Abstract: Provided is an engineered Cas12i nuclease, which comprises one or more of the following mutations based on a reference Cas12i nuclease: (1) replacing one or more amino acids interacting with PAM in the reference Cas12i nuclease with positively charged amino acids; and/or (2) replacing one or more amino acids involved in opening the double strands of DNA, in the reference Cas12i nuclease with amino acids with aromatic rings; and/or (3) replacing one or more amino acids, which interact with a single-stranded DNA substrate and are located in an RuvC domain in the reference Cas12i nuclease, with positively charged amino acids; and/or (4) replacing one or more amino acids interacting with a DNA-RNA double helix in the reference Cas12i nuclease with positively charged amino acids; and/or (5) replacing one or more polar or positively charged amino acids interacting with the DNA-RNA double helix in the reference Cas12i nuclease with hydrophobic amino acids.

Abstract: A drilling machine tool with a cooling liquid purifying and recycling mechanism. The drilling machine tool comprises a platform in which a blanking hole is formed, wherein air cylinders are fixedly mounted at the top of a transverse plate located above the platform, a lifting plate is mounted after the output shaft ends of the air cylinders penetrate through the transverse plate, an isolation cylinder is arranged below the lifting plate, an opening is formed in the bottom of the isolation cylinder, the bottom end of the vertical shaft slidably penetrates through the isolation cylinder and is fixedly provided with a drill bit, the isolation cylinder is connected with the lifting plate through pressing mechanisms, and a cooling liquid conveying mechanism communicating with the interior of the isolation cylinder is arranged on the platform; and a cooling liquid purifying and recycling mechanism is arranged at the bottom of the platform.