Analyses on the binding interaction between rice glutelin and conjugated linoleic acid by multi-spectroscopy and computational docking simulation.

It is an interesting topic to elucidate the interaction among plant proteins and bioactive lipid components. However, there is a shortage of understanding regarding the nature of the interaction between rice protein and conjugated linoleic acid (CLA). In this study, the intrinsic fluorescence intensity of rice glutelin (RG) was quenched upon increasing concentrations of CLA, indicating the occurrence of an interaction between them. Thermodynamic analysis showed that the RG-CLA binding process occurred spontaneously and hydrogen bonds were the primary driving force. Moreover, only one binding site was calculated between RG and CLA by the intrinsic fluorescence data. The surface hydrophobicity of RG was reduced with increasing CLA. Circular dichroism and synchronous fluorescence spectroscopy showed conformational and microenvironmental changes around the chromophores of RG. The α-helical content increased and ß-sheet content declined after the binding reaction. The computational docking program displayed the target site in which CLA and amino acid residues of RG might be linked together. This study provides valuable insights into the nature of the interactions between plant proteins and fatty acids.

Improving ordered arrangement of the short-chain amylose-lipid complex by narrowing molecular weight distribution of short-chain amylose.

To investigate effect of molecular weight distribution on formation of the short-chain amylose-lipid complex, debranched waxy rice starch (Unf) was fractionated into F1, F2 and F3, and the four fractions were used to complex with palmitic acid (C16:0). The peak molecular weight was in the order of F1 < Unf < F2 < F3, and the distribution was in the order of Unf> F3 > F1 > F2. XRD and DSC analysis indicated that the Unf-C16:0 complex was amorphous with the melting temperature (Tm) < 100 °C while the F3-C16:0 complex was highly ordered with Tm > 100 °C. Moreover, the F1-C16:0 complex was more ordered than the Unf-C16:0 complex, although F1 had lower molecular weight. These results suggested that improving homogeneity of short-chain amylose promoted ordered arrangement of the short-chain amylose-lipid complex. Moreover, the F3-C16:0 complex was the most resistant, which accorded with its highest crystallinity.

Investigation on the binding interaction between rice glutelin and epigallocatechin-3-gallate using spectroscopic and molecular docking simulation.

The interaction between plant protein and polyphenol is a topic of considerable interest. However, there is relatively little understanding about the interaction between rice protein and epigallocatechin-3-gallate (EGCG). The spectroscopy and computational docking program were used to investigate the potential interaction between rice glutelin (RG) and EGCG. It was found that the intrinsic fluorescence of RG could be quenched by EGCG, which indicated interaction occurred between them. Thermodynamic analysis elucidated that the interaction process between RG and EGCG happened spontaneously with hydrogen bond as the primary driving force. The ANS-fluorescence indicated that the surface hydrophobicity of RG reduced with the increasing of EGCG. Circular dichroism spectra and synchronous fluorescence gave further information for the conformational and microenvironmental changes of RG. Particularly, the α-helix structure reduced and random coil structure increased after the binding interaction. Furthermore, the computational docking program exhibited target sites in which the amino acid residues of RG and EGCG might be bound together.

Hydrothermal stability of phenolic extracts of brown rice.

The phenolics were extracted and purified from brown rice and twenty-seven compounds were identified, including six phenolic acids, four phenolic acid glycosides, and eight flavonoid glycosides. Afterwards, the hydrothermal stability of phenolic extracts of brown rice was investigated after treatment at 60, 80, or 100 °C for 120 min. After hydrothermal treatment, ferulic acid, p-coumaric acid and free glucose were increased, while the phenolic glycosides were decreased. In addition, the total phenolic and total flavonoid content were decreased by 5.7%-9.2% and 3.5%-5.8% after initial 30 min, and then they were slightly recovered after treatment for 120 min. Consequently, there was a slight reduction (<10%) in the total antioxidant activity of the phenolic extracts after hydrothermal treatment. These results suggest that hydrothermal treatment of phenolic extracts of brown rice made some phenolic glycosides deglycosylated, but does not lead to a large reduction in their overall antioxidant activity.