UNSCHEDULED DNA SYNTHESIS: A QUANTITATIVE INDICATOR OF RESIDUAL IMMUNODETECTABLE PYRIMIDINE DIMERS IN HUMAN FIBROBLASTS AFTER ULTRAVIOLET-B IRRADIATION

We have addressed the question whether the level of UV-B induced DNA damage can be accurately assessed by the measurement of the rate of unscheduled DNA synthesis (UDS). Cultured human fibroblasts were irradiated with UV radiation at 290, 313 or 365 nm. The LD50 was 85 J/m2 at 290 nm, 4500 J/m2 at 313 nm, and 70 kJ/m2 at 365 nm. The analysis of UDS measurements indicate complete arrest of repair processes within 24 h after irradiation, irrespective of the dose (in the range 10-60 J/m2 at 290 nm, and 250-1000 J/m2 at 313 nm). Irradiation at 365 nm failed to yield detectable evidence of UDS. Incubation of irradiated cells with an antiserum directed against both 6-4 type and cyclobutane-type pyrimidine dimers shows a clear parallelism between the disappearance of the antibody-binding determinants and the variation of the rate of UDS vs time after the end of the irradiation. Thus it is concluded that in UV-B irradiated normal cultured human fibroblasts, the lack of UDS reflects the absence of immunodetectable pyrimidine dimers.     

The Application of Site-Specific Natural Isotope Fractionation-Nuclear Magnetic Resonance (SNIF-NMR) to the Analysis of Alcoholic Beverages

The relative deuterium concentration and specific deuterium-site locations in a molecule can be determined using Site-Specific Natural Isotope Fractionation-Nuclear Magnetic Resonance (SNIF-NMR). For a given compound (e.g., ethanol) SNIF-NMR can provide information about the chemical pathway of formation and, in some cases, information about the geographic origin of a sample can also be discerned. SNIF-NMR has been applied to the analysis of wines and other alcoholic beverages. In this work, data were collected on samples of apple brandy, tequila, rum, potato vodka, cognac, and synthetic ethanol. Signal-to-noise considerations limit the samples that can be studied without preconcentration to those with relatively high alcohol contents.     

NILPOTENT ELEMENTS IN THE JACOBSON–WITT ALGEBRA OVER A FINITE FIELD

It is shown in this paper that the number of nilpotent elements in the Jacobson–Witt algebra W _n over a finite field \( {\mathbb F} \) _q is equal to the expected power of q.