Study on the interaction mechanism of purple potato anthocyanins with casein and whey protein
Authors: Gong, Shengxiang; Yang, Chengyu; Zhang, Jianhua; Yu, Ying; Gu, Xinzhe; Li, Wenhui; Wang, Zhengwu
To investigate the interaction mechanism of casein (CA) and whey protein (WP) with anthocyanins from purple potato flour (PPA), multiple spectroscopic techniques and molecular docking simulation were used. After extraction and purification, two non-acylated anthocyanins and three acylated anthocyanins were identified in purple potato flour using UPLC-Q/TOF-MS. The fluorescence quenching experiment found that PPA could effectively quench the intrinsic fluorescence of CA and WP by static quenching. CA had a stronger binding affinity toward PPA than WP did, with respective K-a values of 4.23 x 10(5) M-1 and 1.66 x 10 5 M-1 at 297 K. Structural analysis indicated that PPA bound CA and WP through hydrogen bonds and van der Waals forces, and the number of bound anthocyanin molecules (n) was approximately equal to 1. The AG values of PPA binding with CA and WP were -30.96 kJ mol(-1) and -29.16 kJ mol(-1), respectively, which suggested that the binding reaction was spontaneous. Moreover, the conformational structures of CA and WP were altered by PPA binding with a decrease in alpha-helix and beta-turn contents and an increase in beta-sheet and irregular coil contents. Molecular docking analyses showed that CA and WP had different binding sites with anthocyanins. This study is helpful to better understand the interaction mechanism of CA and WP with anthocyanins and provides guidance for their applications in the food industry.
Anti-poisoning electrode for real-time in-situ monitoring of hydrogen sulfide release
SENSORS AND ACTUATORS B-CHEMICAL
Authors: Jeromiyas, Nithiya; Mani, Veerappan; Chang, Pu-Chieh; Huang, Chih-Hung; Salama, Khaled Nabil; Huang, Sheng-Tung
Electrode poisoning and interferences from complex biological environments are major challenges in the development of in-situ H2S sensors. To circumvent these issues, herein a robust electrode based on reduced graphene oxide-molybdenum disulfide nanohybrid (RGO-MoS2) and polymerized o-phenylenediamine (POPD) is developed. The POPD/RGO-MoS2-modified electrode catalyzed H2S oxidation at a minimized overpotential (+ 0.15 V vs. Ag/AgCl). A new strategy based on inherent material properties was implemented to alleviate the electrode-poisoning problem. The nano-tailored interface blocks 2.5-fold surplus levels of interferences because of its exclusive size-exclusion property and electrostatic interactions. Moreover, this method with a response time of fewer than 5s displayed a detection limit of 10 nM, which covers the endogenous H2S levels. Practicality tests in various biological media yielded valuable recoveries of 96.4-97.8%. The amounts of H2S released from the bacterial cells were quantified in real-time over a continuous time span of 5 h.