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Although the impact of oxidation on human health has been of growing interest, the oxidation of proteins, major component of meat, has received little attention. This paper describes the in vitro effect of five fluoroquinolones (FQs) on carbonylation of sarcoplasmic and myofibrillar proteins of beef when found at concentrations close to the maximum residue limit (MRL). Samples were treated individually with the FQs, determining in each protein fraction the carbonyl index, protein content and oxidized proteins identification, using 2,4-dinitrophenyhydrazine (DNPH) alkaline assay, Western blot and Bradford methods, and mass spectrometry, respectively. Besides, the in vitro effect of these residues on gastric and duodenal digestion of proteins was evaluated. The carbonylation induced by FQs affected both protein fractions being significant with respect to the blank in 73.3% of cases. This damage was correlated with loss of solubility and digestibility, with sarcoplasmic proteins the most affected. Danofloxacin and enrofloxacin were the FQs with greatest oxidant effects, especially affecting glycolysis and glycogen proteins. Our results suggest that these residues induce irreversible oxidative damage on the main beef proteins and could affect their nutritional value.

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Organophosphate pesticides are frequently used to eliminate or prevent insects in poultry. However, their residues may continue in meat after slaughtering. In this study, proteomics and peptidomics approaches were used to evaluate their oxidative impact on myosin and chicken breast proteins under in vitro conditions. Myosin protein was exposed to diazinon and chlorpyrifos showing an increase in its oxidation by increasing times, especially with chlorpyrifos.Then, chicken breast was contaminated with chlorpyrifos to evaluate carbonylation and the effect of simulated gastrointestinal digestion. Proteins were isolated using size-exclusionchromatography and identified by mass spectrometry in tandem. Myosin, β-enolase, CK-M-type and actin were identified as main proteins susceptible to oxidation. Also, oxidised peptides obtained before and after simulated gastrointestinal digestion were identified.Collagen peptides the most susceptible to oxidation. These results suggest that the presence of chlorpyrifos residues on meat could have a negative effect on its final quality and nutritional value.

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4-HNE-modified ankyrins have been described in diseases such as diabetes, renal failure, G6PD deficient, sickle cell trait, and P. falciparum infected erythrocytes with different AB0 blood groups. However, effects at the atomic level of this carbonylation on structure and function of modified protein are not yet fully understood. We present a study based on molecular dynamics simulations of nine 4-HNE modified residues of the ZU5-ANK ankyrin domain with β-spectrin and their binding energy profiles. Results show that 4-HNE induced local conformational changes over all protein systems evaluated, increased mobility in the modification sites, and localized structural changes between the positively charged patch of the ZU5-ANK domain. Carbonylation with 4-HNE on lysine residues decreased the affinity between ZU5-ANK and the 14-β-spectrin repeat by reducing electrostatic and van der Waals interactions. The presented work provides further insight into understanding the loss of human erythrocyte deformation capacity under conditions of oxidative stress in different diseases.

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