Association of myelin basic protein with detergent micelles

Equilibrium measurements of the binding of central nervous system myelin basic protein to sodium dodecyl sulphate, sodium deoxycholate and lysophosphatidylcholine have been obtained by gel permeation chromatography and dialysis. This protein associates with large amounts of each of these surfactants: the apparent saturation weight ratios (surfactant/protein) being $\text{3.58 ± 0.12}\text{and}\text{2.30 ± 0.15}$ for dodecyl sulphate at ionic strengths 0.30 and 0.10, respectively, $\text{1.34 ± 0.10}$ for deoxycholate (at 0.12 ionic strength) and $\text{4.0 ± 0.5}$ for lysophosphatidylcholine. Binding to the ionic surfactants increases markedly close to their critical micelle concentrations. Sedimentation analysis shows that at 0.30 ionic strength in excess dodecyl sulphate the protein is monomeric. It becomes dimeric when the binding ratio falls below 1 at a free detergent concentration of approximately 0.25 mM: below this concentration much of the protein and detergent forms an insoluble complex. The amount of dodecyl sulphate bound at high concentrations and at both above-mentioned ionic strengths corresponds closely to that expected for interaction of a single polypeptide with two micelles. Variability of deoxycholate micelle size on interaction with other molecules precludes a similar analysis for this surfactant. Association was observed only with single micelles of lysophosphatidylcholine. The results provide strong evidence for dual lipid-binding sites on basic protein and indicate that lipid bilayer cross-linking by this protein may be effected by single molecules.     

Size control of styrene oxide-ethylene oxide diblock copolymer aggregates with classical surfactants: DLS, TEM, and ITC study

The interactions between the diblock copolymer S(15)E(63) and the surfactants sodium dodecyl sulfate (SDS), sodium decyl sulfate (SDeS), and sodium octyl sulfate (SOS) have been investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), and isothermal titration calorimetry (ITC). The surfactants with the same headgroup differentiate in their chain length. At 20 degrees C, the block copolymer is associated into micelles with a hydrodynamic radius of 11.6 nm, which is composed of a hydrophobic styrene oxide (S) core and a water-swollen oxypolyethylene (PEO or E) corona. The different copolymer/surfactant systems have been studied at a constant copolymer concentration of 2.5 g dm(-3) and in a vast range of surfactant concentrations, from 7.5 x 10(-6) up to 0.75 M. When SDS and SDeS are added to the block copolymer solution, different regions are observed in the DLS data: at low surfactant concentrations (c < 1.0 x 10(-4) M), single surfactant molecules associate with the copolymer micelle, probably the former being solubilized in the micelle core, leading to a certain disruption of the mixed micelle due to repulsive electrostatic interactions between surfactant headgroups followed by a stabilization of the mixed micelle. At higher concentrations (1.0 x 10(-4) < c < 0.1 M), two types of copolymer-surfactant complexes coexist: one large copolymer-rich/surfactant complex and one small complex consisting of one or a few copolymer chains and rich in surfactants. At higher SDS and SDeS concentrations, complete disintegration of mixed micelles takes place. In contrast, SOS-S(15)E(63) interactions are less important up to surfactant concentrations of 0.05 M due to its higher hydrophilicity, reducing the hydrophobic interactions between surfactant alkyl chains and copolymer micelles. At concentration larger than the critical aggregation concentration (cac) of the system, 0.05 M, disruption of copolymer micelles occurs. These regions have been confirmed by transmission electron microscopy. On the other hand, the titration calorimetric data for SDS and SDeS present an endothermic increase indicating the formation of mixed copolymer-rich-surfactant micelles. From that point, important differences in the ITC plot for both surfactants are present. However, the ITC curve obtained after titration of a SOS solution in the copolymer solution is quite similar to that of its titration in water.     

Role of surfactant on the proteolysis of aqueous bovine serum albumin

Nonionic and ionic surfactants diminish the initial rate of proteolysis of aqueous bovine serum albumin (BSA) by subtilisin Carlsberg. Surfactants studied include: nonionic tetraethylene glycol monododecyl ether (C12E4); anionic sodium dodecyl sulfate (SDS), anionic sodium dodecylbenzenesulfonate (SDBS), and cationic dodecyltrimethylamonium bromide (DTAB). Kinetic data are obtained using fluorescence emission. Special attention is given to enzyme kinetic specificity determined by fitting initial-rate data to the Michaelis-Menten model. All surfactants reduce the rate of proteolysis, most strongly at concentrations near and above the critical micelle concentration (CMC). Circular dichroism (CD), tryptophan/tyrosine fluorescence spectra, and tryptophan fluorescence thermograms indicate that BSA partially unfolds at ionic surfactant concentrations near and above the CMC. Changes in BSA conformation are less apparent at ionic surfactant concentrations below the CMC and for the nonionic surfactant C12E4. Subtilisin Carlsberg activity against the polypeptide, succinyl-Ala-Ala-Pro-Phe-p-nitroanilide, decreased due to enzyme-surfactant interaction. At the concentrations and time frames studied, there was no enzyme autolysis. Importantly, aqueous proteolysis rates are significantly reduced at high surfactant concentrations where protein-micellar-surfactant aggregates occur. To explain the negative effect of surfactant on subtilisin Carlsberg proteolytic activity against BSA, we propose that micelle/protein complexes hinder enzyme access.     

Protein partitioning in weakly charged polymer-surfactant aqueous two-phase systems

The study includes partitioning of proteins in aqueous two-phase systems consisting of the polymer dextran and the non-ionic surfactant C₁₂E₅ (pentaethylene glycol mono-n-dodecyl ether). In this system a micelle-enriched phase is in equilibrium with a polymer-enriched phase. Charges can be introduced into the micelles by the addition of charged surfactants. The charge of the mixed micelles is easily varied in sign and magnitude independently of pH, by the addition of different amounts of negatively charged surfactant, sodium dodecyl sulphate (SDS), or positively charged surfactant dodecyl trimethyl ammonium chloride (DoTAC). A series of water-soluble model proteins (BSA, β-lactoglobulin, myoglobin, cytochrome c and lysozyme), with different net charges at pH 7.1, have been partitioned in non-charged systems and in systems with charged mixed micelles or charged polymer (dextran sulphate). It is shown that partition coefficients for charged proteins in dextran-C₁₂E₅ systems can be strongly affected by addition of charged surfactants (SDS, DoTAC) or polymer (dextran sulphate) and that the effects are directly correlated to protein net charge.     

Interaction of the mouse and bovine myelin basic proteins and two cleavage fragments with anionic detergents

The binding of deoxycholate and dodecyl sulfate to the mouse and bovine myelin basic proteins and two peptide fragments, obtained by cleavage of the bovine basic protein at its single tryptophan residue, was examined. Complete equilibrium binding isotherms for both detergents were obtained by examining their binding to each of the polypeptides immobilized on agarose. The bulk of the binding of dodecyl sulfate was found to be highly cooperative, and at saturation all four polypeptides bound far more detergent than globular, water-soluble proteins. The sum of the dodecyl sulfate bound by each of the two bovine basic protein cleavage fragments was almost twice that bound by the intact protein at saturation, suggesting that cleavage of the bovine basic protein exposes sites for additional binding of dodecyl sulfate. At pH values below pH 8.0, an additional cooperative transition was observed below the critical micelle concentration of sodium dodecyl sulfate in the binding isotherms of all four polypeptides. The midpoint of this transition corresponded to an apparent pK of approximately 5.5; however, the destruction of 90% of the histidine residues in the bovine basic protein had no effect on this transition. At pH 9.2 and moderate ionic strength (I = 0.1), the bulk of the binding of deoxycholate to the mouse and bovine basic proteins occurred at and above the critical micelle concentration of the detergent; and saturation values of deoxycholate binding to these two proteins were considerably higher than that reported for globular, water-soluble proteins. In marked contrast to the results with dodecyl sulfate, neither cleavage fragment was observed to bind deoxycholate. The results suggest that the higher ordered structure of the bovine basic protein may play an important role in the binding of anionic amphiphiles to the protein.     

On the effect of lysophosphatidylcholine, platelet activating factor and other surfactants on calcium permeability in sarcoplasmic reticulum vesicles.

The effect of low concentrations of lysophosphatidylcholine (LPC), platelet-activating factor (PAF) and other surfactants (Triton X-100, C12E8, sodium dodecyl sulfate, sodium cholate and sodium deoxycholate) on membrane permeability of native sarcoplasmic reticulum vesicles and sarcoplasmic reticulum lipid vesicles, has been studied. Triton X-100, C12E8, sodium dodecyl sulfate, sodium cholate and sodium deoxycholate were all able to permeabilize membranes at concentrations of surfactants below their critical micellar concentration (CMC) in both lipid and native vesicles, being the K0.5 of calcium release from native vesicles lower than that from lipid vesicles. The values of these K0.5 were well correlated with the corresponding CMC values for each type of membrane. However, both LPC and PAF behaved in a different way since, although they induced permeabilization of the native vesicles at values of K0.5 close to their CMC, their K0.5 values for permeabilizing vesicles, prepared by using lipids extracted from sarcoplasmic reticulum, were much higher than their corresponding CMC.     

Benzyl alcohol penetration into micelles, dielectric constant of the binding site, partition coefficient and high-pressure squeeze-out

The absorbance maximum, lambda max, of a local anesthetic, benzyl alcohol, is shifted to longer wavelengths when solvent polarity is decreased. The shift was approximately a linear function of the dielectric constant of the solvent. This transition in electronic spectra according to the microenvironmental polarity is used to analyze benzyl alcohol binding to surfactant micelles. A facile method is devised to estimate the micelle/water partition coefficient from the dependence of lambda max of benzyl alcohol on surfactant concentrations. The effective dielectric constants of the sodium decyl sulfate, dodecyl sulfate and tetradecyl sulfate micelles were 29, 31 and 33, respectively. The partition coefficient of benzyl alcohol between the micelles and the aqueous phase was 417, 610 and 1089, respectively, in the mole fraction unit. The pressure dependence of the partition coefficient was estimated from the depression of the critical micelle concentration of sodium dodecyl sulfate by benzyl alcohol under high pressure up to 200 MPa. High pressure squeezed out benzyl alcohol molecules from the micelle until about 120 MPa, then started to squeeze in when the pressure was further increased. The volume change of benzyl alcohol by transfer from the aqueous to the micellar phase was calculated from the pressure dependence of the partition coefficient. The volume change, estimated from the thermodynamic argument, was 3.5 +/- 1.1 cm3.mol-1 at 298.15 K, which was in reasonable agreement with the partial molal volume change determined directly from the solution density measurements, 3.1 +/- 0.2 cm3.mol-1. Benzyl alcohol apparently solvates into the micelles close to surface without losing contact with the aqueous phase.     

Protein-surfactant interactions: a tale of many states

The scientific study of protein surfactant interactions goes back more than a century, and has been put to practical uses in everything from the estimation of protein molecular weights to efficient washing powder enzymes and products for personal hygiene. After a burst of activity in the late 1960s and early 1970s that established the general principles of how charged surfactants bind to and denature proteins, the field has kept a relatively low profile until the last decade. Within this period there has been a maturation of techniques for more accurate and sophisticated analyses of protein-surfactant complexes such as calorimetry and small angle scattering techniques. In this review I provide an overview of different useful approaches to study these complexes and identify eight different issues which define central concepts in the field. (1) Are proteins denatured by monomeric surfactant molecules, micelles or both? (2) How does unfolding of proteins in surfactant compare with "proper" unfolding in chemical denaturants? Recent work has highlighted the role of shared micelles, rather than monomers, below the critical micelle concentration (cmc) in promoting both protein denaturation and formation of higher order structures. Kinetic studies have extended the experimentally accessible range of surfactant concentrations to far above the cmc, revealing numerous different modes of denaturation by ionic surfactants below and above the cmc which reflect micellar properties as much as protein unfolding pathways. Uncharged surfactants follow a completely different denaturation strategy involving synergy between monomers and micelles. The high affinity of charged surfactants for proteins means that unfolding pathways are generally different in surfactants versus chemical denaturants, although there are common traits. Other issues are as follows: (3) Are there non-denaturing roles for SDS? (4) How reversible is unfolding in SDS? (5) How do solvent conditions affect the way in which surfactants denature proteins? The last three issues compare SDS with "proper" membranes. (6) Do anionic surfactants such as SDS mimic biological membranes? (7) How do mixed micelles interact with globular proteins? (8) How can mixed micelles be used to measure the stability of membrane proteins? The growing efforts to understand the unique features of membrane proteins have encouraged the development of mixed micelles to study the equilibria and kinetics of this class of proteins, and traits which unite globular and membrane proteins have also emerged. These issues emphasise the amazing power of surfactants to both extend the protein conformational landscape and at the same time provide convenient and reversible short-cuts between the native and denatured state for otherwise obdurate membrane proteins.     

The effect of surfactants on the aggregation state of amphotericin B

We have studied the effect of two surfactants, one non-ionic, lauryl sucrose (LS) and the other ionic, sodium deoxycholate (DOC), on the aggregation state of amphotericin B (AmB) and its selectivity towards ergosterol and cholesterol. It is shown that the addition of these surfactants has very similar effects on the AmB micelles. Below the critical micellar concentration of the surfactants, mixed micelles with AmB are first formed as a result of the penetration of the surfactant molecules into the AmB micelles. At higher concentrations of the surfactant molecules, the micellar structure is completely destroyed and AmB is found as monomers in solution. When the concentration of the surfactant is further increased, micelles of the surfactant molecules are built up, AmB remaining in monomeric form. However, the critical micellar concentration of LS is modified by the presence of AmB in solution, while that of DOC is not affected, thereby indicating that the interactions of AmB with LS are stronger than those of DOC with AmB. We also show that both surfactants enhance the selectivity of the AmB binding to sterols at exactly the concentrations of the surfactants which induce the monomerization of the antibiotic. It is observed that the maximal selectivity is found at a concentration of the surfactants corresponding to their particular CMC in presence of the antibiotic.     

Solubilization of the Semliki Forest virus membrane with sodium deoxycholate.

The effects of increasing concentrations of sodium deoxycholate on Semliki Forest have been studied. Sodium deoxycholate begins to bind to the virus at less than 0.1 mM free equilibrium concentration and causes lysis of the viral membrane at 0.9 +/- 0.1 mM free equilibrium concentration when 2.2 +/- 0.2 - 103 mol of sodium deoxycholate are bound per mol of virus. Liberation of proteins from the membrane begins at 1.5 +/- 0.1 mM sodium deoxycholate and the proteins released are virtually free from phospholipid above 2.0 mM sodium deoxycholate. The overall mechanism of sodium deoxycholate solubilization of the viral membrane resembles that of Triton X-100 and sodium dodecyl sulphate except that with sodium deoxycholate the various stages of membrane disruption occur at about 10-fold higher equilibrium free detergent concentrations. At sodium deoxycholate concentrations higher than 2.3 mM the viral spike glycoproteins can be separated by sucrose gradient centrifugation or gel filtration into constituent polypeptides E1, E2 and E3. E1 carries the haemagglutinating activity of the virus.     

Size and shape of charged micelles of ionic surfactants in aqueous salt solutions

Light-scattering has been measured on aqueous NaCl solutions of dodecyldimethylammonium chloride and sodium dodecyl sulfate. From molecular weight determination it is confirmed that spherical micelles are formed at low NaCl concentrations, but at high NaCl concentrations the small micelles formed at the critical micelle concentration further associate to form large rod-like micelles with increasing micelle concentration. The reduction of repulsion between charged groups induces the sphere-rod transition of micelle shape. The dependence of molecular weight on ionic strength can be expressed by double logarithmic relations, which are dependent on the micelle shape. While dodecyldimethylammonium chloride dissolves even in 4.00 M NaCl, sodium dodecyl sulfate solutions exhibit some XXX in angular dissymmetry at NaCl concentrations higher than 0.50 M at low temperatures.     

Effect of surfactants and natural detergents on phosphatidylcholine synthesis in photoreceptor membranes.

The synthesis of phosphatidylcholine (PC) in rod outer segments (ROS) catalysed by lysophosphatidylcholine acyltransferase and phosphatidylethanolamine N-methyltransferase (PE N-MTase) was studied and the effects of natural (FA and lysophospholipids) and synthetic (Triton X-100, deoxycholate and CHAPS) surfactants was evaluated. In all experimental conditions used, incorporation of labelled oleate into lysophosphatidylcholine (lysoPC) was at least 40 times greater than oleate incorporation into any other lysophospholipid. Acylation of lysoPC was slightly affected by Triton X-100 and was totally inhibited in the presence of 10 mM sodium deoxycholate (NaDOC) or CHAPS. Below their critical micelle concentration (cmc) Triton X-100 and NaDOC stimulated acylation of all ROS lysophospholipids analysed. The activity of PE N-MTase was stimulated at detergent concentrations below the cmc and inhibited at concentrations above the cmc for all three detergents tested. The effect of FA with differing degree of unsaturation on PC synthesis was evaluated. Oleic acid (10 microM) inhibited methyl group incorporation into total PC, whereas from 100 microM onward, the methylating activity increased with preferential synthesis of PC. Docosahexaenoic acid, in turn, inhibited PE N-MTase activity at every concentration tested. These results suggest that PC synthesis in ROS membranes is modified by bioregulators and surfactants altering the physico-chemical state of the membrane.     

The interaction between Beta-lactoglobulin and sodium N-dodecyl sulphate.

1. The binding of sodium n-dodecyl sulphate to beta-lactoglobulin was studied in the pH range 3.5-7.0 by equilibrium dialysis, ultracentrifugation and microcalorimetry. 2. At low binding concentrations (less than 30 bound surfactants anions per protein molecule) the complexes formed aggregates in solution. 3. At higher binding concentrations aggregation does not occur at low ionic strength (0.01 mol/litre), but continues at high ionic strength (0.1 mol/litre). 4. At 25 degrees C the enthalpy of interaction of sodium n-dodecyl sulphate with beta-lactoglobulin can be interpreted as the sum of the enthalpies of formation of a complex with 2 bound surfactant anions, with an enthalpy change of -9.5 kJ-mol-1 of bound surfactant, and complexes containing at least 22 bound surfactant anions, with limiting enthalpies per bound surfactant anion of -12.4 kJ-mol-1 at pH 3.5 and -3.25 kJ-mol-1 at pH 5.5. 5. The binding of surfactant and the enthalpy of interaction at pH 3.5 ARE NOT SIGNIFICANTLY AFFECTED BY THE ADDITION Of 8 M-urea. 6. The data indicate that at low binding concentrations the interaction is of an ionic nature, and is accompanied by a conformational change in the protein.     

BIOLOGICAL EFFECTS OF SURFACTANTS. V. GROWTH AND ANTHOCYANIN PRODUCTION BY CALLUS CULTURES OF DIMORPHOTHECA

Effects of five homologous series of amphoteric, anionic, and nonionic surfactants on growth and anthocyanin production by callus cultures of Dimorphotheca sinuata were examined. The phytotoxicity of amphoteric sulfobetaines increased with alkyl chain length and reached a plateau at 14 to 16 carbon atoms. In the case of the anionic sodium alkyl sulfates, the dodecyl derivative caused the greatest inhibition. Higher molecular weight ionic detergents were less toxic, probably due to their high Krafft temperatures and concomitant reduced solubility. The nonionic higher alcohol ethoxylates were generally less inhibitory than the ionic detergents and had little or no effect below their critical micelle concentrations. Fresh weights of tissues and anthocyanin production by Dimorphotheca callus cultures declined with increasing surfactant concentrations.     

Interaction of tubulin with octyl glucoside and deoxycholate. 1. Binding and hydrodynamic studies

Tubulin purified from calf brain cytoplasm, normally a compact water-soluble dimer, is able to interact with the mild detergents octyl glucoside (a minimum of 60 detergent molecules) and deoxycholate (95 +/- 8 molecules). Binding is cooperative and approaches saturation below the critical micelle concentration of the amphiphiles. Binding is accompanied by a quenching of the intrinsic protein fluorescence, but no spectral shape changes indicating denaturation such as in the case of sodium dodecyl sulfate are observed. Glycerol, which is known to be preferentially excluded from the tubulin domain and to favor the folded and associated forms of this protein, inhibits the binding of the mild detergents. Octyl glucoside induces a rapidly equilibrating tubulin self-association reaction characterized by a bimodal sedimentation velocity profile with boundaries at approximately 5 and 12 S. Full dissociation of this detergent restores the normal sedimentation behavior to 90% of the protein. Binding of deoxycholate slows the sedimentation velocity of tubulin from s(0)20,w = 5.6 +/- 0.2 S to s(0)20,w = 4.8 +/- 0.3 S. Measurements of the molecular weight of the tubulin-deoxycholate complex indicate an increase from 100,000 to 143,000 +/- 5,000. The diffusion rate consistently decreases from (5.3 +/- 0.5) X 10(-7) to (3.8 +/- 0.2) X 10(-7) cm2 S-1. This is most simply interpreted as an expansion of the undissociated tubulin dimer upon detergent binding (a change in the frictional ratio, f/f min, from 1.35 to 1.86). It is concluded that tubulin shows a reversible transition between the water-soluble state and amphipathic detergent-bound forms which constitute a model system of tubulin-membrane interactions.     

Solubilization of cholesterol and polycyclic aromatic compounds into sodium bile salt micelles (part 2)

The aqueous solubility of cholesterol was determined over the temperature range from 288.2 to 318.2 K with intervals of 5 K by the enzymatic method. The solubility was (3.7+/-0.3)x10(-8) mol dm(-3) (average +/- S.D.) at 308.2 K. The maximum additive concentrations of cholesterol into the aqueous micellar solutions of sodium deoxycholate (NaDC), sodium ursodeoxycholate (NaUDC), and sodium cholate (NaC) were spectrophotometrically determined at different temperatures. The cholesterol solubility increased in the order of NaUDC相似文献   

Protein-decorated micelle structure of sodium-dodecyl-sulfate--protein complexes as determined by neutron scattering

The structure of the complex between sodium dodecyl sulfate (SDS) and a deuterated bifunctional enzyme, N-5'-phosphoribosylanthranilate isomerase/indole-3-glycerol-phosphate synthase (Mr 49,484), has been studied in dilute solution by small-angle neutron scattering. The complex nearly acquired its final size, as shown by molecular-sieve chromatography, at the chosen SDS concentration of 1.6 mM, which is slightly below the critical micelle concentration of 1.8 mM (at the ionic strength of 0.1 M). The 452 amino-acid residues of the bifunctional enzyme were combined with 216 detergent molecules. The complex was found to be composed of three protein-decorated SDS micelles of unequal size, connected by short flexible polypeptide segments. The largest of the three micelles was the middle one. The SDS-protein complex contained the dodecyl hydrocarbon moieties in three globular cores. Each core was surrounded by a hydrophilic shell, formed by the hydrophilic and amphiphilic stretches of the polypeptide chain, and by the sulfate head groups of the detergent. The average thickness of these shells was 0.7-0.8 nm. The three-micelle complex was cleaved with trypsin at a single site, possibly in a micelle-connecting segment, into a single-micelle fragment at the carboxyl-terminal which comprised 73 SDS molecules and 163 amino-acid residues, and a dual-micelle fragment. One of the micelles within this larger fragment contained 42 SDS molecules and about 90 amino-acid residues; the other micelle contained 101 SDS molecules and about 190 amino-acid residues. The individual micelle sizes seemed to be determined by the amino-acid sequence.     

Renaturation and interaction of ribonuclease A with AOT surfactant in reverse micelles

This study extended works on effects of solute on the percolation of reverse micelles to the effects of interactions between protein and surfactants on protein refolding by reverse micelles. The changes in percolation behavior were identified and attributed to the position of solutes in the core aqueous phase and the interaction between the solute and the surfactants. The percolation behavior of reverse micelles with solutes was related to protein renaturation and the reverse micelle. This study aims to highlight the involvement of the interface and the interaction of the protein with the surfactant during protein refolding. Ribonuclease A and AOT reverse micelles together constitute a model system considered here. The systemic parameters of the reverse micelle, water content (W(o)) and pH value, were applied to modify the interaction between the denatured protein molecules and the surfactant interface. The interactions and the locations of the protein molecules were determined from changes in percolation temperature measured by conductivity. The percolation and protein activity show that a stronger interaction of the protein molecules with surfactant corresponds to superior recovery of protein activity. The investigation concludes that the refolding of protein by reverse micelles is not only facilitated by the isolation of reverse micelles but also by the interaction due to the interface of the reverse micelle.     

Mixed Micelles of Sodium Cholate and Sodium Dodecylsulphate 1:1 Binary Mixture at Different Temperatures – Experimental and Theoretical Investigations

Micellisation process for sodium dodecyl sulphate and sodium cholate in 1∶1 molar ratio was investigated in a combined approach, including several experimental methods and coarse grained molecular dynamics simulation. The critical micelle concentration (cmc) of mixed micelle was determined by spectrofluorimetric and surface tension measurements in the temperature range of 0–50°C and the values obtained agreed with each other within the statistical error of the measurements. In range of 0–25°C the cmc values obtained are temperature independent while cmc values were increased at higher temperature, which can be explained by the intensive motion of the monomers due to increased temperature. The evidence of existing synergistic effect among different constituent units of the micelle is indicated clearly by the interaction parameter (β_1,2) calculated from cmc values according to Rubingh. As the results of the conductivity measurements showed the negative surface charges of the SDS-NaCA micelle are not neutralized by counterions. Applying a 10 µs long coarse-grained molecular dynamics simulation for system including 30-30 SDS and CA (with appropriate number of Na⁺ cations and water molecules) we obtained semi-quantitative agreement with the experimental results. Spontaneous aggregation of the surfactant molecules was obtained and the key steps of the micelle formation are identified: First a stable SDS core was formed and thereafter due to the entering CA molecules the size of the micelle increased and the SDS content decreased. In addition the size distribution and composition as well as the shape and structure of micelles are also discussed.