Xi:Irritant;
526-95-4Relevant articles and documents
The reduction of Cr(VI) to Cr(III) by the α and β anomers of D-glucose in dimethyl sulfoxide. A comparative kinetic and mechanistic study
Signorella, Sandra,Lafarga, Rubén,Daier, Verónica,Sala, Luis F.
, p. 127 - 135 (2000)
The reduction of Cr(VI) by α-D-glucose and β-D-glucose was studied in dimethyl sulfoxide in the presence of pyridinium p-toluensulfonate, a medium where mutarotation is slower than the redox reaction. The two anomers reduce Cr(VI) by formation of an intermediate Cr(VI) ester precursor of the slow redox step. The equilibrium constant for the formation of the intermediate chromic ester and the rate of the redox steps are different for each anomer. α-D-Glucose forms the Cr(VI)-Glc ester with a higher equilibrium constant than β-D-glucose, but the electron transfer within this complex is slower than for the β anomer. The difference is attributed to the better chelating ability of the 1,2-cis-diolate moiety of the α anomer. The Cr(V) species, generated in the reaction mixture, reacts with the two anomers at a rate comparable with that of Cr(VI). The EPR spectra show that the α anomer forms several linkage isomers of the five-coordinate Cr(V) bis-chelate, while β-D- glucose affords a mixture of six-coordinate Cr(V) mono-chelate and five- coordinate Cr(V) bis-chelate. The conversion of the Cr(V) mono- to bis- chelate is discussed in terms of the ability of the 1,2-cis- versus 1,2- trans-diolate moieties of the glucose anomers to bind Cr(V). (C) 2000 Elsevier Science Ltd.
Glucose biosensor based on new carbon nanotube-gold-titania nano-composites modified glassy carbon electrode
Wu, Yue-Li,Li, Qi-Wei,Zhang, Xiao-Lu,Chen, Xiao,Wang, Xue-Mei
, p. 1087 - 1090 (2013)
In this paper, a novel biosensor was prepared by immobilizing glucose oxidase (GOx) on carbon nanotube-gold-titania nanocomposites (CNT/Au/TiO 2) modified glassy carbon electrode (GCE). SEM was initially used to investigate the surface morphology of CNT/Au/TiO2 nanocomposites modified GCE, indicating the formation of the nano-porous structure which could readily facilitate the attachment of GOx on the electrode surface. Cyclic voltammogram (CV) and electrochemical impedance spectrum (EIS) were further utilized to explore relevant electrochemical activity on CNT/Au/TiO2 nanocomposites modified GCE. The observations demonstrated that the immobilized GOx could efficiently execute its bioelectrocatalytic activity for the oxidation of glucose. The biosensor exhibited a wider linearity range from 0.1 mmol L-1 to 8 mmol L-1 glucose with a detection limit of 0.077 mmol L-1.
Sol-gel encapsulated glucose oxidase arrays based on a pH sensitive fluorescent dye
Yildirim, Nimet,Odaci, Dilek,Ozturk, Gulsiye,Alp, Serap,Ergun, Yavuz,Dornbusch, Kay,Feller, Karl-Heinz,Timur, Suna
, p. 144 - 148 (2011)
Optical glucose oxidase (GOx) arrays based on pH sensitive fluorescent dye (2-(4-tolyl)-4-[4-(1,4,7,10-tetraoxa-13-azacyclopentadecyl)benzylidene] -5-oxazolone) (CPO) has been constructed. The arrays were prepared by spotting of CPO and GOx together with tetraethoxysilane (TEOS)/Chitosan (CHIT) mixture via a microarrayer. After optimization studies, analytical characterization of enzyme arrays were carried out. The fluorescence intensity of the system was linearly correlated to glucose concentration in the range of 1.0-30.0 mM (in potassium phosphate buffer; 2.5 mM at pH 7.0). Furthermore, the developed arrays were used to analyze glucose in some beverages and HPLC was used as a reference method for independent glucose analysis.
Label-free Si quantum dots as photoluminescence probes for glucose detection
Yi, Yinhui,Deng, Jianhui,Zhang, Youyu,Li, Haitao,Yao, Shouzhuo
, p. 612 - 614 (2013)
Si quantum dots have been demonstrated to be environmentally friendly photoluminescence probes and their fluorescence was quenched by H 2O2 that was produced from the glucose oxidase-catalyzed oxidation of glucose. This strategy could be used to detect glucose with high sensitivity and selectivity.
Diverse applications of TMB-based sensing probes
Huang, Li,Cao, Ying-Juan,Sun, Xiang-Ying,Liu, Bin,Shen, Jiang-Shan
, p. 5667 - 5676 (2018)
Extending the research on 3,3′,5,5′-tetramethylbenzidine (TMB) and its derivatives in analytical chemistry is important, considering that TMB is widely used as an enzyme catalytic substrate. In this work, two TMB derivatives, TMBS and TMBB, were synthesized via a facile and one-step condensation reaction between the -NH2 group of TMB and the -CHO group of salicylaldehyde or benzaldehyde. Because at low pH the two Schiff base compounds can release TMB which can emit strong fluorescence, the probes could show dual-modal signal responses, fluorescence and UV-vis absorption, towards the pH. Practical applications of pH sensing in Chinese rice vinegar and lemon juice samples were successfully demonstrated. On the basis of these findings, a catalytic chromogenic reaction was developed to monitor the pH with the naked eye, too. Furthermore, considering the chemical equilibrium reaction between CO2 and H2O and that glucose oxidase (GOD) can catalyse the dehydrogenation and oxidation reaction of β-d-glucose to produce gluconic acid, both of which can result in lowering the pH values of the two Schiff base systems, highly sensitive and selective dual-modal sensing systems for detecting CO2 and β-d-glucose have also been successfully established. Therefore, the two synthesized TMB derivatives can demonstrate their robust application potential.
Behavior of IrCl3 as a Homogeneous Catalyst on the Oxidation of N-Acetylglucosamine in Acid Medium and Uncatalyzed Reaction in Alkaline Medium with Bromamine-B: Exploration of Kinetic, Mechanistic and Catalytic Chemistry
Shankarlingaiah, Dakshayani,Puttaswamy
, p. 424 - 437 (2018)
Abstract: The experimental rate laws for the oxidation of N-acetylglucosamine with bromamine- B are: ? d[BAB]/dt = k/ [BAB]1 [GlcNAc]0.69 [HClO4]?0.76 [IrCl3]0.48 [BSA]?0.33 in acid medium and –d[BAB]/dt = k/?[BAB]1 [GlcNAc]1 [NaOH]0.79 in alkaline medium. The IrCl3 catalyzed reaction is thirteen fold faster than uncatalyzed reaction. Appropriate mechanisms and rate laws were deduced. Graphical Abstract: The reaction of N-acetylglucosamine with Bromamine-B in acid and alkaline medium is [Figure not available: see fulltext.].
A falling-film microreactor for enzymatic oxidation of glucose
Illner, Sabine,Hofmann, Christian,Loeb, Patrick,Kragl, Udo
, p. 1748 - 1754 (2014)
Many oxidation processes require the presence of molecular oxygen in the reaction media. Reactors are needed that provide favorable conditions for the mass transfer between the gas and the liquid phase. In this study, two recent key technologies, microreactor technology and biotechnology, were combined to present an interesting alternative to conventional methods and open up excellent possibilities to intensify chemical processes in the field of fine chemicals. An enzyme-catalyzed gas/liquid phase reaction in a falling-film microreactor (FFMR) was examined for the first time. The test reaction was the oxidation of β-D-glucose to gluconic acid catalyzed by glucose oxidase (GOx). Various factors influencing the biotransformation, such as oxygen supply, temperature, enzyme concentration, and reaction time were investigated and compared to those in conventional batch systems. The most critical factor, the volumetric mass-transfer coefficient for the efficient use of oxygen-dependent enzymes, was determined by using the integrated online detection of dissolved oxygen in all systems. The extremely large surface-to-volume ratio of the FFMR facilitated the contact between the enzyme solution and the gaseous substrate. Hence, in a continuous bubble-free FFMR system with a residence time of 25 seconds, a final conversion of up to 50 % in enzymatic oxidation was reached, whereas conversion in a conventional bubble column resulted in only 27 %. Finally, an option for scale-up was shown through an enlarged version of the FFMR. Oxygen intake: An enzyme-catalyzed gas/liquid phase reaction in a falling film microreactor (FFMR) was examined for the first time. The test reaction was the oxidation of β-D-glucose to gluconic acid catalyzed by glucose oxidase. As a result of to the large surface-to-volume ratio, extremely high oxygen transfer rates are achieved.
A sandwich-like electrochemiluminescent biosensor for the detection of concanavalin A based on a C60-reduced graphene oxide nanocomposite and glucose oxidase functionalized hollow gold nanospheres
Zhang, Juanjuan,Ruo, Yuan,Chen, Shihong,Zhong, Xia,Wu, Xiaoping
, p. 48465 - 48471 (2014)
A sensitive sandwich-like electrochemiluminescent (ECL) biosensor was designed for the detection of concanavalin A (ConA) using a C60-reduced graphene oxide (C60-rGO) nanocomposite as a platform and glucose oxidase (GOX) decorated hollow gold nanospheres (HGNSs) as a label. First, C60-rGO with a large surface area was prepared for combining with phenoxy-derivatized dextran, which served as the recognition element for interacting with ConA by biospecific carbohydrate-protein (lectin) interactions. Then, GOX decorated HGNSs (GOX-HGNSs) were linked to the electrode surface through the biospecific interaction between the intrinsic carbohydrate residues of GOX and ConA. These localized GOX and HGNSs amplified the ECL signal of luminol intensely, which was achieved by the efficient catalysis of the GOX towards the oxidation of glucose to in situ generate an improved amount of hydrogen peroxide (H2O2) as a coreactant, and the excellent catalysis of HGNSs towards the ECL reaction of luminol-H2O2. The prepared biosensor exhibited a sensitive response for the determination of ConA, ranging from 0.10 to 100 ng mL-1 with a detection limit down to 30 pg mL-1 (signal to noise = 3). With excellent stability, sensitivity, selectivity and simplicity, the prepared biosensor showed great prospects in lectin sensing or carbohydrate sensing. This journal is
Electrical contacting of flavoenzymes and NAD(P)+-dependent enzymes by reconstitution and affinity interactions on phenylboronic acid monolayers associated with Au-electrodes
Zayats, Maya,Katz, Eugenii,Willner, Itamar
, p. 14724 - 14735 (2002)
The preparation of integrated, electrically contacted, flavoenzyme and NAD(P)+-dependent enzyme-electrodes is described. The reconstitution of apo-glucose oxidase, apo-GOx, on a FAD cofactor linked to a pyrroloquinoline quinone (PQQ) phenylboronic acid monolayer yields an electrically contacted enzyme monolayer (surface coverage 2.1 × 10-12 mol cm-2) exhibiting a turnover rate of 700 s-1 (at 22 ± 2 °C). The system is characterized by microgravimetric quartz-crystal microbalance analyses, Faradaic impedance spectroscopy, rotating disk electrode experiments, and cyclic voltammetry. The performance of the enzyme-electrode for glucose sensing is described. Similarly, the electrically contacted enzyme-electrodes of NAD(P)+-dependent enzymes malate dehydrogenase, MaID, and lactate dehydrogenase, LDH, are prepared by the cross-linking of affinity complexes generated between the enzymes and the NADP+ and NAD+ cofactors linked to a pyrroloquinoline quinone phenylboronic acid monolayer, respectively. The MaID enzyme-electrode (surface coverage 1.2 × 10-12 mol cm2) exhibits a turnover rate of 190 s-1, whereas the LDH enzyme-electrode (surface coverage 7.0 × 10-12 mol cm2) reveals a turnover rate of 2.5 s-1. Chronoamperometric experiments reveal that the NAD+ cofactor is linked to the PQQ-phenylboronic acid by two different binding modes. The integration of the LDH with the two NAD+ cofactor configurations yields enzyme assemblies differing by 1 order of magnitude in their bioelectrocatalytic activities.
Low temperature synthesis of Cu2O crystals: Shape evolution and growth mechanism
Sui, Yongming,Fu, Wuyou,Yang, Haibin,Zeng, Yi,Zhang, Yanyan,Zhao, Qiang,Li, Yangen,Zhou, Xiaoming,Leng, Yan,Li, Minghui,Zou, Guangtian
, p. 99 - 108 (2010)
An interesting shape evolution of Cu2O crystals, that is, from cubes, truncated octahedra, octahedra, and finally to nanospheres was first realized in high yield by reducing the copper-citrate complex solution with glucose. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (H RTEM) techniques were employed to characterize the samples. We elucidate the important parameters (including poly (vinyl pyrrolidone) (PVP) concentration, reaction time, and reaction temperature) responsible for the shape-controlled synthesis of Cu2O crystals. The possible formation mechanism for the products with various architectures is presented, which is mainly based on the variation of the ratio (R) of the growth rates along the ( 100) and (111) direction. In addition, the effect of the low supersaturation on the formation of star-shaped samples with six symmetric branches is also taken into account. This polymer-mediated method should be readily extended to the controlled synthesis of other metal oxides and the proposed growth model could also be used to explain and direct the growth of crystals with a cubic structure
Preparation and catalytic activity of poly(N-vinyl-2-pyrrolidone)-protected Au nanoparticles for the aerobic oxidation of glucose
Zhang, Haijun,Li, Wenqi,Gu, Yajun,Zhang, Shaowei
, p. 5743 - 5751 (2014)
PVP-protected Au nanoparticles (NPs) for the aerobic oxidation of glucose were prepared by using NaBH4 reduction method. The effects of processing parameters such as Au3+ ion concentration, reaction temperature, ratio of NaBH4 or PVP to Au3+, and solvent composition on their particle sizes and catalytic activities were studied in detail and the synthesis conditions optimized. As-prepared Au NPs possessed a FCC structure, with an average size varying from about 100 to 2.6 nm depending on their preparation conditions. The size changes affected their catalytic activities in the aerobic oxidation of glucose. The Au NPs with the average size of 2.6 nm prepared under the optimal conditions showed a high instantaneous catalytic activity as well as a high long-time stability. Based on the kinetic study on the glucose oxidation over the PVP-protected Au NPs, the corresponding apparent activation energy was determined as 82 kJ mol-1. Copyright
Cook,Major
, p. 773 (1935)
A kinetic study of d-glucose oxidation by bromine in aqueous solutions
Grgur, Branimir N.,Zugic, Dragana L.,Gvozdenovic, Milica M.,Trisovic, Tomislav Lj.
, p. 1779 - 1787 (2006)
The kinetics of the oxidation of d-glucose to d-gluconic acid by bromine in aqueous solution were studied using potentiometric techniques and theoretical considerations of complex bromine-bromide-pH equilibria. The pH has a strong influence on reaction rate. At pH 9.5, the reaction is further accelerated due to the formation of hypobromite. The proposed kinetics expression for gluconic acid formation, based on the determined kinetic parameters at pH 9.24, is of the form. dc(GA)/dt = 160c2(G)c0(HOBr)c0(H+)c0(Br-).
Insights into the "free state" enzyme reaction kinetics in nanoconfinement
Wang, Chen,Ye, De-Kai,Wang, Yun-Yi,Lu, Tao,Xia, Xing-Hua
, p. 1546 - 1553 (2013)
The investigation of enzyme reaction kinetics in nanoconfined spaces mimicking the conditions in living systems is of great significance. Here, a nanofluidics chip integrated with an electrochemical detector has been designed for studying "free state" enzyme reaction kinetics in nanoconfinement. The nanofluidics chip is fabricated using the UV-ablation technique developed in our group. The enzyme and substrate solutions are simultaneously supplied from two single streams into a nanochannel through a Y-shaped junction. The laminar flow forms in the front of the nanochannel, then the two liquids fully mix at their downstream where a homogeneous enzyme reaction occurs. The "free state" enzyme reaction kinetics in nanoconfinement can thus be investigated in this laminar flow based nanofluidics device. For demonstration, glucose oxidase (GOx) is chosen as the model enzyme, which catalyzes the oxidation of beta-d-glucose. The reaction product hydrogen peroxide (H 2O2) can be electrochemically detected by a microelectrode aligning to the end of nanochannel. The steady-state electrochemical current responding to various glucose concentrations is used to evaluate the activity of the "free state" GOx under nanoconfinement conditions. The effect of liquid flow rate, enzyme concentration, and nanoconfinement on reaction kinetics has been studied in detail. Results show that the "free state" GOx activity increases significantly compared to the immobilized enzyme and bath system, and the GOx reaction rate in the nanochannel is two-fold faster than that in bulk solution, demonstrating the importance of "free state" and spatial confinement for the enzyme reaction kinetics. The present approach provides an effective method for exploiting the "free state" enzyme activity in nanospatial confinement.
KINETICS OF OXIDATION OF D-GLUCOSE BY HEXACHLOROIRIDATE(IV) AND TETRACHLOROAURATE(III)
Gupta, Kalyan Kali Sen,Gupta, Shipra Sen,Chatterejee, Uma,Tarafdar, Archana,Samanta, Tapashi,Shamra, Umashankar
, p. 81 - 88 (1983)
Kinetic data for the oxidation of D-glucose by hexachloroiridate(IV) and tetrachloroaurate(III) are reported.The reactions have been studied spectrophotometrically over a vide range of experimental conditions.Theactivation parameters have been calculated and mechanims are suggested.
Studies on the co-immobilized GOD/CAT on cross-linked chitosan microsphere modified by lysine
Zhang, Jie,Zhou, Xiaohua,Wang, Dan,Wang, Yingli,Zhou, Xing,Wang, Honghui,Li, Qiang,Tan, Shiyu
, p. 80 - 86 (2013)
Glucose oxidase (GOD) and catalase (CAT) were co-immobilized on a novel crosslinked chitosan resin modified by l-lysine. The immobilized system exhibited the best performance when the immobilization process was conducted at 4 C for 3 h with GOD/CAT activity ratio of 1:18 and pH 7.0. Under the optimum pH 4.0 and temperature 40 C, the enzyme system could achieve to the maximum conversion of glucose, which was 68.9%. Acidoresistance and thermotolerance of the enzymes were both strengthened. The Km of the co-immobilized enzyme system obtained in this study was 31.02 mM. The GOD enzyme immobilized in this system could maintain 94% of initial activity after the 12th operational cycle. 95.8% of initial activity was left after 50 weeks' storage at 4 C. GOD achieved better performance in this new immobilized enzyme system due to its effective elimination of H2O2, which showed potential applications for various commercial uses.
Glucose-specific sensing with boronic acid utilizing enzymatic oxidation
Kanekiyo, Yasumasa,Tao, Hiroaki
, p. 852 - 853 (2006)
A novel sensing system for glucose-specific detection has been established based on a combination of a boronic acid and enzymes. To overcome the inherently low biding affinity of glucose toward boronic acids, glucose is converted into gluconic acid by the enzymatic reaction using glucose oxidase (GOx), and then complexed with a fluorescent boronic acid through the α-hydroxycarboxylate moiety. According to the present strategy, glucose concentration is exclusively determined among other saccharides in aqueous solutions. Copyright
Pd(ii) nanoparticles in porous polystyrene: Factors influencing the nanoparticle size and catalytic properties
Tsvetkova, Irina B.,Matveeva, Valentina G.,Doluda, Valentin Y.,Bykov, Alexei V.,Sidorov, Alexander I.,Schennikov, Sergey V.,Sulman, Michael G.,Valetsky, Pyotr M.,Stein, Barry D.,Chen, Chun-Hsing,Sulman, Esther M.,Bronstein, Lyudmila M.
, p. 6441 - 6448 (2012)
In this paper for the first time we present a systematic study of the influence of hydrophobicity of Pd(ii) compounds, (CH3CN) 2PdCl2, (PhCN)2PdCl2, (Sty)(CH 3CN)PdCl2, and (StyPdCl2)2, on nanoparticle (NP) formation in the pores of hydrophobic micro/mesoporous hypercrosslinked polystyrene (HPS). The morphology and composition of HPS-Pd nanocomposites were studied using transmission electron microscopy, X-ray fluorescence measurements, X-ray photoelectron spectroscopy, and liquid nitrogen physisorption. The size and location of Pd compound NPs were found to depend on hydrophobicity of the Pd(ii) environment. Catalytic testing of these nanocomposites in d-glucose oxidation was carried out to illustrate the influence of nanoparticle size and environment on catalytic activity. The highest catalytic activity was achieved for (Sty)(CH3CN)PdCl 2, forming smallest NPs and allowing an optimal hydrophobicity- hydrophilicity balance with HPS. The Royal Society of Chemistry 2012.
Preparation of Au-Pd/C catalysts by adsorption of metallic species in aqueous phase for selective oxidation
Hermans, Sophie,Deffernez, Aurore,Devillers, Michel
, p. 77 - 82 (2010)
Au/C and Au-Pd/C catalysts were prepared on SX PLUS activated carbon using an adsorption method in which the precursor(s)-support interactions in aqueous solution were sought to be optimized. pH windows where maximum adsorption occurs were identified for four bimetallic cases, varying the incorporation order of the adsorbed metallic precursors and the oxidation state of the first metal introduced. All samples were characterized by XPS and SEM/EDXS, and the above-mentioned parameters were found to have an influence on the surface microstructure of the samples and on the activity of the bimetallic catalysts obtained. This preparation method leads to highly active catalysts for the selective oxidation of glucose, with the activity correlated with high surface Pd/C ratios.
Localized Supramolecular Peptide Self-Assembly Directed by Enzyme-Induced Proton Gradients
Rodon Fores, Jennifer,Martinez Mendez, Miguel Leonardo,Mao, Xiyu,Wagner, Déborah,Schmutz, Marc,Rabineau, Morgane,Lavalle, Philippe,Schaaf, Pierre,Boulmedais, Fouzia,Jierry, Lo?c
, p. 15984 - 15988 (2017)
Electrodes are ideal substrates for surface localized self-assembly processes. Spatiotemporal control over such processes is generally directed through the release of ions generated by redox reactions occurring specifically at the electrode. The so-used gradients of ions proved their effectiveness over the last decade but are in essence limited to material-based electrodes, considerably reducing the scope of applications. Herein is described a strategy to enzymatically generate proton gradients from non-conductive surfaces. In the presence of oxygen, immobilization of glucose oxidase (GOx) on a multilayer film provides a flow of protons through enzymatic oxidation of glucose by GOx. The confined acidic environment located at the solid–liquid interface allows the self-assembly of Fmoc-AA-OH (Fmoc=fluorenylmethyloxycarbonyl and A=alanine) dipeptides into β-sheet nanofibers exclusively from and near the surface. In the absence of oxygen, a multilayer nanoreactor containing GOx and horseradish peroxidase (HRP) similarly induces Fmoc-AA-OH self-assembly.
Catalytic deep eutectic solvents for highly efficient conversion of cellulose to gluconic acid with gluconic acid self-precipitation separation
Liu, Feijie,Xue, Zhimin,Zhao, Xinhui,Mou, Hongyu,He, Jing,Mu, Tiancheng
, p. 6140 - 6143 (2018)
A family of FeCl3·6H2O based catalytic deep eutectic solvents (CDESs) were formed and used for the conversion of cellulose to gluconic acid with high efficiency. More importantly, gluconic acid could be separated from the reaction system by self-precipitation.
Enzyme-immobilized hydrogels to create hypoxia for in vitro cancer cell culture
Dawes, Camron S.,Konig, Heiko,Lin, Chien-Chi
, p. 25 - 34 (2017)
Hypoxia is a critical condition governing many aspects of cellular fate processes. The most common practice in hypoxic cell culture is to maintain cells in an incubator with controlled gas inlet (i.e., hypoxic chamber). Here, we describe the design and characterization of enzyme-immobilized hydrogels to create solution hypoxia under ambient conditions for in vitro cancer cell culture. Specifically, glucose oxidase (GOX) was acrylated and co-polymerized with poly(ethylene glycol)-diacrylate (PEGDA) through photopolymerization to form GOX-immobilized PEG-based hydrogels. We first evaluated the effect of soluble GOX on inducing solution hypoxia (O2??5%) and found that both unmodified and acrylated GOX could sustain hypoxia for at least 24?h even under ambient air condition with constant oxygen diffusion from the air-liquid interface. However, soluble GOX gradually lost its ability to sustain hypoxia after 24?h due to the loss of enzyme activity over time. On the other hand, GOX-immobilized hydrogels were able to create hypoxia within the hydrogel for at least 120?h, potentially due to enhanced protein stabilization by enzyme ‘PEGylation’ and immobilization. As a proof-of-concept, this GOX-immobilized hydrogel system was used to create hypoxia for in vitro culture of Molm14 (acute myeloid leukemia (AML) cell line) and Huh7 (hepatocellular carcinoma (HCC) cell line). Cells cultured in the presence of GOX-immobilized hydrogels remained viable for at least 24?h. The expression of hypoxia associated genes, including carbonic anhydrase 9 (CA9) and lysyl oxidase (LOX), were significantly upregulated in cells cultured with GOX-immobilized hydrogels. These results have demonstrated the potential of using enzyme-immobilized hydrogels to create hypoxic environment for in vitro cancer cell culture.
Ruthenium(III) catalyzed oxidation of sugar alcohols by dichloroisocyanuric acid - A kinetic study
Lakshman Kumar,Venkata Nadh,Radhakrishnamurti
, p. 300 - 307 (2016)
Kinetics of ruthenium(III) catalyzed oxidation of biologically important sugar alcohols (myo-inositol, D-sorbitol, and D-mannitol) by dichloroisocyanuric acid was carried out in aqueous acetic acid - perchloric medium. The reactions were found to be first order in case of oxidant and ruthenium(III). Zero order was observed with the concentrations of sorbitol and mannitol whereas, a positive fractional order was found in the case of inositol concentration. An inverse fractional order was observed with perchloric acid in oxidation of three substrates. Arrhenius parameters were calculated and a plausible mechanism was proposed.
A new route to the considerable enhancement of glucose oxidase (GOx) activity: The simple assembly of a complex from CdTe quantum dots and GOx, and its glucose sensing
Cao, Lihua,Ye, Jian,Tong, Lili,Tang, Bo
, p. 9633 - 9640 (2008)
A new complex consisting of CdTe quantum dots (QDs) and glucose oxidase (GOx) has been facilely assembled to achieve considerably enhanced enzymatic activity and a wide active temperature range of GOx; these characteristics are attributed to the conformational changes of GOx during assembly. The obtained complex can be simultaneously used as a nanosensor for the detection of glucose with high sensitivity. A mechanism is put forward based on the fluorescence quenching of CdTe QDs, which is caused by the hydrogen peroxide (H 2O2) that is produced from the GOx-catalyzed oxidation of glucose. When H2O2 gets to the surface of the CdTe QDs, the electrontransfer reaction happens immediately and H2O2 is reduced to O2, which lies in electron hole traps on CdTe QDs and can be used as a good acceptor, thus forming the nonfluorescent CdTe QDs anion. The produced O2 can further participate in the catalyzed reaction of GOx, forming a cyclic electrontransfer mechanism of glucose oxidation, which is favorable for the whole reaction system. The value of the Michaelis-Menton constant of GOx is estimated to be 0.45 mML-1, which shows the considerably enhanced enzymatic activity measured by far. In addition, the GOx enzyme conjugated on the CdTe QDs possesses better thermal stability at 20-80°C and keeps the maximum activity in the wide range of 40-50°C. Moreover, the simply assembled complex as a nanosensor can sensitively determine glucose in the wide concentration range from micro- to millimolar with the detection limit of 0.10 μM, which could be used for the direct detection of low levels of glucose in biological systems. Therefore, the established method could provide an approach for the assembly of CdTe QDs with other redox enzymes, to realize enhanced enzymatic activity, and to further the design of novel nanosensors applied in biological systems in the future.
Real-time monitoring of mass-transport-related enzymatic reaction kinetics in a nanochannel-array reactor
Li, Su-Juan,Wang, Chen,Wu, Zeng-Qiang,Xu, Jing-Juan,Xia, Xing-Hua,Chen, Hong-Yuan
, p. 10186 - 10194 (2010)
To understand the fundamentals of enzymatic reactions confined in micro-/nanosystems, the construction of a small enzyme reactor coupled with an integrated real-time detection system for monitoring the kinetic information is a significant challenge. Nano-enzyme array reactors were fabricated by covalently linking enzymes to the inner channels of a porous anodic alumina (PAA) membrane. The mechanical stability of this nanodevice enables us to integrate an electrochemical detector for the real-time monitoring of the formation of the enzyme reaction product by sputtering a thin Pt film on one side of the PAA membrane. Because the enzymatic reaction is confined in a limited nanospace, the mass transport of the substrate would influence the reaction kinetics considerably. Therefore, the oxidation of glucose by dissolved oxygen catalyzed by immobilized glucose oxidase was used as a model to investigate the mass-transport-related enzymatic reaction kinetics in confined nanospaces. The activity and stability of the enzyme immobilized in the nanochannels was enhanced. In this nano-enzyme reactor, the enzymatic reaction was controlled by mass transport if the flux was low. With an increase in the flux (e.g., >50 μLmin-1), the enzymatic reaction kinetics became the rate-determining step. This change resulted in the decrease in the conversion efficiency of the nano-enzyme reactor and the apparent Michaelis-Menten constant with an increase in substrate flux. This nanodevice integrated with an electrochemical detector could help to understand the fundamentals of enzymatic reactions confined in nanospaces and provide a platform for the design of highly efficient enzyme reactors. In addition, we believe that such nanodevices will find widespread applications in biosensing, drug screening, and biochemical synthesis.
carba Nicotinamide Adenine Dinucleotide Phosphate: Robust Cofactor for Redox Biocatalysis
D?ring, Manuel,Sieber, Volker,Simon, Robert C.,Tafertshofer, Georg,Zachos, Ioannis
supporting information, p. 14701 - 14706 (2021/05/13)
Here we report a new robust nicotinamide dinucleotide phosphate cofactor analog (carba-NADP+) and its acceptance by many enzymes in the class of oxidoreductases. Replacing one ribose oxygen with a methylene group of the natural NADP+ was found to enhance stability dramatically. Decomposition experiments at moderate and high temperatures with the cofactors showed a drastic increase in half-life time at elevated temperatures since it significantly disfavors hydrolysis of the pyridinium-N?glycoside bond. Overall, more than 27 different oxidoreductases were successfully tested, and a thorough analytical characterization and comparison is given. The cofactor carba-NADP+ opens up the field of redox-biocatalysis under harsh conditions.
A Sweet H2S/H2O2Dual Release System and Specific Protein S-Persulfidation Mediated by Thioglucose/Glucose Oxidase
Li, Xiaolu,Ni, Xiang,Qian, Wei-Jun,Shen, Tun-Li,Xian, Ming
, p. 13325 - 13332 (2021/09/03)
H2S and H2O2 are two redox regulating molecules that play important roles in many physiological and pathological processes. While each of them has distinct biosynthetic pathways and signaling mechanisms, the crosstalk between these two species is also known to cause critical biological responses such as protein S-persulfidation. So far, many chemical tools for the studies of H2S and H2O2 have been developed, such as the donors and sensors for H2S and H2O2. However, these tools are normally targeting single species (e.g., only H2S or only H2O2). As such, the crosstalk and synergetic effects between H2S and H2O2 have hardly been studied with those tools. In this work, we report a unique H2S/H2O2 dual donor system by employing 1-thio-β-d-glucose and glucose oxidase (GOx) as the substrates. This enzymatic system can simultaneously produce H2S and H2O2 in a slow and controllable fashion, without generating any bio-unfriendly byproducts. This system was demonstrated to cause efficient S-persulfidation on proteins. In addition, we expanded the system to thiolactose and thioglucose-disulfide; therefore, additional factors (β-galactosidase and cellular reductants) could be introduced to further control the release of H2S/H2O2. This dual release system should be useful for future research on H2S and H2O2.
