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oai:figshare.com:article/34042340 2026-10-01T10:04:41Z category_1 category_4 category_7 category_8 category_12 category_15 category_16 category_24 category_873 category_39 category_64 portal_63 item_type_6 month_year_10_2026

Bulk PM_2.5 Masks Oxidative Potential and Reactive Oxygen Species Responses by Metal–Organic Complexation in PM₁ and PM_1–2.5 Fractions Jianing Liu (140090) Lijin Zeng (25155827) Chen Tang (1917925) Yuting Shen (1713340) Yingjing Miao (6843350) Jiewen Huang (11657181) Ting Fang (155126) Biophysics Biochemistry Medicine Microbiology Cell Biology Neuroscience Physiology Evolutionary Biology Chemical Sciences not elsewhere classified Ecology Cancer reactive oxygen species antagonistic effects seen ascorbic acid assay integrate size fractions 80 – 0 65 – 0 5 </ sub 43 – 0 22 – 0 10 – 0 1 </ sub masks oxidative potential 93 ), ros 1 – 2 81 ), op fractions bulk pm 1 across oxidative potential 88 ), dithiothreitol assay oxidative toxicity bulk pm widely used ros characterization results indicate respiratory deposition particulate matter mitochondrial superoxide mechanistic explanation interaction factors end points 95 ). 78 ). Bulk PM_2.5 measurements are widely used to assess the oxidative toxicity of particulate matter, but they integrate size fractions that differ in composition and respiratory deposition. We show that mixing PM₁ and PM_1–2.5 from a roadside site produces pronounced antagonistic effects on oxidative potential (OP) and reactive oxygen species (ROS) generation, with interaction factors (IFs) below 1 across all end points: OP by the ascorbic acid assay (IF = 0.65–0.81), OP by the dithiothreitol assay (IF = 0.80–0.93), ROS (IF = 0.10–0.88), and mitochondrial superoxide (IF = 0.43–0.78). This antagonism requires metal–organic interactions as metal-free biomass burning PM exhibits strictly additive behaviors. Cu²⁺–humic acid experiments reproduce the antagonistic effects seen in ambient PM (IFs = 0.22–0.95). Electron paramagnetic resonance spectroscopy confirms the formation of complexed Cu and reveals that the conversion of free Cu to complexed Cu is nonlinear with respect to the HA:Cu ratio, providing a mechanistic explanation for the divergent interaction effects reported across studies. These results indicate that bulk PM_2.5 measurements can mask the oxidative toxicity of metal–organic interactions, highlighting the need for size-resolved OP and ROS characterization. 2026-10-01T00:00:00Z Text Journal contribution 10.1021/acs.est.6c09837.s001 https://figshare.com/articles/journal_contribution/Bulk_PM_sub_2_5_sub_Masks_Oxidative_Potential_and_Reactive_Oxygen_Species_Responses_by_Metal_Organic_Complexation_in_PM_sub_1_sub_and_PM_sub_1_2_5_sub_Fractions/34042340 CC BY-NC 4.0