Thermostable Pyrococcus furiosus DNA ligase catalyzes the synthesis of (di)nucleoside polyphosphates.

DNA ligase from the hyperthermophilic marine archaeon Pyrococcus furiosus (Pfu DNA ligase) synthesizes adenosine 5'-tetraphosphate (p4A) and dinucleoside polyphosphates by displacement of the adenosine 5'-monophosphate (AMP) from the Pfu DNA ligase-AMP (E-AMP) complex with tripolyphosphate (P3), nucleoside triphosphates (NTP), or nucleoside diphosphates (NDP). The experiments were performed in the presence of 1-2 microM [alpha-32P]ATP and millimolar concentrations of NTP or NDP. Relative rates of synthesis (%) of the following adenosine(5')tetraphospho(5')nucleosides (Ap4N) were observed: Ap4guanosine (Ap4G) (from GTP, 100); Ap4deoxythymidine (Ap4dT) (from dTTP, 95); Ap4xanthosine (Ap4X) (from XTP, 94); Ap4deoxycytidine (Ap4dC) (from dCTP, 64); Ap4cytidine (Ap4C) (from CTP, 60); Ap4deoxyguanosine (Ap4dG) (from dGTP, 58); Ap4uridine (Ap4U) (from UTP, <3).

[An x-ray diagnostic unit based on a gas-discharge converter].

The authors describe a pulse x-ray unit based on a gas-discharge luminescent converter, including a two-channel high-voltage impulse generator, an x-ray radiator, and a control desk. The high dosage sensitivity of the gas-discharge converter and large dimensions of the operating field as well as small size, mass and power consumption make it possible to use the unit for roentgenoscopic low-dose examination in the medical diagnosis under outpatient conditions.