Acetylcholine Cations Research Articles

INS, DFT and temperature dependent IR studies on dynamical properties of acetylcholine chloride

The acetylcholine chloride (2-acetoxy-N,N,N-trimethylethanaminium chloride) was investigation by inelastic neutron scattering and temperature dependent infrared spectroscopy. The infrared spectra in the temperature range 9–300K were collected. The density functional theory calculation with the periodic boundary conditions was used for an experimental data analysis. Bands assigned to the CH3 torsion vibration in the acetylcholine cation were observed at 207, 296, 345 and 359cm−1 in INS spectrum. Activation energy for reorientational motion of the whole N(CH3)3 fragment was determined by means of band shape analysis performed for symmetric stretching vibration of this group. The estimated energy is equal to Ea=5.3(3)kJ/mol.

New water-soluble polyanionic dendrimers and binding to acetylcholine in water by means of contact ion-pairing interactions

A new water-soluble polyanionic dendrimer containing 81 benzoate termini (diameter: 11+/-1 nm from DOSY NMR spectroscopy) has been synthesized; it interacts with acetylcholine cations in water-soluble assemblies in which each carboxylate terminus reversibly forms contact ion pairs and aggregates at the tether termini, as shown by 1H NMR spectroscopy.

Ab initio and DFT computer studies of complexes of quaternary nitrogen cations: trimethylammonium, tetramethylammonium, trimethylethylammonium, choline and acetylcholine with hydroxide, fluoride and chloride anions

Density functional theory (DFT by B3LYP) and ab initio (MP2) calculations are reported for complexes of the trimethylammonium, tetramethylammonium, trimethylethylammonium, choline and acetylcholine cations with hydroxide, fluoride and chloride anions. Stable structures are predicted in which the anion is bonded to three hydrogen atoms directed away from the cationic head and on each of three methyl groups of these quaternary nitrogen compounds. These are described as reverse complexes and are compared with normal complexes between F− and Cl− and the N–H group in the first of these cations or alternatively between HF and HCl with (CH3)3N. Stable structures are optimised at the B3LYP/6-31+G(d,p) level in all cases and also at the MP2/6-31+G(d,p) level for all complexes studied other than those of choline and acetylcholine. The differences between the DFT and MP2 methods largely follow systematic patterns and are small. Calculated values of structures with reference to Y⋯H distances, binding energies and assignment of harmonic C–H–Y (Y=OH, F and Cl) and other cationic head C–H stretching modes are discussed. The effect of solvents of low (n-hexane) and high (water) relative permittivity on energies are reported and discussed in relation to pharmacological considerations. Some properties of the trans,trans; trans,gauche and gauche,trans conformations of the acetylcholine cation and fluoride are reported. Complexes between quaternary nitrogen cations and the hydroxide, fluoride and chloride anions are described as consequences of hydrogen bonds strengthened by interactions between ions of opposite polarity.

Polyether‐bridged cyclophanes incorporating bisphenol A units as neutral receptors for quats: synthesis, molecular structure and binding properties

AbstractTwo novel neutral polyoxyethylene bridged cyclophanes (2a and 2b) incorporating bisphenol A units were synthesized and characterized by means of x‐ray crystal structure determination. The binding properties of 2a and 2b toward tetramethylammonium, N‐methylpyridinium, and acetylcholine cations were evaluated by means of 1H NMR spectroscopy. Consistent with indications provided by the molecular structure, the cavity in the basket‐like cyclophanes is large enough to accommodate the given guest cations conveniently. Circumstantial evidence was obtained that 1,1,2,2‐tetrachloroethane is too large to enter the cavity of the smaller cyclophane 2a, but can be included in the cavity of the larger cyclophane 2b. Copyright © 2001 John Wiley & Sons, Ltd.

Single-Crystal Neutron Diffraction Analysis of Anion–Cation Interactions in Perdeuteroacetylcholine Bromide at 100 K

The interaction of the neurotransmitter acetylcholine with receptor binding sites has been well studied over the years, but much is still unknown about how intermolecular forces govern the lock-and-key fit. Here we present an analysis of cation–anion hydrogen-bond interactions in a single-crystal of perdeuteroacetylcholine bromide, using pulsed neutron diffraction data to refine the X-ray crystal structure. The molecule crystallizes in space group P21/n, with a = 10.951 (4), b = 13.396 (8), c = 7.072(4) Å, β = 108.88(3)°, Z = 4. The final refinement included anisotropic temperature factors on all atoms and converged to wR(F) = 0.055 (244 parameters). The pyramidal configuration of C--D...Br− contacts observed in the crystal is in good agreement with ab initio molecular orbital predictions of favoured configuration and is consistent with a modest polarization of C--D bonds close to the N atom. There is evidence that close contact with Br− is hindered by the repulsive influence of the ester O atoms, dependent on the conformation of the acetylcholine cation. This is the most detailed picture to date of close interatomic contacts around the cation and analogies are drawn with the bonding of acetylcholine to its receptors.

The spasiba force field of model compounds related to lipids of biomembranes

The vibrational spectroscopic force field spasiba (Spectroscopic Potential Algorithm for SImulating Biomolecular conformational Adaptability), which has been shown to exhibit unique properties over the whole molecular potential energy surface rather than in the vicinity of minima (as current force fields do), has been developed for a series of model compounds related to the lipid component of biological membranes. The structures, relative energies and vibrational spectra of several phosphate anions, acetylcholine cations, phosphorylcholine and some of their deuterated analogs have been investigated in detail. In particular, the root mean square deviation of 11 cm −1 between the observed and the calculated vibrational frequency lends some confidence to the expectation that this force field will give meaningful results when used in molecular dynamics simulations.

Structural and electronic characteristics of the monoboro-analogs of the acetylcholine cation as determined by the semiempirical MNDO computational method

The semiempirical computational method MNDO (modified neglect of diatomic overlap) has been used to calculate the stable conformations and the electronic properties of each of the five possible monoboro-analogs of the acetylcholine cation, ACH + . The thermodynamically most stable analog was determined to be (CH 3 ) 3 NBH 2 CH 2 OC(O)CH 3 , the 5-boro-analog, 5, not the commercially-available isomer (7-boroacetylcholine, H 3 BN(CH 3 ) 2 CH 2 H 2 OC(O)CH 3 , 7)

Hydrogen bonding: Part 33. NMR study of the hydration of choline and acetylcholine halides

The hydration of choline and acetylcholine halides has been studied through observation of the development of 14N to β-CH 2 coupling as H 2O is added in increments to the lowest liquid hydrates of these salts. Choline cation forms an initial strong, anion-independent association with ca. 4.5 H 2O. Further addition of H 2O leads to a larger, looser hydration shell with choline chloride; this effect is not seen with the bromide or iodide. Hydrogen bonding between cation hydroxyl group and Cl − is observed up to about 5 H 2O for choline chloride; this type of interaction is weak or absent in solutions of the Br − and I − salts. Acetylcholine cation forms an initial strong, anion- independent association with ca. 7 H 2O; both Cl − and Br − show subsequent formation of a looser hydration shell up to ca. 10–13 H 2O. This is in accord with a previous phase diagram study that indicated formation of a low temperature crystalline hydrate of acetylcholine chloride with similar H 2O content. Both choline and acetylcholine cations retain the preferred gauche conformations from the lowest liquid hydrate to dilute solutions.

Cation competition in the electrical double-layer at a well-defined electrode surface Li +, Na +, K +, Cs +, H +, Mg 2+, Ca 2+, Ba 2+, La 3+, tetramethylammonium, choline and acetylcholine cations at Pt(111) surfaces containing an ordered layer of cyanide

Immersion of the Pt (111) surface into aqueous KCN solution produced an ordered ionic layer, Pt (111)(2√3×2√3) R30°−KCN. The adlattice consisted of isolated adsorbed CN − anions surrounded by adsorbed HCN molecules, and a layer of K + counter-ions. When immersed at open circuit into aqueous solutions of simple chloride salts this surface underwent cation exchange without loss or rearrangement of the CN −/HCN layer, based upon Auger spectroscopy and LEED. Experiments in which cations were made to adsorb competitively from mixtures of chloride salts revealed that a remarkable degree of selectivity exists in the interaction of cations with this CN − layer. Highly charged cations predominated, followed by cations of relatively small size and those least strongly hydrated. Strength of cation retention varied in the order: La 3+ ≫ Ba 2+ > Ca 2+ ≫ Mg 2+ ≫ K + > Na + = Cs + > NH 4 + > H + ≫ Li + ≫ NH 4 +. Quaternary ammonium cations (tetramethylammonium, choline, acetylcholine), even when present in large excess, were unable to compete with other cations for retention by the double-layer.

Charge transfer between two immiscible electrolyte solutions Part IX. Kinetics of the transfer of choline and acetylcholine cations across the water/nitrobenzene interface

Charge transfer between two immiscible electrolyte solutions Part IX. Kinetics of the transfer of choline and acetylcholine cations across the water/nitrobenzene interface

Charge transfer between two immiscible electrolyte solutions: Part IX. Kinetics of the transfer of choline and acetylcholine cations across the water/nitrobenzene interface

Kinetic and thermodynamic parameters of the transfer of choline and acetylcholine cations across the water/nitrobenzen interface were evaluated using convolution potential sweep voltammetry. In order to trace the factors which control the ion-transfer kinetics the semi-phenomenological theory was used, assuming that: (1) the temperature dependence of the rate constant has the form of the Arrhenius equation; (2) the reaction site is located in the outer Helmholtz plane (oHp); (3) there exists a Brønsted-type relationship between the true activation Gibbs energy and the reaction Gibbs energy for the ion transfer from the oHp in water to that in the organic solvent phase. The apparent rate constants were corrected for the double-layer effect using the capacity data and the Gouy-Chapman theory. It is concluded that the observed potential dependence of the apparent rate constants arises largely from the effect of the potential on the concentration of the transferred ions at the reaction planes. The correlation of the true (corrected) rate constant with the reaction Gibbs energy for a series of the ions with similar structure indicates that the true charge-transfer coefficient α 1≅0.3, which would correspond to the asymmetric potential energy barrier for the ion-transfer step.

Electrolysis at the Interface between Two Immiscible Electrolyte Solutions: Determination of Acetylcholine by Differential Pulse Stripping Voltammetry

Abstract A three-electrode system with the hanging electrolyte drop electrode (HEDE) was developed for the analytical exploitation of electrolysis at the interface between two immiscible electrolyte solutions (ITIES). The use of the differential pulse stripping voltammetry (DPSV) for the quantitative determination of the species which participates in a charge transfer reaction at ITIES was demonstrated with acetylcholine cation transfer across the water/nitrobenzene interface. Trace concentration of acetylcholine in water in the part per million level (ppm) can be determined. It was concluded that the electrolysis at ITIES represents the perspective method of chemical analysis.