| 1. |
- Abad, JM, et al.
(författare)
-
Immobilization of peroxidase glycoprotein on gold electrodes modified with mixed epoxy-boronic acid monolayers
- 2002
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 124:43, s. 12845-12853
-
Forskningsöversikt (refereegranskat)abstract
- The development of bioelectronic enzyme applications requires the immobilization of active proteins onto solid or colloidal substrates such as gold. Coverage of the gold surface with alkanethiol self-assembled monolayers (SAMS) reduces nonspecific adsorption of proteins and also allows the incorporation onto the surface of ligands with affinity for complementary binding sites on native proteins. We present in this work a strategy for the covalent immobilization of glycosylated proteins previously adsorbed through weak, reversible interactions, on tailored SAMS. Boronic acids, which form cyclic esters with saccharides, are incorporated into SAMS to weakly adsorb the glycoprotein onto the electrode surface through their carbohydrate moiety. To prevent protein release from the electrode surface, we combine the affinity motif of boronates with the reactivity of epoxy groups to covalently link the protein to heterofunctional boronateepoxy SAMS. The principle underlying our strategy is the increased immobilization rate achieved by the weak interaction-induced proximity effect between slow reacting oxyrane groups in the SAM and nucleophilic residues from adsorbed proteins, which allows the formation of very stable covalent bonds. This approach is exemplified by the use of phenylboronates-oxyrane mixed monolayers as a reactive support and redox-enzyme horseradish peroxidase as glycoprotein for the preparation of peroxidase electrodes. Quartz crystal microbalance, atomic force microscopy, and electrochemical measurements are used to characterize these enzymatic electrodes. These epoxy-boronate functional monolayers; are versatile, stable interfaces, ready to incorporate glycoproteins by incubation under mild conditions.
|
|
| 2. |
- Adden, R, et al.
(författare)
-
New approaches to the analysis of enzymatically hydrolyzed methyl cellulose. Part 1. Investigation of the influence of structural parameters on the extent of degradation
- 2006
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 7:5, s. 1399-1409
-
Tidskriftsartikel (refereegranskat)abstract
- Six methyl celluloses (MCs), one with a degree of substitution (DS) of 1.32 and five with DS between 1.83 and 1.88, were thoroughly investigated. Monomer composition and methyl distribution in the polymer chain were analyzed after total or partial random hydrolysis and appropriate derivatization with gas chromatography ( GC) and mass spectrometry (MS), respectively, and used as reference data. The same MCs were then hydrolyzed with an enzyme preparation of Trichoderma longibrachiatum and further investigated with size-exclusion chromatography with multiangle light scattering and refractive index detection (SEC-MALS/RI) and MS. Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) in combination with various MS analyzers were compared with respect to quantification of the degradation products directly and after perdeuteriomethylation. The methyl group distribution in the oligomeric fractions and the average DS as a function of chain length were calculated from ESI mass spectra. With help of the reference analysis, patterns could be corrected for the unspecific contribution of end groups. By labeling and ESI tandem MS, our knowledge about the tolerance of the enzymes' sub-sites with respect to the number of methyl groups could be improved.
|
|
| 3. |
- Akerberg, C, et al.
(författare)
-
A kinetic model for enzymatic wheat starch saccharification
- 2000
-
Ingår i: Journal of Chemical Technology and Biotechnology. - 0268-2575. ; 75:4, s. 306-314
-
Tidskriftsartikel (refereegranskat)abstract
- A kinetic model describing the enzymatic saccharification of wheat starch by a mixture of ol-amylase and amyloglucosidase has been developed. The model describes the influence of pH, glucose inhibition and starch and enzyme concentration, The results of experimental saccharification under different physical conditions, eg pH and temperature, were used to determine the parameters in the model. The dominant enzyme in the mixture was amyloglucosidase and the maximum rate of saccharification due to this enzyme was found to be optimal at pH 5, and increased Five-Fold when the temperature was increased from 30 to 55 degrees C, Saccharification due to the action of amyloglucosidase was inhibited by the glucose produced and simulation showed that the maximum rate of saccharification decreased by 58% at a starch concentration of 140gdm(-3) compared with a starch concentration much less than 110 gdm(-3) where the effect of glucose inhibition was negligible, (C) 2000 society of Chemical Industry.
|
|
| 4. |
- Alferov, Sergey, et al.
(författare)
-
Electrical communication of cytochrome enriched Escherichia coli JM109 cells with graphite electrodes
- 2009
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 54:22, s. 4979-4984
-
Konferensbidrag (refereegranskat)abstract
- In the present study three different strains of Escherichia coli (JM 109 - a native "wild type" strain, JM 109/pBSD 1300 - a strain overproducing the membrane anchor domain of Bacillus subtilis succinate-quinone reductase, SQR, a protein that contains two transmembraneously arranged heme groups and JM109/pLUV 1900 - a strain overproducing cytochrome c(550) from B. subtilis, a protein where the cytochrome domain is anchored to the membrane with a transmembrane helix) were immobilised on the surface of a spectrographic graphite electrode and tested for electrical communication using mediators. Such compounds as ferricyanide, 2,6-dichlorophenolindophenol (DCPIP) and ubiquinone (Q(0)) were used as soluble mediators and two flexible osmium redox polymers; poly(1-vinylimidazole)(12)-[Os-(4,4'-dimethyl-2,2'-di'pyridyl)(2)Cl-2](2 +/+) (osmium redox polymer I) and poly(vinylpyridine)-[Os-(N,N'-methylated-2,2'-biimidazole)(3)](2+/3+) (osmium redox polymer II) were co-immobilised with the bacterial cells onto the electrode surface. The effects of applied potential, buffer pH and different substrates were compared for the different combinations bacterial strains - mediators. Through the introduction of the cytochromes in the bacterial membrane it was established that it had great effect on the ability of the bacterial cells to effectively communicate with artificial mediators. The introduction of the transmembraneously arranged heme groups of B. subtilis made it possible for this strain to communicate with the Os-polymers, whereas the introduction of the cytochrome c(550) had an effect especially increasing ability of Q(0) to act as an efficient e(-) acceptor. (C) 2009 Elsevier Ltd. All rights reserved.
|
|
| 5. |
- Andreu, Rafael, et al.
(författare)
-
Direct electron transfer kinetics in horseradish peroxidase electrocatalysis
- 2007
-
Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 111:2, s. 469-477
-
Tidskriftsartikel (refereegranskat)abstract
- The study of direct electron transfer between enzymes and electrodes is frequently hampered by the small fraction of adsorbed proteins that remains electrochemically active. Here, we outline a strategy to overcome this limitation, which is based on a hierarchical analysis of steady-state electrocatalytic currents and the adoption of the "binary activity" hypothesis. The procedure is illustrated by studying the electrocatalytic response of horseradish peroxidase (HRP) adsorbed on graphite electrodes as a function of substrate (hydrogen peroxide) concentration, electrode potential, and solution pH. Individual contributions of the rates of substrate/enzyme reaction and of the electrode/enzyme electron exchange to the observed catalytic currents were disentangled by taking advantage of their distinct dependence on substrate concentration and electrode potential. In the absence of nonturnover currents, adoption of the "binary activity" hypothesis provided values of the standard electron-transfer rate constant for reduction of HRP Compound II that are similar to those reported previously for reduction of cytochrome c peroxidase Compound II. The variation of the catalytic currents with applied potential was analyzed in terms of the non-adiabatic Marcus-DOS electron transfer theory. The availability of a broad potential window, where catalytic currents could be recorded, facilitates an accurate determination of both the reorganization energy and the maximum electron-transfer rate for HRP Compound II reduction. The variation of these two kinetic parameters with solution pH provides some indication of the nature and location of the acid/base groups that control the electronic exchange between enzyme and electrode.
|
|
| 6. |
- Antiochia, Riccarda, et al.
(författare)
-
A new osmium-polymer modified screen-printed graphene electrode for fructose detection
- 2014
-
Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005. ; 195, s. 287-293
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development and performance of the first fructose biosensor based on a commercial screen-printed graphene electrode (SPGE). The electrode was modified with an osmium-polymer, which allowed the efficient wiring of the enzyme fructose dehydrogenase (FDH). The immobilization of both osmium-polymer and FDH was realized in an easy way. Aliquots of 10 mu L, Os-polymer and 10 mu L, FDH were thoroughly mixed with poly(ethylene glycol) (400) diglycidyl ether (PEDGE) and deposited on the electrode surface and left there to dry overnight. The biosensor exhibits a detection limit of 0.8 mu M, a linear range between 0.1 and 8 mM, high sensitivity to fructose (2.15 mu A cm(-2)/mM), good reproducibility (RSD = 1.9%), fast response time (3 s) and a stability of 2 months when stored in the freezer. The proposed fructose biosensor was tested in real food samples and validated with a commercial spectrophotometric enzymatic kit. No significant interference was observed with the proposed biosensor. Published by Elsevier B.V.
|
|
| 7. |
- Antiochia, Riccarda, et al.
(författare)
-
Composite Material Based on Macroporous Polyaniline and Osmium Redox Complex for Biosensor Development
- 2014
-
Ingår i: Electroanalysis. - : Wiley. - 1040-0397. ; 26:7, s. 1623-1630
-
Tidskriftsartikel (refereegranskat)abstract
- Here the feasibility of layers based on the conducting polymer polyaniline (PANI) as component of glucose biosensors using glucose oxidase (GOx) as enzyme and [Os(bpy)(2)(4-aminomethylpyridine)Cl]PF6 (OsCmplx) as electrochemical mediator, is evaluated. Particularly, PANI was employed to obtain a nanostructured macroporous material (m-PANI) around polystyrene nanoparticles taken as template and the mediator was co-immobilized during the polymerizing procedure. The GOx biosensor based on OsCmplx modified m-PANI provides a linear response to glucose concentration in the range 5 up to 65 mM with a sensitivity of 3.54 mu A/mM/cm(2) (on a projected geometric area=0.07 cm(2)), an LOD of 0.8 mM and a good precision (%RSD <= 7, n=5); the biosensor is stable showing a decrease of 10% to the value of the sensitivity after 15 days of use and of about 50% after 40 days.
|
|
| 8. |
- Antiochia, Riccarda, et al.
(författare)
-
Development of a carbon nanotube paste electrode osmium polymer-mediated biosensor for determination of glucose in alcoholic beverages
- 2007
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 22:11, s. 2611-2617
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a new amperometric biosensor for glucose monitoring. The biosensor is based on the activity of glucose dehydrogenase (GDH) and diaphorase (DI) co-immobilized with NAD(+) into a carbon nanotube paste (CNTP) electrode modified with an osmium functionalized polymer. This mediator was demonstrated to shuttle the electron transfer between the immobilized diaphorase and the CNTP electrode, thus, showing a good electrocatalytic activity towards NADH oxidation at potentials around +0.2 V versus Ag vertical bar AgCl, where interfering reactions are less prone to occur. The biosensor exhibits a detection limit of 10 mu mol L-1, linearity up to 8 x 10(-4) mol L-1, a sensitivity of 13.4 mu A cm(-2) mmol(-1) L-1, a good reproducibility (R.S.D. 2.1%, n = 6) and a stability of about 1 week when stored dry at 4 degrees C. Finally, the proposed biosensor was applied for the determination of glucose in different samples of sweet wine and validated with a commercial spectrophotometric enzymatic kit. (c) 2006 Elsevier B.V. All rights reserved.
|
|
| 9. |
- Antiochia, Riccarda, et al.
(författare)
-
Graphene and 2D-Like Nanomaterials : Different Biofunctionalization Pathways for Electrochemical Biosensor Development
- 2017
-
Ingår i: Graphene Bioelectronics. - 9780128133507 - 9780128133491 ; , s. 1-35
-
Bokkapitel (refereegranskat)abstract
- In the last decades, nanotechnology has played a key role in the electrochemical biosensor development based on the mediated and direct electrochemical communication between the biorecognition elements and the electrode surface. In particular, graphene and 2D-like nanomaterials (e.g., boron nitride nanosheets, graphitic carbon nitride (g-C3N4) nanosheets, and various transition metal dichalcogenides) have attracted an increasing interest due to their peculiar properties such as high specific surface area and the ease of biofunctionalization. Moreover, in the last few years, the successful integration of graphene and 2D-like nanomaterials with other nanomaterials such as metal nanoparticles, metal oxides, or quantum dots has dramatically increased the opportunities to develop novel electrochemical biosensors with highly enhanced performances, mainly due to the synergistic effects.In this chapter, we would like to give the state of art of graphene and 2D-like nanomaterials employment for electrochemical biosensors development, by critically discussing the advantages and drawbacks. Successively, the discussion should be separately addressed to three different cases: (1) redox enzyme immobilization, (2) antibody immobilization, and (3) DNA/aptamer immobilization. Finally, we should critically define for which cases graphene and 2D-like nanomaterials are the most suitable electrochemical platform, within some conclusion remarks and future perspectives of both kinds of nanomaterials.
|
|
| 10. |
- Antiochia, Riccarda, et al.
(författare)
-
Rapid and direct determination of fructose in food: A new osmium-polymer mediated biosensor
- 2013
-
Ingår i: Food Chemistry. - : Elsevier BV. - 1873-7072 .- 0308-8146. ; 140:4, s. 742-747
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development and performance of a new rapid amperometric biosensor for fructose monitoring in food analysis. The biosensor is based on the activity of fructose dehydrogenase (FDH) immobilised into a carbon nanotube paste electrode according to two different procedures. The direct wiring of the FDH in a highly original osmium-polymer hydrogel was found to offer a better enzyme entrapment compared to the immobilisation of the enzyme in an albumin hydrogel. The optimised biosensor required only 5 U of FDH and kept the 80% of its initial sensitivity after 4 months. During this time, the biosensor showed a detection limit for fructose of I mu M, a large linear range between 0.1 and 5 mM, a high sensitivity (1.95 mu A cm(-2) mM), good reproducibility (RSD = 2.1%) and a fast response time (4 s). Finally, the biosensor was applied for specific determination of fructose in honey, fruit juices, soft and energy drinks. The results indicated a very good agreement with those obtained with a commercial reference kit. No significant interference was observed with the proposed biosensor. (C) 2012 Elsevier Ltd. All rights reserved.
|
|
