Conjugated oxidation of thiols and amines in the presence of copper complexes

While suggestions concerning the possible role of metals in olfaction and taste date back 50 years, only recently has it been possible to confirm these proposals with experiments involving individual olfactory receptors (ORs). A detailed discussion of recent experimental results demonstrating the key role of metals in enhancing the response of human and other vertebrate ORs to specific odorants is presented against the backdrop of our knowledge of how the sense of smell functions both at the molecular and whole animal levels. This review emphasizes the role of metals in the detection of low molecular weight thiols, sulfides, and other organosulfur compounds, including those found in strong-smelling animal excretions and plant volatiles, and those used in gas odorization. Alternative theories of olfaction are described, with evidence favoring the modified “shape” theory. The use of quantum mechanical/molecular modeling (QM/MM), site-directed mutagenesis and saturation-transfer-difference (STD) NMR is discussed, providing support for biological studies of mouse and human receptors, MOR244-3 and OR OR2T11, respectively. Copper is bound at the active site of MOR244-3 by cysteine and histidine, while cysteine, histidine and methionine are involved with OR2T11. The binding pockets of these two receptors are found in different locations in the three-dimensional seven transmembrane models. Another recently deorphaned human olfactory receptor, OR2M3, highly selective for a thiol from onions, and a broadly-tuned thiol receptor, OR1A1, are also discussed. Other topics covered include the effects of nanoparticles and heavy metal toxicants on vertebrate and fish ORs, intranasal zinc products and the loss of smell (anosmia).

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“…So, Cu(I)/Cu(II) oxidation state transitions between the two oxidation states should be facilitated by the coordination environment. 63a …”

Section: Demonstration Of the Activation Of Olfactory Receptors By mentioning

confidence: 99%

The role of metals in mammalian olfaction of low molecular weight organosulfur compounds

et al. 2017

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“…Thus, it is ascertained that, as in the systems of copper complexes with aliphatic amines that we studied previously, [32,33] in the case of complexes with heterocycles and amides, too, a mixed-ligand copper complex is formed as an intermediate. It is also noteworthy that by analogy with systems containing aliphatic amines, heterocyclic ligands also participate in redox processes that occur in the metal ion coordination sphere.…”

Section: Pyridine Complexesmentioning

confidence: 82%

“…For the catalytic reaction to proceed, it is necessary to use compositions containing copper complexes and excess ligand. In our previous works, [32,33] we have established the mechanism of the process, the schematic view of the mechanism in a simplified way is presented in Scheme 1.…”

Section: Ligands That Undergo Irreversible Oxidation or Reductionmentioning

confidence: 99%

“…Copper complexes were obtained by the reaction of an ethanolic solution of copper(II) chloride with ligands as described in [32,33]. All complexes with nitrogen compounds were insoluble in ethanol.…”

Section: The Synthesis Of Complexesmentioning

confidence: 99%

“…The amount of thiol was measured by potentiometric titration with diammine silver nitrate in the presence of an ion selective argentite electrode as described in [32].…”

Section: Catalytic Experimentsmentioning

confidence: 99%

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Non-innocent ligands in copper complexes catalyzed oxidation of thiols

Gantman

Tarkhanova

Kolyagin

2016

Journal of Sulfur Chemistry

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Copper(II) chloride complexes with nitrogen-containing ligands (amines, amides, heterocycles) were studied as catalysts of selective oxidation of thiols to disulfides. This process has an important biochemical analogue -the formation of disulfide bridge in proteins [Wang C, Wesener SR, Zhang H, Cheng Y-Q. An FAD-dependent pyridine nucleotide-disulfide oxidoreductase is involved in disulfide bond formation in FK228 anticancer depsipeptide. Chem and Biol. 2009;16:585-593]; which affects their activity [Zhang L, Chou CP, Moo-Young M. Disulfide bond formation and its impact on the biological activity and stability of recombinant therapeutic proteins produced by Escherichia coli expression system. Biotech Adv. 2011;29:923-929]. Also, thiol oxidation is an important process of oil sweetening. The search for effective and stable catalysts for this reaction is still topical [Ganguly SK, Das G, Kumar S, Sain B, Garg MO. Mechanistic kinetics of catalytic oxidation of 1-butanethiol in light oil sweetening. Catal Tod. 2012;198:246-251]. This article describes a mechanistic study of thiol oxidation and non-innocent ligands transformations during this reaction. The studied ligands are capable of oxidizing thiols, the reaction being followed by reoxidation of the reduced forms of the ligands with air oxygen. The oxidative activity of the ligand correlates with catalyst activity for thiol oxidation. ARTICLE HISTORY

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Single‐Electron Transfer between CuX₂ and Thiols Determined by Extended X‐Ray Absorption Fine Structure Analysis: Application in Markovnikov‐Type Hydrothiolation of Styrenes

Hong

Song

et al. 2016

Chemistry A European J

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Transition-metal mediated C-S bond formation using thiol compounds has been widely used in recent years. However, there has been less focus on the interaction between the metal and thiol compounds. In this work, we have successfully evidenced the single-electron transfer between CuX and thiophenol utilizing EXAFS. The fitting EXAFS results reveal that two halide anions are coordinated with the Cu center, whereas no sulfur atom is observed in the first coordination sphere. This Cu ate complex serves as the key intermediate for the proton transfer in the application of Markovnikov-type hydrothiolation reactions.

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Conjugated oxidation of thiols and amines in the presence of copper complexes

Cited by 10 publications

References 10 publications

The role of metals in mammalian olfaction of low molecular weight organosulfur compounds

The role of metals in mammalian olfaction of low molecular weight organosulfur compounds

Non-innocent ligands in copper complexes catalyzed oxidation of thiols

Single‐Electron Transfer between CuX₂ and Thiols Determined by Extended X‐Ray Absorption Fine Structure Analysis: Application in Markovnikov‐Type Hydrothiolation of Styrenes

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Conjugated oxidation of thiols and amines in the presence of copper complexes

Cited by 10 publications

References 10 publications

The role of metals in mammalian olfaction of low molecular weight organosulfur compounds

The role of metals in mammalian olfaction of low molecular weight organosulfur compounds

Non-innocent ligands in copper complexes catalyzed oxidation of thiols

Single‐Electron Transfer between CuX2 and Thiols Determined by Extended X‐Ray Absorption Fine Structure Analysis: Application in Markovnikov‐Type Hydrothiolation of Styrenes

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Single‐Electron Transfer between CuX₂ and Thiols Determined by Extended X‐Ray Absorption Fine Structure Analysis: Application in Markovnikov‐Type Hydrothiolation of Styrenes