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1.
J Biotechnol ; 394: 85-91, 2024 Nov 10.
Artículo en Inglés | MEDLINE | ID: mdl-39178917

RESUMEN

The degummed wastewater from silk processing contains a huge amount of amino acids and polypeptides from sericin. The silk degumming water is far from being exploited fully. Sericin in the degumming water is generally wasted and causes environmental pollution. In this study, simulated silk degumming water was hydrolyzed by alkaline protease to produce abundant amino acids and polypeptides. After enzymatic hydrolysis, the maximum free amino groups concentration in the silk degumming water was approximately 54 mM. It facilitated the recycling of silk degumming water for the production of melanin-like amino acid surfactants as raw materials. 4-Tert-butylcatechol was used as the starting material to generate o-quinone via oxidation by ceric ammonium nitrate. o-Quinone was coupled with free amino groups in enzymatic hydrolysates of silk degumming water to synthesize a sericin-based amino acid surfactant as hydrophobic and hydrophilic group, respectively. Through the green and simple synthesis route, the product was characterized to have a novel melanin-like structure. The product exhibited superior surface-active properties by lowering the surface tension to 32.39 mN m-1. Furthermore, it demonstrated good foaming ability and foam stability, with the initial foam volume of 37 mL and the foam half-life time of more than 25 min. The product owned a good emulsification ability in the oil-water emulsion with delamination time of 297 s and 291 s for emulsion formed by soybean oil and liquid paraffin, respectively. The wetting time of the canvas sheet was only 134 s. Consequently, the product showed low surface tension, good foaming, emulsifying, and wetting properties.


Asunto(s)
Aminoácidos , Melaninas , Sericinas , Seda , Tensoactivos , Tensoactivos/química , Aminoácidos/química , Seda/química , Sericinas/química , Melaninas/química , Melaninas/metabolismo , Hidrólisis , Aguas Residuales/química , Agua/química , Tensión Superficial
2.
J Mater Chem B ; 11(47): 11235-11250, 2023 12 06.
Artículo en Inglés | MEDLINE | ID: mdl-37953738

RESUMEN

L-3,4-Dihydroxyphenylalanine (L-DOPA) is widely used in Parkinson's disease treatment and is therefore in high demand. Development of an efficient method for the production of L-DOPA is urgently required. Nanozymes emulating tyrosine hydroxylase have attracted enormous attention for biomimetic synthesis of L-DOPA, but suffered from heterogeneity. Herein, a spherical porous iron-nitrogen-carbon nanozyme was developed for production of L-DOPA. Tannic acid chelated with ferrous ions to form a tannin-iron coordination framework as a carbon precursor. Iron and nitrogen co-doped carbon nanospheres were assembled via an evaporation-induced self-assembly process using urea as a nitrogen source, F127 as a soft template, and formaldehyde as a crosslinker. The nanozyme was obtained after carbonization and acid etching. The nanozyme possessed a dispersive iron atom anchored in the Fe-N coordination structure as an active site to mimic the active center of tyrosine hydroxylase. The material showed spherical morphology, uniform size, high specific surface area, a mesoporous structure and easy magnetic separation. The structural properties could promote the density and accessibility of active sites and facilitate mass transport and electron transfer. The nanozyme exhibited high activity to catalyze the hydroxylation of tyrosine to L-DOPA as tyrosine hydroxylase in the presence of ascorbic acid and hydrogen peroxide. The titer of DOPA reached 1.2 mM. The nanozyme showed good reusability and comparable enzyme kinetics to tyrosine hydroxylase with a Michaelis-Menten constant of 2.3 mM. The major active species was the hydroxyl radical. Biomimetic simulation of tyrosine hydroxylase using a nanozyme with a fine structure provided a new route for the efficient production of L-DOPA.


Asunto(s)
Levodopa , Tirosina 3-Monooxigenasa , Tirosina 3-Monooxigenasa/química , Levodopa/química , Carbono/química , Hierro/química , Porosidad , Taninos
3.
J Agric Food Chem ; 71(49): 19652-19662, 2023 Dec 13.
Artículo en Inglés | MEDLINE | ID: mdl-38019268

RESUMEN

Amino acid surfactants have gained significant importance in overcoming the limitations of conventional surfactants, notably, their low biocompatibility and biodegradability. However, the current amino acid surfactants lack multifunctional properties due to the nonreactivity of their aliphatic chains, necessitating the development of a new type of amino acid surfactant. A novel melanin-like amino acid surfactant and a biomimetic synthesis route were devised by mimicking the biosynthesis of melanin. Renewable natural polyphenol compounds with catechol moieties were utilized as building blocks for the hydrophobic group. In a proof-of-concept experiment, ethyl protocatechuate was oxidized to o-quinone and subsequently covalently linked to the amino group of lysine via Michael addition. The chemical structure was verified using liquid chromatography-tandem mass spectroscopy. The melanin-like amino acid surfactant exhibited excellent surface-active properties, with a critical micelle concentration of 1.59 mN m-1. Furthermore, it demonstrated remarkable emulsifying, foaming, solubilizing, dispersing, and wetting capabilities. Notably, it also possessed multifunctionality, including antibacterial activity, antioxidant activity, robustness, and mildness. These outstanding properties indicate significant potential for various applications. This strategy offers innovative insights and a versatile, modular toolbox for synthesizing multifunctional amino acid surfactants that mimic melanin. The approach allows for the easy interchange of o-quinone building blocks, which is akin to snap jewelry.


Asunto(s)
Joyas , Tensoactivos , Tensoactivos/química , Melaninas , Aminoácidos , Biomimética , Quinonas
4.
Anal Bioanal Chem ; 415(22): 5297-5309, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37439855

RESUMEN

Invertase is the key enzyme involved in several crucial biological processes by hydrolyzing sucrose for production of glucose and fructose. Invertase plays important roles in the fields of food, pharmacy, cosmetics, biofuels, and agriculture. Detection of invertase activity is urgently necessary for scientific research and industrial processes. Herein, a continuous fluorometric method was developed for real-time detection of invertase activity. 8-Isoquinolinylboronic acid responded to fructose by formation of a fluorescent complex in turn-on manner, and served as a fluorescent sensor to selectively recognize fructose in ternary enzymatic mixture containing sucrose and glucose. The limit of detection (LOD) for fructose was 0.07 mM. Progress curve for fructose production was established by directly and continuously monitoring the fluorescence for invertase reaction with sucrose as substrate. Initial velocity was obtained to characterize invertase activity. LOD for invertase assay was 0.10 U·mL-1. Km and υmax for invertase were determined as 7.70 mM and 0.86 mM·min-1, respectively. Copper ion was demonstrated to inhibit the invertase activity with IC50 of 33.61 mM. Applicability in high-throughput screening for inhibitor was demonstrated. The proposed method allows for real-time, simple, and rapidly monitoring the invertase activity. It has a broad range of potential applications for kinetics and screening inhibitor.


Asunto(s)
Glucosa , beta-Fructofuranosidasa , beta-Fructofuranosidasa/química , Fructosa , Sacarosa , Límite de Detección
5.
J Biosci Bioeng ; 136(3): 159-165, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37344280

RESUMEN

l-Lactic acid is a natural α-hydroxy carboxylic acid and is commonly used as an addictive. Quantitation of l-lactic acid is indispensable in food and cosmetic industries. An enzymatic colorimetric method was developed for the determination of l-lactic acid by competitive indicator displacement assay. Boric acid inhibited the colorimetric reaction of l-3,4-dihydroxyphenylalanine (l-DOPA) catalyzed by tyrosinase. l-Lactic acid competitively displaced and released l-DOPA bound with boric acid to serve as substrate, and thus restored the tyrosinase activity. Recovery of color reaction could be spectrophotometrically determined at 475 nm and was proportional to the amount of l-lactic acid. A calibration curve between l-lactic acid concentration and recovery of absorbance were built. The concentration range of the l-lactic acid was 0.25-2.25 mM. The limit of detection (LOD) and the limit of quantification (LOQ) for l-lactic acid was estimated to be 0.05 mM and 0.16 mM, respectively. The method achieved turn-on and visual sensing with good precision, accuracy, specificity, and robustness. The assay method exhibited a promising prospect to determine the content of l-lactic acid in foods and cosmetics.


Asunto(s)
Colorimetría , Levodopa , Monofenol Monooxigenasa , Ácido Láctico/química , Ácidos Carboxílicos
6.
J Biol Inorg Chem ; 28(4): 379-391, 2023 06.
Artículo en Inglés | MEDLINE | ID: mdl-37017773

RESUMEN

Hydroxytyrosol, one of the most powerful natural antioxidants, exhibits certificated benefits for human health. In this study, a biomimetic approach to synthesize hydroxytyrosol from the hydroxylation of tyrosol was established. EDTA-Fe2+ coordination complex served as an active center to simulate tyrosine hydroxylase. H2O2 and ascorbic acid were used as oxygen donor and hydrogen donor, respectively. Hydroxy radical and singlet oxygen contributed to active species. The biomimetic system displayed analogous component, structure, and activity with TyrH. Hydroxytyrosol titer of 21.59 mM, and productivity of 9985.92 mg·L-1·h-1 was achieved with 100 mM tyrosol as substrate. The proposed approach provided efficient and convenient route to quickly produce high amount of hydroxytyrosol.


Asunto(s)
Peróxido de Hidrógeno , Tirosina 3-Monooxigenasa , Humanos , Biomimética
7.
Spectrochim Acta A Mol Biomol Spectrosc ; 296: 122644, 2023 Aug 05.
Artículo en Inglés | MEDLINE | ID: mdl-36963278

RESUMEN

Tyrosinase plays an important role in melanin synthesis. Inhibition against tyrosinase activity has been extensively focused on for pharmaceutical, food, cosmetic, and agricultural purpose. The inhibitory mechanism of scutellarein on tyrosinase was elaborated by coupling enzyme kinetics, multi-spectroscopy and computational simulation. Scutellarein remarkably inhibited tyrosinase activity with an IC50 value of 91 µM. Scutellarein reversibly inhibited tyrosinase in a competitive manner. Fluorescence quenching validated that interaction of scutellarein with tyrosinase occurred to form a complex with a binding constant of 6.11 × 104 M-1. Thermodynamic parameters suggested that scutellarein spontaneously bound with tyrosinase via hydrogen bond and van der Waals force. Three-dimensional fluorescence spectra and circular dichroism spectra revealed that scutellarein induced an obvious conformational change in tyrosinase. Molecular docking result predicted that scutellarein mainly bound with tyrosinase via Arg268 residue. Scutellarein effectively controlled the enzymatic browning of apple slices during storage. This research could give theoretical guiding significance in various application for tyrosinase inhibitors.


Asunto(s)
Inhibidores Enzimáticos , Monofenol Monooxigenasa , Monofenol Monooxigenasa/metabolismo , Simulación del Acoplamiento Molecular , Cinética , Dicroismo Circular , Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/química
8.
J Biotechnol ; 365: 11-19, 2023 Mar 10.
Artículo en Inglés | MEDLINE | ID: mdl-36775069

RESUMEN

Tyrosinase is pivotal for melanin formation. Measuring monophenolase activity is of great importance for both fundamental research and industrial applications. For the first time, a backpropagation (BP) artificial neural network with three-dimensional fluorescence spectroscopy was applied for the real-time determination of tyrosinase monophenolase activity. Principal component analysis (PCA) was utilized for the dimension reduction of three-dimensional fluorescence data. The four principal components served as inputs for the neural network. Network parameters were optimized using a genetic algorithm (GA). BP learning algorithm was applied to train the network model to determine tyrosine levels in a binary mixture containing tyrosine and L-DOPA without any chemical separation. The time course of tyrosine consumption by monophenolase was determined to calculate the initial velocity of the enzymatic reaction. The limit of detection of the monophenolase assay was 0.0615 U·mL-1. This combined strategy of PCA, GAs, and BP artificial neural networks for three-dimensional fluorescence spectroscopy was efficient for the real-time and in-situ determination of monophenolase activity in a cascade reaction.


Asunto(s)
Monofenol Monooxigenasa , Redes Neurales de la Computación , Espectrometría de Fluorescencia , Tirosina
9.
Anal Biochem ; 655: 114838, 2022 10 15.
Artículo en Inglés | MEDLINE | ID: mdl-35961401

RESUMEN

Tyrosinase plays a vital role for melanogenesis and inherently involves both monophenolase activity and diphenolase activity. Monophenolase catalyzes hydroxylation of tyrosine to l-DOPA (L-3,4-dihydroxyphenylalanine). Real-time monophenolase assay method is of outstanding interest for both scientific research and industrial application. A combined strategy of three-dimensional excitation-emission matrix (EEM) fluorescence spectra and artificial neural network was developed to determine monophenolase activity. A quantitation system for tyrosine in presence of l-DOPA was designed based on ELMAN neural network. Principal component analysis (PCA) was conducted to reduce the dimensionality of fluorescence spectra. Four principal components was used as input variables. Whale optimization algorithm (WOA) was implemented to optimize the initial weights and threshold network. Real-time concentration of tyrosine in monophenolase reaction was monitored to calculate the initial velocity for tyrosine consumption. The exclusive monophenolase activity without interference from diphenolase reaction was determined. Limit of detection (LOD) for monophenolase assay is 0.0113 U mL-1. Using the proposed method, enzyme kinetics for monophenolase was investigate. Km was calculated as 14.16 µM. Inhibitor for monophenolase was screened by using model molecule kojic acid with IC50 of 3.49 µM. The assay method exhibited a promising prospect to characterize the kinetics and inhibitor of monophenolase.


Asunto(s)
Agaricales , Levodopa , Agaricales/metabolismo , Algoritmos , Animales , Inhibidores Enzimáticos , Fluorescencia , Cinética , Monofenol Monooxigenasa , Redes Neurales de la Computación , Oxidorreductasas , Tirosina , Ballenas/metabolismo
10.
Luminescence ; 35(7): 1092-1100, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32400076

RESUMEN

Ascorbic acid is a vital nutrient and antioxidant that is commonly used as an additive in commercial products. Quantitation of ascorbic acid is highly desired in the medical, food, and cosmetic industries. A spectrofluorometric assay for sensitive determination of ascorbic acid was developed using l-tyrosine as a fluorescent probe. The native fluorescence intensity of tyrosine was quenched using ascorbic acid. The linear range was 0.03-30.00 µM, and the limit of detection was 0.01 µM. The method exhibited excellent precision, accuracy, specificity, and robustness. Components of pharmaceutical preparations that are commonly found with ascorbic acid did not interfere with detection. The procedure was successfully employed for determination of ascorbic acid content in pharmaceutical tablets, injections, and nutrient supplements with satisfactory results. A Stern-Volmer plot and fluorescence lifetime revealed that quenching was attributed to the inner filter effect and static quenching. Isothermal titration calorimetry confirmed the formation of a complex between tyrosine and ascorbic acid, with a binding constant of 1.68 × 103 M-1 and reaction stoichiometry of 0.94. Thermodynamic parameters suggested spontaneous complexation via hydrophobic interactions as the dominant binding force. This method is promising for the simple and rapid determination of ascorbic in the pharmaceutical industry.


Asunto(s)
Colorantes Fluorescentes , Preparaciones Farmacéuticas , Ácido Ascórbico , Espectrometría de Fluorescencia , Tirosina
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