Ion transfer voltammetry of tryptamine, serotonin, and tryptophan at the nitrobenzene/water interface

Tatsumi, Hirosuke; Ueda, Tatsuya

doi:10.1016/j.jelechem.2011.02.011

Cited by 17 publications

(14 citation statements)

References 23 publications

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“…It is worth noting that the observed difference in the transfer potentials between T and 5-HT corresponds well with that reported in the literature at a much larger nitrobenzene/water interface. 44 Because 5-HT requires a much larger overpotential for its transfer, ASW background interference proves to be an issue for the detection of low concentrations of 5-HT. A 2 mM addition of 5-HT has only a small response relative to ASW, because the two transfer at similar potentials (Figure S4, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Nanopipet-Based Liquid–Liquid Interface Probes for the Electrochemical Detection of Acetylcholine, Tryptamine, and Serotonin via Ionic Transfer

2015

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A nanoscale interface between two immiscible electrolyte solutions (ITIES) provides a unique analytical platform for the detection of ionic species of biological interest such as neurotransmitters and neuromodulators, especially those that are otherwise difficult to detect directly on a carbon electrode without electrode modification. We report the detection of acetylcholine, serotonin, and tryptamine on nanopipet electrode probes with sizes ranging from a radius of ≈7 to 35 nm. The transfer of these analytes across a 1,2-dichloroethane/water interface was studied by cyclic voltammetry and amperometry. Well-defined sigmoidal voltammograms were observed on the nanopipet electrodes within the potential window of artificial seawater for acetylcholine and tryptamine. The half wave transfer potential, E1/2, of acetylcholine, tryptamine, and serotonin were found to be −0.11, −0.25, and −0.47 V vs E1/2,TEA (term is defined later in experimental), respectively. The detection was linear in the range of 0.25–6 mM for acetylcholine and of 0.5–10 mM for tryptamine in artificial seawater. Transfer of serotonin was linear in the range of 0.15–8 mM in LiCl solution. The limit of detection for serotonin in LiCl on a radius ≈21 nm nanopipet electrode was 77 μM, for acetylcholine on a radius ≈7 nm nanopipet electrode was 205 μM, and for tryptamine on a radius ≈19 nm nanopipet electrode was 86 μM. Nanopipet-supported ITIES probes have great potential to be used in nanometer spatial resolution measurements for the detection of neurotransmitters.

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Section: Resultsmentioning

confidence: 99%

Nanopipet-Based Liquid–Liquid Interface Probes for the Electrochemical Detection of Acetylcholine, Tryptamine, and Serotonin via Ionic Transfer

2015

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“…59,60 This is in strong contrast to 5-HT, which has a bulk partitioning coefficient about 3 orders of magnitude lower 49,61,62 than the values found here for fluid PC bilayers. Most recently, Tatsumi and Ueda 63 used precise electrochemical methods to show that the partitioning coefficient between water and nitrobenzene for the cationic form of 5-HT (which dominates at neutral pH) was as low as 0.007. We conclude that 5-HT interacts strongly with PC membranes, and in light of its hydrophilic nature (manifested in low bulk partitioning), the affinity must involve strong contact interactions with the lipid (cf.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Binding of Serotonin to Lipid Membranes

et al. 2013

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Serotonin (5-hydroxytryptamine, 5-HT) is a prevalent neurotransmitter throughout the animal kingdom. It exerts its effect through the specific binding to the serotonin receptor, but recent research has suggested that neural transmission may also be affected by its nonspecific interactions with the lipid matrix of the synaptic membrane. However, membrane-5-HT interactions remain controversial and superficially investigated. Fundamental knowledge of this interaction appears vital in discussions of putative roles of 5-HT, and we have addressed this by thermodynamic measurements and molecular dynamics (MD) simulations. 5-HT was found to interact strongly with lipid bilayers (partitioning coefficient ~1200 in mole fraction units), and this is highly unusual for a hydrophilic solute like 5-HT which has a bulk, oil-water partitioning coefficient well below unity. It follows that membrane affinity must rely on specific interactions, and the MD simulations identified the salt-bridge between the primary amine of 5-HT and the lipid phosphate group as the most important interaction. This interaction anchored cationic 5-HT in the membrane interface with the aromatic ring system pointing inward and a prevailing residence between the phosphate and the carbonyl groups of the lipid. The unprotonated form of 5-HT shows the opposite orientation, with the primary amine pointing toward the membrane core. Partitioning of 5-HT was found to decrease lipid chain order. These distinctive interactions of 5-HT and model membranes could be related to nonspecific effects of this neurotransmitter.

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“…Finally, 5-HT could cross the plasma membrane by passive diffusion, a mechanism generally assumed as improbable in underlying 5-HT release ( Hensler, 2012 ), given that at physiological pH, 5-HT is predominately in its protonated form (5-HTH + ), and charged molecules do not easily partition the membrane. However, it has recently been shown ( Peters et al, 2013 ) that, unusually for a hydrophilic solute, 5-HT partitions strongly in lipid bilayers, having a distribution coefficient (D x or P app,x of ≈1,200 for dimyristoylphosphatidylcholine bilayers; in mole fraction units) comparable to that of highly hydrophobic compounds, ∼100 times higher than the partitioning coefficient of neutral 5-HT form for bulk lipid–water mixtures (P x 0f ≈10.8 for octanol–water mixtures), and >10 5 times higher than that of protonated 5-HT (P “true”,x of ≈0.04 for water–nitrobenzene interface; Tatsumi and Ueda, 2011 ). Consistently, the hypothesis that simple diffusion could underlie 5-HT release in the DRN is further supported by the observation that diffusion of 5-HT from phosphatidylcholine vesicles occurs with the mean lifetime (or time constant, τ) of ∼70 s and the permeability coefficient of ∼4.8 × 10 −8 cm s −1 ( Berry et al, 2013 ).…”

Section: Discussionmentioning

confidence: 95%

Nonexocytotic serotonin release tonically suppresses serotonergic neuron activity

Mlinar

Montalbano

Baccini

et al. 2015

Journal of General Physiology

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Ion transfer voltammetry of tryptamine, serotonin, and tryptophan at the nitrobenzene/water interface

Cited by 17 publications

References 23 publications

Nanopipet-Based Liquid–Liquid Interface Probes for the Electrochemical Detection of Acetylcholine, Tryptamine, and Serotonin via Ionic Transfer

Nanopipet-Based Liquid–Liquid Interface Probes for the Electrochemical Detection of Acetylcholine, Tryptamine, and Serotonin via Ionic Transfer

Binding of Serotonin to Lipid Membranes

Nonexocytotic serotonin release tonically suppresses serotonergic neuron activity

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