Pig kidney diamine oxidase and Agaricus bisporus tyrosinase were observed to be irreversibly inactivated by 253.7 nm ultraviolet (UV) radiation. By means of hydrodynamic and UV spectral studies, the direct accessibility of the catalytic center of diamine oxidase to UV radiation has been shown to be a possible route for the photoinactivation of this oxidase. Fluorescence and thermal denaturation studies indicated that UV, radiation by perturbing the major molecular forces, destabilizes and unfolds the natural structure of tyrosinase, which in turn leads to the inactivation of this enzyme. A comparative analysis of the inactivation data of the two oxidases revealed that photoinactivation was a very complex, “conformation directed” phenomenon involving the disruption of intramolecular forces and the unfolding of the compact and globular conformation of the natural enzyme.

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A monochromatic X-ray irradiation system in the 0.08-0.4 nm wavelength range is described. This uses for the first time, synchrotron radiation at the Photon Factory as an X-ray source (2.5 GeV electron storage ring). It consists of a beam shutter, a Si crystal monochromator, ionization chambers for monitoring exposures, a sample stage, and a control system. The beam is 2.7 × 30 mm at the sample position with a fairly uniform intensity of several kR/min (one C · kg^-1 · min^-1). The wavelength is an extremely pure Δλ/λ ?? 10^-3. A 35 mm culture dish is moved across the vertical height (2.7 mm) of the X-ray beam using a sample scanning stage. This improves the uniformity of the radiation intensity on the sample. The sample can be irradiated under normal or controlled atmospheric conditions. Since 1984, a variety of biological materials have been irradiated, including cultured mammalian cells. Results of yeast cells are presented to illustrate the performance of this irradiation system.

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When ¹⁴C cytosine was incorporated in M13 mp10 phage, in the phage DNA both cytosine and thymine residues were labelled. The single stranded phage DNA was isolated and irradiated in a buffer solution using ⁶⁰Co gamma-rays. After the addition of TCA, the DNA precipitated was filtered. The ratio of the radioactivity of the filtrate to the total increased with increasing radiation dose. The precipitate -was hydrolyzed with acid and the base modification was analyzed by TLC. The modification yield also increased with increasing dose. Chromatograms showed that the main product was urea. In the case of cytosine radiolysis, trans-5, 6-dihydroxy-5, 6-dihydrouracil was found to be the main product before acid treatment; whereas, urea was the main product after acid treatment. This fact suggests that the trans-5, 6-dihydroxy-5, 6-dihydrouracil retained in the irradiated DNA is responsible for the gamma-ray induced C-T transition.

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The cellular uptake of Adriamycin (ADR) by solid tumors consisting of Ehrlich ascites tumor cells (EATC) was investigated. The intracellular levels of ADR in the EATC were measured by flow cytometry. The EATC tumors were heated at various temperatures for 30 min after the in vivo administration of ADR to the mice into which the EATC were inoculared. The amount of intracellular ADR in the EATC excised from the mice treated with 40°C hyperthermia was increased by 80% over that determined for those treated at body temperature. However, the quantity of ADR in the EATC excised from mice which received 43°C hyperthermia was similar to that for those treated at body temperature. These results indicate that combined therapy using hyperthermia and ADR has both synergic and additive effects, depending on the temperatures used for hyperthermia.

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