Donald J. Fluke

Inactivation of Dry T-1 bacteriophage by helium ions, carbon ions, and oxygen ions: comparison of effect for tracks of various ion density.

Dry preparations of T-1 bacteriophage were irradiated with helium ions and with stripped carbon and oxygen ions, extending previous studies of effect of LET to values unattainable with alpha -particles. Over a wide range in LET the effect on phage survival is a function only of the radiation dose, but for heavy ions the efficiency does decrease. A minimum requirement of either one or two ions in a track interval only a few angstrom units long is indicated for inactivation of plaque survival. The indication is against a higher minimum number of ions required. On interpretation in terms of target area, correction for -rays brings the phage target within morphological bounds.

Temperature Dependence of the Direct Action of Ionizing Radiation on Beef Heart Lactate Dehydrogenase: Enzyme Activity, Substrate and Coenzyme Affinities'

Samples of lactate dehydrogenase (LDH), desalted by dialysis, were dried as hard films 0.1 to 0.25

Efficiency of inactivation of dry T-1 bacteriophage by protons, deuterons, and helium ions from a 60-inch cyclotron.

{\rm mg}/{\rm cm}^{2}

Radiation Indication of Subunit Activity of Lactic Dehydrogenase

in average thickness and were irradiated in a vacuum with minimum ionization electrons. After irradiation at controlled temperatures from 65°K to 395°K, samples were returned to ambient temperature, exposed to air, and dissolved in phosphate buffer. For study of effect upon solubility, samples were divided into spontaneous eluate and mechanical resuspendate fractions, each assayed for enzyme activity and for protein content. Both for total recoverable activity and for enzyme specific activity, the temperature dependence of radiation sensitivity is consistent with two principal modes of inactivation, one temperature-independent and the other characterized by an activation energy around 1200 cal/mole. The H4 isozyme and an isozyme mixture gave indistinguishable results. Some temperature dependence was also evident for effect upon protein solubility. The effect of radiation on affinity o...

The Effect of Low Temperature and Drying on the Ultraviolet Action Spectrum of TI Bacteriophage

Dry preparations of T-1 bacteriophage were irradiated with protons, deuterons, and helium ions from a 60-inch cyclotron. Phage assay techniques were adapted for high accuracy in determination of survival ratios and for physical characterization of the ion beams employed. lons yielding LET values differing by factors of up to 15 have all shown about the same effect per uait dose for phsge plaque survival. A comparison of 40-Mev helinm ions and 1.8-Mev protens at the same LET has shown no signficant difference in effect on the phrge. Dry T-1 bacteriophage irradiated in a vacuum requires much higher doses for inactivation than does the phage in protected suspension. Auxiliminary work with gamma rays indicates thst the degree of dryness of the phage may be involved in the difference in sensitivity, (auth)

Dry T-1 bacteriophage in measurement of large doses of ionizing radiation.

Ionizing radiations on dry enzyme preparations have been extensively employed for indication of molecular size associated with catalytic activity (1-3). If dry films containing enzyme material recoverable in active form are irradiated in a vacuum at ordinary temperatures, there is a general correlation of inferred target mass with molecular weight for enzymes, especially in the range of molecular weights below about 100,000 ngm/mole. The correlation is of potential biochemical interest and is here applied to investigation of an enzyme having subunit structure. The result indicates that subunits of lactic dehydrogenase (LDH) can be independently active, in agreement with similar results in other enzymes. Lactic dehydrogenase is especially well characterized as an enzyme consisting of aggregates of subunits. Over a considerable range of tissue sources this enzyme exists in tetramers of two kinds of subunits, designated M and H. There is indication that the two kinds of subunits are genetically independent (4, 5). That they form tetramers by association at random in all unordered combinations of four is indicated by five electrophoretically distinguishable species of LDH and by reassociation experiments. The five species typically found are conventionally designated LDH-1 to LDH-5, or, in terms of subunit composition, MoH4, M1H3, M2H2, M3H1, and M4Ho. Reassociation of a mixture of dissociated MI and H subunits derived from the unmixed types, LDH-1 and LDH-5, yields a distribution of the five isoenzymes in proportions implying a random process (6). The reassociated isoenzymes are active, but activity for subunits independently has not been demonstrated, presumably because of the environment necessary to hold them in a dissociated state. In a study of LDH in relation to metabolic adaptation in a poikilotherm (goldfish), radiation target investigation was included as an index of subunit activity. Although the results are consistent with the independent activity of subunits, the

Temperature Dependence of Ionizing Radiation Effect on Dry Hyaluronidase

The ultraviolet (UV) absorption spectra of pyrimidines have been shown by Scott et al. (1, 2) to reveal detailed structure at low temperature. The UV action spectrum of bacteriophage, as shown for example by Gates (3) for a staphylococcal phage, like the action spectra of other viruses and microorganisms, shows a broad maximum in the region 2500 A to 2800 A, centering at about 2600 A, and attributable to absorption by nucleic acid. An effect of temperature on the UV absorption of components of nucleic acid could result in differences in action spectra, possibly showing the comparative importance of at least the nucleic acid pyrimidines in UV inactivation.

Radiation sensitivity of T1 bacteriophage on various host strain mutants of Escherichia coli

The irradiation of T1 bacteriophage in dry films of nutrient broth in a vacuum at room temperature has been suggested as a biological radiation dosimeter (see, for example, 1) and has been so employed in work with minimum ionizing electrons (2, S). T1 phage is especially suitable for dosimetry within beams of particles from accelerators for these reasons: (1) under the conditions specified above it is sufficiently insensitive to match the high doses usually encountered in such beams; (2) in some contrast with other T phages, it is reasonably stable through drying and resuspension, and can give quite reproducible survival data after such treatment; (3) the dose-effect relation for T1 is dependably logarithmic (4, 5) and independent of LET (rate of energy loss per unit particle track) up to 1000 Mev gm-1 cm2 (6); and (4) the films are easily made thin enough (<0.5 mg/cm2 routine to 0.01 mg/cm2 ultimate) to indicate directly the derivative of the dose-depth relation, often a difficulty in work with accelerated particle beams. The purpose of this paper is to collect results bearing on physical calibration of T1 phage as a dosimeter and to specify appropriate physical and biological conditions. The best figure for T1 radiation sensitivity under such conditions appears to be 570 + 15 krads for survival ratio e-1.

Temperature dependence of ionizing radiation effect on dry lysozyme and ribonuclease.

Dry bovine testicular hyaluronidase in relatively impure preparation has been irradiated with fast electrons at temperatures from 66°K to 433°K. On subsequent recovery of the hyaluronidase into solutions it was assayed for enzymatic activity in digestion of hyaluronic acid to yield detectable oligosaccharides. The activity remaining was found to be approximately logarithmic in relation to the electron dose given. With correction for recovered protein the results as a function of temperature can be reasonably fitted by the sum of two terms, one independent of temperature, and the other characterized by an Arrhenius activation energy of about 1100 cal/mole. In relation to similar work with other enzymes, a larger activation energy usually found at higher temperatures is negligible for hyaluronidase.

The effect of water content and postirradiation storage on radiation sensitivity of brine shrimp cysts (eggs).

A comparison of four host strains for assay of dry T1 phage plaque survival indicates that about 25% of fast electron direct action damage expressed in uvrB/sup -/ hosts is repaired in uvrB/sup +/ hosts. The repair is not associated with a lex or exr gene. In relative amounts, the uvr-repairable damage corresponds with that reported for the T1 phage irradiated by x rays in heavily protected anoxic suspension and assayed for plaque survival on uvr/sup +/ and uvr/sup -/ host strains.