrogenase-based biosensors. However, the presence of oxygenated functionalities on the electrode often causes fouling due to the adsorption of the oxidised form, NAD(+). Here we report an electroanalytical NADH sensor based on DMF-exfoliated graphene. The latter is shown to have a very low oxygen content, facilitating the exceptionally stable and sensitive detection of this important analyte.     

Immobilized-enzyme electrode for nicotinamide adenine dinucleotide (reduced form) (NADH) sensing and application to the kinetic studies of NADH dependent dehydrogenases.

Amperometric determination of nicotinamide adenine dinucleotide (reduced form) (NADH) at an immobilized-diaphorase (Dp) electrode is described. The measurement was conducted using ferrocenylmethanol as a mediator in a stirred solution at 0.20 V versus a saturated calomel electrode. A linear relationship between the steady-state current and the concentration of NADH was found over the range 0.005-0.125 mmol dm-3. The immobilized-Dp electrode showed outstanding stability and the current response reached a steady state within 2-3 seconds upon addition of NADH. The proposed electrode was used to follow the reactions of pig heart lactate dehydrogenase and horse liver alcohol dehydrogenase. The kinetic investigation using the immobilized-Dp electrode gave the kinetic parameters (Michaelis constants, Km values, and maximum velocities, Vm values), which were in satisfactory agreement with those determined by a conventional spectrophotometric method.     

Oxidative activity of organometallic compounds in relation to the coenzymes NADH and NADPH

Kinetic investigations of the interaction of Hg and Sn-containing organometallic compounds with NADH and NADPH using spectro-photometric methods have shown that these compounds may act as oxidizing agents in relation to the coenzyme. Their oxidative activity depends on the nature and number of organic groups in the molecule. Comparison of the kinetic data for the activity of Hg and Sn compounds with those for Fe porphyrins imitating the active centers of redox enzymes indicates the competitiveness of the organometallic compounds and models of natural electron acceptors.M. V. Lomonosov Moscow State University, Moscow 119899, Russia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1036–1040, August, 1999.     

Electrocatalytic Oxidation of NADH by Oxidized s‐Adenosyl‐L‐Methionine (SAMe): Application to NADH and SAMe Determinations

s‐Adenosyl‐L ‐methionine (SAMe) is an adenosine analogue with therapeutical activity against affective disorders and liver dysfunctions. It can be oxidized on graphite electrode yielding a strongly adsorbed electroactive oxidation product for which a quinone‐imine structure is proposed. This compound is capable of electrocatalyzing the NADH oxidation at low potentials, lowering the overvoltage by about 300 mV. An amperometric method for NADH determination at +0.1 V (Ag|AgCl|KCl_sat) is developed using an oxidized‐SAMe‐modified electrode in pH 9. Linear calibration plots were obtained with a detection limit of 2.4 nM. The electrode response time and the relative standard deviation of the slope of the calibration plot for 5 different modified electrodes were 12 s and 5.6% respectively. The catalytic scheme also provides the first method to determine SAMe itself by adsorptive differential pulse voltammetry. The linear range was found to be 42.4–424 nM with a reproducibility of 6.9%. The method was applied to SAMe determination in a pharmaceutical formulation.     

Recent advances in NADH electrochemical sensing design

NADH electrochemical sensor development has been one of the most studied areas of bioelectroanalysis because of the ubiquity of NAD(P)H based enzymatic reactions in nature. The different solutions proposed are still far from the realisation of the “ideal” NADH sensor and the research area is still challenging. The principles and the recent approaches in NADH electrochemical sensing design are reported in this review. An overview of selected examples and novel sensor materials for the electrocatalysis of NADH is given with emphasis on the appropriate design to obtain improved performances. The literature data taken in consideration has been grouped depending on the strategy used in: surface modified electrodes for NADH sensing, surface redox mediated NADH probes, and bulk modified electrodes for the electrocatalytic oxidation of NADH. A list of already reported dehydrogenase-based biosensors is also given.     

聚苯乙烯固载NADH辅酶模型化合物的合成及应用

设计、合成了一类新型的高分子还原试剂--聚苯乙烯固载烟酰胺辅酶模型化合物1-苄基-1,4-二氢烟酰胺(BNAH)4.该还原剂可以在温和条件下有效的还原活化烯烃,而且可以循环再生,但循环再生后有效BNAH含量下降.     

Iron-doping Accelerating NADH Oxidation over Carbon Nitride

As a state-of-the-art conjugated polymer photocatalyst, graphitic carbon nitride(abbreviated as g-C₃N₄)has shown great potential in photocatalytic cofactor(reduced form of nicotinamide adenine dinucleotide, NADH) regene-ration. Herein, Fe-doped g-C₃N₄ was engineered for photocatalytic NADH oxidation. The π-π interaction between the NADH molecule and the conjugated heptazine building block facilitates the adsorption of NADH onto the framework, as revealed by density functional theory(DFT) calculations. Furthermore, iron doping promoted the oxidation kinetics of NADH under blue LED illumination. The conversion ratio of NADH to its oxidized form could be up to 85.7% in 20 min, comparing with 59.4% for metal-free counterpart. Enzyme assay employing formate dehydrogenase(FDH) further verified the selectivity of the products, with 67.5%±2.6% of enzymatically active 1,4-NADH being regenerated following the oxidation process. Scavenger experiments suggest the dominant role of photo-induced electrons in the oxidation of NADH. This work could shed light on developing a novel cofactor regeneration route through the synergistic effect between the metal doping and noncovalent interaction based on the conjugated polymer.