Oxidative damage to β-crystallin in vitro by iron compounds formed in physiological buffers.

β-crystallin aggregation due to oxidative damage in the presence of HO and ferric chloride was studied in-vitro under conditions close to physiological. It was shown that the protein aggregation characterized by the nucleation time and the aggregation rate significantly depended on the composition of the isoosmotic buffers used, and decreased in the series HEPES buffer > Tris buffer > PBS. Ferric chloride at neutral pH was converted into water-insoluble iron hydroxide III (≡FeOH). According to the data of scanning electron microscopy the ≡FeOH particles formed in HEPES buffer, Tris buffer, and PBS practically did not differ in structure. However, the sizes of ≡FeOH floating particles measured by dynamic light scattering differed significantly and were 44 ± 28 nm, 93 ± 66 nm, 433 ± 316 nm (Z ± SD) for HEPES buffer, Tris buffer, and PBS, respectively. It was found by the spin trap method that the ability of ≡FeOH to decompose HO with the formation of a OH decreases in the series HEPES buffer, Tris buffer, and PBS. The authors suggest that the ability to generate OH during the decomposition of HO is determined by the total surface area of ≡FeOH particles, which significantly depends on the composition of the buffer in which these particles are formed.