Interaction Of Chlorpromazine Research Articles

Electrochemical oxidation of Fe (II) using chlorpromazine drug at boron-doped diamond electrode: application to in vivo mechanism study interaction of chlorpromazine on hemoglobin iron and evaluation of some biomolecules

In this study, the electrochemical properties of aqueous chlorpromazine hydrochloride (CPZ) in the presence of Fe (II) were investigated by cyclic voltammetry at a boron-doped diamond (BDD) electrode. The results showed that an EC′ reaction mechanism occurs, where electrochemically generated CPZ species (cation radical) are reduced by Fe (II) back to the parent CPZ, and Fe (II) is oxidized to Fe (III). The detection limit, sensitivity, and dynamic concentration ranges were 2.8 μM, 0.0188 μA μM−1 and 10–166 μM. Based on the electrochemical results, the interaction of chlorpromazine (CPZ), a widely used antipsychotic tranquillizer, with the allosteric protein, hemoglobin, has been studied. First, four groups of six female rats weighing 400–450 g were selected. The rats were injected with different concentrations of chlorpromazine over a 3-week period, and the concentrations of hemoglobin, methemoglobin, red blood cells (RBCs), and hematocrit (HCT) were analyzed in the blood of each rat. After injection of different concentrations of the drug, the amount of hemoglobin) as a source of Fe (II)) decreased, but the amount of methemoglobin (as a source of Fe (III) increased. In addition, UV spectroscopic measurements in the range of 200–700 nm indicate the conversion of hemoglobin to methemoglobin in chlorpromazine-treated rats compared to the normal sample, and there was a direct relationship between the increasing methemoglobin concentration of chlorpromazine. Furthermore, the amount of RBC and HCT was measured. The results showed that RBC (21.05%–56.52%) and HCT (10.04%–53.19%) decreased. Finally, this study demonstrates a new mechanism for the effects of CPZ on hemoglobin iron in rat blood based on electrochemical results.

High-throughput electrochemical sensing platform for screening nanomaterial–biomembrane interactions

A high-throughput, automated screening platform has been developed for the assessment of biological membrane damage caused by nanomaterials. Membrane damage is detected using the technique of analyzing capacitance-current peak changes obtained through rapid cyclic voltammetry measurements of a phospholipid self-assembled monolayer formed on a mercury film deposited onto a microfabricated platinum electrode after the interaction of a biomembrane-active species. To significantly improve wider usability of the screening technique, a compact, high-throughput screening platform was designed, integrating the monolayer-supporting microfabricated electrode into a microfluidic flow cell, with bespoke pumps used for precise, automated control of fluid flow. Chlorpromazine, a tricyclic antidepressant, and a citrate-coated 50 nm diameter gold nanomaterial (AuNM) were screened to successfully demonstrate the platform's viability for high-throughput screening. Chlorpromazine and the AuNM showed interactions with a 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) monolayer at concentrations in excess of 1 µmol dm-3. Biological validity of the electrochemically measured interaction of chlorpromazine with DOPC monolayers was confirmed through quantitative comparisons with HepG2 and A549 cytotoxicity assays. The platform also demonstrated desirable performance for high-throughput screening, with membrane interactions detected in <6 min per assay. Automation contributed to this significantly by reducing the required operating skill level when using the technique and minimizing fluid consumption.

Kinetics and Thermodynamics of Chlorpromazine Interaction with Lipid Bilayers: Effect of Charge and Cholesterol

Passive transport across cell membranes is the major route for the permeation of xenobiotics through tight endothelia such as the blood–brain barrier. The rate of passive permeation through lipid bilayers for a given drug is therefore a critical step in the prediction of its pharmacodynamics. We describe a detailed study on the kinetics and thermodynamics for the interaction of chlorpromazine (CPZ), an antipsychotic drug used in the treatment of schizophrenia, with neutral and negatively charged lipid bilayers. Isothermal titration calorimetry was used to study the partition and translocation of CPZ in lipid membranes composed of pure POPC, POPC:POPS (9:1), and POPC:Chol:POPS (6:3:1). The membrane charge due to the presence of POPS as well as the additional charge resulting from the introduction of CPZ in the membrane were taken into account, allowing the calculation of the intrinsic partition coefficients (K(P)) and the enthalpy change (ΔH) associated with the process. The enthalpy change upon partition to all lipid bilayers studied is negative, but a significant entropy contribution was also observed for partition to the neutral membrane. Because of the positive charge of CPZ, the presence of negatively charged lipids in the bilayer increases both the observed amount of CPZ that partitions to the membrane (KP(obs)) and the magnitude of ΔH. However, when the electrostatic effects are discounted, the intrinsic partition coefficient was smaller, indicating that the hydrophobic contribution was less significant for the negatively charged membrane. The presence of cholesterol strongly decreases the affinity of CPZ for the bilayer in terms of both the amount of CPZ that associates with the membrane and the interaction enthalpy. A quantitative characterization of the rate of CPZ translocation through membranes composed of pure POPC and POPC:POPS (9:1) was also performed using an innovative methodology developed in this work based on the kinetics of the heat evolved due to the interaction of CPZ with the membranes.

Thermodynamics of Chlorpromazine Association with Lipid Bilayers

Passive transport across cell membranes is the major route for the permeation of xenobiotics through tight epithelia, such as the vascular endothelium that constitutes the Blood Brain Barrier. The rate of passive permeation through lipid bilayers for a given drug is therefore a critical step in the prediction of its in vivo efficacy. This parameter is usually evaluated from the drug hydrophobicity with little consideration for the rate of interaction and/or translocation through the lipid bilayer. Our research group is developing a global model to quantitatively describe the rate of passive permeation through tight endothelia and one of the outcomes is that in most cases the rate of the interaction (rather then the equilibrium partition) is the most relevant parameter.In this work we present a detailed study on the kinetics and thermodynamics for the interaction of chlorpromazine (CPZ) with neutral and negatively charged lipid bilayers. CPZ is an antipsychotic drug used in the treatment of schizophrenia and is an ideal candidate for studies of passive permeation of the BBB by active drugs.The partition and translocation of CPZ in lipid membranes was studied by Isothermal Titration Calorimetry (ITC) and the lipid bilayers were composed of pure POPC, POPC:POPS (9:1) and POPC:Chol:POPS (6:3:1). The charge imposed by CPZ in the membrane was taken into account allowing the calculation of the intrinsic partition coefficients (KP) and the enthalpy change (ΔH) associated with this process. The relative rate of the partition and translocation processes was obtained following the uptake and release protocol [1]. A quantitative evaluation of the rate of translocation is also given for some systems using an innovative methodology.[1] Tsamaloukas, A. D., Keller, S. and Heerklotz, H. (2007) Nat. Prot. 2, 695-704

PH-dependent interaction of psychotropic drug with glycerophospholipid monolayers studied by the Langmuir technique

We have earlier investigated the interaction of the antipsychotic drugs chlorpromazine(CPZ) and olanzapine(OLP) with glycerophospholipid monolayers. These experiments were carried out at high and low temperatures and showed that OLP had a more pronounced effect on the packing of the phospholipid (PL) monolayers than CPZ. At pH 7.36, where OLP consists of one positive and one neutral species. In the present work we have studied the interaction of the drugs with monolayers of PLs by the Langmuir technique at pH 6.00 and 10.00 at 37 °C. The PLs were palmitoylphosphatidyl-choline(DPPC), 1-stearoyl-2-arachinodonoylphoshatidylcholine(SAPC),dipalmitoylphosphatidyl-serine(DPPS) and 1-palmitoyl-2-oleoylphosphatidylserine(POPS). OLP has a pKa around 7.4, with one neutral and one positive species at pH 6.00 and pH 10.00, respectively. CPZ has pKa value around 9.4, and is positively charged at pH 6.00 and neutral at pH 10.00. Our studies revealed that the surface area of DPPC with CPZ in the subphase did not change at pH 6.00. In contrast, OLP increased the mean molecular area(MMA) of DPPC at pH 6.00, while CPZ caused distinct increase in MMA on the monolayer packing of all the other PLs, including monolayers of DPPC at pH 10.00. OLP, increased MMA of all PLs at both pHs. Further, OLP increased MMA of DPPC (pH 10.00), SAPC (pH 10.00), DPPS (pH 6.00) and POPS (pH 6.00) at 30 mN/m, the expected MMA of biological membranes. CPZ had the more pronounced effect at lift-off and gave an effect of the monolayers with negatively charged head groups in accordance our earlier experiments. However, CPZ affected the packing of the SAPC monolayer both at pH 6.00 and 10.00, and DPPC at pH 10.00. Both these PLs have neutral choline head group. Our results suggest that both drugs intercalate in the PL monolayers, and that the intercalation might involve electrostatic interaction with the head groups or hydrophobic interaction with the acyl chains of the PLs, or both. Probably the drugs intercalate to different extents depending on charge of both the drugs and the PL head groups. Our investigation may suggest that the interaction of CPZ and OLP with membrane PLs could be linked to both the psychotropic and the side effects.

Interactions of chlorpromazine with phospholipid monolayers: Effects of the ionization state of the drug

Molecular dynamics simulations have been performed to investigate the interactions between chlorpromazine (CPZ) and Langmuir monolayers of the zwitterionic dipalmitoylphosphatidylcholine (DPPC) and the anionic dipalmitoylphosphatidylglycerol (DPPG). Simulations for a fixed surface density and different charge states — neutral and protonated CPZ — were able to capture important features of the CPZ–phospholipid monolayer interaction. Neutral CPZ is predominantly found in the hydrophobic tail region, whereas protonated CPZ is located at the lipid–water interface. Specific interactions (hydrogen bonds) between protonated CPZ and the lipid head groups were found for both zwitterionic and anionic monolayers. We computed lipid tail order parameters and investigated the effects of the drug upon tail ordering. We also computed electrostatic surface potentials and found qualitative good agreement with experimental results.

Thermodynamic and Infrared Analyses of the Interaction of Chlorpromazine with Phospholipid Monolayers

An investigation has been made of the interaction between chlorpromazine (CPZ) and monolayers of 1,2-dipalmitoyl-sn-3-glycerophosphatidylcholine (DPPC) and 1,2-dipalmitoyl-sn-3-glycero[phospho-rac-(1-glycerol)] (DPPG), both at the air/water interface and in transferred Langmuir-Blodgett films. The Gibbs free energy, DeltaG, and the compressibility modulus (C(S)(-1)), obtained from the surface pressure isotherms, indicated changes in the in-plane interactions of CPZ/DPPG mixed monolayers, with positive values of DeltaG. The arrangement of CPZ in the zwitterionic DPPC monolayers causes a weaker interaction in CPZ/DPPC mixed monolayers, with the DeltaG fluctuating around zero. IR measurements in transferred monolayers showed that CPZ did not affect the conformational order of the acyl chains, its effects being limited to the bands corresponding to the headgroups. Furthermore, since no shift was observed for the acyl chain bands, the phase transition induced by CPZ is not a liquid expanded (LE) to liquid condensed (LC) transition, as the latter is associated with chain ordering. Taken together, the IR and compressibility results demonstrate that the effect from CPZ cannot be correlated with temperature changes in the subphase for pure monolayers, in contrast to models proposed by other authors.

Concentration and time dependant behavior of chlorpromazine interaction with supported bilayer lipid membrane

The interaction of chlorpromazine (CPZ) with supported bilayer lipid (dipalmitoyphosphatidylcholine) membrane (s-BLM) on the glassy carbon electrode (GCE) was investigated using cyclic voltammetry and ac impedance spectroscopy. The experimental data, based on the voltammetric response of Ru(NH 3) 6 3+ associated with the oxidation of CPZ on the electrode, indicated that the interaction of CPZ with s-BLM was concentration and time dependant. The interaction between them could be divided into three stages by the concentration of CPZ: low, middle and high concentration. At the first stage, s-BLM was not affected by CPZ and the interaction was only a penetration of a small quantity of CPZ molecule into s-BLM. At the second stage, the defects formed in s-BLM due to the penetration of more CPZ molecule into s-BLM. At the last stage, a high CPZ:lipid ratio reached in s-BLM, resulting in the solubilization of s-BLM. The interaction time had different effect at three stages.

Importance of polyunsaturated acyl chains in chlorpromazine interaction with phosphatidylserines: A 13C and 31P solid-state NMR study

The polyunsaturated fatty acid docosahexaenoic acid (DHA, c22:6, n-3) is found at a level of about 50% in the phospholipids of neuronal tissue membranes and appears to be crucial to human health. Dipalmitoyl phosphatidylcholine (DPPC, 16:0/16:0 PC), 1-palmitoyl-2-oleoyl phosphatidylserine (POPS) and the DHA containing 1-stearaoyl-2-docosahexenoyl phosphatidylserine (SDPS) were used to make DPPC (60%)/POPS (29%)/SDPS (11%) bilayers with and without 10 mol% chlorpromazine (CPZ), a cationic, amphiphilic phenothiazine. The T 1 relaxation measurements make it clear that the saturated acyl chains carbons (palmitic, stearic and most of the oleic chain) and the choline head group are not affected by CPZ addition. The observed increased signal intensity and T 1-values of DHA indicate reduced mobility of C 4 and C 5 due to CPZ binding. 31P NMR spectra confirm that CPZ binding to the phosphatidylserines in the bilayer enhances phospholipid head group mobility.

Chlorpromazine interaction with phosphatidylserines: A 13C and 31P solid-state NMR study

Chlorpromazine (CPZ), a cationic, amphiphilic phenothiazine derivative is widely used as an antipsychotic drug because it antagonizes dopaminergic receptors. 13C and 31P solid-state NMR techniques were employed on phospholipid bilayers with and without CPZ. Phosphatidylserine from pig brain (PBPS), 1-palmitoyl-2-oleoyl phosphatidylserine (POPS), synthetic 1,2-dipalmitoyl phosphatidylcholine (DPPC) and chlorpromazineHCl were used to make phospholipid bilayers containing two types of phospholipids: DPPC (60%)/PBPS (40%) as well as POPS and PBPS bilayers without and with 10% CPZ. CPZ is found to prefer binding to the phosphate of phosphatidylserine, but also binding to the carboxyl of the serine head group in the DPPC/PBPS/CPZ bilayer is present. 31P-NMR spectra indicate an effect of acyl chain unsaturation on the anisotropic motion of the charged serine head group. This implies that the serine head group anisotropic motion is restricted by intermolecular rather than intramolecular effects. The degree of phospholipid acyl chain unsaturation determines part of the CPZ bilayer interaction. The PBPS bilayer has the 22:6 acyl chain at 34 mol% and the C4C5 group of this acyl appears to be a determinant for CPZ bilayer interdigitation.

ESR studies on the effect of cholesterol on chlorpromazine interaction with saturated and unsaturated liposome membranes

In this study, the effects of chlorpromazine (CPZ) on lipid order and motion in saturated (DMPC, DMPG) and unsaturated (SOPC) liposome membranes were investigated by electron spin resonance (ESR) spin labeling technique. We have shown that above the main phase transition temperature of membrane lipids ( T M), CPZ slightly increases lipid order in membranes without cholesterol, whereas below T M it has a strong opposite effect. Addition of 30 mol% of cholesterol into DMPC and SOPC membranes changes significantly the CPZ effects both above and below T M. Additionally, above T M, the ordering effect of CPZ on pure SOPC membrane is stronger at pH 7.4 than at pH 9.0, whereas below T M, as well as in the presence of cholesterol, pH does not seem to play a role in CPZ effect on both membranes. Because of the strong influence of membrane composition on CPZ effect on membranes, the use of cholesterol as a marker of CPZ photosensitized reactions has been discussed.

Chlorpromazine interaction with phosphatidylserines: A 13C and 31P solid-state NMR study

Chlorpromazine (CPZ), a cationic, amphiphilic phenothiazine derivative is widely used as an antipsychotic drug because it antagonizes dopaminergic receptors. 13C and 31P solid-state NMR techniques were employed on phospholipid bilayers with and without CPZ. Phosphatidylserine from pig brain (PBPS), 1-palmitoyl-2-oleoyl phosphatidylserine (POPS), synthetic 1,2-dipalmitoyl phosphatidylcholine (DPPC) and chlorpromazineHCl were used to make phospholipid bilayers containing two types of phospholipids: DPPC (60%)/PBPS (40%) as well as POPS and PBPS bilayers without and with 10% CPZ. CPZ is found to prefer binding to the phosphate of phosphatidylserine, but also binding to the carboxyl of the serine head group in the DPPC/PBPS/CPZ bilayer is present. 31P-NMR spectra indicate an effect of acyl chain unsaturation on the anisotropic motion of the charged serine head group. This implies that the serine head group anisotropic motion is restricted by intermolecular rather than intramolecular effects. The degree of phospholipid acyl chain unsaturation determines part of the CPZ bilayer interaction. The PBPS bilayer has the 22:6 acyl chain at 34 mol% and the C 4C 5 group of this acyl appears to be a determinant for CPZ bilayer interdigitation.

Interactions of chlorpromazine with alpha-, beta- and gamma-crystallins.

The binding parameters (binding affinity constant, K and number of binding sites, p) has been determined spectrofluorometrically for chlorpromazine (CPZ) binding to the lens proteins--alphaL-crystallin, betaL-crystallin and gamma-crystallin. The binding affinity constants for CPZ binding to alphaL- and gamma-crystallins are higher than the binding affinity constants for 3betaL-crystallin, although the number of CPZ binding sites for betaL-crystallin is comparatively higher than the number for the other two lens proteins. CPZ causes local conformational changes around the tryptophan moieties of the protein molecules but does not cause any gross conformational change within the protein moieties. Binding of CPZ to alphaL-crystallin does not significantly alter the anti-aggregation properties of the molecular chaperone, alphaL-crystallin against oxidation-induced aggregation of gamma-crystallin at 37 degrees C and thermal aggregation of alcohol dehydrogenase (ADH) at 48 degrees C. Therefore, CPZ induced alteration in chaperone activity of alphaL-crystallin is probably not associated with the formation of cataracts.

Chlorpromazine and Sodium Dodecyl Sulfate Mixed Micelles Investigated by Small Angle X-Ray Scattering

Small-angle X-ray scattering (SAXS) studies are reported on the interaction of chlorpromazine (CPZ) with micelles of anionic surfactant sodium dodecyl sulfate (SDS). Isotropic solutions of SDS (40 and 100 mM) at pH 4.0, 7.0, and 9.0 in the absence and presence of CPZ (2–25 mM) were investigated at the National Laboratory of Synchrotron Light (LNLS, Campinas, Brazil). The data were analyzed through the modeling of the micellar form factor and interference function. The results evidence a micellar shape transformation from prolate ellipsoid to cylinder accompanied by micellar growth and surface charge screening as the molar ratio CPZ : SDS increases in the complex. Small ellipsoids with axial ratio ν=1.5±0.1 at 40 mM SDS grow and reassemble into cylinder-like aggregates upon 5 mM drug incorporation (1 CPZ : 8 SDS monomers) with a decrease of the micelle surface charge. At 10 mM CPZ : 40 mM SDS cylindrical micelles are totally screened with an axial ratio ν≈2.5. The data also indicate the presence of small prolate ellipsoids (ν=1.7±0.1) in solutions of 100 mM SDS (no drug) and micellar growth (ν≈2.0 and 4.0) when 10 and 25 mM CPZ are added to the system. In the latter case, the aggregate is also better represented by a cylinder-like form. Therefore, our results demonstrate that the axial ratio and shape evolution of the surfactant : phenothiazine complex are both SDS concentration and drug : SDS molar ratio dependent. The drug location close to the SDS polar headgroup region without disrupting in a significant way both the paraffinic hydrophobic core and the polar shell thickness is inferred. SAXS data made it possible to obtain the shapes and dimensions of CPZ/SDS aggregates.

Interaction of Chlorpromazine and Trifluoperazine with Anionic Sodium Dodecyl Sulfate (SDS) Micelles: Electronic Absorption and Fluorescence Studies

The characteristics of binding of two phenothiazine antipsychothic drugs, chlorpromazine (CPZ) and trifluoperazine (TFP), to anionic sodium dodecyl sulfate (SDS) monomers and/or micelles were investigated using electronic absorption and fluorescence spectroscopies. Binding constants Kb and pKa values for the drugs in SDS micelles were estimated using the red shifts of the maximum absorption and changes in absorption upon alkalization or in the presence of surfactant. The pKa shift of CPZ due to its interaction with SDS micelles is about 0.7 unit to higher values, as compared to the reported value of pKa obtained in buffer around 9.3. For TFP the pKa shift is 0.4 unit to higher values compared to that in buffer, reported as 4.0. The electronic absorption spectroscopic data suggest a biphasic interaction as a function of detergent concentration which is quite dependent of the protonation states of the drugs. In the case of TFP a very strong binding takes place when the drug is fully protonated (pH 2.0) and a distinct binding takes place at stoichiometric (low) surfactant concentrations (interaction via surfactant monomers) and at higher concentrations (in the presence of micelles). Static fluorescence probe analysis using pyrene was used to study the nature of the phenothiazine–surfactant premicellar and self-aggregates. The I3/I1 and I475/I1 ratios associated to pyrene fluorescence vibronic bands and excimer intensities ratios, respectively, were monitored for several ratios [SDS]/[drug] and significant changes, dependent of the drug presence and its protonation state, have been observed revealing a hydrophobic microenvironment provided by TFP–SDS aggregates in comparison with CPZ both at pH 7.0 and 4.0. Static anisotropy was also used to monitor the changes of the self-aggregates and micellar packing in the presence of the phenothiazine drugs. In aqueous solutions the anisotropy of the fluorescent probe dipyridamole (DIP) is quite low, being around 0.005 at pH 7.0 and 0.025 at pH 4.0, and the addition of detergent leads to an increase in the values of anisotropy to 0.030 at pH 7.0 and 0.070 at pH 4.0. In the presence of the phenothiazine drugs, and in the premicellar detergent concentration range, the anisotropy of DIP increases to 0.134 and 0.111 (dependent on drug concentration) for CPZ and TFP, respectively, at pH 4.0. These results suggest that the presence of both phenotiazine drugs makes the premicellar aggregates more rigid by decreasing the probe mobility, and are consistent with a more polar localization of the CPZ in the micelles as compared with TFP. At pH 7.0 the anisotropy changes are smaller, suggesting a slight decrease in CMC induced by the phenothiazines.

Chlorpromazine interaction with glycerophospholipid liposomes studied by magic angle spinning solid state 13C-NMR and differential scanning calorimetry

Phosphatidylserine (PS) extracted from pig brain and synthetic dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) were used to make DPPC/DMPC and DPPC/PS large unilamellar liposomes with a diameter of ∼1 μm. Chlorpromazine-HCl (CPZ), an amphipathic cationic psychotropic drug of the phenothiazine group, is known to partition into lipid bilayer membranes of liposomes with partition coefficients depending on the acyl chain length and to alter the bilayer structure in a manner depending on the phospholipid headgroups. The effects of adding CPZ to these membranes were studied by differential scanning calorimetry and proton cross polarization solid state magic angle spinning 13C-nuclear magnetic resonance spectroscopy (CP-MAS- 13C-NMR). CP-MAS- 13C-NMR spectra of the DPPC (60%)/DMPC (40%) and the DPPC (54%)/DMPC (36%)/CPZ (10%) liposomes, show that CPZ has low or no interaction with the phospholipids of this neutral and densely packed bilayer. Conversely, the DPPC (54%)/PS (36%)/CPZ (10%) bilayer at 25°C demonstrates interaction of CPZ with the phospholipid headgroups (PS). This CPZ interaction causes about 30% of the acyl chains to enter the gauche conformation with low or no CPZ interdigitation among the acyl chains at this temperature (25°C). The DPPC (54%)/PS (36%)/CPZ (10%) bilayer at a sample temperature of 37°C ( T C=31.2°C), shows CPZ interdigitation among the phospholipids as deduced from the finding that ∼30% of the phospholipid acyl chains carbon resonances shift low-field by 5–15 ppm.

Interaction of chlorpromazine and trifluoperazine with ionic micelles: electronic absorption spectroscopy studies

The characteristics of binding of two phenothiazine antipsychotic drugs, namely, chlorpromazine (CPZ) and trifluoperazine (TFP), to cationic cetyltrimethylammonium chloride (CTAC), zwitterionic N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS), neutral t-octylphenoxypolyethoxyethanol (TRITON X-100) and polyoxyethylene dodecyl ether (Brij-35) micelles were investigated using electronic absorption spectroscopy. Binding constants Kb and pKa values of drugs in micelles were estimated using the red shifts of the maximum absorption upon alkalization or in the presence of detergents. The pKa of TFP seems to be shifted by 2.5–4.1 units to lower values in the presence of different surfactants as compared to the experimental value of pKa obtained in buffer which is around 7.0. Consideration of the second pKa around 4.0 reported in the literature for TFP leads to a better rationalization of pKa changes for this compound. The changes in pKa contributed by electrostatic effects are all positive, small for CTAC (+0.2), and greater for HPS (+0.9). For CPZ the pKa shift due to its interaction with micelles is in the 0.7–2.3 range, the direction of the shift depending on the charge of the polar head. The electrostatic contribution for the shift is great for CTAC (−0.8) and smaller for HPS (+0.2). This result suggests a more polar localization in the micelle of CPZ as compared to TFP. The values of binding constants Kb for TFP and CPZ in different protonation states show that electrostatic interactions are essential in the affinity of the drugs to micelles bearing different charges on their headgroups (CTAC, HPS). Data for Brij-35 demonstrate that the additional charge on the TFP ring at pH 2.0 leads to a decrease of binding constant probably due to the repulsion of the phenothiazine ring from the protons accumulated at the polar head of the micelle at acidic pH values. For this micelle at pH 5.0 TFP has a Kb 3-fold greater than that for CPZ while at pH 2.0 Kb for TFP is 3-fold less than that for CPZ. So, for more hydrophobic TFP electrostatic interactions due to protonation of the ring are quite important even considering its deeper penetration into the micelle interior as compared to CPZ.

Interaction of Chlorpromazine with Phospholipid Membranes: A Monolayer and a Microelectrophoresis Approach

Chlorpromazine penetration into the lipid core of the membrane was demonstrated through measurements on lipid monolayers (surface pressure and surface potential). The surface pressure measurements allow us to calculate the intrinsic binding constant (partition coefficient) for the lipid−Chlorpromazine interaction. This latter value is in correct agreement with the obtained results by electrophoretic mobilities measurements on liposomes.

Influence of Fixed Charge and Polyunsaturated Compounds on the Monomolecular Gramicidin Channel Function in Phospholipid Monolayers: Further Studies

An investigation into the effect of adsorbed and incorporated fixed charge and incorporated polyunsaturated compounds in dioleoylphosphatidylcholine (DOPC) monolayers on the translocation of Tl+ through the monomolecular gramicidin channel is reported in this paper. The work also includes a study of the interaction of the tricyclic neuroleptic drug chlorpromazine with DOPC monolayers and the influence of chlorpromazine on the transport of Tl+ through the gramicidin channel. Techniques used were out-of-phase AC voltammetry and cyclic voltammetry and chronoamperometry of the Tl(I)/Tl(Hg) couple. It was shown that negatively charged phosphatidylserine (PS) when incorporated into DOPC layers increases the gramicidin-mediated permeability of the layers by increasing the concentration of Tl+ on the monolayer surface and increasing the rate of translocation of the ion in the channel. Positively charged ions which adsorb onto lipid layers have the opposite effect. Polyunsaturated compounds when incorporated into DOPC monolayers have influences on gramicidin-mediated Tl+ translocation similar to those of negative fixed charge. The chlorpromazine interaction with DOPC layers and its influence on the transport of Tl+ in the pore depends on its charge. At high solution pH above its pKa of 9.3 its effect on the gramicidin-mediated permeability is similar to that of a polyunsaturated compound. At low solution pH its positive charge dominates its influence on the transport of Tl+ in the channel, decreasing the gramicidin-mediated permeability.

Second-derivative spectrophotometric study on the interactions of chlorpromazine and triflupromazine with bovine serum albumin

The second-derivative spectra of chlorpromazine (CPZ) or triflupromazine (TFZ) in buffer solutions (pH 7.4) containing various amounts of BSA (the reference solutions contained the same amount of BSA) showed derivative isosbestic points. The residual background signals derived from incomplete suppression of BSA signals can be entirely eliminated in the second-derivative spectra and BSA has spectrophotometrically one kind of binding site for CPZ or TFZ. The fractions of the drugs bound to BSA were calculated from the derivative intensity differences (ΔD values) of CPZ or TFZ before and after the addition of BSA. Scatchard plot experiments suggested that the binding of the drugs to BSA could be explained as a partition like non-specific binding model. The association constants (K) of CPZ or TFZ with BSA were calculated from the ΔD values according to the non-specific binding model by a nonlinear least-squares method. The K values were almost constant for all of the drug concentrations studied, and good reproducibility was obtained. The fractions predicted by the K values were in good coincidence to the observed values. These results confirm the usefulness of the proposed derivative method which does not need any separation procedures.