Heavy metal ions such as cadmium (Cd²⁺), lead (Pb²⁺), and mercury (Hg²⁺) are ubiquitous environmental pollutants that pose serious risks to biological systems. Proteins, being essential biomolecules, are primary targets of heavy metal-induced damage: metal salts can bind to proteins, induce misfolding or aggregation, and impair their function. In this study, we investigate the structural and functional consequences of exposing model proteins (bovine serum albumin, lysozyme, and a representative enzyme) to heavy metal salts in vitro. We employed circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering (DLS), SDS-PAGE, and enzymatic assays to assess conformational changes, aggregation, and loss of activity. Our findings indicate that even low micromolar concentrations of Cd²⁺, Pb²⁺, and Hg²⁺ induce significant structural perturbations, reduce thermal stability, promote aggregation, and inhibit enzyme function. We also discuss these effects in light of regional environmental studies: in Uzbekistan, for example, heavy metal contamination in soil and water has been documented and may pose a risk to local biota and livestock (Komiljonov, Zarifov, Raximberganov, & Qurbanov, 2025). Moreover, our data resonate with broader environmental-toxicological reviews from Russian scholars emphasizing the role of heavy metals in ecosystem bioaccumulation and pollution (Teplaya, 2013). These results support a mechanistic model of heavy-metal proteotoxicity that complements classical oxidative-stress paradigms and underscore the importance of evaluating protein-level effects in environmental health risk assessments.

Heavy metals; Protein misfolding; Protein aggregation; Cadmium (Cd²⁺); Lead (Pb²⁺); Mercury (Hg²⁺); Protein stability; Protein–metal interactions; Environmental toxicology; Proteotoxic stress; Oxidative stress; Circular dichroism; Fluorescence spectroscopy; Enzyme inhibition.

Esbergenova, B. Z., et al. (2020). Purification of wastewater from ions of iron, manganese, copper and cadmium, using natural minerals (glauconite). Uzbek Chemical Journal, 5.

Heavy metal toxicity leads to accumulation of insoluble proteins and induces endoplasmic reticulum stress–specific unfolded protein response in Arabidopsis thaliana. (2024). Plant Journal / Molecular Biology.

Heavy Metals and Human Health: Possible Exposure Pathways and the Competition for Protein Binding Sites. (2021). Review Article.

Komiljonov, K. K., Zarifov, H. R., Raximberganov, B. S., & Qurbanov, A. I. (2025). Studying the effects of heavy metal salts on the blood proteins of agricultural animals using albumin protein imitation laboratory methods. Web of Medicine: Journal of Medicine, Practice and Nursing, 3(6), 196–203.

Narmuratova, Z., et al. (2022). Antioxidant properties related to divalent metal chelation.

Seydaliyeva, L. T. (2024). Calcium metabolism and features of its regulation under the influence of heavy metals.

Tamás, M. J., Sharma, S. K., Ibstedt, S., Jacobson, T., & Christen, P. (2014). Heavy metals and metalloids as a cause for protein misfolding and aggregation. Biomolecules, 4(1), 252–267. https://doi.org/10.3390/biom4010252

Teplaya, G. A. (2013). Тяжёлые металлы как фактор загрязнения окружающей среды: обзор литературы [Heavy metals as a factor of environmental pollution: literature review]. Астраханский вестник экологического образования, 1(23), 182–192.

Карачева, М. А. (2022). Тяжелые металлы как фактор загрязнения вод (обзор). Молодой учёный.