EPR investigation of the gamma-ray irradiated natural and tanned collagen

Free radicals produced in natural and tanned collagen by gamma-ray irradiat ion within 1-15 kGy absorbed dose ranges were investigated by EPR spectrosc opy. Tanned collagen was prepared using formaldehyde as well as aluminum ba sic salts [Al(OH)SO4] tanning processes. Both natural and formaldehyde-tann ed irradiated collagen show the same kind of EPR spectrum consisting of a s ingle broad, slightly asymmetric line. Irradiated collagen tanned by alumin um basic salts process displayed a complex EPR spectrum consisting of a sup erposition of broad and narrow lines. A computer simulation of this spectru m allowed to evidence the presence of seven different kinds of paramagnetic centers, including those observed in the irradiated natural collagen. Corr esponding Spin Hamiltonian parameters (g-factor, hyperfine splitting consta nt) as well as relative concentrations of these centers were calculated. Ex perimentally determined relative concentrations display a positive correlat ion with the absorbed dose described by a linear-type dependence. After thr ee weeks of storage at room temperature, the concentration of some centers diminished by about 50%. The possible nature of these centers is discussed in connection with the local structure of the tanned collagen. (C) 2001 Els evier Science Ltd. All rights reserved.