RESUMO
The rare decay K_{L}âπ^{0}νν[over ¯] was studied with the dataset taken at the J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of (7.20±0.05_{stat}±0.66_{syst})×10^{-10}, three candidate events were observed in the signal region. After unveiling them, contaminations from K^{±} and scattered K_{L} decays were studied, and the total number of background events was estimated to be 1.22±0.26. We conclude that the number of observed events is statistically consistent with the background expectation. For this dataset, we set an upper limit of 4.9×10^{-9} on the branching fraction of K_{L}âπ^{0}νν[over ¯] at the 90% confidence level.
RESUMO
The usefulness of Ampullaria beta-glucuronidase as a reagent for the hydrolysis of steroid glucuronides was examined. The purified enzyme showed an optimum pH of 4, and was stable between pH 4.5 and 7.5. The enzyme from Ampullaria and Helix pomatia hydrolyzed various artificial substrates and conjugated steroids. Affinity of the Ampullaria enzyme for 17-hydroxycorticosteroid glucuronide was 7-fold the affinity of the Helix pomatia enzyme. Hydrolysis of urinary steroid conjugates was completed by an incubation with 320 Fishman units of Ampullaria beta-glucuronidase at 60 degrees C for 1 h. A close correlation was obtained between the values of steroid conjugates hydrolyzed by the Ampullaria enzyme and those by the bovine liver enzyme used conventionally. Ampullaria beta-glucuronidase is suitable for hydrolysis of urinary steroid conjugates because of its higher affinity for steroid substrate and the thermal stability.