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Main observation and conclusion: An enzyme‐free amperometric sensor based on a heptadecapeptide possessing an electroactive ferrocene (Fc) linker as ferrocene‐Gly‐Gly‐Gly‐Gly‐Phe‐Gly‐His‐Ile‐His‐Glu‐Gly‐Tyr‐Gly‐Gly‐Gly‐Gly‐Lys‐(CH2)4‐dithiocyclopentane self‐assembled on gold substrate was designed and fabricated for specific determination of L‐arginine (L‐Arg). The detection mechanism is based on conformational change of surface‐immobilized peptide induced by the target L‐Arg, which was confirmed via SEM, TEM, AFM, XPS, and SPR studies. The binding affinity and the recognition feasibility of immobilized specific and non‐specific peptides were also assessed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The proposed method can serve as "signal‐on" sensor for detection of L‐Arg down to 31 pmol/L with broad linear range (0.0001 to 10 μmol/L). Furthermore, the Fc‐conjugated specific peptide sensor was successfully applied to the determination of L‐Arg in pig serums with a recovery rate of 97.5%—106.9%, and its test results are in good agreement with that of chromatographic instrument, evidencing that the oligopeptide‐based sensor can be served as a simple and enzyme‐free biosensing platform towards L‐Arg for future application. [ABSTRACT FROM AUTHOR]

In order to develop a highly efficient H 2 S gas sensor at low working temperature, in this work, a kind of novel Ce-doped ZnCo 2 O 4 hollow microspheres (Ce/ZnCo 2 O 4 HMSs) were successfully synthesized using a template-free one-pot method, showing a sensitive response toward H 2 S. The microstructure and morphology of the material were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The gas-sensing performance of the composite was investigated, showing that the ZnCo 2 O 4 doped with 6 mol% Ce had the highest response to 20 ppm H 2 S at a low operating temperature of 160 °C with a response value of 67.42, which was about 2 times higher than that of original ZnCo 2 O 4 . The prepared Ce/ZnCo 2 O 4 HMS sensor in response to H 2 S exhibited a linear range of 0.1-200 ppm with a low detection limit of 0.1 ppm under the conditions of ambient humidity of 45% and ambient temperature of 20 °C. Meanwhile, it also possessed good selectivity, repeatability and reproducibility. The response value of the sensor decreased by 5.32% after 7 months of continuous monitoring of H 2 S in an atmospheric environment of a pig farm, indicating that the sensor had a long-term stability and continuous service life with important application prospects.

L-Tryptophan is a nutritionally essential amino acid for monogastric animals and preweaning ruminants because it cannot be synthesized in the body. Besides serving as a building block for proteins, tryptophan is a critical nutrient for the functions of nervous and immune systems. Over the past decades, much attention has been directed to study the role of tryptophan as a limiting amino acid in mammalian and avian nutrition. However, emerging evidence from recent studies shows that tryptophan and its metabolites (e.g., serotonin (5-hydroxytryptamine, 5-HT) and melatonin)) can regulate feed intake, reproduction, immunity, neurological function, and anti-stress responses. Additionally, tryptophan may modulate gene expression and nutrient metabolism to impact whole-body homeostasis in organisms. Thus, adequate intake of this amino acid from the diet is crucial for growth, development, and health of animals and humans.