An in-silico layer-by-layer adsorption study of the interaction between Rebaudioside A and the T1R2 human sweet taste receptor: modelling and biosensing perspectives

Ginkgolic Acid as a carbapenem synergist against KPC-2 positive Klebsiella pneumoniae

The successful evolution of KPC-2 in bacteria has limited the clinical practice of carbapenems. This dilemma deteriorated the prognosis of associated infections and hence attracted increasing attention from researchers to explore alternative therapeutic options. Here, the enzyme inhibition assay was first performed to screen for a potent KPC-2 inhibitor. The synergistic effect of the candidate with carbapenems was further confirmed by checkboard minimum inhibitory concentration (MIC) assay, time-killing assay, disk diffusion method, and live/dead bacteria staining analysis. The mechanisms by which the candidate acts were subsequently explored through molecular dynamics (MD) simulations, etc. Our study found that Ginkgolic Acid (C13:0) (GA) exhibited effective KPC-2 inhibitory activity in both laboratory strain and clinical strain containing KPC-2. It could potentiate the killing effect of carbapenems on KPC-2-positive Klebsiella pnenmoniae (K. pnenmoniae). Further explorations revealed that GA could competitively bind to the active pocket of KPC-2 with meropenem (MEM) via residues Trp104, Gly235, and Leu166. The secondary structure and functional groups of KPC-2 were subsequently altered, which may be the main mechanism by which GA exerted its KPC-2 inhibitory effect. In addition, GA was also found to synergize with MEM to disrupt membrane integrity and increase membrane permeability, which may be another mechanism by which GA reinforced the bactericidal ability of carbapenems. Our study indicated that GA was a significant KPC-2 inhibitor that could prolong the lifespan of carbapenems and improve the prognosis of patients.

Identification of flavor peptides based on virtual screening and molecular docking from Hypsizygus marmoreuss

Hypsizygus marmoreuss is an under-explored source of flavor peptides that can enhance the flavor of NaCl or MSG, allowing products to be reformulated in line with reduction policies. This study utilized advanced techniques, including UPLC-Q-TOF MS/MS and molecular docking, to identify H. marmoreuss peptides. Sensory evaluations revealed 10 peptides with pronounced umami flavors and seven with dominantly salty tastes. VLPVPQK scored highest for umami intensity (5.2), and EGNPAHQK for salty intensity (6.2). Further investigation influenced by 0.35 % MSG or 0.35 % NaCl exposed peptides with elevated umami and salty thresholds. LDSPATPEK, VVEGEPSLK, and QKLPEKPER had umami-enhancing thresholds of 0.18, 0.18, and 0.35 mM, while LDSPATPEK and VVEGEPSLK had similar thresholds for salt (0.09 mM). Molecular docking revealed that taste receptor proteins interacted with umami peptides through hydrogen, carbon-hydrogen, alkyl, and van der Waals forces. Specific amino acids in the umami receptor T1R1 had roles in bonding with umami peptides through hydrogen and carbon-hydrogen interactions. In conclusion, molecular docking proved to be an effective and efficient method for flavor peptide screening. Further, this study demonstrated that flavor peptides from H. marmoreuss had the capacity to enhance NaCl and MSG flavours and might be useful tools for reformulation, reducing salt and MSG contents.

Computational simulations on the taste mechanism of steviol glycosides based on their interactions with receptor proteins

Steviol glycoside (SG) is a potential natural sugar substitute. The taste of various SG structures differ significantly, while their mechanism has not been thoroughly investigated. To investigate the taste mechanism, molecular docking simulations of SGs with sweet taste receptor TAS1R2 and bitter taste receptor TAS2R4 were conducted. The result suggested that four flexible coils (regions) in TAS1R2 constructed a geometry open pocket in space responsible for the binding of sweeteners. Amino acids that form hydrogen bonds with sweeteners are located in different receptor regions. In bitterness simulation, fewer hydrogen bonds were formed with the increased size of SG molecules. Particularly, there was no interaction between RM and TAS2R4 due to its size, which explains the non-bitterness of RM. Molecular dynamics simulations further indicated that the number of hydrogen bonds between SGs and TAS1R2 was maintained during a simulation time of 50 ns, while sucrose was gradually released from the binding site, leading to the break of interaction. Conclusively, the high sweetness intensity of SG can be attributed to its durative concurrent interaction with the receptor's binding site, and such behavior was determined by the structure feature of SG.

Evaluation of the catalytic activity of graphene oxide and zinc oxide nanoparticles on the electrochemical sensing of T1R2-Rebaudioside A complex supported by in silico methods

Herein, we report on the performance of graphene oxide (GOx) and zinc oxide nanoparticles (ZnONPs) on a platinum (Pt) electrode, immobilized with the human T1R2 sweet taste receptor subunit for the detection of rebaudioside A (Reb-A). The characterization studies performed in this work confirmed the thin-layered structure of GOx and the polydispersed nature of ZnONPs. The elucidation of the mass loss observed by TGA demonstrates the stability of GOx. The cyclic voltammetry results for Pt/GOx revealed good catalytic activity over Pt/ZnONPs for adsorption of the T1R2-Reb-A complex. In addition, a series of computational modelling studies were carried out to better understand the surface adsorption phenomena of GOx and ZnONPs to mimic the layer-by-layer electrode modification strategies independently. The strongest interaction energy observed (−573 kcal mol−1) for the direct interaction of ZnONPs onto the Pt electrode surface, demonstrates a stronger adsorption in contrast to the GOx modified Pt electrode (−23 kcal mol−1). However, the overall results for the layered-nanocomposite revealed that the GOx (−256 kcal mol−1) were more strongly adsorbed in contrast to ZnONPs (−231 kcal mol−1) for the detection of the T1R2-ReB-A complex, demonstrating the reliability of our GOx electrode functionalization strategy. The results of this study can potentially be used to improve the design of rapid Reb-A sensors for the food and beverage industry.