Time-Dependent Variations in Structure of Sheep Wool Irradiated by Electron Beam

Abstract

Wool scoured in tap water with no special degreasing and containing a balanced humidity responding to usual laboratory conditions was irradiated by accelerated electron beam in the range of 0–350 kGy dose. Time variations of the wool structure were measured using FTIR, Raman, and EPR spectroscopy. The aim was to determine whether preexposure treatment of the wool, as well as postexposure time, affects the properties of the irradiated wool. Reactive products such as S-sulfonate, cystine monoxide, cystine dioxide, cysteic acid, disulphides, and carboxylates displayed a considerable fluctuation in quantity depending on both the absorbed dose and time. Mutual transformations of S-oxidized products into cysteic acid appeared to be faster than those in dry and degreased wool assuming that the present humidity inside the fibres is decisive as an oxygen source. EPR results indicated a longer lifetime for free radicals induced by lower doses compared with the radicals generated by higher ones. The pattern of the conformational composition of the secondary structure (α-helix, β-sheet, random, and residual conformations) also showed a large variability depending on absorbed dose as well as postexposure time. The most stable secondary structure was observed in nonirradiated wool but even this showed a small but observable change after a longer time, too.

Why Natural or Electron Irradiated Sheep Wool Show Anomalous Sorption of Higher Concentrations of Copper(II)

“…The sorption isotherms (Figure 1) transformed into dependence of the sorption on absorbed dose for the particular Cu(II) concentrations offers interesting evidence (Figure 7); firstly, all curves show a sudden turn at 20 kGy dose; secondly, in consideration of the 0 kGy absorbed dose, the curves can be divided into two groups: (a) the curves for lower concentrations (12.5 and 25 mM) and the ones for higher concentrations (50 to 80 mM). Regarding time-dependent structural variations described by Hanzlíková et al [31] and providing that the structure has already been stabilized approximately, in this range of 20 kGy dose the amount of disulphide S-S bonds should be changed only a little. At the same time, the amount of S-sulphonate −normalS−SO3−−, cystine monoxide –SO-S- and carboxylate –COO − run through a minimum and the presence of cystine dioxide -SO 2 -S- is negligible in practice.…”

Role of Post-Exposure Time in Co(II) Sorption of Higher Concentrations on Electron Irradiated Sheep Wool

“…Electron beam irradiation of sheep wool splits disulphide bonds of keratin with following oxidation of radicals generated and consecutive transformation of the transitive species for up to cysteic acid [18,19]. In this way, in the exposed wool, additional acidic groups are added capable of forming Co-salts and subsequently complexes with available ligands.…”

“…In this way, in the exposed wool, additional acidic groups are added capable of forming Co-salts and subsequently complexes with available ligands. As found, primary but also secondary structure of the radiation-modified wool varies with time [19]. It is a gradual complex transformation of conformations in the secondary structure initiated by the absorbed dose of energy and linked with chemical changes.…”

Radiation-modified wool for adsorption of redox metals and potentially for nanoparticles

“…In addition, neither plasma nor corona treatment is feasible on an industrial scale, unlike electron irradiation. The dependence of physical-chemical properties of the electron-modified wool on absorbed dose as well as sorption of some metal cations are examined [26][27][28][29]. The actual results show enhancement of the metals sorption.…”

“…, and these all are transformed into cysteic acid R-SO 3 H step by step [26,27]. The main reaction pathway of radiation-damaged disulphide bonds involves one electron addition that yields the radical anion (SS˙−) according to the reaction:…”