BackgroundOxidative stress (OS) plays a key role in many pathologies, yet the non-invasive, label-free, and cost-effective detection remains a challenge. This study evaluates Hyperspectral Imaging (HSI) combined with AI to detect OS by identifying changes in red blood cell (RBC) membranes.MethodsAn OS model for the HSI procedure is established by treating EDTA-anticoagulated whole blood with 1.5% hydrogen peroxide (H2O2) to induce stress without cell lysis. Membrane fatty acid composition (lipidome) is analysed via gas chromatography, while HSI in dark-field microscopy captures spectral signatures and their distributions in healthy and insulted RBC. The HSI methodology is then applied to RBC samples from 31 neurotypical (NT) children and 27 children with Autism Spectrum Disorder (ASD), a condition linked to OS. A deep learning algorithm is used to classify the clinical samples based on the identified OS signatures.ResultsHere, we show that significant spectral distribution differences are present in OS-exposed RBCs, which correlate with membrane lipidome remodelling. Notably, the OS-induced spectral differences in the H2O2 model mirror those observed between the ASD and NT groups. The AI-assisted analysis successfully classifies the pediatric cohort, achieving 93.2% accuracy in identifying ASD subjects.ConclusionsHSI, guided by OS-specific modeling and integrated with AI, provides a robust, scalable method for membrane diagnostics. This approach offers a promising pathway for personalized medicine and the non-invasive monitoring of oxidative stress-related conditions.

The reaction of the HS•/S•- radical (pKa ~3.4), generated selectively from H2S by γ-irradiated N2-flushed aqueous solutions at pH 5, with purine nucleosides (dG or dA), a 10-mer double-stranded oligodeoxynucleotide (ds-ODNs), and calf thymus (ct) DNA was investigated, under various experimental conditions. Concurrent quantification of the four purine 5',8-cyclo-2'-deoxynucleosides (cPu) and two 8-oxo-7,8-dihydro-2'-deoxypurines (8-oxo-Pu) by LC-MS/MS analysis using isotopomeric internal standards was achieved. The formation of 8-oxo-Pu is several tens of times larger than cPu. Mechanistic schemes for the formation of the two product groups are proposed. Hydrogen atom abstraction from C5'-H by S•- produces the cPu via cyclization of the C5' radical onto C8, forming a new covalent bond, C5'-C8. The unexpected formation of 8-oxo-Pu should be mechanistically more complex. We propose that an S•- (coupled with H+) adds to the base rings, followed by the elimination of HS- to form the corresponding radical cation; subsequent reactions with H2O and radical disproportionation with another S•- lead to 8-oxo-Pu. A comparison of S•- with the available literature data for HO• reactivity towards ct-DNA in de-oxygenated aqueous solutions is also presented. Before the present findings, cPu lesions were attributed exclusively to HO• reactivity toward ct-DNA. The reaction of the thiyl radical (HOCH2CH2S•) with ct-DNA was also investigated, yielding results similar to those of S•- obtained under comparable experimental conditions. Our results contributed to a better understanding of DNA damage induced by reactive sulfur species (RSS), particularly the formation of purine lesions and the relative abundance of cPu versus 8-oxo-Pu.

PURPOSE:This review summarizes the discoveries of 8-bromopurine nucleosides (8-Br-Pu), particularly 8-bromo-2'-deoxyadenosine (8-Br-dA) and 8-bromo-2'-deoxyguanosine (8-Br-dG), in chemistry and biology over the past two decades. It compiles available data on the reactions of hydrated electrons (eaq-) with various 8-bromopurines, as determined by pulse radiolysis and supported by theoretical studies. Three distinct mechanistic pathways are identified: dissociative electron attachment, sequential electron transfer-proton transfer, and concerted electron-proton transfer. This review also highlights the use of 8-Br-dA and 8-Br-dG in the synthesis of a library of 5',8-cyclopurine nucleosides (cPu) for quantifying them in genetic material and incorporating them into oligonucleotides (ODNs) for DNA repair research. Additionally, the summary covers the use of 8-Br-dA and 8-Br-dG embedded in various ODNs to study excess electron transfer (EET), their potential as radiosensitizers, and their formation in vivo via hypobromous acid. CONCLUSION:Based on radiation chemistry, our understanding of the one-electron reduction of 8-Br-dA and 8-Br-dG has been enhanced substantially. This mechanistic background is crucial for a better understanding of and addressing their significant roles in the biological environment, such as DNA radiosensitizers for cancer radiation therapy or as biomarkers for early inflammation.

Methionine residues in proteins and peptides are frequently oxidized by losing one electron. The presence of nearby amide groups is crucial for this process, enabling methionine to participate in long-range electron transfer. Hydroxyl radical (HO•) plays an important role being generated in aerobic organisms by cellular metabolisms as well as by exogenous sources such as ionizing radiations. The reaction of HO• with methionine mainly affords the one-electron oxidation of the thioether moiety through two consecutive steps (HO• addition to the sulfur followed by HO− elimination). We recently investigated the reaction of HO• with model peptides mimicking methionine and its cysteine-methylated counterpart, i.e., CH3C(O)NHCHXC(O)NHCH3, where X = CH2CH2SCH3 or CH2SCH3 at pH 7. The reaction mechanism varied depending on the distance between the sulfur atom and the peptide backbone, but, for a better understanding of various suggested equilibria, the analysis of the flux of protons is required. We extended the previous study to the present work at pH 4 using pulse radiolysis techniques with conductivity and optical detection of transient species, as well as analysis of final products by LC-MS and high-resolution MS/MS following γ-radiolysis. Comparing all the data provided a better understanding of how the presence of nearby amide groups influences the one-electron oxidation mechanism.

Most DNA damage caused by oxidative metabolism consists of single lesions that can accumulate in tissues. This review focuses on two classes of lesions: the two 8-oxopurine (8-oxo-Pu) lesions that are repaired by the base excision repair (BER) enzyme and the four 5′,8-cyclopurine (cPu) lesions that are repaired exclusively by the nucleotide excision repair (NER) enzyme. The aim is to correlate the simultaneous quantification of these two classes of lesions in the context of neurological disorders. The first half is a summary of reactive oxygen species (ROS) with particular attention to the pathways of hydroxyl radical (HO•) formation, followed by a summary of protocols for the quantification of six lesions and the biomimetic chemistry of the HO• radical with double-stranded oligonucleotides (ds-ODN) and calf thymus DNA (ct-DNA). The second half addresses two neurodegenerative diseases: xeroderma pigmentosum (XP) and Cockayne syndrome (CS). The quantitative data on the six lesions obtained from genomic and/or mitochondrial DNA extracts across several XP and CS cell lines are discussed. Oxidative stress contributes to oxidative DNA damage by resulting in the accumulation of cPu and 8-oxo-Pu in DNA. The formation of cPu is the postulated culprit inducing neurological symptoms associated with XP and CS.

Reactive oxygen and nitrogen species (ROS/RNS) are generated as a result of normal intracellular metabolism [...]

Disulfide radical anions (RSSR•−) derive both from the direct electron attachment to disulfide-containing compounds and the reaction of thiyl radicals with thiolate, being also reversible (RS• + RS− ⇆ RSSR•−). The investigation of these reactive intermediates started in 1960s by pulse radiolysis (PR) technique and electron spin resonance (ESR) spectroscopy, and more recently, their generation was studied in organic chemistry and biological mechanisms. The present review addresses a compendium on structural, chemical and spectroscopical properties of disulfide radical anions, as well as their involvement in synthetical and biological processes. Particular emphasis is given to disulfide moieties as reactive sites in proteins, and to the generation of small sulfur-centered radicals, from the desulfurization of disulfide radical anions in proteins, as well as from hydrogen sulfide (H2S) and hydrogen disulfide (HSSH), connected to the discovery of a mechanism of tandem protein-lipid damage. Other important biologically related processes involving disulfide radical anions are treated in the review, such as: its formation from the glutathione thiyl radical GS• (GS• + GS− ⇆ GSSG•−), resulting from the antioxidant reactivity of glutathione (GSH/GS–), and the reduction of a ketone moiety by the disulfide radical anion at the active site of the enzymes ribonucleotide reductase (RNRs), the latter used for establishing a bioinspired reduction process in organic synthesis.

Radical reactions in water or aqueous media are important for organic synthesis, realizing high-yielding processes under non-toxic and environmentally friendly conditions. This overview includes (i) a general introduction to organic chemistry in water and aqueous media, (ii) synthetic approaches in, on, and with water as well as in heterogeneous phases, (iii) reactions of carbon-centered radicals with water (or deuterium oxide) activated through coordination with various Lewis acids, (iv) photocatalysis in water and aqueous media, and (v) synthetic applications bioinspired by naturally occurring processes. A wide range of chemical processes and synthetic strategies under different experimental conditions have been reviewed that lead to important functional group translocation and transformation reactions, leading to the preparation of complex molecules. These results reveal how water as a solvent/medium/reagent in radical chemistry has matured over the last two decades, with further discoveries anticipated in the near future.

The lipid cis-trans isomerase (Cti) is a periplasmic heme-c enzyme found in several bacteria including Pseudomonas aeruginosa, a pathogen known for causing nosocomial infections. This metalloenzyme catalyzes the cis-trans isomerization of unsaturated fatty acids in order to rapidly modulate membrane fluidity in response to stresses that impede bacterial growth. As a consequence, breakthrough in the elucidation of the mechanism of this metalloenzyme might lead to new strategies to combat bacterial antibiotic resistance. We report the first comprehensive biochemical, electrochemical and spectroscopic characterization of a Cti enzyme. This has been possible by the successful purification of Cti from P. aeruginosa (Pa-Cti) in favorable yields with enzyme activity of 0.41 μmol/min/mg when tested with palmitoleic acid. Through a synergistic approach involving enzymology, site-directed mutagenesis, Raman spectroscopy, Mössbauer spectroscopy and electrochemistry, we identified the heme coordination and redox state, pinpointing Met163 as the sixth ligand of the FeII of heme-c in Pa-Cti. Significantly, the development of an innovative assay based on liposomes demonstrated for the first time that Cti catalyzes cis-trans isomerization directly using phospholipids as substrates without the need of protein partners, answering the important question about the substrate of Cti within the bacterial membrane.

In this review, we focus on the one-electron oxidation of DNA, which is a multipart event controlled by several competing factors. We will discuss the oxidation free energies of the four nucleobases and the electron detachment from DNA, influenced by specific interactions like hydrogen bonding and stacking interactions with neighboring sites in the double strand. The formation of a radical cation (hole) which can migrate through DNA (hole transport), depending on the sequence-specific effects and the allocation of the final oxidative damage, is also addressed. Particular attention is given to the one-electron oxidation of ds-ODN containing G:C pairs, including the complex mechanism of the deprotonation vs. hydration steps of a G:C•+ pair, as well as to the modes of formation of the two guanyl radical tautomers after deprotonation. Among the reactive oxygen species (ROS) generated in aerobic organisms by cellular metabolisms, several oxidants react with DNA. The mechanism of stable product formation and their use as biomarkers of guanine oxidation in DNA damage are also addressed.

Most DNA damages induced through oxidative metabolism are single lesions which can accumulate in tissues. Here, we present a protocol for the simultaneous quantification of oxidative purine lesions (cPu and 8-oxo-Pu) in DNA. We describe steps for enzymatic digestion of DNA and sample pre-purification, followed by quantification through liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. We optimized this protocol in commercially available calf thymus DNA and used genomic and mitochondrial DNA extracted from cell cultures and animal and human tissues.

Xeroderma pigmentosum (XP) is caused by defective nucleotide excision repair of DNA damage. This results in hypersensitivity to ultraviolet light and increased skin cancer risk, as sunlight -induced photoproducts remain unrepaired. However, many XP patients also display early -onset neurodegeneration, which leads to premature death. The mechanism of neurodegeneration is unknown. Here, we investigate XP neurodegeneration using pluripotent stem cells derived from XP patients and healthy relatives, performing functional multi-omics on samples during neuronal differentiation. We show substantially increased levels of 5 ' ,8-cyclopurine and 8-oxopurine in XP neuronal DNA secondary to marked oxidative stress. Furthermore, we find that the endoplasmic reticulum stress response is upregulated and reversal of the mutant genotype is associated with phenotypic rescue. Critically, XP neurons exhibit inappropriate downregulation of the protein clearance ubiquitin-proteasome system (UPS). Chemical enhancement of UPS activity in XP neuronal models improves phenotypes, albeit inadequately. Although more work is required, this study presents insights with intervention potential.

Gestational diabetes mellitus (GDM) is a disorder which manifests itself for the first time during pregnancy and is mainly connected with glucose metabolism. It is also known that fatty acid profile changes in erythrocyte membranes and plasma could be associated with obesity and insulin resistance. These factors can lead to the development of diabetes. In the reported study, we applied the untargeted analysis of plasma in GDM against standard glucose-tolerant (NGT) women to identify the differences in metabolomic profiles between those groups. We found higher levels of 2-hydroxybutyric and 3-hydroxybutyric acids. Both secondary metabolites are associated with impaired glucose metabolism. However, they are products of different metabolic pathways. Additionally, we applied lipidomic profiling using gas chromatography to examine the fatty acid composition of cholesteryl esters in the plasma of GDM patients. Among the 14 measured fatty acids characterizing the representative plasma lipidomic cluster, myristic, oleic, arachidonic, and α-linoleic acids revealed statistically significant changes. Concentrations of both myristic acid, one of the saturated fatty acids (SFAs), and oleic acid, which belong to monounsaturated fatty acids (MUFAs), tend to decrease in GDM patients. In the case of polyunsaturated fatty acids (PUFAs), some of them tend to increase (e.g., arachidonic), and some of them tend to decrease (e.g., α-linolenic). Based on our results, we postulate the importance of hydroxybutyric acid derivatives, cholesteryl ester composition, and the oleic acid diminution in the pathophysiology of GDM. There are some evidence suggests that the oleic acid can have the protective role in diabetes onset. However, metabolic alterations that lead to the onset of GDM are complex; therefore, further studies are needed to confirm our observations.

We examined the reaction of hydroxyl radicals (HO•) and sulfate radical anions (SO4•−), which is generated by ionizing radiation in aqueous solutions under anoxic conditions, with an alternating GC doubled-stranded oligodeoxynucleotide (ds-ODN), i.e., the palindromic 5′-d(GCGCGC)-3′. In particular, the optical spectra of the intermediate species and associated kinetic data in the range of ns to ms were obtained via pulse radiolysis. Computational studies by means of density functional theory (DFT) for structural and time-dependent DFT for spectroscopic features were performed on 5′-d(GCGC)-3′. Comprehensively, our results suggest the addition of HO• to the G:C pair moiety, affording the [8-HO-G:C]• detectable adduct. The previous reported spectra of one-electron oxidation of a variety of ds-ODN were assigned to [G(-H+):C]• after deprotonation. Regarding 5′-d(GCGCGC)-3′ ds-ODN, the spectrum at 800 ns has a completely different spectral shape and kinetic behavior. By means of calculations, we assigned the species to [G:C/C:G]•+, in which the electron hole is predicted to be delocalized on the two stacked base pairs. This transient species was further hydrated to afford the [8-HO-G:C]• detectable adduct. These remarkable findings suggest that the double-stranded alternating GC sequences allow for a new type of electron hole stabilization via delocalization over the whole sequence or part of it.

Xeroderma pigmentosum (XP) is characterized by defective repair of ultraviolet radiation(UVR)-induced DNA damage. Patients have UVR hypersensitivity and increased skin cancer risk. Effective photoprotection has reduced childhood cancer-related deaths, but revealed adolescence-onset neurodegeneration, arising through unknown mechanisms. Here, we investigate XP neurodegeneration using pluripotent stem cells derived from XP patients and healthy relatives, performing functional multi-omics on samples during neuronal differentiation. We find endoplasmic reticulum stress is upregulated, preceded by oxidative stress, causing substantial 5’,8-cyclopurine and 8-oxopurine DNA damage. Critically, XP neurons exhibit inappropriate downregulation of the protein clearance ubiquitin-proteasome system (UPS). Chemical enhancement of UPS activity improves phenotypes, albeit inadequately, implying that early detection/prevention strategies are necessary to produce clinically impactful outcomes. Thus, we develop an early detection assay predicting neurodegeneration in at-risk patients.

Lipid membrane turnover and myelin repair play a central role in diseases and lesions of the central nervous system (CNS). The aim of the present study was to analyze lipid composition changes due to inflammatory conditions. We measured the fatty acid (FA) composition in erythrocytes (RBCs) and spinal cord tissue (gas chromatography) derived from mice affected by experimental allergic encephalomyelitis (EAE) in acute and remission phases; cholesterol membrane content (Filipin) and GM1 membrane assembly (CT-B) in EAE mouse RBCs, and in cultured neurons, oligodendroglial cells and macrophages exposed to inflammatory challenges. During the EAE acute phase, the RBC membrane showed a reduction in polyunsaturated FAs (PUFAs) and an increase in saturated FAs (SFAs) and the omega-6/omega-3 ratios, followed by a restoration to control levels in the remission phase in parallel with an increase in monounsaturated fatty acid residues. A decrease in PUFAs was also shown in the spinal cord. CT-B staining decreased and Filipin staining increased in RBCs during acute EAE, as well as in cultured macrophages, neurons and oligodendrocyte precursor cells exposed to inflammatory challenges. This regulation in lipid content suggests an increased cell membrane rigidity during the inflammatory phase of EAE and supports the investigation of peripheral cell membrane lipids as possible biomarkers for CNS lipid membrane concentration and assembly.

Plasmalogens are membrane phospholipids with two fatty acid hydrocarbon chains linked to L-glycerol, one containing a characteristic cis-vinyl ether function and the other one being a polyunsaturated fatty acid (PUFA) residue linked through an acyl function. All double bonds in these structures display the cis geometrical configuration due to desaturase enzymatic activity and they are known to be involved in the peroxidation process, whereas the reactivity through cis-trans double bond isomerization has not yet been identified. Using 1-(1Z-octadecenyl)-2-arachidonoyl-sn-glycero-3-phosphocholine (C18 plasm-20:4 PC) as a representative molecule, we showed that the cis-trans isomerization can occur at both plasmalogen unsaturated moieties, and the product has characteristic analytical signatures useful for omics applications. Using plasmalogen-containing liposomes and red blood cell (RBC) ghosts under biomimetic Fenton-like conditions, in the presence or absence of thiols, peroxidation, and isomerization processes were found to occur with different reaction outcomes due to the particular liposome compositions. These results allow gaining a full scenario of plasmalogen reactivity under free radical conditions. Moreover, clarification of the plasmalogen reactivity under acidic and alkaline conditions was carried out, identifying the best protocol for RBC membrane fatty acid analysis due to their plasmalogen content of 15–20%. These results are important for lipidomic applications and for achieving a full scenario of radical stress in living organisms.

Geometrical mono-trans isomers of arachidonic acid (mtAA) are endogenous products of free radical-induced cis-trans double bond isomerization occurring to natural fatty acids during cell metabolism, including lipid peroxidation (LPO). Very little is known about the functional roles of mtAA and in general on the effects of mono-trans isomers of polyunsaturated fatty acids (mtPUFA) in various types of programmed cell death, including ferroptosis. Using HT1080 and MEF cell cultures, supplemented with 20 μM PUFA (i.e., AA, EPA or DHA) and their mtPUFA congeners, ferroptosis occurred in the presence of RSL3 (a direct inhibitor of glutathione peroxidase 4) only with the PUFA in their natural cis configuration, whereas mtPUFA showed an anti-ferroptotic effect. By performing the fatty acid-based membrane lipidome analyses, substantial differences emerged in the membrane fatty acid remodeling of the two different cell fates. In particular, during ferroptosis mtPUFA formation and their incorporation, together with the enrichment of SFA, occurred. This opens new perspectives in the role of the membrane composition for a ferroptotic outcome. While pre-treatment with AA promoted cell death for treatment with H2O2 and RSL3, mtAA did not. Cell death by AA supplementation was suppressed also in the presence of either ferroptosis inhibitors, such as the lipophilic antioxidant ferrostatin-1, or NADPH oxidase (NOX) inhibitors, including diphenyleneiodonium chloride and apocynin. Our results confirm a more complex scenario for ferroptosis than actually believed. While LPO processes are active, the importance of environmental lipid levels, balance among SFA, MUFA and PUFA in lipid pools and formation of mtPUFA influence the membrane phospholipid turnover, with crucial effects in the occurrence of cell death by ferroptosis.

Radical reactions in water or aqueous media are important for organic synthesis, realizing high yielding processes under non-toxic and environmentally friendly conditions. This overview includes (i) a general introduction to organic chemistry in water and aqueous media, (ii) synthetic approaches in-, on- and with-water as well as in heterogeneous phase, (iii) reaction of carbon-centered radicals with water (or deuterium oxide) activated through coordination with various Lewis acids, (iv) photocatalysis in water and aqueous media, and (v) synthetic applications bioinspired from naturally occurring processes. A wide range of chemical processes and synthetic strategies under different experimental conditions have been reviewed that lead to important functional group translocation and transformation reactions, leading to the preparation of complex molecules. These results reveal how water as a solvent/medium/reagent in radical chemistry has matured over the last two decades and how further discoveries are foreseen to come in the near future.

In recent years, nucleic acids have emerged as powerful biomaterials, revolutionizing the field of biomedicine. This review explores the multifaceted applications of nucleic acids, focusing on their pivotal role in various biomedical applications. Nucleic acids, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), possess unique properties such as molecular recognition ability, programmability, and ease of synthesis, making them versatile tools in biosensing and for gene regulation, drug delivery, and targeted therapy. Their compatibility with chemical modifications enhances their binding affinity and resistance to degradation, elevating their effectiveness in targeted applications. Additionally, nucleic acids have found utility as self-assembling building blocks, leading to the creation of nanostructures whose high order underpins their enhanced biological stability and affects the cellular uptake efficiency. Furthermore, this review delves into the significant role of oligonucleotides (ODNs) as indispensable tools for biological studies and biomarker discovery. ODNs, short sequences of nucleic acids, have been instrumental in unraveling complex biological mechanisms. They serve as probes for studying gene expression, protein interactions, and cellular pathways, providing invaluable insights into fundamental biological processes. By examining the synergistic interplay between nucleic acids as powerful biomaterials and ODNs as indispensable tools for biological studies and biomarkers, this review highlights the transformative impact of these molecules on biomedical research. Their versatile applications not only deepen our understanding of biological systems but also are the driving force for innovation in diagnostics and therapeutics, ultimately advancing the field of biomedicine.