Bożenna Różycka-Roszak

Calorimetric studies of the micellization of some amphiphilic betaine ester derivatives

Abstract Critical micelle concentrations and the changes in enthalpy, entropy, and free energy that accompany micelle formation of betaine chloride alkyl esters (of the general formula (CH3)3N+CH2COOCnH2n+1Cl−, where n = 10, 12, 14, 16) were determined by means of titration calorimetry in an aqueous solution at 298.16 K. It was found that the critical micelle concentrations of the studied compounds are close to those of n-alkyltrimethylammonium chlorides with an alkyl chain longer by two CH2 groups.

A comparison of the micellization of selected amphiphilic N,N′-bisdimethyl-1,2-ethanediamine derivatives with some amphiphilic betaine ester derivatives

Abstract Critical micelle concentrations and the changes in enthalpy, entropy, and free energy that accompany micelle formation of selected amphiphilic N,N′ -bisdimethyl-1,2-ethanediamine derivatives (of general formula [C n H 2 n +1 OOCCH 2 (CH 3 ) 2 NCH 2 CH 2 N(CH 3 ) 2 CH 2 COOC n H 2 n +1 ] 2+ · 2Cl − where n = 8, 10, 12, 14, 16) were determined by means of titration calorimetry in an aqueous solution at 298.16 K. It was found that the critical micelle concentrations and thermodynamic data of the studied compounds are close to those of betaine chloride alkyl esters (of general formula [(CH 3 ) 3 NCH 2 COOC n H 2 n +1 ] + · Cl − ) with the alkyl chain longer by four CH 2 groups.

Interaction between N-dodecyl-N,N-dimethyl-N-benzylammonium halides and phosphatidylcholine bilayers-the effect of counterions.

The interaction of N-dodecyl-N,N-dimethyl-N-benzylammonium halides (DBeAX) with two types of phospholipid vesicles (MLV and SUV) was investigated using DSC and 1H NMR. It was suggested that the benzyl group like the micellisation process (J. Colloid Interface Sci. 218 (1999) 529) changes its position when interacting with phosphatidylcholine bilayers and incorporates into the bilayer. In order to enhance counterion-water interactions, the surfactants were added either to the water phase or directly to the lipid phase (a mixed film was formed). It follows from the obtained results that for both types of liposomes and both manners in which the surfactant was added, the interaction of DBeAX with liposomes and consequent changes in the phospholipid bilayer organisation depend on the kind of counterion. Results are discussed in terms of counterion ability to modify water structure.

Micellization of some amphiphilic quaternary ammonium chlorides

Abstract The micellization processes of N -dodecyl- N,N -dimethyl- N -[3-(β-methyl-β-nitrovinyl)-6-methoxybenzyl] ammonium chloride ( I-A ), N -dodecyl- N,N -dimethyl- N -benzylammonium chloride ( I-B ), N -dodecyl- N, N,N -trimethylammonium chloride ( I-C ), N -dodecyl-[3-(β-methyl-β-nitrovinyl)-4-methoxybenzyl] morpholinium chloride ( IV-A ), N -dodecyl- N -benzylmorpholinium chloride ( IV-B ), N -dodecyl- N -methylmorpholinium chloride ( IV-C ), and N -dodecyl- N -methylpiperidinium chloride ( VI-C ) were studied by means of the calorimetric titration method. The critical micelle concentrations and enthalpies of micellization were determined. It is suggested that the benzyl groups of I-B and IV-B and the nitrovinylbenzyl groups of I-A and IV-A behave as second chains during the micellization.

Influence of Counterions on the Interaction of Pyridinium Salts with Model Membranes

Abstract The interaction of pyridinium salts (PS) with red blood cells and planar lipid membranes was studied. The aim of the work was to find whether certain cationic surfactant counterion influence its possible biological activity. The counterions studied were Cl- , Br-, I-, ClO4-, BF4- and NO3-. The model membranes used were erythrocyte and planar lipid membranes (BLM). At high concentration the salts caused 100% erythrocyte hemolysis (C 100) or broke BLMs (CC). Both parameters describe mechanical properties of model membranes. It was found that the efficiency of the surfactant to destabilize model membranes depended to some degree on its counterion. In both, erythrocyte and BLM experiments, the highest efficiency was observed for Br-, the lowest for NO3-. The influence of all other anions on surfactant efficiency changed between these two extremities; that of chloride and perchlorate ions was similar. Some differences were found in the case o f BF4- ion. Its influence on hemolytic possibilities of PS was significant while BLM destruction required relatively high concentration of this anion. Apparently, the influence of various anions on the destructive action of PS on the model membrane used may be attributed to different mobilities and radii of hydrated ions and hence, to different possibilities of particular anions to modify the surface potential of model membranes. This can lead to a differentiated interaction of PS with modified bilayers. Moreover, the effect of anions on the water structure must be taken into account. It is important whether the anions can be classified as water ordering kosmotropes that hold the first hydration shell tightly or water disordering chaotropes that hold water molecules in that shell loosely.

Effect of Counterions on the Influence of Dodecyltrimethylammonium Halides on Thermotropic Phase Behaviour of Phosphatidylcholine Bilayers

Abstract Effects of dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium iodide (DTAI) on thermotropic phase behaviour of phosphatidylcholine bilayers as well as on 1H NMR spectra were studied. In order to enhance the effect of counterions on water structure two series of experiments were performed. In the first one the surfactants were added to the water phase and in the other one directly to lipid phase (a mixed film was formed). The effects of particular surfactants on the main phase-transition temperature were more pronounced when they were added to the water phase (1st method) instead of the lipid phase (2nd method). Furthermore, in the case of the first method the transitions were found asymmetrical while in the second method nearly symmetrical. It is suggested that surfactant-poor and surfactant-rich domains are formed when surfactants are added to the water phase.

Micelle hydration by1H-NMR

Abstract1H-NMR studies were carried out for solution of amphiphilic betaine ester derivatives (of the general formula (CH3)3N+CH2COOCn H2n+1Cl− (V-n), wheren=10, 12, 14, and 16) andn-dodecyltrimethylammonium chloride (I-12). The spectra were taken at concentrations above and below critical micelle concentrations and chemical shifts were analyzed. It was stated that micelles are hydrated at the depth of the two CH2 groups in the case ofV-n and the CH2COO group in the case ofI-12. Therefore, the CH2COO group during the micellization behaves as if it were CH2CH2 group.

Counterion Effects on Interaction of Amphiphilic Quaternary Ammonium Salts with Model Membranes

The micellization as well as the interaction with model membranes of dodecyltrimethylammonium halides (DTAX) and N-dodecyl-N,N-dimethyl-N-benzylammonium halides (DBeAX) were studied at 298K and 313K by means of titration calorimetry. The calorimetric curves reflect both the counterion and benzyl group effects on the interaction of the surfactants studied with the lipid bilayer. Bromide as counterion enhanced the interactions more than chloride of both DTAX and DBeAX compounds with model membranes. Further, we studied the influence of DTAX and DBeAX on calcium ion desorption from the liposome membrane using a radioactive tracer method. DBeAX proved more efficient in desorption of calcium than DTAX. Iodides of these compounds enhanced this process more than bromides and chlorides.

Influence of dodecyltrimethylammonium halides on thermotropic phase behaviour of phosphatidylcholine/cholesterol bilayers.

Abstract Effects of dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium iodide (DTAI) on thermotropic phase behaviour of phosphatidylcholine bilayers containing cholesterol as well as on 1H NMR spectra were studied. Two series of experiments were performed. In the first one the surfactants were added to the water phase while in the other directly to the lipid phase (a mixed film from cholesterol, surfactant and phosphatidylcholine was formed). The effects of particular surfactants on the main phase transition temperature, Tm, were more pronounced when added to the lipid phase (2nd method) than to the water phase ( 1st method); the opposite happened when cholesterol was absent (Różycka-Roszak and Pruchnik 2000, Z. Naturforsch. 55c, 240-244). Furthermore, in the case of the first method the transitions were asymmetrical while in the second method nearly symmetrical. It is suggested that surfactant poor and surfactant rich domains are formed when surfactants are added to the water phase.

Influence of dodecyltrimethylammonium halides on interaction of phenyltin compounds with model membranes.

The effects were studied of dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium iodide (DTAI) on thermotropic phase behaviour of phosphatidylcholine bilayers, as well as on 1H NMR and 31P NMR spectra, in the presence of diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT). The obtained results indicate that in the presence of the surfactant studied the interaction of phenyltin compounds with model membranes was changed and the changes depended on the kind of the counterion. The surfactants studied (especially DTAC) decrease the ability of phenyltin compounds to induce structural changes in the bilayer. It is suggested that DTAB, and especially DTAC, prevent DPhT induced interdigitated phase formation as well as formation of an inverted hexagonal phase (HII) in the case of TPhT/DPPC liposomes