Identification of novel umami molecules via QSAR models and molecular docking

Umami substances can increase the overall taste of food and bring pleasure to people. However, it is still challenging to identify the umami molecules through virtual screening due to the crystal structure of the umami receptor being undefined. Herein, based on the hypothesis that the molecules with bitter and sweet taste characteristics may be umami molecules, this study proposed an in silico method to identify novel umami-tasting molecules in batch from SWEET-DB and BitterDB databases via the QSAR models, PCA, molecular docking and electronic tongue analysis. In total, 169 potential umami molecules were identified through QSAR modeling, PCA, and molecular docking. Of the 169 molecules, 18 were randomly selected, and all were identified as umami molecules via electronic tongue analysis. Among the 18 chosen molecules, 10 molecules could be traced back to their concentration range in food, and finally, 8 molecules were predicted to be nontoxic. This work provides a simple and efficient strategy to identify novel umami molecules, holding an excellent promise for demonstrating the crystal structure of umami receptors and taste-sensing mechanisms. Furthermore, this study opens the possibility for the practical application of new umami molecules in food.

Controlled synthesis of metal-organic frameworks with skeletal and pore-filling iron(III) porphyrins for electrochemical oxygen reduction

Electrocatalysts derived from porphyrinic metal-organic frameworks (MOFs) have exhibited very promising electrochemical performances toward oxygen reduction reaction (ORR). Nevertheless, porphyrinic MOFs have been limited to skeleton- or the pore-modified ones mostly by Fe porphyrin (FeP), which only provide insufficient ORR active sites. Herein, we report controlled synthesis of PCN-222 decorated by both pore-filling Hemin and skeletal iron(III) meso-tetra(4-carboxyphenyl) porphyrin (Fe[Formula: see text]TCPP) that partially substitutes original backbone TCPP. Subsequent pyrolysis of the composite PCN-222 led to the synthesis of nanorod electrocatalysts with atomically dispersed Fe-N-C sites, which exhibit efficient activity and durability toward ORR in both alkaline and acidic media. Moreover, it appears that the atomically dispersed Fe-N-C sites might possess a distorted octahedral configuration of (O/N)2-Fe[Formula: see text]-N4 as evidenced by extended X-ray absorption fine structure spectra (EXAFS), aberration-corrected high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), and X-ray photoelectron spectroscopy (XPS). To the best of our knowledge, controlled modification to both the skeleton and the pore of MOFs with FeP for the synthesis of Fe-N-C electrocatalysts has not been reported prior to this study. This study offers a new avenue to manipulate the density of Fe-N-C sites of electrocatalysts, which may be applied to other composite MOFs with various functionalities.