Quercetin modulates the aggregation behavior of bovine hemoglobin.

The effect of different concentrations of quercetin (QUER) on bovine hemoglobin (BHb) conformation and thermal stability was investigated using differential scanning microcalorimetry (µDSC), circular dichroism (CD), dynamic light scattering (DLS), Thioflavin T, Congo Red, and ANS binding assays. Both QUER concentration and incubation temperature modulate the aggregation behavior of BHb. Low concentrations of QUER stabilize the protein structure, while high concentrations promote protein aggregation, as µDSC measurements revealed for the samples incubated at 277 K. With increasing concentration, non-bound QUER acts as a promoter of protein aggregation after incubation for 96 h at 310 K. The changes in the secondary structure of BHb, evaluated by CD, point to an increase in β structure after incubation at 310 K, indicating aggregate formation in the presence of QUER. DLS measurements highlight the aggregation effect of polyphenol on the unfolded protein structure after thermal incubation. Congo Red (CR), Thioflavin T (ThT), and 8-anilino-1-napthalenesulfonic acid (ANS) assays support the formation of aggregates. The results provide valuable insights into the polyphenol-mediated effect on protein thermal behavior and contribute to the development of hemoglobin-based biomaterials, protein stabilization strategies, and biopharmaceutical formulations.