Indirect determination of pepsin activity in human seric protein samples by polyphenol oxidase electrodes

Forzani, Erica; Bernardi, Marı́a E.; Sisti, Ada; Zarzur, Jorge A.; Solı́s, V.

doi:10.1016/s0003-2670(02)00231-3

Cited by 6 publications

(4 citation statements)

References 15 publications

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“…For pepsin, after incubation with PS MPs (0, 50, 100, 200 mg/L) for 2 h at 37 °C, pepsin activities were determined by the Folin method . For lipase, after incubation with PS MPs (0, 40, 80, 160 mg/L) for 2 h at 37 °C, the lipase activities were determined by a turbidimetric method .…”

Section: Materials and Methodsmentioning

confidence: 99%

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Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

Tan

Yue

et al. 2020

Environ. Sci. Technol.

141

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Microplastics (MPs) are unavoidably ingested by humans, and their gastrointestinal processes and impact on lipid digestion are unknown. In the present work, all five MP types used, including polystyrene (PS), polyethylene terephthalate, polyethylene, polyvinyl chloride, and poly(lactic-co-glycolic acid) (80 mg/L in small intestine), significantly reduced lipid digestion in the in vitro gastrointestinal system. PS MPs exhibited the highest inhibition (12.7%) among the five MPs. Lipid digestion decreased with increasing PS concentration, but independent of PS size (50 nm, 1 μm, 10 μm). PS MPs after photoaging by simulated sunlight also significantly decreased lipid digestion. Confocal imaging shows that PS MPs could interact with both lipid droplets and lipases. Two mechanisms underlying the PS-induced digestion inhibition were revealed using both experimental and molecular dynamics simulation approaches: (1) PS MPs decreased the bioavailability of lipid droplets via forming large lipid-MPs heteroaggregates due to the high MP hydrophobicity; and (2) PS MPs adsorbed lipase, and reduced its activity by changing the secondary structure and disturbing the essential open conformation. The first mechanism (MP-lipid interaction) played a more important role in lipid digestion reduction based on interaction energy calculation. These findings reveal potential risk of MPs to human digestion health and nutrient assimilation.

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Section: Materials and Methodsmentioning

confidence: 99%

“…37 °C, pepsin activities were determined by the Folin method. 26 For lipase, after incubation with PS MPs (0, 40, 80, 160 mg/L) for 2 h at 37 °C, the lipase activities were determined by a turbidimetric method. 27 The changes in the secondary structures of digestive enzymes were investigated by circular dichroism (CD, J-815, JASCO, Japan).…”

Section: Methodsmentioning

confidence: 99%

Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

Tan

Yue

et al. 2020

Environ. Sci. Technol.

141

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“…This enzyme catalyses two chemical reactions: the oxidation of phenols or some of their derivatives, giving off the corresponding catechols (cresolase or monophenolase activity), and the dehydrogenation of these molecules, giving off o-quinones (catecholase or diphenolase activity). Applications of PPO in biosensors have allowed the determination of phenol and catechol derivatives 39 as well as L-Tyr-containing peptides 40 and enzymatic inhibitors. 41 The comprehension of the behavior of self-assembled multilayers containing PPO provides a basis for the kinetic study of the bioelectrode response, an essential feature when assessing the optimal working conditions of PPO biosensors.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Polycation Nature on the Structure of Layer-by-Layer Electrostatically Self-Assembled Multilayers of Polyphenol Oxidase

et al. 2003

Self Cite

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Self-assembled multilayers comprised of alternate layers of polyphenol oxidase (PPO) and poly(allylamine) (PAH) or PPO and poly(diallyldimethylamine) (PDDA), deposited on a 3-mercaptopropanesulfonic acid (MPS)-modified gold surface, were studied "in-situ" (under water) by means of ellipsometry and quartz crystal microbalance (QCM), and "ex-situ" (in open air) by ellipsometry and fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS). Optical ellipsometric properties of (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) multilayers were obtained at two wavelengths, employing an isotropic single-layer model with the substrate parameters measured after thiol adsorption. Film thickness as well as ellipsometric mass values based on the de Feijter equation were also evaluated. The quartz crystal impedance analysis showed that self-assembled multilayers behaved as acoustically thin films, and therefore, the shifts observed in the film inductive impedance parameter were interpreted in terms of gravimetric mass. The enzyme mass up-take in each adsorption step was determined on PAH or on PDDA topmost layer. A comparative study between the ellipsometric thickness and acoustic mass values allowed us to obtain average values of "apparent" densities of (2.1 +/- 0.1) and (2.4 +/- 0.1) g cm(-3) for (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) multilayers, respectively. The content of water included in the open polymer-enzyme structure was evaluated by comparison of QCM and ellipsometric mass values. FT-IRRAS spectra of each layer in (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) films were recorded, and the intensity ratio of the amide bands was evaluated to obtain information about layer-by-layer enzyme conformation. An enzyme/polycation distribution model for (PAH)(n)(PPO)(n)and (PDDA)(n)(PPO)(n) multilayer structures is presented on the basis of combined ellipsometric, QCM, and FT-IRRAS results.

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“…The chronoamperometric method can be used to detect biomolecules [33] and free radicals [34]. We also attempted to investigate the amperometric response of DA and AA at the modified electrode.…”

Section: Amperometric Sensing Of Da and Aamentioning

confidence: 99%

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano‐Gold Self‐Assembled Glassy Carbon Electrode

Guo

Shao

2009

Electroanalysis

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Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self-assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self-assembling gold nanoparticles on the surface of l-cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well-defined redox peaks of DA on the GNP/LC/GCE was obtained at E pa ¼ 0.197 V and E pc ¼ 0.146 V, respectively. And the peak separation between DA and AA is about 0.2 V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0 Â 10, with the detection limit of 2.0 Â 10 À8 mol L À1 and 3.0 Â 10 À7 mol L À1 (S/N ¼ 3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result.

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Indirect determination of pepsin activity in human seric protein samples by polyphenol oxidase electrodes

Cited by 6 publications

References 15 publications

Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

Effect of the Polycation Nature on the Structure of Layer-by-Layer Electrostatically Self-Assembled Multilayers of Polyphenol Oxidase

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano‐Gold Self‐Assembled Glassy Carbon Electrode

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