Search

A search for the neutrinoless quadruple beta decay of 136Xe was conducted with the liquid-xenon detector XMASS-I using 327 kg ×800.0 days of the exposure. The pulse shape discrimination based on the scintillation decay time constant which distinguishes γ-rays including the signal and β-rays was used to enhance the search sensitivity. No significant signal excess was observed from the energy spectrum fitting with precise background evaluation, and we set a lower limit of the half life of 3.7 × 1024 years at 90% confidence level. This is the first experimental constraint of the neutrinoless quadruple beta decay of 136Xe.

In vitro reconstitution of whole cellular events is one of the important goals in synthetic biology. Using a cell-free protein synthesis (CFPS) system reconstituted with human translation factors and chaperones, we reproduced the biogenesis of β-actin, synthesis, folding, and polymerization in a test tube. This system enabled us to define which step of the β-actin biogenesis was defective in genetic mutations related to diseases. Hence, the CFPS system reconstituted with human factors may be a useful tool for analyzing proteostasis in eukaryotes.