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Towards new fluorometric methodologies based on the in-situ generation of gold nanoclusters. Talanta 2024; 266:125119. [PMID: 37657379 DOI: 10.1016/j.talanta.2023.125119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 08/16/2023] [Accepted: 08/23/2023] [Indexed: 09/03/2023]
Abstract
In this manuscript a method for the fluorometric determination of tyramine is described. It is based on the direct reaction between Au(III) and tyramine in a phosphate buffer which produces fluorescent gold nanoclusters (AuNC) (λexc = 320 nm, λem = 410 nm) with a diameter of 1.50 ± 0.06 nm. The Au(III) and buffer solutions are mixed and after 140 s, tyramine solution is added; which produces a fast and stable fluorescence signal. The formation of AuNC is demonstrated by STEM and, more importantly, this reaction could be followed by Atomic Fluorescence Microscopy (AFM). The method allows the determination of tyramine in the range from 6.0x10-7 M (limit of quantification) up to 1.2x10-4 M; with a relative standard deviation (RSD) ranges from 1.8% to 4.4% depending on the tyramine concentration. The mechanism of AuNC formation involves the Au(III) reduction via the phenol group and the complexation with the amine group. Putrescine and cadaverine do not produce interference, meanwhile histamine causes a proportional decrease in the signal which can be overcome by the standard addition method. The method was applied to the determination of tyramine in a tuna and cheese samples and the results obtained are in statistical agreement with these obtained using a validated or standard method.
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Portable colorimetric enzymatic disposable biosensor for histamine and simultaneous histamine/tyramine determination using a smartphone. Anal Bioanal Chem 2023; 415:1777-1786. [PMID: 36790459 PMCID: PMC9992026 DOI: 10.1007/s00216-023-04583-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 01/27/2023] [Accepted: 02/01/2023] [Indexed: 02/16/2023]
Abstract
Tyramine oxidase (TAO), peroxidase (HRP), and Amplex Red (AR) have been immobilized on cellulose to obtain disposable biosensors for the determination of histamine. During the enzymatic reaction, AR is oxidized and a pink spot is obtained. Using a smartphone and measuring the G (green) color coordinate, histamine can be determined in the presence of other biogenic amines (putrescine and cadaverine) in concentrations ranging from 2·10-5 M to 5·10-4 M with a 7.5·10-6 M limit of detection (LoD). Despite tyramine interference, experimental conditions are provided which allow rapid and simple histamine and simultaneous histamine/tyramine (semi)quantitative determination in mixtures. Finally, tyramine and histamine were determined in a tuna extract with good results (compared to the reference HPLC-MS method). The methodology can also be applied in solution allowing histamine (and simultaneous histamine/tyramine) determination with a lower LoD (1.8·10-7 M) and a similar selectivity.
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Tectomer-Mediated Optical Nanosensors for Tyramine Determination. SENSORS (BASEL, SWITZERLAND) 2023; 23:2524. [PMID: 36904726 PMCID: PMC10007293 DOI: 10.3390/s23052524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
The development of optical sensors for in situ testing has become of great interest in the rapid diagnostics industry. We report here the development of simple, low-cost optical nanosensors for the semi-quantitative detection or naked-eye detection of tyramine (a biogenic amine whose production is commonly associated with food spoilage) when coupled to Au(III)/tectomer films deposited on polylactic acid (PLA) supports. Tectomers are two-dimensional oligoglycine self-assemblies, whose terminal amino groups enable both the immobilization of Au(III) and its adhesion to PLA. Upon exposure to tyramine, a non-enzymatic redox reaction takes place in which Au(III) in the tectomer matrix is reduced by tyramine to gold nanoparticles, whose reddish-purple color depends on the tyramine concentration and can be identified by measuring the RGB coordinates (Red-Green-Blue coordinates) using a smartphone color recognition app. Moreover, a more accurate quantification of tyramine in the range from 0.048 to 10 μM could be performed by measuring the reflectance of the sensing layers and the absorbance of the characteristic 550 nm plasmon band of the gold nanoparticles. The relative standard deviation (RSD) of the method was 4.2% (n = 5) with a limit of detection (LOD) of 0.014 μM. A remarkable selectivity was achieved for tyramine detection in the presence of other biogenic amines, especially histamine. This methodology, based on the optical properties of Au(III)/tectomer hybrid coatings, is promising for its application in food quality control and smart food packaging.
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Enzymatically mediated fluorescent copper nanocluster generation for tyramine determination. Anal Bioanal Chem 2023; 415:2037-2044. [PMID: 36759389 PMCID: PMC10079739 DOI: 10.1007/s00216-023-04571-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/18/2023] [Accepted: 01/25/2023] [Indexed: 02/11/2023]
Abstract
This work details the enzymatic generation of fluorescence nanomaterials and the use of this optical signal as the analytical parameter for the quantification of the substrate. More specifically, fluorescent copper nanoclusters have been obtained during the enzymatic reaction of tyramine oxidase and tyramine in the presence of Cu(II); the fluorescence intensity being proportional to the concentration of tyramine. The nanoclusters obtained show fluorescence at 445 nm by being excited at 320 nm and have been characterized by TEM, EDX, and XPS. The formation mechanism has also been studied, suggesting that under the optimal conditions (0.1 M MES buffer and pH = 6), the formation of the nanoclusters is due to the reducing properties of the product of the enzymatic reaction (p-hydroxybenzaldehyde) in MES buffer. The method shows a linear relationship with the concentration of tyramine in the range from 1.0·10-5 to 2.5·10-4 M, a RSD of 3% (n = 5) and a LOD of 6.3·10-6 M. The method has been applied to the determination of tyramine in sausage with good results.
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Solving Color Reproducibility between Digital Devices: A Robust Approach of Smartphones Color Management for Chemical (Bio)Sensors. BIOSENSORS 2022; 12:341. [PMID: 35624642 PMCID: PMC9139083 DOI: 10.3390/bios12050341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 05/07/2022] [Accepted: 05/09/2022] [Indexed: 12/02/2022]
Abstract
In the past twelve years, digital image colorimetry (DIC) on smartphones has acquired great importance as an alternative to the most common analytical techniques. This analysis method is based on fast, low-cost, and easily-accessible technology, which can provide quantitative information about an analyte through the color changes of a digital image. Despite the fact that DIC is very widespread, it is not exempt from a series of problems that are not fully resolved yet, such as variability of the measurements between smartphones, image format in which color information is stored, power distribution of the illuminant used for the measurements, among others. This article proposes a methodology for the standardization and correction of these problems using self-developed software, together with the use of a 3D printed light box. This methodology is applied to three different colorimetric analyses using different types and brands of smartphones, proving that comparable measurements between devices can be achieved. As color can be related to many target analytes, establishing this measurement methodology can lead to new control analysis applicable to diverse sectors such as alimentary, industrial, agrarian, or sanitary.
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Gold nanoparticle formation as an indicator of enzymatic methods: colorimetric l-phenylalanine determination. Anal Bioanal Chem 2022; 414:2641-2649. [PMID: 35064303 PMCID: PMC8888390 DOI: 10.1007/s00216-022-03900-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 12/30/2021] [Accepted: 01/12/2022] [Indexed: 11/28/2022]
Abstract
An enzymatic-colorimetric method has been developed based on the reaction between l-phenylalanine (l-Phe) and the l-amino acid oxidase (LAAO) in the presence of Au(III), which has led to the formation of gold nanoparticles. The intensity of the localized surface plasmon resonance (LSPR) band of the generated nanoparticles (550 nm) can be related to the concentration of l-Phe in the sample. The mechanism of the LAAO-l-Phe enzyme reaction in the presence of Au(III) has been studied through the evaluation and optimization of experimental conditions. These studies have reinforced the hypothesis that the catalytic center of the enzyme helps the Au(III) reduction and, thanks to the protein, the Au0 form is stabilized as gold nanoparticles (AuNPs). In the calibration study, a sigmoidal relationship between the concentration of the substrate and the LSPR of the nanoparticles was observed. The linearization of the signal has allowed the determination of l-Phe in the range from 17 to 500 µM with an RSD% (150 μM) of 4.8% (n = 3). The method is free of other amino acid interference normally found in blood plasma. These highly competitive results open the possibility of further development of a rapid method for l-Phe determination based on colorimetry.
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Direct minimally invasive enzymatic determination of tyramine in cheese using digital imaging. Anal Chim Acta 2021; 1164:338489. [PMID: 33992221 DOI: 10.1016/j.aca.2021.338489] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/02/2021] [Accepted: 04/04/2021] [Indexed: 10/21/2022]
Abstract
An enzymatic method for the direct (without pretreatment) minimally invasive tyramine determination in cheese is proposed. Colorimetric test strips containing tyramine oxidase (TAO), peroxidase and 3,3',5,5'-tetramethylbenzidine (Q-TAO), allow tyramine determination through the RGB chromatic coordinates of the observed blue colour (LOD = 2.6·10-6 M, LOQ = 8.7·10-6 M, RSD% (n = 5; 1.8·10-4 M) = 3.2%). The strips are inserted in the sample for 2 min and then the RGB coordinates are measured using a smartphone. Previously, these Q-TAO strips have been also optimized for tyramine determination in cheese extract. To do that, a spectrophotometric method in solution for tyramine determination in cheese extracts has been developed, which included an in-depth study of the indicating reaction; this study has allowed to gain new information about the spectroscopic properties of different TMB species and, which it is more important, to detect cross-reactions between TAO and TMB species. A mathematical model has also been developed which relate the RGB signals obtained with the tyramine concentrations, the instrumental characteristics of the smartphone and the spectroscopic properties of the absorbing product of the enzymatic reaction.
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Abstract
![]()
Reactions of polyhydrides OsH6(PiPr3)2 (1)
and IrH5(PiPr3)2 (2) with rollover cyclometalated
hydride complexes have been investigated in order to explore the influence
of a metal center on the MHn unit of the
other in mixed valence binuclear polyhydrides. Hexahydride 1 activates an ortho-CH bond of the heterocyclic
moiety of the trihydride metal–ligand compounds OsH3{κ2-C,N-[C5RH2N-py]}(PiPr3)2 (R = H (3), Me (4), Ph (5)). Reactions of 3 and 4 lead to the hexahydrides
(PiPr3)2H3Os{μ-[κ2-C,N-[C5RH2N-C5H3N]-N,C-κ2]}OsH3(PiPr3)2 (R = H (6), Me (7)),
whereas 5 gives the pentahydride (PiPr3)2H3Os{μ-[κ2-C,N-[C5H3N-C5(C6H4)H2N]-C,N,C-κ3]}OsH2(PiPr3)2 (8).
Pentahydride 2 promotes C—H bond activation of 3 and the iridium-dihydride IrH2{κ2-C,N-[C5H3N-py]}(PiPr3)2 (9)
to afford the heterobinuclear pentahydride (PiPr3)2H3Os{μ-[κ2-C,N-[C5H3N-C5H3N]-N,C-κ2]}IrH2(PiPr3)2 (10) and the homobinuclear tetrahydride (PiPr3)2H2Ir{μ-[κ2-C,N-[C5H3N-C5H3N]-N,C-κ2]}IrH2(PiPr3)2 (11), respectively. Complexes 6–8 and 11 display HOMO delocalization
throughout the metal–heterocycle-metal skeleton. Their sequential
oxidation generates mono- and diradicals, which exhibit intervalence
charge transfer transitions. This notable ability allows the tuning
of the strength of the hydrogen–hydrogen and metal–hydrogen
interactions within the MHn units. The influence of a metal center on the
MHn unit of the other in binuclear osmium-
and iridium-polyhydride
complexes bearing rollover cyclometalated bipyridines as a bridging
ligand has been studied.
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Scanning densitometry and mass spectrometry for HPTLC analysis of lipids: The last 10 years. J LIQ CHROMATOGR R T 2021. [DOI: 10.1080/10826076.2020.1866600] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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10
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Globotriaosylceramide-related biomarkers of fabry disease identified in plasma by high-performance thin-layer chromatography - densitometry- mass spectrometry. J Chromatogr A 2021; 1638:461895. [PMID: 33477028 DOI: 10.1016/j.chroma.2021.461895] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/04/2021] [Accepted: 01/05/2021] [Indexed: 11/29/2022]
Abstract
Identification of 19 molecular species of globotriaosylceramides (Gb3) in extracts from a Fabry's plasma patient and a healthy control was performed by High-Performance Thin-Layer Chromatography (HPTLC)-densitometry and online coupling to Mass Spectrometry (MS). Separation was carried out on LiChrospher plates using Automated Multiple Development (AMD). Densitometry was performed on twin plates by combining detection in the visible at 550 nm, through previous on-plate orcinol derivatization, and by Ultraviolet 190 nm, using a non-impregnated plate. The latter was directly coupled to an ion-trap mass spectrometer through an automated elution-based interface. Gb3 molecular species, which were identified by HPTLC- Electrospray Mass Spectrometry (+)-MS and confirmed by MS/MS or HPTLC-Atmospheric Pressure Chemical Ionization Mass Spectrometry (+)-MS, are: five isoforms of saturated Gb3; seven isoforms of methylated Gb3; and seven species with two additional double bonds. Twelve of these species were previously reported as biomarkers of Fabry's lysosomal disorder using a Liquid Chromatography-MS-based method, and the other seven are structurally similar, closely related to them. Saturated Gb3 isoforms migrated on LiChrospher plate in one of the separated peaks corresponding to the migration zone of ceramide trihexosides standard. Instead, methylated and unsaturated Gb3 species co-migrated with sphingomyelin species. Ion intensity ESI-MS profiles show that saturated Gb3 species in Fabry's plasma were in higher concentration than in control sample. Before applying the Thin-Layer Chromatography (TLC)-MS interface on HPTLC separated peaks, its positioning precision was first studied using ceramide tri-hexosides as model compound. This provided information on Gb3 peak broadening and splitting during its migration.
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Colorimetric-enzymatic determination of tyramine by generation of gold nanoparticles. Mikrochim Acta 2020; 187:174. [PMID: 32072299 DOI: 10.1007/s00604-020-4141-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 01/24/2020] [Indexed: 12/31/2022]
Abstract
In this paper, it has been demonstrated that Au(III) is able to act instead of O2 in the oxidase enzymatic reaction, so that it becomes reduced to purple gold nanoparticles (AuNPs). The plasmon band (at 540 nm) can be used as the analytical signal. Tyramine has been determined using its enzymatic reaction with tyramine oxidase (TAO). The kinetic of the AuNP formation has been studied in the light of both the Avrami equation for crystallization and the Finke-Watsy mechanism for AuNP nucleation and growth. The effects of the Au(III), TAO and tyramine concentrations on the corresponding kinetic constants have been investigated. Working at room temperature, under optimal conditions (phosphate buffer pH 7.0, TAO 0.5 U.mL-1 Au(III) 1 mM), the linear response ranges from 2.5 × 10-5 M to 3.3 × 10-4 M Tyramine (5.6% RSD) and the LOD is 2.9 × 10-6 M. Under these conditions, the signal is measured after 30 min reaction (to obtain the highest sensitivity), but this time can be significantly reduced by increasing the temperature (the reaction is finished after 4 min when working at 50 °C). The method has been applied to tyramine determination in a cheese sample with good results. The new scheme proposed in this paper can be extended, in principle, to other enzymatic methods based on oxidase enzymes. Graphical abstractTyramine is determined by measuring the plasmon band of the gold nanoparticles formed during its enzymatic reaction with Tyramine oxidase. Moreover, a mathematical model has been developed to explain the formation of the gold nanoparticles during the reaction.
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Analytical possibilities of Putrescine and Cadaverine enzymatic colorimetric determination in tuna based on diamine oxidase: A critical study of the use of ABTS. Talanta 2020; 208:120392. [DOI: 10.1016/j.talanta.2019.120392] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 09/23/2019] [Accepted: 09/26/2019] [Indexed: 10/25/2022]
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13
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HPTLC coupled to ESI-Tandem MS for identifying phospholipids associated to membrane proteins in photosynthetic purple bacteria. J LIQ CHROMATOGR R T 2019. [DOI: 10.1080/10826076.2018.1561465] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Gold nanoclusters as a quenchable fluorescent probe for sensing oxygen at high temperatures. Mikrochim Acta 2018; 185:171. [PMID: 29594649 DOI: 10.1007/s00604-018-2676-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 01/11/2018] [Indexed: 11/29/2022]
Abstract
Gold nanoclusters (AuNCs) capped with lipoic acid (LA) or templated with bovine serum albumin (BSA) are shown to be viable fluorescent probes for oxygen (O2) which acts as a collisional quencher. Quenching of fluorescence, with its lifetimes in the order of 123 ± 9 ns (LA) and 153 ± 15 ns (BSA) (in aqueous solution), is best measured at excitation/emission wavelengths of 400/680 nm and 375/650 nm respectively. It follows the Stern-Volmer model, whose quenching constants (Ksv) and quenching efficiencies (γ) are 1400 M-1 and 0.52 for AuNC@LA and 4479 M-1 and 0.90 for AuNC@BSA. The probes were immobilized on a silica support and tested for response to O2 in gas phase using a commercial instrument. The effect of temperature on the fluorescence of AuNC@LA was studied in the range from 30 to 210 °C. Fluorescence intensity slightly decreases with temperature in the first heating cycle but remains constant in further cycles. The AuNC@LA were studied for their response to O2 in the temperature range from 30 to 100 °C, and even at 100 °C they respond to O2, with a Ksv that slightly drops with increasing temperature. Measuring in gas phase at 100 °C, the sensor has a detection limit of 3% (V/V) of O2 at a signal-to-noise ratio of 3. Graphical Abstract Gold-nanoclusters (AuNCs) fluorescence intensity (λexc = 400 nm, λem = 680 nm) remains constant from 30 to 210 °C and is quenched by O2 following a collisional mechanism. The Stern-Volmer constant (Ksv) slightly changes from 25 °C to 100 °C (at least).
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Enzymatic methods for choline-containing water soluble phospholipids based on fluorescence of choline oxidase: Application to lyso-PAF. Anal Biochem 2017; 519:30-37. [PMID: 27956151 DOI: 10.1016/j.ab.2016.12.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/01/2016] [Accepted: 12/08/2016] [Indexed: 11/25/2022]
Abstract
In this paper we present methods to determine water soluble phospholipids containing choline (wCh-PL). The analytes were hydrolyzed by the enzyme phospholipase D and the choline formed was oxidized by the enzyme Choline Oxidase (ChOx); the fluorescence changes of the ChOx are followed during the enzymatic reaction, avoiding the necessity of an indicating step. Both reactions (hydrolysis and oxidation) can be combined in two different ways: 1) a two-step process (TSP) in which the hydrolysis reaction takes place during an incubation time and then the oxidation reaction is carried out, the analytical signal being provided by the intrinsic fluorescence of ChOx due to tryptophan; 2) a one-step process (OSP) in which both enzymatic reactions are carried out simultaneously in the same test; in this case the analytical signal is provided by the ChOx extrinsic fluorescence due to a fluorescent probe (Ru (II) chelate) linked to the enzyme (ChOx-RuC). The analytical capabilities of these methods were studied using 1,2-dioctanoyl-sn-glycero-3-phosphocholine (C8PC), a water soluble short alkyl chain Ch-PL as a substrate, and 1-O-hexadecyl-sn-glyceryl-3-phosphorylcholine (lyso-PAF). The analytical features of merit for both analytes using both methods were obtained. The TSP gave a 10-fold sensitivity and lower quantification limit (1.0*10-5 M for lyso-PAF), but OSP reduced the determination time and permitted to use the same enzyme aliquot for several measurements. Both methods gave similar precision (RSD 7%, n = 5). The TSP was applied to the determination of C8PC and lyso-PAF in spiked synthetic serum matrix using the standard addition method. The application of this methodology to PLD activity determination is also discussed.
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The intrinsic fluorescence of FAD and its application in analytical chemistry: a review. Methods Appl Fluoresc 2016; 4:042005. [DOI: 10.1088/2050-6120/4/4/042005] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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17
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A reagentless enzymatic fluorescent biosensor for glucose based on upconverting glasses, as excitation source, and chemically modified glucose oxidase. Talanta 2016; 160:586-591. [DOI: 10.1016/j.talanta.2016.07.062] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 07/22/2016] [Accepted: 07/25/2016] [Indexed: 11/27/2022]
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18
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Rapid enzymatic method for the determination of phosphoryl choline using the fluorescence of the enzyme choline oxidase. Sequential determination of choline and phosphorylcholine in milk powder for children. Microchem J 2015. [DOI: 10.1016/j.microc.2015.06.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Fluorescence of the Flavin group in choline oxidase. Insights and analytical applications for the determination of choline and betaine aldehyde. Talanta 2015; 147:253-60. [PMID: 26592604 DOI: 10.1016/j.talanta.2015.09.060] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 09/18/2015] [Accepted: 09/24/2015] [Indexed: 12/20/2022]
Abstract
Choline oxidase (ChOx) is a flavoenzyme catalysing the oxidation of choline (Ch) to betaine aldehyde (BA) and glycine betaine (GB). In this paper a fundamental study of the intrinsic fluorescence properties of ChOx due to Flavin Adenine Dinucleotide (FAD) is presented and some analytical applications are studied in detail. Firstly, an unusual alteration in the excitation spectra, in comparison with the absorption spectra, has been observed as a function of the pH. This is ascribed to a change of polarity in the excited state. Secondly, the evolution of the fluorescence spectra during the reaction seems to indicate that the reaction takes place in two consecutive, but partially overlapped, steps and each of them follows a different mechanism. Thirdly, the chemical system can be used to determine the Ch concentration in the range from 5×10(-6)M to 5×10(-5)M (univariate and multivariate calibration) in the presence of BA as interference, and the joint Ch+BA concentration in the range 5×10(-6)-5×10(-4)M (multivariate calibration) with mean errors under 10%; a semiquantitative determination of the BA concentration can be deduced by difference. Finally, Ch has been successfully determined in an infant milk sample.
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A modified commercial gas chromatograph for the continuous monitoring of the thermal degradation of sunflower oil and off-line solid phase extraction gas-chromatography-mass spectrometry characterization of released volatiles. J Chromatogr A 2015; 1388:52-9. [PMID: 25725960 DOI: 10.1016/j.chroma.2015.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/03/2015] [Accepted: 02/03/2015] [Indexed: 11/29/2022]
Abstract
A homemade flow cell attached to a commercial Gas Chromatograph equipped with a Flame Ionization Detector (FID) has been designed for the continuous monitoring of volatile compounds released during heating edible oils. Analytical parameters such as mass of sample, temperature and flow rates have been optimized and the obtained results have been compared with the corresponding thermographs from standard TG systems. Results show that under optimum conditions, the profiles of volatiles released upon heating are comparable to the profiles of TG curves, suggesting that the FID based system could be an alternative to TGA. Additionally, volatiles have been retained in a Lichrolut EN(®) resin, eluted and analyzed by Gas Chromatography-Mass Spectrometry. In this case, forty five compounds have been identified (acids, alcohols, alkanes, aldehydes, ketones and furans) and compared with the FID signals, working both in air or nitrogen atmosphere. It has been concluded that the oxidative thermal degradation is prevented in the presence of a nitrogen atmosphere.
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Spectrally matched upconverting luminescent nanoparticles for monitoring enzymatic reactions. ACS APPLIED MATERIALS & INTERFACES 2014; 6:15427-33. [PMID: 25090410 DOI: 10.1021/am5038643] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report on upconverting luminescent nanoparticles (UCLNPs) that are spectrally tuned such that their emission matches the absorption bands of the two most important species associated with enzymatic redox reactions. The core-shell UCLNPs consist of a β-NaYF4 core doped with Yb(3+)/Tm(3+) ions and a shell of pure β-NaYF4. Upon 980 nm excitation, they display emission bands peaking at 360 and 475 nm, which is a perfect match to the absorption bands of the enzyme cosubstrate NADH and the coenzyme FAD, respectively. By exploiting these spectral overlaps, we have designed fluorescent detection schemes for NADH and FAD that are based on the modulation of the emission intensities of UCLNPs by FAD and NADH via an inner filter effect.
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Enzyme-induced modulation of the emission of upconverting nanoparticles: Towards a new sensing scheme for glucose. Biosens Bioelectron 2014; 59:14-20. [DOI: 10.1016/j.bios.2014.02.076] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/26/2014] [Accepted: 02/27/2014] [Indexed: 10/25/2022]
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An optical sensor for pesticide determination based on the autoindicating optical properties of peroxidase. Talanta 2014; 122:251-6. [DOI: 10.1016/j.talanta.2014.01.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 01/03/2014] [Accepted: 01/07/2014] [Indexed: 10/25/2022]
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24
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Analytical applications of the optical properties of ferric hemoglobin: A theoretical and experimental study. Microchem J 2014. [DOI: 10.1016/j.microc.2013.12.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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25
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Evaluation of a fluorometric-enzymatic method based on 3alpha-hydroxysteroid dehydrogenase for the mycotoxin zearalenone determination in corn. Talanta 2012; 64:196-201. [PMID: 18969588 DOI: 10.1016/j.talanta.2004.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Revised: 12/19/2003] [Accepted: 02/06/2004] [Indexed: 10/26/2022]
Abstract
A new method for the fluorometric determination of zearalenone (ZEN) based on its reaction with betaNADH in the presence of the enzyme 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) is described. The procedure is based on the change in fluorescence intensity that takes place during the enzymatic reaction (excitation at 340nm and emission at 454nm). The optimum reaction conditions and the analytical characteristics were studied; linear response range (1-10mgl(-1)) and reproducibility (8mgl(-1), 2.7%, n=7). Moreover, a mathematical model explaining the analytical signal is proposed. The method has been applied to zearalenone determination in a spiked corn sample.
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Direct determination of uric acid in serum by a fluorometric-enzymatic method based on uricase. Talanta 2012; 54:847-54. [PMID: 18968307 DOI: 10.1016/s0039-9140(01)00335-6] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2000] [Revised: 01/24/2001] [Accepted: 01/24/2001] [Indexed: 12/01/2022]
Abstract
The present paper describes a method for the fluorometric determination of uric acid in blood serum by its reaction with uricase (UOx). The procedure is based on the changes in fluorescence that take place during the enzymatic reaction of UOx with uric acid when the solution is excited at 287 nm and the emission is measured at 330 nm. A mathematical model which relates the analytical signal to the analyte concentration was developed and the model also served to obtain some of the thermodynamic constants of the system (the Michaelis constant and the turnover number). The optimum reaction conditions and its analytical characteristics were studied, linear response range (3x10(-5)-6x10(-4) M) and reproducibility (4%, n=7). The method was applied to the determination of uric acid in three blood serum samples. The results were compared with those obtained by a commercial clinical analyzer and no systematic errors were observed.
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Autoindicating optical properties of laccase as the base of an optical biosensor film for phenol determination. Anal Bioanal Chem 2012; 404:351-9. [DOI: 10.1007/s00216-012-6061-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/26/2012] [Accepted: 04/18/2012] [Indexed: 11/27/2022]
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28
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Changes in fluorescent emission of cationic fluorophores in the presence of n-alkanes and alcohols in different polarity solvents. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2010.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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29
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Selective peracetic acid determination in the presence of hydrogen peroxide using a label free enzymatic method based on catalase. Anal Bioanal Chem 2010; 398:2117-24. [DOI: 10.1007/s00216-010-4145-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 08/18/2010] [Indexed: 11/28/2022]
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30
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CCD detectors for molecular absorption spectrophotometry. A theoretical and experimental study on characteristics and performance. Analyst 2010; 135:564-9. [DOI: 10.1039/b919480k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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A blood-assisted optical biosensor for automatic glucose determination. Talanta 2009; 78:846-51. [DOI: 10.1016/j.talanta.2008.12.060] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Revised: 12/17/2008] [Accepted: 12/22/2008] [Indexed: 11/25/2022]
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32
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The environmental effect on the fluorescence intensity in solution. An analytical model. Analyst 2009; 134:2286-92. [DOI: 10.1039/b912063g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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Simultaneous Determination of Glucose and Choline Based on the Intrinsic Fluorescence of the Enzymes. J Fluoresc 2008; 19:583-91. [DOI: 10.1007/s10895-008-0448-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Accepted: 11/24/2008] [Indexed: 11/30/2022]
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34
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Reagentless optical biosensors for organic compounds based on auto-indicating proteins. Protein Pept Lett 2008; 15:772-8. [PMID: 18855747 DOI: 10.2174/092986608785203782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Optical reagentless biosensors are one of the most promising alternatives for producing selective, sensitive and autonomous sensors for real life applications. These devices are based on the efficient use of the spectroscopic properties of bioreagents, mainly proteins, as transducers; avoiding in this way the use of chemical colorant/fluorophores which usually limit sensors performance. In this paper a brief state of the art of the bioreagents being used in biosensors as well as recent alternatives are discussed. The advantages of flavoenzymes and hemeproteins as the basis for reagentless biosensors are particularly stressed.
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35
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A theoretical approach for designing fluorescent reagentless biosensors: The optical model. Anal Chim Acta 2008; 615:148-57. [DOI: 10.1016/j.aca.2008.03.063] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 03/23/2008] [Accepted: 03/26/2008] [Indexed: 11/26/2022]
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36
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Uric acid determination using uricase and the autotransducer molecular absorption properties of peroxidase. Anal Chim Acta 2008; 607:211-8. [DOI: 10.1016/j.aca.2007.11.051] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Revised: 11/22/2007] [Accepted: 11/26/2007] [Indexed: 11/29/2022]
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Direct glucose determination in blood using a reagentless optical biosensor. Biosens Bioelectron 2007; 22:2876-83. [PMID: 17275275 DOI: 10.1016/j.bios.2006.12.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 11/21/2006] [Accepted: 12/01/2006] [Indexed: 11/17/2022]
Abstract
This paper demonstrates that glucose determination in blood can be done directly (without sample pretreatment) using a reagentless reversible biosensor based on the intrinsic spectroscopic properties of peroxidase (HRP). The biosensor, prepared by HRP and glucose oxidase entrapment in a polyacrylamide gel matrix, works in continuous mode, presents a linear response range from 1.5 x 10(-6) up to 5.5 x 10(-5)M and can be used for at least 750 measurements; in the best conditions (0.1 M pH 6 phosphate buffer, HRP and GOx amounts in the polymersation mixture for the sensor film preparation 0.0165 and 0.0010 g, respectively) the minimum samples rate is 30 h(-1). For glucose determination, blood is simply diluted in water (until haemolysis is completed) and fed into the sensor without a cleaning step between samples; the blood absorption is corrected in a simple way by working at a proper reference wavelength. The biosensor signals have been mathematically modeled in order to facilitate the design of sensors based on the same idea for other biochemical compounds.
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39
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Uncertainty due to the quantification step in analytical methods. Talanta 2007; 71:1339-44. [DOI: 10.1016/j.talanta.2006.07.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Revised: 06/19/2006] [Accepted: 07/06/2006] [Indexed: 10/24/2022]
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40
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Hydrogen peroxide and peracetic acid determination in waste water using a reversible reagentless biosensor. Anal Chim Acta 2007; 583:332-9. [PMID: 17386564 DOI: 10.1016/j.aca.2006.10.054] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 10/16/2006] [Accepted: 10/26/2006] [Indexed: 11/21/2022]
Abstract
During the reversible reaction between peroxidase (HRP) and peroxides, several peroxidase intermediate species, showing different molecular absorption spectra, are formed which can be used for their determination. On this basis, a reversible reagentless optical biosensor based on HRP for hydrogen peroxide and peracetic acid determinations has been developed. The biosensor (which can be used for at least 3 months and/or more than 200 measurements) is prepared by HRP entrapment in a polyacrylamide gel matrix. A mathematical model (in which optical, kinetic and transport aspects are considered) relating the measured absorbance with the analyte concentration is also presented. Both peroxides show similar responses in the sensor film. Under the recommended working conditions, the biosensor shows linear response ranges from 6x10(-7) to 1.0x10(-4) M using FIA mode, and from 2x10(-7) to 1.5x10(-5) M using continuous mode for both peroxides; the precision, expressed as R.S.D., is about 4%. This biosensor has been applied for peroxide determination in waste water samples previously treated with peroxides.
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A reagentless optical biosensor based on the intrinsic absorption properties of peroxidase. Biosens Bioelectron 2007; 22:956-64. [PMID: 16750620 DOI: 10.1016/j.bios.2006.04.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Revised: 03/16/2006] [Accepted: 04/03/2006] [Indexed: 11/25/2022]
Abstract
During the reversible reaction between peroxidase (HRP) and H(2)O(2), several peroxidase intermediate species, showing different molecular absorption spectra, are formed which can be used for H(2)O(2) determination; when H(2)O(2) is generated in a previous enzymatic reaction, the substrate involved in this reaction can also be determined. On this basis, a new family of fully reversible reagentless optical biosensors containing HRP is presented; glucose determination is used as a model. The biosensor (which can be used for at least 6 months and/or more than 750 measurements) is prepared by HRP and glucose oxidase entrapment in a polyacrylamide gel matrix. A mathematical model (in which optical, kinetic and transport aspects are considered) relating the measured absorbance with the substrate concentration is also presented together with a simple methodology for characterization of this kind of biosensor. Regarding the optical model, the Kubelka-Mulk theory of reflectance does not give good results and the biosensors are better described by the Rayleigh theory of polymer solutions. Under working conditions, linear response ranges from 1.5x10(-6) to 3.0x10(-4)M glucose and CV was about 4%. This biosensor has been applied for glucose determination in fruit juices and synthetic serum samples without sample pretreatment.
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Abstract
This paper demonstrates that the spectrophotometric properties of blood hemoglobin (Hb) can be used for the direct determination of biochemical compounds in blood. Glucose is used as a model, but the methodology can be applied to many other compounds (only a previous enzymatic reaction producing H(2)O(2) is needed). In order to develop the method, a model relating the Hb absorbance variation during the reaction with the glucose concentration has been developed to provide theoretical support for the method and to predict its application to other compounds. In addition, clear blood samples need to be prepared without pre-treatment and lateral reactions of H(2)O(2) with other blood constituents need to be blocked; this has been achieved with 100 : 1 v/v blood dilution in bi-distilled water and azide addition. The linear response range of the method can be fitted between 2 and 540 mg dL(-1) glucose relative to the original blood sample (RSD about 4%, 70 mg dL(-1)). The analyte concentration can be obtained by an absolute calibration method or by the standard addition method; both have been applied for direct glucose determination in several blood samples and good correlations with those obtained by an automatic analyzer have been obtained.
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Application of Molecular Absorption Properties of Horseradish Peroxidase for Self-Indicating Enzymatic Interactions and Analytical Methods. J Am Chem Soc 2005; 127:1038-48. [PMID: 15656642 DOI: 10.1021/ja046830k] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this paper an in depth study is presented of the use of the horseradish peroxidase (HRP) enzyme as a self-indicating biorecognition reagent in UV-vis molecular absorption spectrometry. The HRP/H2O2 reaction mechanism in the absence of an external substrate has been clarified, and the interaction between HRP and glucose oxidase (GOx) has been studied. It has been demonstrated that GOx can act as a substrate of HRP; in both cases the kinetic constants have been obtained and mathematical models have been developed. Second, the HRP/H2O2 reaction is used to follow a H2O2-producing enzymatic reaction, the glucose reaction with GOx being used as a model. As an application of this, two methodologies have been proposed for glucose determination: with or without previous incubation of glucose with GOx. In both cases mathematical models relating HRP absorbance changes to glucose concentration have been developed and tested; both methods have been optimized, analytically characterized, and tested for glucose determination in samples. The methodology described could be applied to other heme-proteins and to other H2O2-producing enzymatic reactions. The models permit the reaction constants to be calculated. From the analytical chemistry point of view the models allow the prediction of the method sensitivity for other analytes involved in this type of reaction if the kinetic constants are known and can be used in the design of optical sensors.
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Choline determination based on the intrinsic and the extrinsic (chemically modified) fluorescence of choline oxidase. Anal Biochem 2004; 334:207-15. [PMID: 15494126 DOI: 10.1016/j.ab.2004.04.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Indexed: 11/19/2022]
Abstract
This paper describes two methods for the fluorometric determination of choline in serum by its reaction with the enzyme choline oxidase (ChOx). The first method, is based on changes in the intrinsic fluorescence of the enzyme (lambda(excitation)=28 nm and lambda(emission)=336 nm). The second method follows changes in the fluorescence intensity of a chemical modificant bonded to the enzyme (ChOx-FS), with excitation and emission maxima at 492 and 516 nm, respectively. Both methods have a similar response range (from 5 x 10(-7) to 10(-5) M or to 5 x 10(-5) M, depending on the analytical parameter) and precision (about 5%). The origin of the enzyme fluorescence changes has been elucidated and a mathematical model explaining the analytical signal is presented. This model can be applied to other enzymatic reactions based on flavin-containing enzymes and enables prediction of the sensitivity of new methods based on the Km values. Both methods have been applied to choline determination in synthetic serum samples. Moreover, the use of ChOx-FS avoids sample pretreatment.
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Removal of naphthalene, phenanthrene, and pyrene by sorbents from hot gas. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2001; 35:2395-2400. [PMID: 11414051 DOI: 10.1021/es000152u] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It is the first time that the removal of polycyclic aromatic hydrocarbons (PAH) containing different aromatic rings number [naphthalene (Np), phenanthrene (Phe), and pyrene (Py)] from combustion hot gas has been carried out. The aim was to relate the sorbents textural characteristics with the adsorption capacity of these 2-4-ring PAH at the conditions emitted at energy generation. The sorbents textural parameters [total micropore volume (VN2), narrow micropore volume (VCO2), mesopore volume (VBJH), and the free active sites] were analyzed trying to correlate them with their Np, Phe, and Py adsorption capacities. To get this aim, single and multiple linear regressions (MLR) were applied to the three PAH. A principal component analysis was performed to generate new and uncorrelated variables. It enabled us to show that the relations between the textural parameters were analyzed using a principal components regression (PCR). The PCR analysis had a good statistical quality, but neither did it allow differentiating free active site types nor did VN2 and VCO2. The correlations were thus set up applying a MLR to the original variables. The regression statistical quality was similar to the PCR analysis, and it could give an easier explanation of the parameters that affected the adsorption. In Np adsorption, the 87% data variance was explained, and the adsorption was positively correlated to VCO2 and the micropore mean diameter (I.). In the Phe regression there was 98% variance explained, and its adsorption was positively correlated to the VN2 and the micropore distribution, n. Finally, in the Py adsorption, the 96% data variance was explained, and this adsorption was positively correlated to VN2 and VBJH. These dependencies were according to the molecular parameters of these compounds (molecular diameter and volatility) because the higher the number of aromatic rings of the PAH, the more favored the adsorbate-adsorbate interactions. Besides, the higher the mean diameter micropores, the lower the diffusional problems showed by Np, Phe, and Py.
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Integrated analytical pervaporation–gas-phase absorptiometry: theoretical aspects and applications. Anal Chim Acta 2001. [DOI: 10.1016/s0003-2670(01)00823-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Intrinsic fluorescence of enzymes and fluorescence of chemically modified enzymes for analytical purposes: a review. LUMINESCENCE 2001; 16:199-210. [PMID: 11312548 DOI: 10.1002/bio.633] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In recent years our research group has developed new alternatives for fluorescence enzymatic determinations. First, we observed that the intrinsic fluorescence of enzymes changes during enzymatic reactions, proportionally to the substrate concentration, avoiding the combination of the enzymatic reaction with a fluorophore-involving reaction. The main disadvantage of this method is that the excitation and emission wavelengths of the enzymes are in the UV region of the spectrum. An alternative to overcome this problem consisted of covalently bonding the enzyme to a fluorophore. In this paper, an overview is given of all of the applications and future developments on both types of alternatives that we have developed. Apart from the analytical characteristics of the methods, we have also reviewed all of the information about mathematical models we have elaborated to date.
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Determination of direct-bilirubin by a fluorimetric-enzymatic method based on bilirubin oxidase. FRESENIUS' JOURNAL OF ANALYTICAL CHEMISTRY 2000; 368:516-21. [PMID: 11227536 DOI: 10.1007/s002160000503] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A method for the determination of direct bilirubin by reaction with bilirubin oxidase (BOx) is reported. The procedure is based on the changes in fluorescence which take place during the enzymatic reaction of BOx with any of the three forms of bilirubin (free, conjugated and with albumin) when the solution is excited at 240 nm and the emission is measured at 440 nm. The change in fluorescence was studied thoroughly. It seems mainly due to the fluorescence of one of the reaction products. A theoretical study was carried out to relate the changes in fluorescence observed to the species taking part in the reaction and to establish some of the enzymatic reaction constants. The optimum reaction conditions were studied for each of the three types of bilirubin together with their analytical characteristics (linear range and precision). Selective determination of direct bilirubin was carried out for various synthetic samples with good results. A linear response up to 7 mg L(-1) of direct bilirubin was obtained. Using optimum conditions, the precision for free and conjugated bilirubin was 3.4% (n = 5) and 3.0% (n = 5), respectively.
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49
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Heated flow-cell for gas phase UV-visible detector in gas chromatography of polycyclic aromatic hydrocarbons. Chromatographia 1999. [DOI: 10.1007/bf02490652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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50
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Simultaneous determination of propanol and butanol by a fluorometric enzymatic method based on the intrinsic fluorescence of the enzyme. ACTA ACUST UNITED AC 1999. [DOI: 10.1007/s002160051278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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