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.