V8 proteolysis of a low molecular weight fraction of aqueous wheat bran extract promotes the formation of fused nanospheres.

The objective of this work was to explore whether the formation of protein nanoparticles, reported in a previous study, occurs in a fraction of an aqueous extract of wheat bran with a particular composition. Using a bottom-up strategy, an aqueous extract of wheat bran was first fractionated by size exclusion chromatography. Each of the chromatographic fractions was hydrolyzed with V8 protease in a reaction medium containing Ca2+. The chromatographic fractions and their hydrolysates were subjected to chemical characterization, electrophoresis, UV-Vis spectroscopy, infrared spectroscopy, and scanning electron microscopy. Six chromatographic fractions from 0.3 to 102.8 kDa were obtained. The chemical and spectroscopic characterization results revealed the presence of protein-polysaccharide-ferulic acid complexes in four of the fractions. In the hydrolysate of a 15.1 kDa fraction, longitudinally fused nanospheres were found, forming chains. Occasionally, fusion occurred at different angles, providing attachment sites for branching. It is discussed how the composition of this fraction and the added Ca2+ ions could determine both the formation of the nanospheres and their arrangement.