Nitration of tyrosine and its effect on DNA hybridization

A selective electrochemical chiral interface based on a carboxymethyl-β-cyclodextrin/Pd@Au nanoparticles/3D reduced graphene oxide nanocomposite for tyrosine enantiomer recognition

Palladium@gold nanoparticle modified three-dimensional-reduced graphene oxide was coupled with carboxymethyl-β-cyclodextrin to form a novel nanocomposite, which served as an effective chiral sensing interface for electrochemical enantiorecognition.

Melatonin, Its Metabolites and Their Interference with Reactive Nitrogen Compounds

Melatonin and several of its metabolites are interfering with reactive nitrogen. With the notion of prevailing melatonin formation in tissues that exceeds by far the quantities in blood, metabolites come into focus that are poorly found in the circulation. Apart from their antioxidant actions, both melatonin and N¹-acetyl-5-methoxykynuramine (AMK) downregulate inducible and inhibit neuronal NO synthases, and additionally scavenge NO. However, the NO adduct of melatonin redonates NO, whereas AMK forms with NO a stable product. Many other melatonin metabolites formed in oxidative processes also contain nitrosylatable sites. Moreover, AMK readily scavenges products of the CO₂-adduct of peroxynitrite such as carbonate radicals and NO₂. Protein AMKylation seems to be involved in protective actions.

ZIF-Based Nanoparticles Combine X-Ray-Induced Nitrosative Stress with Autophagy Management for Hypoxic Prostate Cancer Therapy

Although reactive oxygen species (ROS)-mediated tumor treatments are predominant in clinical applications, ROS-induced protective autophagy promotes cell survival, especially in hypoxic tumors. Herein, X-ray triggered nitrite (NO₂ ^- ) is used for hypoxic prostate cancer therapy by inhibiting autophagy and inducing nitrosative stress based on an electrophilic zeolitic imidazole framework (ZIF-82-PVP). After internalization of pH-responsive ZIF-82-PVP nanoparticles, electrophilic ligands and Zn²⁺ are delivered into cancer cells. Electrophilic ligands can not only consume GSH under hypoxia but also capture low-energy electrons derived from X-rays to generate NO₂ ^- , which inhibits autophagy and further elevates lethal nitrosative stress levels. In addition, dissociated Zn²⁺ specifically limits the migration and invasion of prostate cancer cells through ion interference. In vitro and in vivo results indicate that ZIF-82-PVP nanoparticles under X-ray irradiation can effectively promote the apoptosis of hypoxic prostate cancer cells. Overall, this nitrosative stress-mediated tumor therapy strategy provides a novel approach targeting hypoxic tumors.

Diazotization-Coupling Reaction-Based Determination of Tyrosine in Urine Using Ag Nanocubes by Surface-Enhanced Raman Spectroscopy

A novel, simple, and highly sensitive method was developed to detect the concentration of tyrosine-derived azo dye indirectly using silver nanocubes (AgNCs) as a substrate on a super-hydrophobic silver film by surface-enhanced Raman spectroscopy (SERS). Diazotization-coupling reaction occurred between diazonium ions and the phenolic tyrosine, resulting in three new typical peaks in the SERS spectrum of the azo dye that was formed on the AgNCs, indicating strong SERS activity. Subsequently, the limit of detection of this approach was as low as 10^-12 M for tyrosine. Moreover, the SERS intensities of the three typical SERS signals of the analyte were linearly correlated with the logarithm of concentration of the Tyrosine. The proposed method shows great potential for tyrosine detection in the urine samples of normal humans.