A robust ultra-performance liquid chromatography-tandem mass spectrometry method for simultaneous determination of 10 components in glutathione cycle.

Glutathione (GSH) is an important antioxidant that is generated and degraded via the GSH cycle. Quantification of the main components in the GSH cycle is necessary to evaluate the process of GSH. In this study, a robust ultra-performance liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of 10 components (GSH; γ-glutamylcysteine; cysteinyl-glycine; n-acetylcysteine; homocysteine; cysteine; cystine; methionine; glutamate; pyroglutamic acid) in GSH cycle was developed. The approach was optimized in terms of derivative, chromatographic, and spectrometric conditions as well as sample preparation. The unstable thiol groups of GSH, γ-glutamylcysteine, cysteinyl-glycine, n-acetylcysteine, cysteine, and homocysteine were derivatized by n-ethylmaleimide. The derivatized and underivatized analytes were separated on an amino column with gradient elution. The method was further validated in terms of selectivity (no interference), linearity (R2 > 0.99), precision (% relative standard deviation [RSD%] range from 0.57 to 10.33), accuracy (% relative error [RE%] range from -3.42 to 10.92), stability (RSD% < 5.68, RE% range from -2.54 to 4.40), recovery (RSD% range from 1.87 to 7.87) and matrix effect (RSD% < 5.42). The validated method was applied to compare the components in the GSH cycle between normal and oxidative stress cells, which would be helpful in clarifying the effect of oxidative stress on the GSH cycle.

Discovery and Identification of Three Homocysteine Metabolites by Chemical Derivatization and Mass Spectrometry Fragmentation.

Discovery and identification of a new endogenous metabolite are typically hindered by requirements of large sample volumes and multistage purifications to guide synthesis of the standard. Presented here is a metabolomics platform that uses chemical tagging and tandem mass spectrometry to determine structure, direct synthesis, and confirm identity. Three new homocysteine metabolites are reported: N-succinyl homocysteine, 2-methyl-1,3-thiazinane-4-carboxylic acid (MTCA), and homolanthinone.

Ultrasmall CuMn-His Nanozymes with Multienzyme Activity at Neutral pH: Construction of a Colorimetric Sensing Array for Biothiol Detection and Disease Identification.

Biothiol assays offer vital insights into health assessment and facilitate the early detection of potential health issues, thereby enabling timely and effective interventions. In this study, we developed ultrasmall CuMn-Histidine (His) nanozymes with multiple enzymatic activities. CuMn-His enhanced peroxidase (POD)-like activity at neutral pH was achieved through hydrogen bonding and electrostatic effects. In addition, CuMn-His possesses laccase (LAC)-like and superoxide dismutase (SOD)-like activities at neutral pH. Based on three different enzyme mimetic activities of CuMn-His at neutral pH, the colorimetric sensing array without changing the buffer solution was successfully constructed. The array was successfully used for the identification of three biothiols, glutathione (GSH), cysteine (Cys), and homocysteine (Hcy). Subsequently, excellent application results were shown in complex serum and cellular level analyses. This study provides an innovative strategy for the development of ultrasmall bimetallic nanozymes with multiple enzymatic activities and the construction of colorimetric sensing arrays.

Biothiols-activated near-infrared frequency up-conversion luminescence probe for early evaluation of drug-induced hepatotoxicity.

A novel biothiols-sensitive near-infrared (NIR) fluorescent probe RhDN based on a rhodamine skeleton was developed for early detection of drug-induced hepatotoxicity in living mice. RhDN can be used not only as a conventional large stokes shift fluorescent (FL) probe, but also as a kind of anti-Stokes frequency upconversion luminescence (FUCL) molecular probe, which represents a long wavelength excitation (808 nm) to short wavelength emission (760 nm), and response to Cys/Hcy/GSH with high sensitivity. Compared with traditional FL methods, the FUCL method exhibited a lower detection limit of Cys, Hcy, and GSH in 75.1 nM, 101.8 nM, and 84.9 nM, respectively. We exemplify RhDN for tracking endogenously biothiols distribution in living cells and further realize real-time in vivo bioimaging of biothiols activity in mice with dual-mode luminescence system. Moreover, RhDN has been successfully applied to visualize the detection of drug-induced hepatotoxicity in living mice. Overall, this report presents a unique approach to the development of large stokes shift NIR FUCL molecular probes for in vitro and in vivo biothiols biosensing.

A metal-phenolic coordination framework nanozyme exhibits dual enzyme mimicking activity and its application is effective for colorimetric detection of biomolecules.

Biomolecules play vital roles in many biological processes and diseases, making their identification crucial. Herein, we present a colorimetric sensing method for detecting biomolecules like cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). This approach is based on a reaction system whereby colorless 3,3',5,5'-tetramethylbenzidine (TMB) undergoes catalytic oxidation to form blue-colored oxidized TMB (ox-TMB) in the presence of hydrogen peroxide (H2O2), utilizing the peroxidase and catalase-mimicking activities of metal-phenolic coordination frameworks (MPNs) of Cu-TA, Co-TA, and Fe-TA nanospheres. The Fe-TA nanospheres demonstrated superior activity, more active sites and enhanced electron transport. Under optimal conditions, the Fe-TA nanospheres were used for the detection of biomolecules. When present, biomolecules inhibit the reaction between TMB and H2O2, causing various colorimetric responses at low detection limits of 0.382, 0.776 and 0.750 µM for Cys, Hcy and GSH. Furthermore, it was successfully applied to real water samples with good recovery results. The developed sensor not only offers a rapid, portable, and user-friendly technique for multi-target analysis of biomolecules at low concentrations but also expands the potential uses of MPNs for other targets in the environmental field.

A two-photon fluorescent probe for highly selective detection of Cys over GSH and Hcy based on the Michael addition and transcyclization mechanism and its application in bioimaging and protein straining in SDS-PAGE.

BACKGROUND: Cysteine (Cys), glutathione (GSH), and homocysteine (Hcy), as three major biothiols are involved in a variety of physiological processes and play a crucial role in plant growth. Abnormal levels of Cys can cause plants to fail to grow properly. To date, although a very large number of fluorescent probes have been reported for the detection of biothiols, very few of them can be used for the selective discrimination of Cys from GSH and Hcy due to their structural similarity, and only a few of them can be used for plant imaging. RESULTS: Here, three fluorescent probes (o-/m-/p-TMA) based on TMN fluorophore and the ortho-/meta-/para-substituted maleimide recognition groups were constructed to investigate the selective response effect of Cys. Compared to the o-/m-TMA, p-TMA can selectively detect Cys over GSH and Hcy with a rapid response time (10 min) and a low detection limit (0.26 µM). The theoretical calculation confirmed that the intermediate p-TMA-Cys-int has shorter interatomic reaction distances (3.827 Å) compared to o-/m-TMA-Cys (5.533/5.287 Å), making it more suitable for further transcyclization reactions. Additionally, p-TMA has been employed for selective tracking of exogenous and endogenous Cys in Arabidopsis thaliana using both single-/two-photon fluorescence imaging. Furthermore, single cell walls produced obvious two-photon fluorescence signals, indicating that p-TMA can be used for high-concentration Cys analysis in single cells. Surprisingly, p-TMA can be used as a fluorescent dye for protein staining in SDS-PAGE with higher sensitivity (7.49 µg/mL) than classical Coomassie brilliant blue (14.11 µg/mL). SIGNIFICANCE: The outstanding properties of p-TMA make it a promising multifunctional molecular tool for the highly selective detection of Cys over GSH and Hcy in various complex environments, including water solutions, zebrafish, and plants. Additionally, it has the potential to be developed as a fluorescent dye for a simple and fast SDS-PAGE fluorescence staining method.

A lateral flow strip for on-site detection of homocysteine based on a truncated aptamer.

An elevated level of homocysteine (Hcy) in serum is closely related to the development of various diseases. Therefore, homocysteine has been widely employed as a biomarker in medical diagnosis and the on-site detection of homocysteine is highly desired. In this study, a truncated highly specific aptamer for homocysteine was screened and used to design a lateral flow strip (LFS) for the detection of homocysteine. The aptamer was derived from a previously reported sequence. Based on the result of molecular docking, the original sequence was subjected to truncation, resulting in a reduction of the length from 66 nt to 55 nt. Based on the truncated aptamer, the LFS was designed for the detection of homocysteine. In the presence of homocysteine, the aptamer selectively binds to it, releasing cDNA from the aptamer/cDNA duplex. This allows cDNA to bind to the capture probe immobilized on the T zone of the strip, resulting in a red signal on the T zone from gold nanoparticles (AuNPs). The strip enables the visual detection of homocysteine in 5 min. Quantitative detection can be facilitated with the aid of ImageJ software. In this mode, the linear detection range for homocysteine is within 5-50 µM, with a detection limit of 4.18 µM. The strip has been effectively utilized for the detection of homocysteine in human serum. Consequently, the combination of the truncated aptamer and the strip offers a method that is sensitive, quick, and economical for the on-site detection of homocysteine.

Synthesis and performance of a nanosensing platform for homocysteine detection: A series of iridium(III) complexes containing aldehyde group as probe and MOF as supporting substrate.

The low cost and simple detection method for Hcy (homocysteine) is highly desired in analytical and biological fields since Hcy has been regarded as a bio-marker for multiple diseases. In this work, five Ir(C^N)2(N^N)+ compounds having -CHO group in their C^N or N^N ligand were synthesized and tried for Hcy sensing. Electron-donating groups such as -NH2 and -CH3 were incorporated into the C^N or N^N ligand. Their geometric structure, electronic structure, and optical parameters (with or without Hcy) were analyzed and compared carefully to explore their Hcy sensing potential. The sensing mechanism was revealed by NMR titration and theoretical simulation as a cyclization reaction between the -CHO group and Hcy. The optimal compounds, which showed increased emission quantum yield (2.5-fold) and emission blue-shift (by âˆ¼ 100 nm) upon Hcy, were then covalently grafted into a porous host bio-MOF-1. Linear working plots were fitted, with good selectivity, LOD of 0.15 µM, and response time of 33 s. The novelty of this work was the eye-sensitive emission color change of this nanosensing platform from red (without Hcy) to green (with Hcy).

Hyperhomocysteinemia as an Independent Risk Factor for Coronary Heart Disease. Comparison with Conventional Risk Factors / Hiper-homocisteinemia como fator de risco independente para doença coronariana: comparação com fatores de risco convencionais

The present study was designed to evaluate the strength of association of raised plasma homocysteine concentration as a risk factor for coronary heart disease independent of conventional risk factor. It was a case control study conducted at Punjab Institute of Cardiology Lahore. A total of 210 subjects aged 25 to 60 years comprising of 105 newly admitted patients of CHD as cases and 105 age and sex matched healthy individuals with no history of CHD as control were recruited for the study. Fasting blood samples were obtained from cases and controls. Plasma homocysteine was analyzed by fluorescence polarization immunoassay (FPIA) method on automated immunoassay analyzer (Abbott IMX). Total cholesterol, triglyceride and HDL cholesterol were analyzed using calorimetric kit methods. The concentration of LDL cholesterol was calculated using Friedewald formula. The patients were also assessed for traditional risk factors such as age, sex, family history of CVD, hypertension, smoking and physical activity, and were compared with control subjects. The collected data was entered in SPSS version 24 for analysis and interpretation.The mean age in controls and experimental groups were 43.00± 8.42 years and 44.72± 8.59 years with statistically same distribution (p- value= 0.144). The mean plasma homocysteine for cases was 22.33± 9.22 µmol/L where as it was 12.59±3.73 µmol/L in control group. Highly significant difference was seen between the mean plasma level of homocysteine in cases and controls (p˂0.001).Simple logistic regression indicates a strong association of coronary heart disease with hyperhomocysteinemia (OR 7.45), which remained significantly associated with coronary heart disease by multivariate logistic regression (OR 7.10, 95%C1 3.12-12.83, p=0.000). The present study concludes that elevated levels of Plasma homocysteine is an independent risk factor [...].

O presente estudo foi desenhado para avaliar a força da associação da concentração elevada de homocisteína no plasma como um fator de risco para doença cardíaca coronária independente do fator de risco convencional. Foi um estudo de caso-controle realizado no Punjab Institute of Cardiology Lahore. Um total de 210 indivíduos com idade entre 25 e 60 anos, compreendendo 105 pacientes recém-admitidos de CHD como casos e 105 indivíduos saudáveis pareados por idade e sexo sem histórico de CHD como controle, foi recrutado para o estudo. Amostras de sangue em jejum foram obtidas de casos e controles. A homocisteína plasmática foi analisada pelo método de imunoensaio de polarização de fluorescência (FPIA) em analisador de imunoensaio automatizado (Abbott IMX). Colesterol total, triglicerídeos e colesterol HDL foram analisados usando métodos de kit calorimétrico. A concentração de colesterol LDL foi calculada pela fórmula de Friedewald. Os pacientes também foram avaliados para fatores de risco tradicionais, como idade, sexo, história familiar de DCV, hipertensão, tabagismo e atividade física, e foram comparados com indivíduos de controle. Os dados coletados foram inseridos no SPSS versão 24 para análise e interpretação. A média de idade nos grupos controles e experimentais foi de 43,00 ± 8,42 anos e 44,72 ± 8,59 anos com distribuição estatisticamente igual (p-valor = 0,144). A homocisteína plasmática média para os casos foi de 22,33 ± 9,22 µmol / L, enquanto no grupo controle foi de 12,59 ± 3,73 µmol / L. Diferença altamente significativa foi observada entre o nível plasmático médio de homocisteína em casos e controles (p ˂ 0,001). A regressão logística simples indica uma forte associação de doença cardíaca coronária com hiper-homocisteinemia (OR 7,45), que permaneceu significativamente associada com doença cardíaca coronária por multivariada regressão logística (OR 7,10, 95% C1 3,12-12,83, p = 0,000). O presente estudo conclui [...].

[Association of small dense low-density lipoprotein cholesterol with H-type hypertension and MTHFR gene polymorphism].

To investigate the expression of small dense low-density lipoprotein cholesterol (sdLDL-C) in patients with H-type hypertension and its association with H-type hypertension and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms. The retrospective study method was used,and a total of 207 hospitalized hypertensive patients (76 males and 131 females, aged 40-82 years, median age 66 years) admitted to the Zibo First Hospital from March 2021 to March 2022 were enrolled in this study. The levels of homocysteine (Hcy), sdLDL-C, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), triglyceride (TG) and lipoprotein (a) [Lp(a)] were measured. The patients were divided into H-type hypertensive group (n=105, 40 males and 65 females) and non-H-type hypertensive group (n=102, 36 males and 66 females) according to Hcy levels. The C677T polymorphism of methylenetetrahydrofolate reductase (MTHFR) gene was detected in each group. Logistic regression analysis was performed for the related factors of H-type hypertension. The serum sdLDL-C levels were (0.92±0.31) and (0.65±0.28) mmol/L in H-type hypertension group and non-H-type hypertension group, respectively. The sdLDL-C levels in H-type hypertension group were significantly higher than those in non-H-type hypertension group (t=6.500, P<0.01). There was no significant difference in the serum sdLDL-C levels between males and females in H-type hypertension group (t=-1.543, P=0.129). The CC, CT, TT genotypes and C and T allele frequencies of MTHFR C677T in H-type hypertension group were significantly different from those in non-H-type hypertension group (P<0.05). The Hcy and sdLDL-C levels in different genotypes of MTHFR in H-type hypertension group were significantly different (H=12.742, P=0.002; F=3.345, P=0.042). Among them, Hcy levels were higher in TT genotype than in CT and CC genotypes, respectively (Z=-28.099, P=0.003; Z=-16.112, P=0.040), and sdLDL-C levels were higher in TT genotype than in CC genotype (t=-2.587, P=0.012). Logistic regression analysis showed that age, sdLDL-C, and MTHFRC677T TT genotypes were associated with the development for H-type hypertension. In conclusion, the level of sdLDL-C is associated with MTHFR gene polymorphisms and may be associated with the development of H-type hypertension.

Pleural homocysteine for malignant pleural effusion: A prospective and double-blind diagnostic test accuracy study.

OBJECTIVE: To assess the accuracy of pleural fluid homocysteine for discriminating malignant pleural effusion (MPE) and benign pleural effusion (BPE). METHODS: A total of 194 patients from two cohorts (Hohhot and Changshu) with undiagnosed pleural effusion were prospectively enrolled. Their pleural homocysteine was measured, and its diagnostic accuracy and net benefit for MPE were analyzed by receiver operating characteristic (ROC) curve analysis and decision curve analysis, respectively. RESULTS: In the Hohhot cohort (n = 136) and the Changshu cohort (n = 58), MPE patients had significantly higher homocysteine levels than BPE patients. The areas under the ROC curves of homocysteine for the diagnosis of MPE were 0.61 (p = 0.027) and 0.59 (p = 0.247), respectively. The decision curves of homocysteine were close to the reference line in both the Hohhot cohort and the Changshu cohort. CONCLUSION: The diagnostic accuracy of pleural fluid homocysteine for MPE was low.

A simple lysosome-targeted fluorescent probe based on flavonoid for detection of cysteine in living cells.

Cysteine (Cys) is one of the most important biothiols that plays a crucial role in many physiological and pathological processes, and therefore it is of great importance to detect and analyze Cys in subcellular environments, such as in lysosomes. However, only a few fluorescent probes were reported to be capable of detecting Cys in lysosomes selectively. In this wok, we designed and developed a simple, accessible flavone-based fluorescent probe LFA for detecting Cys in lysosomes. Morpholine was employed as the targeting unit for lysosome, and acrylate group was chosen as the Cys-response unit. The probe was easily prepared by a two-step procedure and displayed large Stokes shift, high sensitivity, turn-on response toward Cys over homocysteine (Hcy), glutathione (GSH), and other amino acids. With low cytotoxicity and good cell permeability, the probe could be successfully applied for fluorescence imaging of Cys in living cells. Furthermore, colocalization experiment revealed that lysosomal-targetable ability of LFA was significant. These results indicated that such simple fluorescent probe could provide a promising tool for detection of lysosomal Cys in living biological systems.

An indanone-based fluorescent probe for detection and imaging of Cys/Hcy in living cells.

Effective detection of Cys and Hcy plays an important role in the diagnosis of diseases. In this work, a novel indanone-based fluorescent probe INIAc-CN for sensitively and effectively detecting Cys and Hcy was developed. The probe exhibited weak fluorescence, but obvious fluorescent enhancement after reacted with Cys/Hcy. Moreover, the good anti-interference and low cytotoxicity of the probe made it successfully applied for monitoring Cys and Hcy of in living cells.

[Establishment of a method for detection of thiols in seminal plasma and its application in patients with hyperuricemia].

OBJECTIVE: To establish a method of reversed-phase ultra-performance liquid chromatography with fluorescence (UPLC-FL) detection for simultaneous determination of homocysteine (Hcy), cysteine (Cys), cysteine glycine (CysGly) and glutathione (GSH) and analysis of the contents of the four thiols in the seminal plasma of normal men and patients with hyperuricemia (HUA). METHODS: Seminal plasma samples were collected from 30 normal sperm donors and 30 HUA patients and reduced with tris (2-carboxyethyl) phosphine hydrochloride. Then, the samples were subjected to protein precipitation with trichloroacetic acid solution, derivative reaction with 7-fluorobenzofuran-4-sulfate and isolation with a C18 column, with 0.025 mol/L KH2PO4 (pH 3.0) for mobile phase A and pure methanol for B, followed by equal gradient elution with an excitation wavelength of 380 nm and an emission wavelength of 510 nm. RESULTS: The correlation coefficients (R2) of the four thiols all exceeded 0.999, with an average recovery rate of 94.23－107.87%. Compared with the normal sperm donors, the HUA patients showed significantly increased contents of Cys (ï¼»108.01 ± 48.03ï¼½ vs ï¼»250.10 ± 55.87ï¼½ µmol/L, P < 0.05), Hcy (ï¼»113.97 ± 6.32ï¼½ vs ï¼»48.35 ± 15.07ï¼½ µmol/L, P < 0.05), and GSH (ï¼»3.15 ± 1.48ï¼½ vs ï¼»4.63 ± 1.17ï¼½ µmol/L, P < 0.05), but a decreased level of CysGly (ï¼»12.79 ± 3.18ï¼½ vs ï¼»5.94 ± 0.99ï¼½ µmol/L, P < 0.05). CONCLUSIONS: The method of reversed-phase UPLC-FL detection established in this study has made it possible simultaneous detection of Hcy, Cys, CysGly and GSH in the seminal plasma, which is applicable to laboratory research and clinical routine examination. Patients with hyperuricemia may incur oxidative damage to the reproductive system.

A quantitative method for the assessment of homocysteine thiolactonase enzyme activity.

This assay elucidates an accurate, simple, and precise protocol to quantify the activity of homocysteine thiolactonase (HTase). To establish HTase activity, the enzyme samples were incubated with a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, which contained suitable concentrations of the homocysteine thiolactone as a substrate. To stop the enzyme's reaction, the CUPRAC reagent (Cu(Nc)22+) was added after a suitable incubation time. The reduction of Cu(II)-neocuproine complex (Cu(Nc)22+) to highly coloured Cu(I)-neocuproine complex (Cu(Nc)2+) by the produced homocysteine was quantified spectrophotometrically at 450 nm (CUPRAC method). The increase in the absorbance of the coloured Cu(I)-neocuproine complex (Cu(Nc)2+) was correlated directly to the activity of HTase. ANOVA analysis was utilised to validate the new method against homocysteine thiolactonase activity using the H+ ions liberating method in matched samples. In conclusion, according to the obtained correlation coefficient (0.9995) from the comparison of the current method with the reference method, the current method is effective in assay HTase activity with high reliability.

Alteration of intrapancreatic serotonin, homocysteine, TNF-α, and NGF levels as predisposing factors for diabetes following exposure to 900-MHz waves.

Exposure to mobile phone radiation causes deleterious health effects on biological systems. The objects of this study were to investigate the effect of 900-MHz radiofrequency waves (RFW) emitted from base transceiver station antenna on intrapancreatic homocysteine (Hcy), tumor necrosis factor-α (TNF-α), and nerve growth factor (NGF) as predisposing factors involved in pancreatic beta cell damage. Thirty male rats (Sprague-Dawley, 200 ± 10 g) were randomly divided into the control (without any exposure) and exposed groups: short time (2 h/day), long time (4 h/day), and exposed to 900-MHz RFW for 30 consecutive days. On the last days of the experiment, animals were killed and pancreas tissue was dissected out for evaluation of serotonin, Hcy, TNF-α, and NGF. There was a significant decrease in the serotonin and NGF levels in the pancreatic tissue of exposed groups compared to the control group (p < 0.05). Also, the levels of serotonin and NGF in the long-time exposure were significantly lower than the short-time exposure (p < 0.05). However, levels of Hcy and TNF-α were significantly increased in the pancreas of exposed groups compared to the control groups (p < 0.05). Exposure to 900-MHz RFW decreased pancreatic NGF and serotonin levels and increased the proinflammatory markers (Hcy and TNF-α), which can be a predisposing factor for type 2 diabetes.

Nanozyme based on graphene oxide modified with Fe3O4, CuO, and cucurbit[6]uril for colorimetric determination of homocysteine.

A nanozyme based on graphene oxide modified with Fe3O4 NPs, CuO NPs, and cucurbit[6]uril has been successfully fabricated by a simple sonochemical technique. By employing CB[6] as a specific binding pocket and Fe3O4@CuO-GO as a peroxidase mimic, this novel nanozyme (BN I) is equipped with molecular recognition ability and enhanced peroxidase-like activity. On the basis of the inhibition effect of homocysteine (Hcy) towards the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) catalyzed by BN I, a simple colorimetric method is established for the sensitive and selective determination of Hcy. This proposed method displays a good linear response in the range 5-200 µM with a detection limit of 1.8 µM. In the practical assay of human plasma samples, the relative standard deviations (RSD) are lower than 11% and the recoveries are between 98.0 and 104.9%. In the assay of human urine samples, the RSD are below 9.0% and the recoveries range from 94.0 to 103.5%. The colorimetric method presented offers a convenient and accurate way for the determination of biomarkers in point-of-care testing (POCT).

Colorimetric detection of homocysteine by a pyridylazo dye-based Cu2+ complex via indicator displacement mechanism.

A BrPAPS based Cu2+ complex has been developed as a colorimetric probe for the selective recognition of homocysteine (Hcy) over cysteine (Cys) and glutathione (GSH) in an aqueous solution via the indicator displacement assay. BrPAPS formed a complex with Cu2+ in a 1:1 ratio (BrPAPS-Cu2+) accompanied by the color change from yellow to red. Detecting Hcy is based on high affinity of Hcy for Cu2+. The addition of Hcy to BrPAPS-Cu2+ caused the complex formation of Hcy with Cu2+ in a 2:1 stoichiometry, resulting a hypsochromic shift with change back of color from red to yellow by the release of BrPAPS from BrPAPS-Cu2+. The absorption response is linear with the Hcy concentration in the range of 0-20 µM with a detection limit of 1.46 µM. Moreover, the detection of Hcy was not significantly affected by other amino acids from the competition experiments. Thus, BrPAPS-Cu2+ can be used as a simple probe for Hcy in aqueous solution.