Spectral analysis of radical metalloenzyme using EPR in Hydrolases

One of the categories of hydrolase is acid phosphatase which is isolated from sweet potato (spAP). It contains metal ions such as Zn, Mn, Fe etc. with molecular weight 110kDa. An aqueous epr spectrum in buffer (pH 5.6) exhibits class II mixed valence nature of Fe+3 together with Fe+2, Mn+2, Zn+2 and Cu+2 metallobiosites. It indicates reduced form of enzyme with gMn(II)= 2.0084 and grad= 2.0041 signals with radical signal. The localized electron interaction with 55Mn+2 nucleus is evidenced by six-hyperfine splitted spin allowed transitions flanked by ten satellite lines. Allowed and forbidden doublets are computed with A (55Mn) coupling constant~96 G and Zfs parameter D=0.029 cm-1. The spin integration of Tyrradical signal is shown in lyophilized sample spectrum (1.029 x 1015 spins /gm). It also shows DNA cleavage activity with pUC 19 plasmid DNA.

On the Structural Analysis ofγ-Ray Induced Primary Free Radicals in UHMWPE and Vitamin E Stabilized UHMWPE by ESR Spectroscopy

Oriented allyl radicals are detected at room temperature in gamma irradiated UHMWPE. The effects of vitamin E and storage at room temperature on this oriented structure are also investigated during the study. While testing powder as well as compression-molded solids, with or without vitamin E, a typical ESR spectrum was recorded at room temperature following 100 kGy gamma dose and subsequent storage at −78.5°C for one year. The simulated results show that the relative abundance of 5% alkyl, 68% allyl, and 27% polyenyl produced a 98.7% best fit of experimental ones. Furthermore, the allyl radical signal gives approximately 20% of random orientations and 80% of oriented molecules. In oriented PE, measured at −196°C, Ohnishi et al. (1916) observed 25 lines within a total magnetic field width of approximately 133 G. Our spectra also show 25 lines spread over 136 G in UHMWPE powder samples and at room temperature after one year of storage.

Novel Hybrid Inorganic–organic Film Based on the Tungstophosphate Acid–polyacrylamide System: Photochromic Behavior and Mechanism

A novel photochromic complex composed of Keggin-type tungstophosphate acid (PW12) and polyacrylamide (PAM) was prepared. Atomic force microscopy (AFM), thermogravimetric study, Fourier transform infrared spectra (FTIR), ultraviolet–visiblea bsorption spectra (UV-VIS), and electron resonance spectra (ESR) were used to investigate the surface topography, composition, and photochromic behavior and mechanism of the film. Under UV irradiation, the film was reduced photochemically to yield a blue species. AFM images indicated that surface topography of the polymer matrix changed after adding PW12. FTIR results showed that the Keggin geometry of PW12 was still preserved inside the matrix, and a charge-transfer bridge was built between PW12 and PAM by hydrogen bonding. The characteristic signal of W (V) and the formation of a radical signal in ESR spectra indicated that PAM was a hydrogen donor and the photoreduced process was in accordance with the radical mechanism.The diffusion of oxygen in the polymeric network plays an important role in the reversibility of photochromism.