Qiuda Xu

• The stimuli contents in phosphoproteomic were set by their allosteric constants. • Sweet and umami stimuli cause the closed form of RyR1 channel. • A “metabolic clock” notion based on nutrient sensing is proposed.

The G protein cascade amplification system couples with several receptors to sense/amplify the cellular signal, implying universal application. In order to explore whether GPCRs can trigger G protein signal amplification in tissues/cells from different species, bombykol receptor was isolated and purified from antennas of male Bombyx mori, which subsequently self-assembled on the cell membrane in rat taste buds/rat vomeronasa/catfish tentacles/taste bud tissues of rabbits/pig/cattle in those lacking endogenous bombykol receptor, followed by immobilization between two sheets of nucleopore membranes fixed by sodium alginate-starch gel, forming the sandwich-type sensing membrane, which in turn was immobilized on the glass-carbon electrode. Thus, bombykol receptor sensors were established with different tissues. The response current of bombykol receptor sensor toward bombykol was measured with an electrochemical workstation. Every bombykol receptor sensor could sense bombykol based on enzyme-substrate kinetics. The double reciprocal plot and the activation constant values of bombykol receptor sensors assembled with rat taste buds, rat vomeronasa, catfish tentacles, rabbit taste buds, pig taste buds, and cattle taste buds were calculated. Approximately 2-3 receptors could trigger the G protein cascade amplification system and achieve the maximum signal output. Moreover, the detection lower limit indicated that the bombykol receptor self-assembled on the cell membranes of different tissues that transmitted and amplified the bombykol signal with hypersensitivity. Also, cattle taste bud tissues served as an ideal system for heterogeneous GPCRs self-assembly and signal sensing/amplification. This sensing technique and method had promising potential in studies of biological pest control, sex pheromone detection, and receptor structure and function.

An electrochemical double-layer Au nanoparticle membrane immunosensor was developed using an electrochemical biosensing signal amplification system with Au nanoparticles, thionine, chitosan, and horseradish peroxidase, which was fabricated using double self-adsorption of Au nanoparticle sol followed by anti-α-fetoprotein Balb/c mouse monoclonal antibody adsorption. The AuNPs sol was characterized by spectrum scanning and transmission electron microscopy. The immunosensor was characterized by atomic force microscopy, cyclic voltammetry, and alternating-current impedance during each stage of adsorption and assembly. The amperometric I-t curve method was used to measure α-fetoprotein (AFP) diluted in phosphate buffered saline. The result indicated a wide linear range, and the change rate of steady-current before and after immune response had linear correlation within the range 0.1–10⁴ pg/mL AFP. The current change rate equation was △I = 5.82334 lgC + 37.01195 (R² = 0.9922). The lowest limit of detection was 0.03 pg/mL (S/N = 3), and the reproducibility of the sensor was good. Additionally, the sensor could be stably stored above phosphate buffered saline at 4 °C for more than 24 days. More importantly, the sensor is label-free, reagentless and low fouling, making it capable of assaying AFP in real serum samples without suffering from significant interference or biofouling.