Radicals initiated by gamma rays in selected amino acids and collagen

Abstract

Calf skin collagen and three amino acids essential for its structure, namely glycine, L-proline and 4-hydroxyl-L-proline, were irradiated with gamma rays up to a dose of 10 kGy. Conversion of radicals over time or after thermal annealing to selected temperatures was monitored by X-band electron paramagnetic resonance (EPR) spectroscopy. Some experimental spectra were compared with signals simulated based on literature data from the electron nuclear double resonance (ENDOR) studies. The following phenomena were confirmed in the tested amino acids: abstraction of hydrogen atom (glycine, proline, hydroxyproline, collagen), deamination (glycine, hydroxyproline), decarboxylation (hydroxyproline). Chain scission at glycine residues, radiation-induced decomposition of side groups and oxidative degradation were observed in irradiated collagen. The decay of radicals in collagen saturated with water occurred at lower temperatures than in macromolecules having only structural water. The paramagnetic centres were the most stable in an oxygen-free atmosphere (vacuum). Radical processes deteriorated the structure of collagen; hence, radiation sterilization of skin grafts requires careful pros and cons analysis.

Effect of Gamma Radiation on Novel Gelatin Extracted from Camel Skin for Pharmaceutical Application

“…In fact, spectrum EPR demonstrated the augmentation of the free radical concentration after irradiation with Co gamma rays and the spectrum changed notably as a function of doses. Macromolecules generate a three-dimensional hydrogen network actively contributing in the transfer of protons to make possible the conversion/ recombination of radicals (Przybytniak et al, 2019). These results provide important data for studying the feasibility of gelatin for biological and medical applications in the future.…”

Pigmentation Chemistry and Radical‐Based Collagen Degradation in Alkaptonuria and Osteoarthritic Cartilage

“…Molecular dynamics indicate that the formation of a glycyl radical is accompanied by large changes in the backbone dihedral angles, [34] since hydrogen abstraction occurs at C a of glycines, [35] and have been observed in EPR of powdered collagen (freeze-dried and rehydrated) subjected to gamma rays. [36] While glycyl radicals are known to be key to many enzymatic processes, they are not usually oxygen-stable. [37][38][39] However, in this case, Figure S7.…”

Pigmentierungschemie und radikalbasierter Kollagenabbau bei Alkaptonurie und Arthrose

“…Wir schlagen vor, dass die vorübergehende Bildung von Glycylradikalen der in der aktuellen Studie beobachteten Störung der Wasserstoffbindung im pigmentierten Knorpel zugrunde liegt. Die Molekulardynamik zeigt, dass die Bildung eines Glycylradikals mit großen Änderungen der Rückgrat‐Diederwinkel einhergeht, da die Wasserstoffabstraktion an den C α von Glycinen auftritt und in der EPR an pulverisiertem Kollagen beobachtet wurde (gefriergetrocknet und rehydratisiert), das Gammastrahlen ausgesetzt wurde . Obwohl Glycylradikale als Schlüssel für viele enzymatische Prozesse bekannt sind, sind sie normalerweise nicht sauerstoffstabil .…”