Hydrogen peroxide diffusion across the red blood cell membrane occurs mainly by simple diffusion through the lipid fraction.

Hydrogen peroxide (HO) is an oxidant produced endogenously by several enzymatic pathways. While it can cause molecular damage, HO also plays a role in regulating cell proliferation and survival through redox signaling pathways. In the vascular system, red blood cells (RBCs) are notably efficient at metabolizing HO.

The chemical biology of dinitrogen trioxide.

Dinitrogen trioxide ( ) mediates low-molecular weight and protein S- and N-nitrosation, with recent reports suggesting a role in the formation of nitrating intermediates as well as in nitrite-dependent hypoxic vasodilatation. However, the reactivity of in biological systems results in an extremely short half-life that renders this molecule essentially undetectable by currently available technologies. As a result, evidence for formation derives from the detection of nitrosated products as well as from kinetic determinations, isotopic labeling studies, and spectroscopic analyses.

Photoproperties of favipiravir and its 6-substituted analogues: fluorescence controlled through halogen substitution and tautomerism.

Herein, we have showed the photophysical properties of favipiravir and its 6-substituted analogues. Also, we interpreted the origin of fluorescence of favipiravir and its 6-substituted analogues as a function of tautomerism modulation in ground and excited states. Favipiravir, the 6-fluorine derivative, showed the best photophysical profile, exhibiting a dominant emission wavelength of 430 nm, a high quantum yield (Q.

Biophysical tools to study the oligomerization dynamics of Prx1-class peroxiredoxins.

Peroxiredoxins (Prx) are ubiquitous, highly conserved peroxidases whose activity depends on catalytic cysteine residues. The Prx1-class of the peroxiredoxin family, also called typical 2-Cys Prx, organize as head-to-tail homodimers containing two active sites. The peroxidatic cysteine C of one monomer reacts with the peroxide substrate to form sulfenic acid that reacts with the resolving cysteine (C) of the adjacent subunit to form an intermolecular disulfide, that is reduced back by the thioredoxin/thioredoxin reductase/NADPH system.

Oxidative Stress in Healthy and Pathological Red Blood Cells.

Red cell diseases encompass a group of inherited or acquired erythrocyte disorders that affect the structure, function, or production of red blood cells (RBCs). These disorders can lead to various clinical manifestations, including anemia, hemolysis, inflammation, and impaired oxygen-carrying capacity. Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense mechanisms, plays a significant role in the pathophysiology of red cell diseases.

Oxidants and Antioxidants in the Redox Biochemistry of Human Red Blood Cells.

Red blood cells (RBCs) are exposed to both external and internal sources of oxidants that challenge their integrity and compromise their physiological function and supply of oxygen to tissues. Autoxidation of oxyhemoglobin is the main source of endogenous RBC oxidant production, yielding superoxide radical and then hydrogen peroxide. In addition, potent oxidants from other blood cells and the surrounding endothelium can reach the RBCs.

Fluorescence Lifetime Phasor Analysis of the Decamer-Dimer Equilibrium of Human Peroxiredoxin 1.

Protein self-assembly is a common feature in biology and is often required for a myriad of fundamental processes, such as enzyme activity, signal transduction, and transport of solutes across membranes, among others. There are several techniques to find and assess homo-oligomer formation in proteins. Naturally, all these methods have their limitations, meaning that at least two or more different approaches are needed to characterize a case study.

The permeability of human red blood cell membranes to hydrogen peroxide is independent of aquaporins.

Hydrogen peroxide (HO) not only is an oxidant but also is an important signaling molecule in vascular biology, mediating several physiological functions. Red blood cells (RBCs) have been proposed to be the primary sink of HO in the vasculature because they are the main cellular component of blood with a robust antioxidant defense and a high membrane permeability. However, the exact permeability of human RBC to HO is neither known nor is it known if the mechanism of permeation involves the lipid fraction or protein channels.

Photo-Induced Partially Aromatized Intramolecular Charge Transfer.

Diverse models of intramolecular charge transfer (ICT) have been proposed for interpreting the origin of the charge-transfer (CT) state in donor-acceptor (D-A) dyes. However, a large variety of fused-heterocyclic dyes containing a pseudo-aromatic ring in the rigid structure have shown to be incompatible with them. To approximate a solution within the ICT concept, we reported a novel ICT model called partially aromatized intramolecular charge transfer (PAICT).

Detection and quantification of nitric oxide-derived oxidants in biological systems.

The free radical nitric oxide (NO) exerts biological effects through the direct and reversible interaction with specific targets ( soluble guanylate cyclase) or through the generation of secondary species, many of which can oxidize, nitrosate or nitrate biomolecules. The NO-derived reactive species are typically short-lived, and their preferential fates depend on kinetic and compartmentalization aspects. Their detection and quantification are technically challenging.

Acceleration of the autoxidation of nitric oxide by proteins.

Lipoproteins and lipid membranes accelerate NO autoxidation by increasing local concentration of NO and O. Although the idea that proteins could also accelerate this reaction was presented some time ago, it was largely criticized and dismissed. Herein the effect of proteins on NO autoxidation rates was studied following NO disappearance with a selective electrode.

Kinetic studies reveal a key role of a redox-active glutaredoxin in the evolution of the thiol-redox metabolism of trypanosomatid parasites.

Trypanosomes are flagellated protozoan parasites (kinetoplastids) that have a unique redox metabolism based on the small dithiol trypanothione (T(SH)). Although GSH may still play a biological role in trypanosomatid parasites beyond being a building block of T(SH), most of its functions are replaced by T(SH) in these organisms. Consequently, trypanosomes have several enzymes adapted to using T(SH) instead of GSH, including the glutaredoxins (Grxs).

Kinetic and stoichiometric constraints determine the pathway of HO consumption by red blood cells.

Red blood cells (RBC) are considered as a circulating sink of HO, but a significant debate remains over the role of the different intraerythocyte peroxidases. Herein we examined the kinetic of decomposition of exogenous HO by human RBC at different cell densities, using fluorescent and oxymetric methods, contrasting the results against a mathematical model. Fluorescent measurements as well as oxygen production experiments showed that catalase was responsible for most of the decomposition of HO at cell densities suitable for both experimental settings (0.

Diffusion of nitric oxide and oxygen in lipoproteins and membranes studied by pyrene fluorescence quenching.

Oxygen and nitric oxide are small hydrophobic molecules that usually need to diffuse a considerable distance to accomplish their biological functions and necessarily need to traverse several lipid membranes. Different methods have been used to study the diffusion of these molecules in membranes and herein we focus in the quenching of fluorescence of pyrenes inserted in the membrane. The pyrene derivatives have long fluorescence lifetimes (around 200 ns) that make them very sensitive to fluorescence quenching by nitric oxide, oxygen and other paramagnetic species.

The Chemical Basis of Thiol Addition to Nitro-conjugated Linoleic Acid, a Protective Cell-signaling Lipid.

Nitroalkene fatty acids are formed in vivo and exert protective and anti-inflammatory effects via reversible Michael addition to thiol-containing proteins in key signaling pathways. Nitro-conjugated linoleic acid (NO-CLA) is preferentially formed, constitutes the most abundant nitrated fatty acid in humans, and contains two carbons that could potentially react with thiols, modulating signaling actions and levels. In this work, we examined the reactions of NO-CLA with low molecular weight thiols (glutathione, cysteine, homocysteine, cysteinylglycine, and β-mercaptoethanol) and human serum albumin.