ORCID Profile
0000-0001-8343-9657
Current Organisation
Lunds Universitet
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Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2SM06700E
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.COLSURFB.2014.05.019
Abstract: Based on its outstanding antifungal properties, it is reasonable to believe that fengycin might be efficient to topically treat localized dermatomycoses. Since most of the fungi species involved in the formation of those mycotic skin diseases colonize primarily the stratum corneum (SC), studying the interaction between fengycin and SC-mimicking lipid membranes is a primary step to determine the potential of fengycin to overcome the physical barrier of the skin. In this respect, multilamellar lipid vesicles (MLVs), with a lipid composition mimicking that of the SC, were prepared and characterized by differential scanning calorimetry (DSC). The critical micelle concentration (CMC) of fengycin was also assessed under skin conditions and found to be 1.2±0.1μM. The molecular interactions of fengycin with SC-mimicking MLVs were investigated by both DSC and isothermal titration calorimetry (ITC). Results showed that the interactions were considerably affected by changes in lipid phase behaviour. At 40°C and below, fengycin induced exothermic changes in the lipid structures suggesting that less-ordered lipid domains became more-ordered in presence of fengycin. At 60°C, clearly endothermic interaction enthalpies were observed, which could arise from the "melting" of remaining solid domains enriched in high melting lipids that without fengycin melt at higher temperatures.
Publisher: American Chemical Society (ACS)
Date: 03-12-2009
DOI: 10.1021/LA9036327
Abstract: This study shows that DNA (linearized plasmid, 4331 base pairs and salmon sperm, 2000 base pairs, respectively) adsorbs to model membranes of zwitterionic liquid crystalline phospholipid bilayers in solutions containing alent Ca(2+) cations, and also in solutions containing monovalent Na(+). The interaction between DNA and surface-supported model membranes was followed in situ using null ellipsometry, quartz crystal microbalance with dissipation, as well as neutron reflectometry. In the presence of Na(+) (in the absence of multivalent ions), DNA adopts an extended coil conformation upon adsorption. The solvent content in the adsorbed layer is high, and DNA is positioned on top of the membrane. In the presence of alent Ca(2+), the driving force for the adsorption of DNA is electrostatic, and the adsorbed DNA film is not as dilute as in a solution containing Na(+). Cryo-TEM and SANS were further used to investigate the interaction in bulk solution using vesicles as model membrane systems. DNA adsorption could not be identified in the presence of Na(+) using SANS, but cryo-TEM indicates the presence of DNA between neighboring unilamellar vesicles. In the presence of Ca(2+), DNA induces the formation of multilamellar vesicles in which DNA intercalates the lamellae. Possible electrostatic and hydrophobic mechanisms for the adsorption of DNA in solutions containing monovalent salt are discussed and compared to the observations in alent salt.
Publisher: Elsevier BV
Date: 2010
Publisher: American Chemical Society (ACS)
Date: 25-07-2013
DOI: 10.1021/CN400066T
Publisher: Proceedings of the National Academy of Sciences
Date: 13-06-2016
Abstract: Parkinson’s disease is the second most prevalent neurodegenerative disorder and is characterized by the presence in the brains of patients of proteinaceous deposits whose main component is α-synuclein. This protein interacts with membranes as part of its biological function, but this interaction also modulates its kinetics of aggregation. Here, we show that, despite the fact that α-synuclein binds to different types of membranes, it only forms amyloid fibrils in the presence of the most soluble lipids investigated here. This finding is of particular significance because it shows that modifications of the chemical properties of lipids, such as those associated with oxidation and ageing, could be a key determinant of the switch between functional and deleterious interactions between α-synuclein and membranes.
Publisher: American Chemical Society (ACS)
Date: 13-08-2014
DOI: 10.1021/LA5010825
Abstract: Here we show that transport-generated phase separation at the air-liquid interface in systems containing self-assembling hiphilic molecules and polymers can be controlled by the relative humidity (RH) of the air. We also show that our observations can be described quantitatively with a theoretical model describing interfacial phase separation in a water gradient that we published previously. These phenomena arises from the fact that the water chemical potential corresponding to the ambient RH will, in general, not match the water chemical potential in the open aqueous solution. This implies nonequilibrium conditions at the air-water interface, which in turn can have consequences on the molecular organization in this layer. The experimental setup is such that we can control the boundary conditions in RH and thereby verify the predictions from the theoretical model. The polymer-surfactant systems studied here are composed of polyethylenimine (PEI) and hexadecyltrimethylammonium bromide (CTAB) or didecyldimethylammonium bromide (DDAB). Grazing-incidence small-angle X-ray scattering results show that interfacial phases with hexagonal or lamellar structure form at the interface of dilute polymer-surfactant micellar solutions. From spectroscopic ellipsometry data we conclude that variations in RH can be used to control the growth of micrometer-thick interfacial films and that reducing RH leads to thicker films. For the CTAB-PEI system, we compare the phase behavior of the interfacial phase to the equilibrium bulk phase behavior. The interfacial film resembles the bulk phases formed at high surfactant to polymer ratio and reduced water contents, and this can be used to predict the composition of interfacial phase. We also show that convection in the vapor phase strongly reduces film formation, likely due to reduction of the unstirred layer, where diffusive transport is dominating.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4NR05968A
Abstract: The assembly of nucleic acid nanostructures with controlled size and shape has large impact in the fields of nanotechnology, nanomedicine and synthetic biology.
Publisher: American Chemical Society (ACS)
Date: 13-06-2012
DOI: 10.1021/LA204431Q
Abstract: The objective of this work is to establish under which conditions short RNA molecules (similar to miRNA) associate with zwitterionic phospholipids and how this differs from the association with cationic surfactants. We study how the base pairing (i.e., single stranded versus double stranded nucleic acids) and the length of the nucleic acid and the charge of the lipid/surfactant monolayer affect the association behavior. For this purpose, we study the adsorption of nucleic acids to monolayers composed of dipalmitoyl phosphatidylcholine (DPPC) or dioctadecyl-dimethyl-ammoniumbromide (DODAB) using the surface film balance, neutron reflectometry, and fluorescence microscopy. The monolayer studies with the surface film balance suggested that short single-stranded ssRNA associates with liquid expanded zwitterionic phospholipid monolayers, whereas less or no association is detected for double-stranded dsRNA and dsDNA. In order to quantify the interaction and to determine the location of the nucleic acid in the lipid/surfactant monolayer we performed neutron reflectometry measurements. It was shown that ssRNA adsorbs to and penetrates the liquid expanded monolayers, whereas there is no penetration of nucleic acids into the liquid condensed monolayer. No adsorption was detected for dsDNA to zwitterionic monolayers. On the basis of these results, we propose that the association is driven by the hydrophobic interactions between the exposed hydrophobic bases of the ssRNA and the hydrocarbon chains of the phospholipids. The addition of ssRNA also influences domain formation in the DPPC monolayer, leading to fractal-like interconnected domains. The experimental results are discussed in terms of the implication for biological processes and new leads for applications in medicine and biotechnology.
Publisher: Elsevier BV
Date: 04-2010
DOI: 10.1016/J.BBAMEM.2009.12.009
Abstract: The aim of the present study is to establish under which conditions tRNA associates with phospholipid bilayers, and to explore how this interaction influences the lipid bilayer. For this purpose we have studied the association of tRNA or DNA of different sizes and degrees of base pairing with a set of model membrane systems with varying charge densities, composed of zwitterionic phosphatidylcholines (PC) in mixtures with anionic phosphatidylserine (PS) or cationic dioctadecyl-dimethyl-ammoniumbromide (DODAB), and with fluid or solid acyl-chains (oleoyl, myristoyl and palmitoyl). To prove and quantify the attractive interaction between tRNA and model-lipid membrane we used quartz crystal microbalance with dissipation (QCM-D) monitoring to study the tRNA adsorption to deposit phospholipid bilayers from solutions containing monovalent (Na(+)) or alent (Ca(2+)) cations. The influence of the adsorbed polynucleic acids on the lipid phase transitions and lipid segregation was studied by means of differential scanning calorimetry (DSC). The basic findings are: i) tRNA adsorbs to zwitterionic liquid-crystalline and gel-phase phospholipid bilayers. The interaction is weak and reversible, and cannot be explained only on the basis of electrostatic attraction. ii) The adsorbed amount of tRNA is higher for liquid-crystalline bilayers compared to gel-phase bilayers, while the presence of alent cations show no significant effect on the tRNA adsorption. iii) The adsorption of tRNA can lead to segregation in the mixed 1,2-dimyristoyl-sn-glycerol-3-phosphatidylcholine (DMPC)-1,2-dimyristoyl-sn-glycero-3-phosphatidylserine (DMPS) and DMPC-DODAB bilayers, where tRNA is likely excluded from the anionic DMPS-rich domains in the first system, and associated with the cationic DODAB-rich domains in the second system. iv) The addition of shorter polynucleic acids influence the chain melting transition and induce segregation in a mixed DMPC-DMPS system, while larger polynucleic acids do not influence the melting transition in these system. The results in this study on tRNA-phospholipid interactions can have implications for understanding its biological function in, e.g., the cell nuclei, as well as in applications in biotechnology and medicine.
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 2015
No related grants have been discovered for Emma Sparr.