Structure characterization of protein fractions from lotus (Nelumbo nucifera) seed

Protein fractionation of lotus seed was carried out and the structures of the protein fractions were studied. Fourier transform infrared spectroscopy (FTIR) as well as ultraviolet visible spectroscopy (UV–vis) was used to investigate changes in molecular structures of the protein fractions. FTIR and UV–vis spectra showed the protein fractions had different protein molecular structures. FTIR spectra showed β-sheets and β-turns as the major secondary structures in the individual protein fractions, while the amounts of α-helix and random coil structures among the different fractions did not significantly change. The amounts of β-sheet structures of albumin and globulin were significantly higher than ones of prolamin and glutelin, implying albumin and globulin had high stabilities because of the high content in β-sheet structures. The observed similarity in the amounts of α-helix, random coil, β-sheet and β-turn structures shared by albumin and globulin indicated that their interior conformations were similar.

► FTIR and UV spectra showed the protein fractions had different molecular structures.
► The β-sheets and β-turns as the major secondary structures in the individual protein fractions.
► The amounts of β-sheet of albumin and globulin were higher than ones of prolamin and glutelin.
► The albumin and globulin had higher stabilities than prolamin and glutelin.