Amphiphilic effects of dibucaine·HCl on rotational mobility of n-(9-anthroyloxy)stearic acid in neuronal and model membranes

β-Lactoglobulin as a potential carrier for bioactive molecules

In this study, the interaction and binding behavior of anesthetic tetracaine (TET) with bovine β-lactoglobulin (LGB) isoform A and a mixture of isoforms A and B were investigated under varying environmental conditions (pH, ionic strength, concentration, LGB-TET complex molar ratio). A wide range of analytical techniques (dynamic light scattering (DLS), electrophoretic mobility, UV-Vis spectroscopy, circular dichroism (CD), quartz crystal microbalance (QCM-D) were used to analyze the physicochemical properties of the complexes in bulk solution and on the surface of gold. The experiments revealed that TET, which is amphiphilic, could bind with LGB not only in the β-barrel but also onto the surface. The zeta potential of the LGB becomes more positively charged upon interaction with TET due to electrostatic interaction of the amino group present in the TET structure. Changes in the zeta potential values are mostly visible above pH 6 for all tested systems. CD spectra show that interaction with the ligand does not change the secondary structure of the protein. The physicochemical properties of LGB-TET complex were examined in an adsorbed state on a gold surface using the QCM-D method. Additionally, molecular docking was used to evaluate the most likely binding site for TET with LGB.

Decreasing Effect of Lidocaine·HCl on the Thickness of the Neuronal and Model Membrane

This study examined the mechanism of action of a local anesthetic, lidocaine·HCl. Energy transfer between the surface fluorescent probe, 1-anilinonaphthalene-8-sulfonic acid, and the hydrophobic fluorescent probe, 1,3-di(1-pyrenyl) propane, was used to determine the effect of lidocaine·HCl on the thickness (D) of the synaptosomal plasma membrane vesicles (SPMV) isolated from the bovine cerebral cortex, and liposomes of the total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. The thickness (D) of the intact SPMV, SPMVTL and SPMVPL were 1.044±0.008, 0.914±0.005 and 0.890±0.003 (arbitrary units, n=5) at 37℃ (pH 7.4), respectively. Lidocaine·HCl decreased the thickness of the neuronal and model membrane lipid bilayers in a dose-dependent manner with a significant decrease in the thickness, even at 0.1 mM. The decreasing effect of lidocaine·HCl on the membrane thickness might be responsible for some, but not all of its anesthetic action.

The Effect of Lidocaine · HCl on the Fluidity of Native and Model Membrane Lipid Bilayers

The purpose of this study is to investigated the mechanism of pharmacological action of local anesthetic and provide the basic information about the development of new effective local anesthetics. Fluorescent probe techniques were used to evaluate the effect of lidocaine·HCl on the physical properties (transbilayer asymmetric lateral and rotational mobility, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMV) isolated from bovine cerebral cortex, and liposomes of total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. An experimental procedure was used based on selective quenching of 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer from the tryptophans of membrane proteins to Py-3-Py. Lidocaine·HCl increased the bulk lateral and rotational mobility of neuronal and model membrane lipid bilayes, and had a greater fluidizing effect on the inner monolayer than the outer monolayer. Lidocaine·HCl increased annular lipid fluidity in SPMV lipid bilayers. It also caused membrane proteins to cluster. The most important finding of this study is that there is far greater increase in annular lipid fluidity than that in lateral and rotational mobilities by lidocaine·HCl. Lidocaine·HCl alters the stereo or dynamics of the proteins in the lipid bilayers by combining with lipids, especially with the annular lipids. In conclusion, the present data suggest that lidocaine, in addition to its direct interaction with proteins, concurrently interacts with membrane lipids, fluidizing the membrane, and thus inducing conformational changes of proteins known to be intimately associated with membrane lipid.

The effect of methanol on the structural parameters of neuronal membrane lipid bilayers

The structures of the intact synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortexs, and the outer and the inner monolayer separately, were evaluated with 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,3-di(1-pyrenyl)propane (Py-3-Py) as fluorescent reporters and trinitrophenyl groups as quenching agents. The methanol increased bulk rotational and lateral mobilities of SPMVs lipid bilayers. The methanol increased the rotational and lateral mobilities of the outer monolayers more than of the inner monolayers. n-(9-Anthroyloxy)stearic acid (n-AS) were used to evaluate the effect of the methanol on the rotational mobility at the 16, 12, 9, 6, and 2 position of aliphatic chains present in phospholipids of the SPMVs outer monolayers. The methanol decreased the anisotropy of the 16-(9-anthroyloxy)palmitic acid (16-AP), 12-(9-anthroyloxy)stearic acid (12-AS), 9-(9-anthroyloxy)stearic acid (9-AS), and 6-(9-anthroyloxy)stearic acid (6-AS) in the SPMVs outer monolayer but it increased the anisotropy of 2-(9-anthroyloxy)stearic acid (2-AS) in the monolayers. The magnitude of the increased rotational mobility by the methanol was in the order at the position of 16, 12, 9, and 6 of aliphatic chains in phospholipids of the outer monolayers. Furthermore, the methanol increased annular lipid fluidity and also caused membrane proteins to cluster. The important finding is that was far greater increase by methanol in annular lipid fluidity than increase in lateral and rotational mobilities by the methanol. Methanol alters the stereo or dynamics of the proteins in the lipid bilayers by combining with lipids, especially with the annular lipids. In conclusion, the present data suggest that methanol, in additions to its direct interaction with proteins, concurrently interacts with membrane lipids, fluidizing the membrane, and thus inducing conformational changes of proteins known to be intimately associated with membranes lipids.

The effect of bupivacaine.HCl on the physical properties of neuronal membranes

Fluorescent probe techniques were used to evaluate the effect of bupivacaine.HCl on the physical properties (transbilayer asymmetric lateral and rotational mobilities, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortex. An experimental procedure was used based on selective quenching of both 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer (RET) from the tryptophans of membrane proteins to Py-3-Py. Bupivacaine.HCl increased the bulk lateral and rotational mobilities, and annular lipid fluidity in SPMVs lipid bilayers, and had a greater fluidizing effect on the inner monolayer than that of the outer monolayer. The magnitude of increasing effect on annular lipid fluidity in SPMVs lipid bilayer induced by bupivacaine.HCl was significantly far greater than magnitude of increasing effect of the drug on the lateral and rotational mobilities of bulk SPMVs lipid bilayer. It also caused membrane proteins to cluster. These effects of bupivacaine.HCl on neuronal membranes may be responsible for some, though not all, of the local anesthetic actions of bupivacaine.HCl.