High UV Sensitivity Research Articles

High sensitivity of murine teratocarcinoma cells to UV radiation and the effect of post-irradiation treatment with caffeine

The radiosensitivity of murine teratocarcinoma cells was investigated. Our findings are as follows: (1) the undifferentiated teratocarcinoma cells are 3 times more sensitive to UV than their differentiated counterpart and BALB/3T3 cells; (2) X-ray sensitivity of the undifferentiated cells is comparable to that of BALB/3T3 cells; (3) post-irradiation treatment with caffeine strongly sensitizes a fraction of the undifferentiated cells to UV and X-rays resulting in biphasic survival curves of the cells; (4) high UV sensitivity and hyper-sensitization by caffeine is lost upon differentiation of the cells. Possible mechanisms for the unusually high sensitivity of undifferentiated teratocarcinoma cells to radiation and post-irradiation treatment with caffeine will be discussed.

Sensitizing pigment in the fly

The sensitizing pigment hypothesis for the high UV sensitivity in fly photoreceptors (R1–6) is further substantiated by measurements of the polarisation sensitivity in the UV. The quantum yield of the energy transfer from sensitizing pigment to rhodopsin was estimated by electrophysiological measurements of the UV sensitivity and the rhabdomeric absorptance (at 490 nm) in individual receptor cells. The transfer efficiency is ≥ 0.75 in receptors with an absorptance in the rhabdomeres of 0.55–0.95. This result suggests that the sensitizing pigment is bound in some way to the rhodopsin. A ratio of two molecules of sensitizing pigment per one rhodopsin is proposed.

High efficiency inversion layer solar cells on polycrystalline silicon by the application of silicon nitride

Plasma enhanced CVD silicon nitride is introduced for the fabrication of inversion layer solar cells on p-type polycrystalline silicon. The same high interface quality as obtained for Si-nitride on monocrystalline silicon could also be achieved for polycrystalline silicon. This includes high interface charge densities up to 6.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and high UV sensitivity of the cells. For 4-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> polycrystalline metal-insulator-semiconductor inversion layer (MIS/IL) solar cells active area efficiencies up to 13.4 percent (12.3-percent total area efficiency) under AM1 illumination could be reached, the highest values yet reported for polycrystalline silicon inversion layer solar cells on a total area basis. For the coprocessed MIS/IL cells on monocrystalline 0.7-ω. cm p-Si

Silicon nitride for the improvement of silicon inversion layer solar cells

It is demonstrated that CVD Si-nitride films as transparent dielectric satisfy all requirements for achieving MIS/IL solar cells with high efficiency and long term stability. Deposited on silicon by the SiH 4/NH 3 reaction at temperatures lower than usual (between 600° and 650°C) fixed positive interface charge densities Q N / q up to 7 × 10 12 cm −2 with excellent stability have been obtained. Utilizing the Si-nitride charge storage effect, the highest known Q N / q values (> 10 13 cm −2) combined with low values of N it have been achieved. The charge distribution is discussed and an energy band diagram modified according to new analytical results is presented. MIS/IL solar cells with AM1 efficiencies of 15% (active area) and high UV sensitivity have been obtained.

Photodiodes and junction field-effect transistors with high UV sensitivity

Silicon photodiodes and photo-FET's with high blue and UV sensitivity have been produced by a special boron diffusion process. Diodes with a junction depth around 0.2 µm exhibit a responsivity of 0.1 A/W at 253 nm; the maximum responsivity (with a quantum efficiency close to 100 percent) is reached at 440 nm. The responsivity of the photo-FET's operating in the photoconductive mode (V GS = 0) exceeds 103A/W at 350 nm. The spectral response curve and the large-signal behavior of the photo-FET's are strongly dependent on the operating conditions.

UV sensitivity of several genetic markers of Haemophilus influenzae DNA.

Studies on inactivation by UV of several genetic markers of the streptomycin and novobiocin resistance regions of H. influenzae DNA have shown that two kinds of markers may be found with respect to frequency of integration, UV sensitivity and reactivability. One class of markers has high integration frequency and low UV sensitivity, which can be partly explained by the reactivability of the irradiated markers. The second class of markers has low integration frequency and high UV sensitivity. Markers of each class have been found in the novobiocin region.-In one recipient strain with decreased transformability the difference in integration frequency between the two classes is enhanced.

UV-induced replicating instability in fission yeast Schizosaccharomyces pombe

A system of forward mutations was used to study UV-induced replicating instability in the fission yeast Schizosaccharomyces pombe at 5 adenine-dependent loci which precede the ad-7 locus in the adenine synthetic pathway. Mutations resulting from realization of replicating instabilities were observed in 270 cell generations investigated. Realization of replicating instabilities may lead to both forward and reverse mutations, the frequency of forward being much higher than that of reverse or suppressor mutations. In strains of normal and high UV sensitivity the frequencies of secondary mosaicism in the progeny of primary mosaics were 5.5 and 0.39%, respectively. In the strain with normal UV sensitivity the presence of caffeine in the plating medium of primary mosaics decreased the level of secondary mosaicism from 12.8 to 0.14%. Cells from red colonies taken from the caffeine-containing medium yielded further mosaics at a rate of 34.3% in the absence of caffeine and of 0.6% in its presence.

The adenosine triphosphate pool and the adenyl cyclase activity in Escherichia coli strains with different UV sensitivity.

Two genetically relatedEscherichia coli strains were tested for the ATP pool and for the adenyl cyclase activity in the cell membrane fractions. TheEscherichia coli strain BS1with a high UV sensitivity showed a higher ATP level than the wild typeEscherichia coli B strain. The adenyl cyclase activity was found to be lower in the sensitive strain than in the wild typeEscherichia coli.

FLUORESCENCE EMISSION OF MITOCHONDRIAL DPNH AS A FACTOR IN THE ULTRAVIOLET SENSITIVITY OF VISUAL RECEPTORS.

The photodissociation of the CO compound of cytochrome a/sub 3/ at liquid nitrogen temperatures was demonstrated. Since the recombination of CO does not occur in a measurable rate at 77 deg K, the system provides a quantum counter for intracellular luminescence. A considerably higher uv sensitivity was found in mitochondrial suspensions and intact cells that contain DPNH than was observed in purified cytochrome oxidase (free of DPNH). Results are consistent with the viewpoint that excitation fluorescence of DPNH (maximum 340 m mu ) provides a highly efficient fluorescence emission in the region of 410--500 m mu . (H.M.G.)