5 Conclusion

Incubation of BSA with three different long-chain dien-aldehyde (trans, trans-2,4-heptadienal, trans,trans-2,4-nonadienal and trans, trans-2,4-decadienal) all led to protein side chain modification and formation of fluorescent lipofuscin, as well as changes of protein structure and protein aggregation. The three aldehyde-protein adducts showed different degrees of a yellowish-brown color, and their UV-Vis absorption curves were similar. In general, the degree of protein modification by the three dialdehydes showed significant concentration dependence, and was also affected by modifier chain length. In addition, the reaction rules of the three aldehydes with BSA, as well as the product characteristics, were found to be very similar. In general, the three aldehydes without oxygen-containing side chains selected in the experiment were comparable in BSA modification at low concentrations. However, at high concentrations, we found that the shorter the chain length, the more significant the modification effect; this was also consistent with the PCA results. In the concentration range selected in the experiment, a correlation study was performed to establish links between oxidative modification parameters and concentration of aldehydes. We found relatively clear correlations between formation of protein bound carbonyls, the retention ratio of free amino content, the maximum UV-Vis absorption value, and the concentration of aldehydes. However, the correlation between LFLP and the concentration of aldehydes was not linear. PCA of the relationship between the various oxidation parameters demonstrated that fluorescence lipofuscin was highly correlated with PC2, while other oxidation parameters were highly correlated with PC1.
Results from this study are helpful for us to better understand the properties of proteins modified by long-chain unsaturated aldehydes without oxygen-containing side chains, and can enrich our knowledge about aldehyde-protein adducts. We will consider further mechanism exploration in future research.