Ions Modulate Stress-Induced Nanotexture in Supported Fluid Lipid Bilayers.

Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of ∼20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membrane's properties on a length scale of ∼20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton.

Islet Amyloid Polypeptide Membrane Interactions: Effects of Membrane Composition.

Amyloid formation by islet amyloid polypeptide (IAPP) contributes to ß-cell dysfunction in type 2 diabetes. Perturbation of the ß-cell membrane may contribute to IAPP-induced toxicity. We examine the effects of lipid composition, salt, and buffer on IAPP amyloid formation and on the ability of IAPP to induce leakage of model membranes. Even low levels of anionic lipids promote amyloid formation and membrane permeabilization. Increasing the percentage of the anionic lipids, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS) or 1,2-dioleoyl-sn-glycero-3-phospho(1'-rac-glycerol), enhances the rate of amyloid formation and increases the level of membrane permeabilization. The choice of zwitterionic lipid has no noticeable effect on membrane-catalyzed amyloid formation but in most cases affects leakage, which tends to decrease in the following order: 1,2-dioleoyl-sn-glycero-3-phosphocholine > 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine > sphingomyelin. Uncharged lipids that increase the level of membrane order weaken the ability of IAPP to induce leakage. Leakage is due predominately to pore formation rather than complete disruption of the vesicles under the conditions used in these studies. Cholesterol at or below physiological levels significantly reduces the rate of vesicle-catalyzed IAPP amyloid formation and decreases the susceptibility to IAPP-induced leakage. The effects of cholesterol on amyloid formation are masked by 25 mol % POPS. Overall, there is a strong inverse correlation between the time to form amyloid and the extent of vesicle leakage. NaCl reduces the rate of membrane-catalyzed amyloid formation by anionic vesicles, but accelerates amyloid formation in solution. The implications for IAPP membrane interactions are discussed, as is the possibility that the loss of phosphatidylserine asymmetry enhances IAPP amyloid formation and membrane damage in vivo via a positive feedback loop.

Ferritin-supported lipid bilayers for triggering the endothelial cell response.

Hybrid nanoassemblies of ferritin and silica-supported lipid bilayers (ferritin-SLBs) have been prepared and tested for the adhesion, spreading and proliferation of retinal microvascular endothelial cells (ECs). Lipid membranes with varying surface charge were obtained by mixing cationic 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC) with zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at increasing POPC/POEPC ratios. The supported bilayer formation and their subsequent interaction processes with ferritin were studied at the pH of 7.4 at different protein concentrations, by using the quartz crystal microbalance with dissipation monitoring and by atomic force microscopy. Both kinetics and viscoelastic parameters of the protein-lipid membrane interface were scrutinized, as well as surface coverage. Phase-contrast optical microscopy analyses of the ferritin-SLBs substrates after their interaction with endothelial cells evidenced the highest cell adhesion (2-4h of incubation time) and proliferation (from 24h to 5 days) for the membranes of POPC/POEPC (75:25 ratio). Moreover, ferritin increased both cell adhesion and proliferation in comparison to control glass (respectively 1.5- and 1.75-fold) as well as proliferation in comparison to bare POPC/POEPC (95:5 ratio) (2 fold). Results are very promising in the goal of modulating the endothelial cell response through the interplay of viscoelastic/charge properties of the solid-supported membranes and the SLB-conditioned ferritin activity.

Simulations of Membrane-Disrupting Peptides I: Alamethicin Pore Stability and Spontaneous Insertion.

An all-atom molecular dynamics simulation of the archetype barrel-stave alamethicin (alm) pore in a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer at 313 K indicates that ∼7 µs is required for equilibration of a preformed 6-peptide pore; the pore remains stable for the duration of the remaining 7 µs of the trajectory, and the structure factors agree well with experiment. A 5 µs simulation of 10 surface-bound alm peptides shows significant peptide unfolding and some unbinding, but no insertion. Simulations at 363 and 413 K with a -0.2 V electric field yield peptide insertion in 1 µs. Insertion is initiated by the folding of residues 3-11 into an α-helix, and mediated by membrane water or by previously inserted peptides. The stability of five alm pore peptides at 413 K with a -0.2 V electric field demonstrates a significant preference for a transmembrane orientation. Hence, and in contrast to the cationic antimicrobial peptide described in the following article, alm shows a strong preference for the inserted over the surface-bound state.

Synthesis, characterization and inclusion into liposomes of a new cationic pyrenyl amphiphile.

The aggregation properties of a new cationic fluorescent amphiphile tagged on the hydrophobic tail with a pyrene moiety and bearing two hydroxyethyl functionalities on the polar headgroup were investigated by fluorescence experiments as pure components or in mixed liposomes containing an unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine, at different molar ratios. The obtained results put in evidence that the conformation and the miscibility of the lipids in the aggregates strongly influence the excimer/monomer ratio. Mixed monolayers at the same composition were investigated by Langmuir compression isotherms to deepen the understanding of lipid organization and miscibility, both in the polar and in the hydrophobic regions. The presence of two hydroxyethyl functionalities on the polar headgroup of the newly synthesized amphiphile exerts a shielding effect of the charge of the amphiphile increasing the compressibility of lipid components in contrast with the disturbing effect of the unsaturated acyl chains of the phospholipid.

The influence of NBD fluorescent probe on model membranes containing POPC and DPPC.

To investigate the effect of fluorescent probe on the properties of membranes, we studied model membranes composed of 1,2- dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl 2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the presence and absence of fluorescent probe. The morphology of giant unilamellar vesicles (GUVs) has been observed as a function of temperature and composition by fluorescence microscopy using NBD-DOPE or C6-NBD-PC as the probe. The phase behavior of model membranes containing no fluorescent probe was investigated by 2H-NMR spectroscopy. We found that the bright phase observed on GUVs was the fluid phase enriched in POPC and the dark phase was the gel phase enriched in DPPC. NBD-DOPE and C6-NBD-PC preferentially participated in the fluid-phase domains when GUVs were in the gel + fluid phase coexistence. Inclusion of both fluorescent probes (1 mol%) lowered the transition temperature of POPC/DPPC membranes. In addition, C6-NBD-PC exhibited a stronger effect than NBD-DOPE, which was considered to be associated with the structures of fluorescent molecules.

Comparative atomic-scale hydration of the ceramide and phosphocholine headgroup in solution and bilayer environments.

Previous studies have used neutron diffraction to elucidate the hydration of the ceramide and the phosphatidylcholine headgroup in solution. These solution studies provide bond-length resolution information on the system, but are limited to liquid samples. The work presented here investigates how the hydration of ceramide and phosphatidylcholine headgroups in a solution compares with that found in a lipid bilayer. This work shows that the hydration patterns seen in the solution samples provide valuable insight into the preferential location of hydrating water molecules in the bilayer. There are certain subtle differences in the distribution, which result from a combination of the lipid conformation and the lipid-lipid interactions within the bilayer environment. The lipid-lipid interactions in the bilayer will be dependent on the composition of the bilayer, whereas the restricted exploration of conformational space is likely to be applicable in all membrane environments. The generalized description of hydration gathered from the neutron diffraction studies thus provides good initial estimation for the hydration pattern, but this can be further refined for specific systems.

Lipid vesicles loading aluminum phthalocyanine chloride: Formulation properties and disaggregation upon intracellular delivery.

Aluminum phthalocyanine chloride (AlClPc) is a second-generation photodynamic therapy (PDT) photosensitizer characterized for its high hydrophobicity and self-aggregation tendency in aqueous media, which hamper its potential application. Aiming at AlClPc solubilization we proposed here the use of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) at different proportions to form mixed lipid vesicles (LVs) as a drug delivery system. LVs were prepared by ethanol injection method and formed nano-sized vesicles (about 100nm) with suitable polydispersity index, negative zeta potential, and stable in aqueous medium for at least 50days. AlClPc strongly interacts with LV (high binding constant values), especially due to aluminum-phosphate specific interactions, which gives a surface localization to AlClPc molecules as demonstrated by fluorescence quenching data. Anisotropy, static and time-resolved fluorescence measurements corroborated with these results and demonstrated that AlClPc self-aggregation occurred even in the liposomes. However, formulation uptake by oral squamous cell carcinoma (OSCC) the AlClPc was distributed in cellular organelles and suffered a disaggregation process demonstrated by fluorescence life-time imaging microscopy. This amazing behavior is new and increases the scientific knowledge about the intracellular mechanism of action of PDT photosensitizers. In addition, these results open a new perspective to the potential use of AlClPc-LV formulations for photodynamic treatment.

The Effect of a Fluorophore Photo-Physics on the Lipid Vesicle Diffusion Coefficient Studied by Fluorescence Correlation Spectroscopy.

Fluorescence Correlation Spectroscopy (FCS) is a technique, which allows determination of the diffusion coefficient and concentration of fluorescent objects suspended in the solution. The measured parameter is the fluctuation of the fluorescence signal emitted by diffusing molecules. When 100 nm DOPC vesicles labeled with various fluorescent dyes (Fluorescein-PE, NBD-PE, Atto488 DOPE or ßBodipy FL) were measured, different values of diffusion coefficients have been obtained. These diffusion coefficients were different from the expected values measured using the dynamic light scattering method (DLS). The FCS was initially developed for solutions containing small fluorescent molecules therefore the observed inconsistency may result from the nature of vesicle suspension itself. The duration of the fluorescence signal may depend on the following factors: the exposure time of the labeled object to the excitation beam, the photo-physical properties (e.g., stability) of a fluorophore, the theoretical model used for the calculations of the diffusion coefficient and optical properties of the vesicle suspension. The diffusion coefficients determined for differently labeled liposomes show that its dependence on vesicle size and quantity of fluorescent probed used for labeling was significant demonstrating that the fluorescence properties of the fluorophore itself (bleaching and/or blinking) were critical factors for a correct outcome of FCS experiment. The new, based on combined FCS and DLS measurements, method for the determination of the focal volume prove itself to be useful for the evaluation of a fluorescence dye with respect to its applicability for FCS experiment.

A Parameterization of Cholesterol for Mixed Lipid Bilayer Simulation within the Amber Lipid14 Force Field.

The Amber Lipid14 force field is expanded to include cholesterol parameters for all-atom cholesterol and lipid bilayer molecular dynamics simulations. The General Amber and Lipid14 force fields are used as a basis for assigning atom types and basic parameters. A new RESP charge derivation for cholesterol is presented, and tail parameters are adapted from Lipid14 alkane tails. 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers are simulated at a range of cholesterol contents. Experimental bilayer structural properties are compared with bilayer simulations and are found to be in good agreement. With this parameterization, another component of complex membranes is available for molecular dynamics with the Amber Lipid14 force field.

Phase separation in lipid bilayer membranes induced by intermixing at a boundary of two phases with different components.

We have demonstrated that dynamic phase separation is induced by coalescence of two self-spreading supported lipid bilayers (SLBs) with different components. Coalescence between a phosphocholine/sphingolipid SLB and a phosphocholine/cholesterol one forms raft-like liquid ordered (Lo) domains, which can be observed by fluorescence microscopy at the boundary of two phases. This phase separation process indicates that lipid molecules, such as sphingolipid and cholesterol, are intermixed. When saturated phospholipid is used instead of sphingolipid, small Lo domains are formed. Cholesterol is harder to incorporate with domains of saturated phospholipid than that of sphingolipid. This technique is very useful for observation of lipid-lipid interactions.

MOF nanoparticles coated by lipid bilayers and their uptake by cancer cells.

We report the synthesis of MOF@lipid nanoparticles as a versatile and powerful novel class of nanocarriers based on metal-organic frameworks (MOFs). We show that the MOF@lipid system can effectively store dye molecules inside the porous scaffold of the MOF while the lipid bilayer prevents their premature release. Efficient uptake of the MOF@lipid nanoparticles by cancer cells makes these nanocarriers promising for drug delivery and diagnostic purposes.

Selective Recognition of Phosphatidylcholine Lipids by a Biomimetic Calix[6]tube Receptor.

Phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) are usually the most abundant phospholipids in membranes. Only a few examples of artificial macrocyclic receptors capable of binding these zwitterionic lipids were reported, and in most cases, their mode of action differs from that of natural receptors. NMR studies show that calix[6]arenes 4-6 behave as heteroditopic receptors that can efficiently bind 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in nonpolar solvents. Similarly to natural systems, the recognition proceeds through the establishment of specific interactions with the zwitterionic head of the lipid. In a protic environment, calix[6]tube 4 binds DOPC much more strongly than 5 and 6, thanks to the higher acidity of its H-bonding thiourea groups and the better preorganization of its binding site. Moreover, 4 is reluctant to the corresponding PE, highlighting a unique selectivity for PCs over PEs. A high selectivity for DOPC over dodecylphosphocholine (DPC) was also observed, and computer modeling studies showed that it may likely originate from the curved shape of the tubular recognition system of 4, which is well-adapted to the native conformation of DOPC. From a biomimetic point of view, the complex 4⊃DOPC shows remarkable similarities with a natural complex formed between a PC and the human phosphatidylcholine transfer protein.

Unusual triskelion patterns and dye-labelled GUVs: consequences of the interaction of cholesterol-containing linear-hyperbranched block copolymers with phospholipids.

Cholesterol (Ch) linked to a linear-hyperbranched block copolymer composed of poly(ethylene glycol) (PEG) and poly(glycerol) (hbPG) was investigated for its membrane anchoring properties. Two polyether-based linear-hyperbranched block copolymers with and without a covalently attached rhodamine fluorescence label (Rho) were employed (Ch-PEG30-b-hbPG23 and Ch-PEG30-b-hbPG17-Rho). Compression isotherms of co-spread 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with the respective polymers were measured on the Langmuir trough and the morphology development of the liquid-condensed (LC) domains was studied by epi-fluorescence microscopy. LC domains were strongly deformed due to the localization of the polymers at the domain interface, indicating a line activity for both block copolymers. Simultaneously, it was observed that the presence of the fluorescence label significantly influences the domain morphology, the rhodamine labelled polymer showing higher line activity. Adsorption isotherms of the polymers to the water surface or to monolayers of DPPC and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), respectively, were collected. Again the rhodamine labelled polymer showed higher surface activity and a higher affinity for insertion into lipid monolayers, which was negligibly affected when the sub-phase was changed to aqueous sodium chloride solution or phosphate buffer. Calorimetric investigations in bulk confirmed the results found using tensiometry. Confocal laser scanning microscopy (CLSM) of giant unilamellar vesicles (GUVs) also confirmed the polymers' fast adsorption to and insertion into phospholipid membranes.

Heterogeneities in Cholesterol-Containing Model Membranes Observed by Pulsed Electron Paramagnetic Resonance of Spin Labels.

Biological membranes are supposed to have heterogeneous structure containing lipid rafts-lateral micro- and nanodomains enriched in cholesterol (chol) and sphingolipids. In this work, lipid bilayers containing a small amount of the spin-labeled chol analogue 3ß-doxyl-5α-cholestane (chlstn) were studied using electron spin echo (ESE) spectroscopy, which is a pulsed version of electron paramagnetic resonance (EPR). Bilayers were prepared from an equimolecular mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with chol added at different concentrations. The ESE decays recorded at 77 K become faster with increase of chlstn concentration. The chlstn-dependent contribution to ESE decay is remarkably nonexponential; however, the logarithm of this contribution can be rescaled for different chlstn concentrations to a universal function with the rescaling factor approximately proportional to concentration. This result shows that the chlstn-dependent contribution to the ESE decay can be employed to estimate the local (at the nanometer scale of distances) chlstn concentration. Analogous rescaling behavior is also observed for the bilayers with different chol concentrations, with the rescaling factor increasing with increase of the chol concentration. This result is evidence that chlstn molecules are distributed heterogeneously in the chol-containing bilayer and form clusters with enhanced chlstn (and probably chol) local concentration. The local concentration of chlstn molecules for large chol content (∼30 mol %) was enhanced by at least ∼70% versus chol-free bilayers. The suggested approach appears to be useful for exploring heterogeneities in lipid composition of biological membranes of different types.

ToF-SIMS observation for evaluating the interaction between amyloid ß and lipid membranes.

The adsorption behaviour of amyloid beta (Aß), thought to be a key peptide for understanding Alzheimer's disease, was investigated by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS). Aß aggregates depending on the lipid membrane condition though it has not been fully understood yet. In this study, Aß samples on different lipid membranes, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), were observed with ToF-SIMS and the complex ToF-SIMS data of the Aß samples was interpreted using data analysis techniques such as principal component analysis (PCA), gentle-SIMS (G-SIMS) and g-ogram. DOPC and DMPC are liquid crystal at room temperature, while DPPC is gel at room temperature. As primary ion beams, Bi3(+) and Ar cluster ion beams were used and the effect of an Ar cluster ion for evaluating biomolecules was also studied. The secondary ion images of the peptide fragment ions indicated by G-SIMS and g-ogram were consistent with the PCA results. It is suggested that Aß is adsorbed homogeneously on the liquid-crystalline-phase lipid membranes, while it aggregates along the lipid on the gel-phase lipid membrane. Moreover, in the results using the Ar cluster, the influence of contamination was reduced.

Equivalent Isopropanol Concentrations of Aromatic Amino Acids Interactions with Lipid Vesicles.

We show that the interaction of aromatic amino acids with lipid bilayers can be characterized by conventional 1D [Formula: see text]H NMR spectroscopy using reference spectra obtained in isopropanol-d8/D[Formula: see text]O solutions. We demonstrate the utility of this method with three different peptides containing tyrosine, tryptophan, or phenylalanine amino acids in the presence of 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphoserine lipid membranes. In each case, we determine an equivalent isopropanol concentration (EIC) for each hydrogen site of aromatic groups, in essence constructing a map of the chemical environment. These EIC maps provide information on relative affinities of aromatic side chains for either PC or PS bilayers and also inform on amino acid orientation preference when bound to membranes.

Analysis of exosome purification methods using a model liposome system and tunable-resistive pulse sensing.

Exosomes are vesicles which have garnered interest due to their diagnostic and therapeutic potential. Isolation of pure yields of exosomes from complex biological fluids whilst preserving their physical characteristics is critical for downstream applications. In this study, we use 100 nm-liposomes from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol as a model system as a model system to assess the effect of exosome isolation protocols on vesicle recovery and size distribution using a single-particle analysis method. We demonstrate that liposome size distribution and ζ-potential are comparable to extracted exosomes, making them an ideal model for comparison studies. Four different purification protocols were evaluated, with liposomes robustly isolated by three of them. Recovered yields varied and liposome size distribution was unaltered during processing, suggesting that these protocols do not induce particle aggregation. This leads us to conclude that the size distribution profile and characteristics of vesicles are stably maintained during processing and purification, suggesting that reports detailing how exosomes derived from tumour cells differ in size to those from normal cells are reporting a real phenomenon. However, we hypothesize that larger particles present in most purified exosome samples represent co-purified contaminating non-exosome debris. These isolation techniques are therefore likely nonspecific and may co-isolate non-exosome material of similar physical properties.

Contribution of temperature to deformation of adsorbed vesicles studied by nanoplasmonic biosensing.

With increasing temperature, biological macromolecules and nanometer-sized aggregates typically undergo complex and poorly understood reconfigurations, especially in the adsorbed state. Herein, we demonstrate the strong potential of using localized surface plasmon resonance (LSPR) sensors to address challenging questions related to this topic. By employing an LSPR-based gold nanodisk array platform, we have studied the adsorption of sub-100-nm diameter 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid vesicles on titanium oxide at two temperatures, 23 and 50 °C. Inside this temperature range, DPPC lipid vesicles undergo the gel-to-fluid phase transition accompanied by membrane area expansion, while DOPC lipid vesicles remain in the fluid-phase state. To interpret the corresponding measurement results, we have derived general equations describing the effect of deformation of adsorbed vesicles on the LSPR signal. At the two temperatures, the shape of adsorbed DPPC lipid vesicles on titanium oxide remains nearly equivalent, while DOPC lipid vesicles become less deformed at higher temperature. Adsorption and rupture of DPPC lipid vesicles on silicon oxide were also studied for comparison. In contrast to the results obtained on titanium oxide, adsorbed vesicles on silicon oxide become more deformed at higher temperature. Collectively, the findings demonstrate that increasing temperature may ultimately promote, hinder, or have negligible effect on the deformation of adsorbed vesicles. The physics behind these observations is discussed, and helps to clarify the interplay of various, often hidden, factors involved in adsorption of biological macromolecules at interfaces.

Hydrolysis of hydrophobic esters in a bicontinuous microemulsion catalysed by lipase†B from Candida antarctica.

Selective enzyme-catalysed biotransformations offer great potential in organic chemistry. However, special requirements are needed to achieve optimum enzyme activity and stability. A bicontinuous microemulsion is proposed as reaction medium because of its large connected interface between oil and water domains at which a lipase can adsorb and convert substrates in the oil phase of the microemulsion. Herein, a microemulsion consisting of buffer-n-octane-nonionic surfactant Ci Ej was used to investigate the key factors that determine hydrolyses of p-nitrophenyl esters catalysed by the lipase B from Candida antarctica (CalB). The highest CalB activity was found around 44 °C in the absence of NaCl and substrates with larger alkyl chains were better hydrolysed than their short-chained homologues. The CalB activity was determined using two different co-surfactants, namely the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and the sugar surfactant decyl ß-D-glucopyranoside (ß-C10 G1 ). The results show the CalB activity as linear function of both enzyme and substrate concentration with an enhanced activity when the sugar surfactant is used as co-surfactant.