Specific iron binding to natural sphingomyelin membrane induced by non-specific co-solutes

Journal Article · 29 September 2024 · Journal of Colloid and Interface Science

DOI: https://doi.org/10.1016/j.jcis.2024.09.194 · OSTI ID:2475172

Wang, Wenjie  ^[1]; Zhang, Honghu  ^[2]; Nayak, Binay P.  ^[2]; Vaknin, David  ^[2]

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1. Ames Laboratory (AMES), Ames, IA (United States)
2. Ames Laboratory, and Iowa State University, Ames, IA (United States)

Sphingomyelin (SPM), a crucial phospholipid in the myelin sheath, plays a vital role in insulating nerve fibers. We hypothesize that iron ions selectively bind to the phosphatidylcholine (PC) template within the SPM membrane under near-physiological conditions, resulting in disruptions to membrane organization. These interactions could potentially contribute to the degradation of the myelin sheath, thereby playing a role in the development of neurodegenerative diseases. We utilized synchrotron-based X-ray spectroscopy and diffraction techniques to study the interaction of iron ions with a bovine spinal-cord SPM monolayer (ML) at the liquid-vapor interface under physiological conditions. The SPM ML serves as a model system, representing localized patches of lipids within a more complex membrane structure. The experiments assessed iron binding to the SPM membrane both in the presence of salts and with additional evaluation of the effects of various ion species on membrane behavior. Grazing incidence X-ray diffraction was employed to analyze the impact of iron binding on the structural integrity of the SPM membrane. Furthermore, our results demonstrate that iron ions in dilute solution selectively bind to the PC template of the SPM membrane exclusively at near-physiological salt concentrations (e.g., NaCl, KCl, KI, or CaCl₂) and are pH-dependent. In-significant binding was detected in the absence of these salts or at near-neutral pH with salts. The surface adsorption of iron ions is correlated with salt concentration, reaching saturation at physiological levels. In contrast, multivalent ions such as La³⁺ and Ca²⁺ do not bind to SPM under similar conditions. Notably, iron binding to the SPM membrane disrupts its in-plane organization, suggesting that these interactions may compromise membrane integrity and contribute to myelin sheath damage associated with neurological disorders.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: AC02-06CH11357; AC02-07CH11358
• OSTI ID: 2475172
• Report Number(s): IS-J--11,454
• Journal Information: Journal of Colloid and Interface Science, Journal Name: Journal of Colloid and Interface Science Vol. 679; ISSN 0021-9797
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English