Cooperative Electronic Structure Modulator of Fe Single-Atom Electrocatalyst for High Energy and Long Cycle Li-S Pouch Cell.

High-energy and long cycle lithium-sulfur (Li-S) pouch cells are limited by the insufficient capacities and stabilities of their cathodes under practical electrolyte/sulfur (E/S), electrolyte/capacity (E/C), and negative/positive (N/P) ratios. Herein, an advanced cathode comprising highly active Fe single-atom catalysts (SACs) is reported to form 320.2 W h kg-1 multistacked Li-S pouch cells with total capacity of ≈1 A h level, satisfying low E/S (3.0), E/C (2.8), and N/P (2.3) ratios and high sulfur loadings (8.4 mg cm-2 ). The high-activity Fe SAC is designed by manipulating its local environments using electron-exchangeable binding (EEB) sites. Introducing EEB sites comprising two different types of S species, namely, thiophene-like-S (-S) and oxidized-S (-SO2 ), adjacent to Fe SACs promotes the kinetics of the Li2 S redox reaction by providing additional binding sites and modulating the Fe d-orbital levels via electron exchange with Fe. The -S donates the electrons to the Fe SACs, whereas -SO2 withdraws electrons from the Fe SACs. Thus, the Fe d-orbital energy level can be modulated by the different -SO2 /-S ratios of the EEB site, controlling the electron donating/withdrawing characteristics. This desirable electrocatalysis is maximized by the intimate contact of the Fe SACs with the S species, which are confined together in porous carbon.

A new LC-MS/MS method for the quantification of endogenous and vinyl chloride-induced 7-(2-Oxoethyl)guanine in sprague-dawley rats.

Vinyl chloride (VC) is an industrial chemical that is known to be carcinogenic to animals and humans. VC primarily induces hepatic angiosarcomas following high exposures (≥50 ppm). VC is also found in Superfund sites at ppb concentrations as a result of microbial metabolism of trichloroethylene and perchloroethylene. Here, we report a new sensitive LC-MS/MS method to analyze the major DNA adduct formed by VC, 7-(2-oxoethylguanine) (7-OEG). We used this method to analyze tissue DNA from both adult and weanling rats exposed to 1100 ppm [(13)C(2)]-VC for 5 days. After neutral thermal hydrolysis, 7-OEG was derivatized with O-t-butyl hydroxylamine to an oxime adduct, followed by LC-MS/MS analysis. The limit of detection was 1 fmol, and the limit of quantitation was 1.5 fmol on the column. The use of stable isotope VC allowed us to demonstrate for the first time that endogenous 7-OEG was present in tissue DNA. We hypothesized that endogenous 7-OEG was formed from lipid peroxidation and demonstrated the formation of [(13)C(2)]-7-OEG from the reaction of calf thymus DNA with [(13)C(18)]-ethyl linoleate (EtLa) under peroxidizing conditions. The concentrations of endogenous 7-OEG in liver, lung, kidney, spleen, testis, and brain DNA from adult and weanling rats typically ranged from 1.0 to 10.0 adducts per 10(6) guanine. The exogenous 7-OEG in liver DNA from adult rats exposed to 1100 ppm [(13)C(2)]-VC for 5 days was 104.0 ± 23.0 adducts per 10(6) guanine (n = 4), while concentrations in other tissues ranged from 1.0 to 39.0 adducts per 10(6) guanine (n = 4). Although endogenous concentrations of 7-OEG in tissues in weanling rats were similar to those of adult rats, exogenous [(13)C(2)]-7-OEG concentrations were higher in weanlings, averaging 300 adducts per 10(6) guanine in liver. Studies on the persistence of [(13)C(2)]-7-OEG in adult rats sacrificed 2, 4, and 8 weeks postexposure to [(13)C(2)]-VC demonstrated a half-life of 7-OEG of 4 days in both liver and lung.

Genetic damage, but limited evidence of oxidative stress markers in diethyl maleate-induced glutathione depleted mouse lymphoma L5178Y (TK(+/-)) cell cultures.

Depletion of glutathione (GSH) in cells exposed to certain xenobiotics has been proposed to result in oxidative stress, which could lead to damage of cellular macromolecules such as proteins, lipids, and DNA. Diethyl maleate (DEM) is known to conjugate with GSH and rapidly lower cellular GSH levels. The objective of this study was to investigate the influence of DEM-induced GSH depletion on various genotoxicity and gene expression end points in mouse lymphoma L5178Y (TK(+/-)) cell cultures. Cells were exposed to DEM for 4 h at concentrations of 0, 6.7, 13.5, 26.9, 53.8, 107.6, 215.3, and 430.6 µg/mL (0.039-2.5 mM). Genotoxicity was evaluated by examining the induction of in vitro micronuclei (20 h post-treatment) and DNA strand breaks as measured by comet (immediately following treatment), and correlating these observations to cellular GSH levels. In the current study, GSH was decreased more than 50% at the lowest test concentration (6.7 µg/mL) and more than 95% at ≥ 107.6 µg/mL. A significant increase in micronuclei and DNA strand breaks was observed at concentrations of ≥ 26.9 µg/mL. Gene expression of seven apoptosis and oxidative-stress related genes showed significant alterations in only three genes only at the highest test concentration. Quantifiable levels of 8-OH-dG (≥ 2 adducts per 1 × 10(8) NT) were not detected at any treatment concentration. These results demonstrate an association between DEM-induced genotoxicity and GSH depletion in mouse lymphoma L5178Y (TK(+/-)) cells, but not with other oxidative markers.

Accumulation of M1dG DNA adducts after chronic exposure to PCBs, but not from acute exposure to polychlorinated aromatic hydrocarbons.

Oxidative DNA damage is one of the key events thought to be involved in mutation and cancer. The present study examined the accumulation of M1dG, 3-(2'-deoxy-beta-D-erythro-pentofuranosyl)-pyrimido[1,2-a]-purin-10(3H)-one, DNA adducts after single dose or 1-year exposure to polyhalogenated aromatic hydrocarbons (PHAH) in order to evaluate the potential role of oxidative DNA damage in PHAH toxicity and carcinogenicity. The effect of PHAH exposure on the number of M1dG adducts was explored initially in female mice exposed to a single dose of either 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or a PHAH mixture. This study demonstrated that a single exposure to PHAH had no significant effect on the number of M1dG adducts compared to the corn oil control group. The role of M1dG adducts in polychlorinated biphenyl (PCB)-induced toxicity and carcinogenicity was further investigated in rats exposed for a year to PCB 153, PCB 126, or a mixture of the two. PCB 153, at doses up to 3000 microg/kg/day, had no significant effect on the number of M1dG adducts in liver and brain tissues from the exposed rats compared to controls. However, 1000 ng/kg/day of PCB 126 resulted in M1dG adduct accumulation in the liver. More importantly, coadministration of equal proportions of PCB 153 and PCB 126 resulted in dose-dependent increases in M1dG adduct accumulation in the liver from 300 to 1000 ng/kg/day of PCB 126 with 300-1000 microg/kg/day of PCB 153. Interestingly, the coadministration of different amounts of PCB 153 with fixed amounts of PCB 126 demonstrated more M1dG adduct accumulation with higher doses of PCB 153. These results are consistent with the results from cancer bioassays that demonstrated a synergistic effect between PCB 126 and PCB 153 on toxicity and tumor development. In summary, the results from the present study support the hypothesis that oxidative DNA damage plays a key role in toxicity and carcinogenicity following long-term PCB exposure.

Rational Design of 1D Partially Graphitized N-Doped Hierarchical Porous Carbon with Uniaxially Packed Carbon Nanotubes for High-Performance Lithium-Ion Batteries.

N-doped hierarchical porous carbon with uniaxially packed carbon nanotubes (CNTs) was prepared by copolymer single-nozzle electrospinning, carbonization, and KOH activation. Densely and uniaxially aligned CNTs improve the electrical conductivity and act as a structural scaffold, enhancing the electrochemical performance of the anode. A partially graphitized N-doped carbon shell, which has a rapid ion accessible pore network and abundant redox sites, was designed to expand the redox sites from the surface of the material to the whole material, including the inner part. As an anode, this material exhibited a superior reversible capacity of 1814.3 mA h g-1 at 50 mA g-1 and of 850.1 mA h g-1 at 1000 mA g-1. Furthermore, the reversible capacity decreased by only 36% after 400 cycles and showed superior rate capability to that of the same material without CNTs, indicating that the CNT acted successfully as a structural scaffold and enhanced the electrical conductivity. This study not only allowed the rational design of the ideal structure of CNT-based carbonaceous anode material, which has both a rapid ion accessible structure and fast electron-transfer path, but also shed light on a potential strategy by which to use CNTs to modify the nitrogen bonding configuration in N-doped carbon for better electrochemical performance.

Pyrimido[1,2-a]-purin-10(3H)-one, M1G, is less prone to artifact than base oxidation.

Pyrimido[1,2-a]-purin-10(3H)-one (M1G) is a secondary DNA damage product arising from primary reactive oxygen species (ROS) damage to membrane lipids or deoxyribose. The present study investigated conditions that might lead to artifactual formation or loss of M1G during DNA isolation. The addition of antioxidants, DNA isolation at low temperature or non-phenol extraction methods had no statistically significant effect on the number of M1G adducts measured in either control or positive control tissue samples. The number of M1G adducts in nuclear DNA isolated from brain, liver, kidney, pancreas, lung and heart of control male rats were 0.8, 1.1, 1.1, 1.1, 1.8 and 4.2 M1G/10(8) nt, respectively. In rat liver tissue, the mitochondrial DNA contained a 2-fold greater number of M1G adducts compared with nuclear DNA. Overall, the results from this study demonstrated that measuring M1G is a reliable way to assess oxidative DNA damage because the number of M1G adducts is significantly affected by the amount of ROS production, but not by DNA isolation procedures. In addition, this study confirmed that the background number of M1G adducts reported in genomic DNA could have been overestimated by one to three orders of magnitude in previous reports.

Crucial Role of Oxidation Debris of Carbon Nanotubes in Subsequent End-Use Applications of Carbon Nanotubes.

A facile purification method for oxidized carbon nanotubes (CNTs) is developed to preserve acidic carbon compounds (ACCs) for achieving high-quality dispersion of CNTs. The remaining ACCs, which originated from the surface destruction of CNTs during the oxidation process, are considered to play a crucial role in the dispersion of CNTs in water and various polar protic solvents. To elucidate the concrete role of ACCs, a direct titration method is applied to quantitatively investigate the degree of ionization of both CNTs and ACCs in their aqueous dispersions. While ACCs with strong carboxylic groups (pKa of around 2.9) are easily removed by the neutral or base washing of oxidized CNTs, which is common in the purification process, ACC-selective purification using acid washing preserves the ACCs attached to CNTs, thereby effectively stabilizing CNT dispersions in aqueous solutions. Additionally, the Hansen solubility parameters of ACC-preserved and ACC-removed CNTs were determined by the inverse gas chromatography method to estimate their miscibility in various solvents. The preserved ACCs significantly influenced the dispersibility of CNTs in polar protic solvents, which may widen the possible application of CNTs. Specifically, the ACC-preserved high-quality CNT dispersion produces high-performance CNT buckypaper with densely packed nanostructures. The Young's modulus and tensile strength of these buckypapers reach up to 12.0 and 91.0 MPa, respectively, which exceed those of ACC-removed CNTs in previous reports.

Formation of M1G-dR from endogenous and exogenous ROS-inducing chemicals.

The present study provides fundamental information regarding the production of M1G-dR by ROS. To investigate the production of M1G-dR from deoxyribose damage as caused by ROS, calf thymus DNA (CT-DNA) was incubated with NAD(P)H, CuCl2, and various concentrations of hydrogen peroxide (H2O2). The incubation of CT-DNA with H2O2 resulted in concentration-dependent increases in the number of M1G-dR adducts. In subsequent experiments, 1,4-tetrachlorobenzoquinone or catechol estrogens were evaluated for their effects on M1G-dR formation. In addition, the role of lipid peroxidation in the formation of M1G-dR was verified using an in vitro lipid peroxidation model which consisted of methyl esters of either fish oil or purified fatty acids found in cellular membranes. This experiment confirmed that M1G-dR is a major DNA adduct produced by lipid peroxidation. Furthermore, the number of double bonds in polyunsaturated fatty acids was found to be the key factor in the formation of M1G-dR. The findings obtained from this study provide important information regarding the molecular pathways for M1G-dR formation by ROS, which is an essential element in understanding and evaluating the genotoxicity of a variety of ROS-inducing chemicals.

LC-MS/MS simultaneous quantitation of 2-hydroxyethylated, oxidative, and unmodified DNA nucleosides in DNA isolated from tissues of mice after exposure to ethylene oxide.

2-Hydroxyethylated and oxidative DNA nucleosides (DNA adduct biomarkers), such as O6-(2-hydroxyethyl)-2'-deoxyguanosine (O6HEdG), N6-(2-hydroxyethyl)-2'-deoxyadenosine (N6HEdA), 1-(2-hydroxyethyl)-2'-deoxyadenosine (N1HEdA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG), N2,3-etheno-2'-deoxyguanosine (N2,3-ethenodG), α-methyl-γ-hydroxy-1,N2-propano-2'-deoxyguanosine (CrotondG), are important proposed biomarkers for exploring the genotoxicity mechanism of ethylene oxide (EO) in vivo. A liquid chromatography-tandem mass spectrometric method was developed for the simultaneous determination of O6HEdG, N6HEdA, N1HEdA, 8-OHdG, CrotondG, and N2,3-ethenodG together with regular 2'-deoxyguanosine (dG), and 2'-deoxyadenosine (dA) nucleosides in the DNA extracted from mouse lung tissues for the assessment of exposure to EO after inhalation. The lower limits of quantitation for 8-OHdG, CrotondG, N2,3-EthenodG, O6HEdG, N1HEdA, N6HEdA, dG, and dA were 0.025, 0.00125, 0.025, 0.00125, 0.025, 0.01, 2342, and 2500ng/mL, respectively. The linearity of the calibration curves for all analytes were >0.989. The intra-day assay precision relative standard deviation (RSD) values for quality control (QC) samples for all analytes were ≤13.5% with accuracy values ranging from 86.5% to 111%. The inter-day assay precision (RSD) values for all analytes were ≤18.8% with accuracy values ranging from 87.9% to 119%. This method was used for simultaneous determination of the levels of 8-OHdG, CrotondG, N2,3-EthenodG, O6HEdG, dG, N1HEdA, N6HEdA, and dA in DNA enzymatic hydrolysates from DNA extracted from mouse lung after 12 weeks' inhalation exposure to EO at atmospheric concentrations of 0, 100, and 200ppm. Overall, N2,3-ethenodG was not detected in any samples. 8-OHdG, CrotondG, dG, and dA were all quantifiable in all samples. O6HEdG, N1HEdA, and N6HEdA were quantifiable in most samples and the ratio of the corresponding adduct versus their corresponding DNA base (dG or dA) [×10 (e6)] was increased as the EO exposure concentration increased.

Measurement of deoxyinosine adduct: Can it be a reliable tool to assess oxidative or nitrosative DNA damage?

Adenosine deaminases (ADA) are key enzymes that deaminate adenosine (A) or deoxyadenosine (dA) and produce inosine or deoxyinosine (dI), respectively. While ADA only deaminates free dA, reactive nitrogen species (RNS) or reactive oxygen species (ROS) deaminate adenine base on the DNA and leave dI, which is a pre-mutagenic lesion. Therefore, dI adduct in the genomic DNA has been considered a biomarker of DNA damage caused by RNS or by ROS. In the presented study, genomic DNA was isolated from frozen calf thymus in low or room temperature, with or without an addition of antioxidant. The number of dI in the DNA was measured using liquid chromatography-tandem mass spectrometry. While low temperature (LT) work-up with an addition of antioxidant in reagents helped to prevent artifactual formation of oxidative DNA lesions in the calf thymus DNA (CTD), it also significantly inhibited activities of proteinase, which in turn resulted in significant ADA contamination in the final DNA samples. ADA remained in LT-CTD completely deaminated most dA when the DNA was subjected to enzymatic hydrolysis to single nucleosides. The ADA contamination in the DNA was significantly reduced when DNA was isolated from pre-isolated nuclear fraction rather than from entire tissue homogenates. However, enzymes used for DNA hydrolysis were confirmed to contain significant amounts of ADA. Therefore, these enzymes would increase deamination of dA during DNA hydrolysis. Artifactual dI production by contaminated ADA was dramatically reduced by an addition of EHNA (erythro-9-(2-hydroxy-3-nonyl)adenine), which is a potent inhibitor of ADA. However, time- and temperature-dependent dI production from dA in phosphate buffer solution was observed. More importantly, TEMPO, an antioxidant commonly used to prevent DNA oxidation, was found to deaminate dA independent to ADA. Overall, these findings indicate that assay methods measuring dI or other dA DNA adducts in genomic DNA should be carefully validated to minimize artificial errors caused by dA deamination. Recommendations to overcome those technical challenges were discussed in this presentation.

Biomarkers in toxicology and risk assessment: informing critical dose-response relationships.

Tremendous advances have been made in the study of biomarkers related to carcinogenesis during the past 20 years. This perspective will briefly review improvements in methodology and instrumentation that have increased our abilities to measure the formation, repair, and consequences of DNA adducts. These biomarkers of exposure, along with surrogates such as protein adducts, have greatly improved our understanding of species differences in metabolism and effects of chemical stability and DNA repair on tissue differences in molecular dose. During this same time frame, improvements in assays for biomarkers of effect have provided better data and an improved understanding of the dose responses for both gene and chromosomal mutations. A framework analysis approach was used to examine the mode of action of genotoxic chemicals and the default assumption that cancer can be expected to be linear at very low doses. This analysis showed that biomarkers of exposure are usually linear at low doses, with the exception being when identical adducts are formed endogenously. Whereas biomarkers of exposure extrapolate down to zero, biomarkers of effect can only be interpolated back to the spontaneous or background number of mutations. The likely explanation for this major difference is that at high exposures, the biology that results in mutagenesis is driven by DNA damage resulting from the chemical exposure. In contrast, at very low exposures, the biology that results in mutagenesis is driven by endogenous DNA damage. The shapes of the dose-response curves for biomarkers of exposure and effect can be very different, with biomarkers of effect better informing quantitative estimates of risk for cancer, a disease that results from multiple mutations. It is also clear, however, that low dose data on mutagenesis are needed for many more chemicals.

Quantitation of glutathione by liquid chromatography/positive electrospray ionization tandem mass spectrometry.

Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine. It is present in practically all cells and has several important roles, such as preventing the oxidation of the sulfhydryl groups of proteins within a cell. Evidence for GSH deficiency or depletion has been found in a variety of diseases and toxicity-related studies, including diabetes and induction of oxidative stress to form reactive oxygen species which cause DNA, lipid, and protein oxidations. A simple, selective, and sensitive analytical method for measuring low levels of GSH in biological fluids would therefore be desirable to conduct GSH deficiency or depletion-related mechanistic toxicity studies. Here a method for both low- and high-level quantitation of GSH from cultured cells and rat liver tissues via liquid chromatography/positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has been developed. The lower limit of quantitation (LOQ) of the method was 5 ng/mL. The method is linear over a wide dynamic concentration range of 5.0 to 5000.0 ng/mL, with a correlation coefficient R2 > 0.99. The intra-day assay precision relative standard deviation (RSD) values for all quality control (QC) samples were < or =16.31%, with accuracy values ranging from 94.13 to 97.80%. The inter-day assay precision RSD values for all QC samples were < or =15.94%, with accuracy values ranging from 94.51 to 100.29%. With this method, low levels of GSH from diethyl maleate (DEM)-treated mouse lymphoma cells, and GSH in rat liver tissues, were quantified.

Low utilization of circulating glucose after food withdrawal in Snell dwarf mice.

Glucose metabolism is altered in long-lived people and mice. Although it is clear that there is an association between altered glucose metabolism and longevity, it is not known whether this link is causal or not. Our current hypothesis is that decreased fasting glucose utilization may increase longevity by reducing oxygen radical production, a potential cause of aging. We observed that whole body fasting glucose utilization was lower in the Snell dwarf, a long-lived mutant mouse. Whole body fasting glucose utilization may be reduced by a decrease in the production of circulating glucose. Our isotope labeling analysis indicated both gluconeogenesis and glycogenolysis were suppressed in Snell dwarfs. Elevated circulating adiponectin may contribute to the reduction of glucose production in Snell dwarfs. Adiponectin lowered the appearance of glucose in the media over hepatoma cells by suppressing gluconeogenesis and glycogenolysis. The suppression of glucose production by adiponectin in vitro depended on AMP-activated protein kinase, a cell mediator of fatty acid oxidation. Elevated fatty acid oxidation was indicated in Snell dwarfs by increased utilization of circulating oleic acid, reduced intracellular triglyceride content, and increased phosphorylation of acetyl-CoA carboxylase. Finally, protein carbonyl content, a marker of oxygen radical damage, was decreased in Snell dwarfs. The correlation between high glucose utilization and elevated oxygen radical production was also observed in vitro by altering the concentrations of glucose and fatty acids in the media or pharmacologic inhibition of glucose and fatty acid oxidation with 4-hydroxycyanocinnamic acid and etomoxir, respectively.

LC/MS/MS method for the quantitation of trans-2-hexenal-derived exocyclic 1,N(2)-propanodeoxyguanosine in DNA.

trans-2-Hexenal is an alpha,beta-unsaturated aldehyde to which humans are exposed daily in small amounts. Hexenal has demonstrated mutagenicity and genotoxicity in vitro and reacts with deoxyguanosine to form diastereomeric hexenal-derived exocyclic 1,N(2)-propanodeoxyguanosine (Hex-PdG) adducts. A highly sensitive and specific method for the measurement of Hex-PdG in DNA has not previously been available. An LC/MS/MS assay for the quantitation of Hex-PdG, using [(13)C4(15)N2]Hex-PdG as an internal standard, was developed, to assess binding of hexenal to DNA. Samples were purified prior to analysis by centrifuge filtration and solid phase extraction and analyzed by LC/MS/MS in the selected reaction monitoring (SRM) mode (SRM m/z 366.2 --> 250.2 for Hex-PdG; SRM m/z 372.2 --> 256.2 for [(13)C4(15)N2]Hex-PdG). Recovery of standards was 89% or greater, and quantitation was unaffected by the addition of increasing concentrations of calf thymus DNA (ctDNA). The limit of quantitation, determined in samples of 200 microg of ctDNA spiked with analyte standard, was 0.015 fmol/microg DNA, which corresponds to approximately 5 Hex-PdG/10(9) unmodified nucleotides. Hex-PdG was detected in ctDNA treated with 0.021 microM, 0.21 microM, or 2.1 mM hexenal but not in untreated DNA. Furthermore, Hex-PdG was not detected in DNA exposed to reactive oxygen species-mediated deoxyribose attack and lipid peroxidation, which resulted in a significant increase in the malondialdehyde-derived pyrimido[1,2-a]purin-10(3H)one. Hex-PdG was not detected in DNA of untreated rat liver, but Hex-PdG in hexenal-treated calf thymus DNA was quantifiable when spiked into the rat liver DNA at 0.035 or 0.35 fmol/microg DNA. These data indicate that Hex-PdG is formed following hexenal treatment and that this method is suitable for in vitro or in vivo assessment of Hex-PdG formation.

Analysis of M1G-dR in DNA by aldehyde reactive probe labeling and liquid chromatography tandem mass spectrometry.

A novel method for the measurement of pyrimido[1,2-a]purin-10(3H)one (M1G) has been developed. Previous methods for analysis of M1G have been confounded by the fact that this lesion exists in equilibrium between a ring-closed form and a ring-opened aldehyde form. Poor detection sensitivity of the aldehydic form can result from loss of the adduct during analysis by its reaction with amines or proteins. We utilized the aldehyde reactive probe (ARP) to produce a stable ARP-M1G-deoxyribose (ARP-M1G-dR) conjugate to minimize adduct loss. This conjugate has increased the hydrophobicity that enhances separation of ARP-M1G-dR from unmodified DNA nucleosides by using solid phase extraction. In addition, measuring ARP-M1G-dR by selective reaction monitoring (SRM) of the [ARP-M1G-dR + H]+ (635) --> [M1G + H]+ (188) transition increases the detection sensitivity by nearly an order of magnitude relative to the measurement of M1G-dR by SRM. For accurate measurement, analytical standard (AS) DNA and internal standard (IS) DNA were used. High purity 15N-labeled DNA was isolated from Escherichia coli that had been grown in minimum salt medium containing (15NH4)2SO4. The 15N-DNA and calf thymus DNA were treated with malondialdehyde to induce a high number of M1G adducts to prepare the IS and AS DNA, respectively. A consistent calibration curve was established from the analysis of 200 microg of blank DNA, 23 ng of IS DNA (400 fmol of 15N5-M1G-dR), and AS DNA containing 0-810 fmol of M1G-dR. With the use of this novel IS DNA and selective labeling, this assay is a useful tool for monitoring oxidative stress-induced DNA damage from small amounts of DNA without the need of a specific antibody or laborious procedures. By this assay, two M1G adducts/10(8) guanines can readily be detected. Furthermore, this approach should be applicable to the analysis of other aldehydic DNA adducts as well as the measurement of an array of DNA lesions.