Cadmium(ii) N-acetylcysteine complex formation in aqueous solution

Abstract

The complex formation between Cd(II) ions and N-acetylcysteine (H(2)NAC) in aqueous solution was investigated using Cd K- and L(3)-edge X-ray absorption and (113)Cd NMR spectroscopic techniques. Two series of 0.1 M Cd(II) solutions with the total N-acetylcysteine concentration c(H2NAC) varied between 0.2-2 M were studied at pH 7.5 and 11.0, respectively. At pH = 11 a novel mononuclear [Cd(NAC)(4)](6-) complex with the average Cd-S distance 2.53(2) Å and the chemical shift δ((113)Cd) = 677 ppm was found to dominate at a concentration of the free deprotonated ligand [NAC(2-)] > 0.1 M, consistent with our previous reports on cadmium tetrathiolate complex formation with cysteine and glutathione. At pH 7.5 much higher ligand excess ([HNAC(-)] > 0.6 M) is required to make this tetrathiolate complex the major species. The (113)Cd NMR spectrum of a solution containing c(Cd(II)) = 0.5 M and c(H2NAC) = 1.0 M measured at 288 K showed three broad signals at 421, 583 and 642 ppm, which can be attributed to CdS(3)O(3), CdS(3)O and CdS(4) coordination sites, respectively, in oligomeric Cd(II)-NAC species with single thiolate bridges between the cadmium ions.

Structural changes during HCN channel gating defined by high affinity metal bridges

“…The ability of Cd 2+ to produce high affinity effects on double cysteine mutant channels indicates that the sulfhydryl groups of the introduced cysteines can approach each other closely, within ∼5 Å (Naylor et al, 1998; Jalilehvand et al, 2009a,b, 2011; Mah and Jalilehvand, 2010). This does not necessarily indicate that the “normal” apposition of these sulfhydryl groups is so close, as their proximity may occur in a rare conformation that is visited only occasionally in the normal conformational ensemble.…”

The chemistry and biological activities of N-acetylcysteine

“…NAC is capable of binding transition metal ions, such as Cu(II) and Fe(III) [76], and heavy metal ions such as Cd(II) [77], Hg(II) [78] and Pb(II) [79] (Table 1), which make the importance of these reactions under physiological conditions doubtful. In contrast, NAC readily reacts with highly oxidizing radicals such as OH, NO 2 and CO 3 and can…”

Synthesis, Characterization of Some Ferrocenoyl Cysteine and Histidine Conjugates, and Their Interactions with Some Metal Ions

“…Cd II has serious effects on human health, causing damage to kidneys and lungs, and triggers bone diseases and potentially leads to cancer. [23][24][25][26] The structural similarity of Cd 2+ to Zn 2+ has prompted thorough comparisons of the coordination properties of the two ions and studies of the metal selectivity for Zn 2+ , for example, in mammalian metal transporters, such as zinc influx transporters. [21,22] This has led to further research focusing on the development of chelating agents to prevent the uptake of Cd II by cells.…”