Electron-paramagnetic-resonance studies on a photochemically produced species of horseradish peroxidase compound I

Strong electron-paramagnetic-resonance signals in the g = 2.00 region were detected after irradiation of horseradish peroxidase Compound I at temperatures of 10 and 100 K. These signals establish the presence of new free-radical species in the peroxidase system. The new species are interpreted in terms of a haem-photosensitized oxidation of the protein's peptide groups close to the Compound I radical site. On warming to room temperature, the radicals decayed irreversibly to a species having a weak asymmetric electron-paramagnetic-resonance signal at 100 K, which could still be observed after incubation at room temperature for more than 1 h.

Women's health beliefs about breast cancer and breast self-examination

To investigate the nature of women's health beliefs about breast cancer and breast self-examination (BSE) and the extent of BSE practice, a questionnaire was administered to 122 women. Ninety-seven percent (118) scored high in perceived benefits of BSE in reducing the threat of breast cancer and 87 percnet (106) scored high in perceived susceptibility to breast cancer. Forty percent (48) practiced BSE monthly, but over 20 percent of the sample had high beliefs and were nonpracticers. Thus, it cannot be concluded that beliefs cause behavior. Other factors such as embarrassment or religious upbringing influence health beliefs and practices, it was found. A majority of women who did practice BSE, furthermore, were unsure of their ability to detect abnormalities. A separate group of 20 women with a history of breast lumps or cancer surgery had higher susceptibility beliefs, a higher rate of practice, no embarrassment in examining themselves, and more confidence in ability to detect abnormalities than the remainder of the sample.

Low temperature magnetic circular dichroism spectra of met- and myoglobin derivatives

1. Low temperature magnetic circular dichroism spectra of high and low spin derivatives of metmyoglobin and myoglobin have been measured in the Soret and high wavelength regions. 2. The large difference in intensity of the Soret magnetic circular dichroism bands suggest that a correlation exists between the signal intensity and spin state of the heme-iron. 3. From a comparison of the high and low spin sepctra of the myoglobin derivatives it is concluded that oxymyoglobin contains between 10 and 20% of a ferrous high spin component below 100 degrees K.

Photochemical reactions of horseradish peroxidase compounds I and II at room temperature and 13 degrees K

Some photochemical reactions of horseradish peroxidase compounds I and II (HRP-I and HRP-II, respectively) have been studied by electronic absorption spectroscopy over the temperature range 297 degrees K-10 degrees K. In glassy matrices below 80 degrees K HRP-I is rapidly converted to hrp-ii when irradiated with low power white light. The native enzyme and HRP-II are not photochemically active at these temperatures with low power irradiation. At room temperature the spontaneous decay of both HRP-I and HRP-II is catalyzed by irradiation with white light. It is shown that the photolysis is dependent upon light in the region 450-320 nm. It is concluded that the HRP-I and HRP-II conformations are closely related with only a low transition energy in the presence of electrons generated by the light. The conversion of HRP-II to HRP is accompanied by large conformational changes and so is inhibited at low temperatures.