The amino acid compositions， secondary structure， and self-assembly of oat protein isolate (OPI)， which was purified from the high-protein Chinese oat， have been investigated by using a combination of amino acid analysis， Fourier transform infrared spectroscopy (FTIR)， and tapping mode atomic force microscopy (TP-AFM). OPI， with molecular weights ranging from 14.0 kDa to 66.0 kDa， was rich in essential amino acids and contained 24.7% glutamic acid and 8.1% leucine. The amino acid contents of OPI are 4.5-8.7 times higher than those of oat flour. The secondary structures of OPI have been quantified by the deconvolution of the amide I band of the FTIR spectrum of OPI， which were found to contain ... More
The amino acid compositions， secondary structure， and self-assembly of oat protein isolate (OPI)， which was purified from the high-protein Chinese oat， have been investigated by using a combination of amino acid analysis， Fourier transform infrared spectroscopy (FTIR)， and tapping mode atomic force microscopy (TP-AFM). OPI， with molecular weights ranging from 14.0 kDa to 66.0 kDa， was rich in essential amino acids and contained 24.7% glutamic acid and 8.1% leucine. The amino acid contents of OPI are 4.5-8.7 times higher than those of oat flour. The secondary structures of OPI have been quantified by the deconvolution of the amide I band of the FTIR spectrum of OPI， which were found to contain approximately 7% beta-turn， 19% alpha-helix， and 74% beta-sheet. Tapping mode AFM results further suggest that the oat protein isolate has two major types of shapes， ellipsoidal and disk-like. At protein concentrations below 0.5 mg/mL， most of the OPI molecules are in the isolated form. However， when the concentration of OPI reaches 1.0 mg/mL， some of the OPI molecules self-assembled into large and heterogeneous protein aggregates.
