Oxidation Of Cysteamine Research Articles

Spectroscopy of Oxygen-Sensitive Material for Measuring Contact Lens Oxygen Transmissibility

ABSTRACTPurpose: Oxygen permeability or transmissibility is a crucial parameter for contact lenses to ensure that extended wear will not induce corneal hypoxia. This work tests a new method of using the oxidation of cysteamine, an oxygen-sensitive chemical, to quantify the oxygen transmissibility of current commercial contact lenses and contact lenses loaded with vitamin E.Methods: 3D printing was used to modify eye drop bottles and quartz cuvettes to create systems that allowed insertion of a contact lens in between the cysteamine solution and air. Both systems were exposed to atmospheric conditions where the only path of entry for oxygen was through the contact lens. The entering oxygen reacted with cysteamine, and the rate of cysteamine oxidation was measured using UV-vis spectrophotometry. The rate was then stoichiometrically related to oxygen transmissibility.Results: The eye drop method predicted transmissibility values within 9% of established, commercial values. The cuvette method predicted values within 10% of established values for silicone hydrogel lenses without any correction factor and within 11% for poly-hydroxyethyl-methacrylate lenses after correcting for oxygen entering the system. Incorporation of 20% (w/w) vitamin E into Acuvue® Oasys® lenses did not have a significant impact on the oxygen transmissibility.Conclusions: Both methods presented in this work can reliably measure oxygen transmissibility of contacts lenses or other materials. Further improvements in manufacturing could lead to improved accuracy and reliability, allowing wider use of this method for quantifying the oxygen transport in contact lenses.

A Voltammetric Sensor Based on NiO Nanoparticle‐Modified Carbon‐Paste Electrode for Determination of Cysteamine in the Presence of High Concentration of Tryptophan

A carbon‐paste electrode modified with ferrocenecarboxaldehyde and NiO nanoparticle (NiO/NPs) was used for the sensitive and selective voltammetric determination of cysteamine in the presence of tryptophan. The oxidation of cysteamine at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperometry, and square‐wave voltammetry (SWV). The values of the catalytic rate constant (kh) and diffusion coefficient (D) for cysteamine were calculated. The modified electrode exhibits an efficient electron‐mediating behavior together with well‐separated oxidation peaks for cysteamine and tryptophan. At the optimum pH of 7.0 in a 0.1 M phosphate buffer solution, the SWV anodic peak currents showed a linear relationship versus cysteamine concentrations in the range of 0.09–300.0 µM and a detection limit of 0.06 µM. Finally, the proposed method was also examined as a selective, simple, and precise electrochemical sensor for the determination of cysteamine in real samples such as urine and capsule.

Taurine Biosynthesis by Neurons and Astrocytes

The physiological roles of taurine, a product of cysteine degradation and one of the most abundant amino acids in the body, remain elusive. Taurine deficiency leads to heart dysfunction, brain development abnormalities, retinal degradation, and other pathologies. The taurine synthetic pathway is proposed to be incomplete in astrocytes and neurons, and metabolic cooperation between these cell types is reportedly needed to complete the pathway. In this study, we analyzed taurine synthesis capability as reported by incorporation of radioactivity from [(35)S]cysteine into taurine, in primary murine astrocytes and neurons, and in several transformed cell lines (human (SH-SY5Y) and murine (N1E-115) neuroblastoma, human astrocytoma (U-87 MG and 1321 N1), and rat glioma (C6)). Extensive incorporation of radioactivity from [(35)S]cysteine into taurine was observed in rat glioma cells as well as in primary mouse astrocytes and neurons, establishing the presence of an intact taurine synthesis pathway in these cells. Interestingly, exposure of cells to cysteine or cysteamine resulted in elevated intracellular hypotaurine without a corresponding increase in taurine levels, suggesting that oxidation of hypotaurine limits taurine synthesis in cells. Consistent with its role as an organic osmolyte, taurine synthesis was stimulated under hypertonic conditions in neurons.

Electrocatalytic Oxidation and Determination of Cysteamine by Poly‐N,N‐dimethylaniline/Ferrocyanide Film Modified Carbon Paste Electrode

AbstractFunctionalized poly‐N,N‐dimethylaniline film was prepared by adsorption of ferrocyanide onto the polymer forming at the surface of carbon paste electrode (CPE) in aqueous solution by using potentiostatic method. The electrocatalytic ability of poly‐N,N‐dimethylaniline/ferrocyanide film modified carbon paste electrode (PDMA/FMCPE) was demonstrated by oxidation of cysteamine. Cyclic voltammetry and chronoamperometry techniques were used to investigate this ability. Results showed that pH 7.00 is the most suitable for this purpose. It is found that the catalytic reaction rate constant, (kh), is equal to 2.142×103 M−1 s−1 by the data of chronoamperometry. The catalytic reduction peak current was linearly dependent on the cysteamine concentration and the linearity range obtained was 8.00×10−5 M–1.14×10−2 M. Detection limit was determined 7.97×10−5 M (2σ). This method has been successfully employed for quantification of cysteamine in real sample.

3T3-L1 Adipocytes and Rat Adipose Tissue Have a High Capacity for Taurine Synthesis by the Cysteine Dioxygenase/Cysteinesulfinate Decarboxylase and Cysteamine Dioxygenase Pathways

Taurine is the most abundant free amino acid in the body and is synthesized in mammals by 2 pathways. Taurine is synthesized either from the oxidation of cysteine via cysteine dioxygenase (CDO), which generates cysteinesulfinate that is decarboxylated by cysteinesulfinic acid decarboxylase (CSAD), or from the oxidation of cysteamine by cysteamine (2-aminoethanethiol) dioxygenase (ADO). Both pathways generate hypotaurine, which is oxidized to taurine. To determine whether these pathways for taurine synthesis are present in the adipocyte, we studied 3T3-L1 cells during their adipogenic conversion and fat from rats fed diets with varied sulfur-amino acid content. CDO, CSAD, and ADO protein levels increased during adipogenic differentiation of 3T3-L1 cells and all of these enzymes were significantly increased when cells achieved a mature adipocyte phenotype. Furthermore, these changes were accompanied by an increased hypotaurine and taurine production, particularly when cells were treated with cysteine or cysteamine. CDO mRNA levels also responded robustly to cysteine or cysteamine treatment in adipocytes but not in undifferentiated 3T3-L1 cells. Furthermore, CDO protein and activity were greater in adipose tissue from rats fed a high protein or cystine-supplemented low protein (LP) diet than in adipose tissue from rats fed a LP diet. Overall, our results demonstrate that CDO is regulated at both the level of enzyme abundance and the level of mRNA in mature adipocytes.

Cysteamine oxidation by lentil seedling amine oxidase

Cysteamine is oxidatively deaminated by lentil amine oxidase. It shows saturation kinetic K(m) = 9 x 10(-4) M like other substrates, but the aldehyde produced leads to loss of enzyme activity, which is restored by dialysis. When putrescine is the substrate of the amine oxidase cysteamine behaves like a competitive inhibitor, and shows Ki = 5 x 10(-5) M. The possible involvement of the oxidation of cysteamine and the inhibitory effects of thioacetaldehyde in the cystamine oxidation by amine oxidase is discussed.