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  • 1.
    Aslund, Ingrid
    et al.
    Lunds universitet.
    Cabaleiro-Lago, Celia
    Lunds universitet.
    Söderman, Olle
    Lunds universitet.
    Topgaard, Daniel
    Lunds universitet.
    Diffusion NMR for determining the homogeneous length-scale in lamellar phases.2008In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 10, p. 2782-2794Article in journal (Refereed)
    Abstract [en]

    The size of the anisotropic domains in a lyotropic liquid crystal is estimated using a new protocol for diffusion NMR. Echo attenuation decays are recorded for different durations of the displacement-encoding gradient pulses, while keeping the effective diffusion time and the range of the wave vectors constant. Deviations between the sets of data appear if there are non-Gaussian diffusion processes occurring on the time-scale defined by the gradient pulse duration and the length-scale defined by the wave vector. The homogeneous length-scale is defined as the minimum length-scale for which the diffusion appears to be Gaussian. Simulations are performed to show that spatial variation of the director orientation in an otherwise homogeneous system is sufficient to induce non-Gaussian diffusion. The method is demonstrated by numerical solutions of the Bloch-Torrey equation and experiments on a range of lamellar liquid crystals with different domain sizes.

  • 2.
    Assarsson, A.
    et al.
    Lund University.
    Nasir, I.
    Lund University.
    Lundqvist, M.
    Lund University.
    Cabaleiro-Lago, Celia
    Lund Univeristy.
    Kinetic and thermodynamic study of the interactions between human carbonic anhydrase variants and polystyrene nanoparticles of different size2016In: RSC Advances, E-ISSN 2046-2069, Vol. 6, no 42, p. 35868-35874Article in journal (Refereed)
    Abstract [en]

    The activity and adsorption of three variants of human carbonic anhydrase (HCA) with similar topology but variation in charge and stability were studied in the presence of carboxyl-modified polystyrene nanoparticles of different sizes ranging from 25 nm to 114 nm. The balance of forces driving the adsorption of carbonic anhydrase variants is affected by the physicochemical properties of the protein and the nanoparticle size. All enzymes are totally inhibited upon adsorption due to the transition towards a molten globule like state that lacks enzymatic activity. The size of the particle affects the adsorption of human carbonic anhydrase I and N-terminal truncated human carbonic anhydrase II. Investigations on pH effects indicate that the size of the particle modulates the lateral interactions at the protein layer for these particular variants whose adsorption is mainly driven by electrostatic forces. A third variant, human carbonic anhydrase II, instead shows no strong influence of nanoparticle size which supports an adsorption process mainly driven by the hydrophobic effect.

  • 3.
    Assarsson, Anna
    et al.
    Lund University.
    Hellstrand, Erik
    Lund University.
    Cabaleiro-Lago, Celia
    Lund University.
    Linse, Sara
    Lund University.
    Charge dependent retardation of amyloid β aggregation by hydrophilic proteins2014In: ACS Chemical Neuroscience, E-ISSN 1948-7193, Vol. 5, no 4, p. 266-74Article in journal (Refereed)
    Abstract [en]

    The aggregation of amyloid β peptides (Aβ) into amyloid fibrils is implicated in the pathology of Alzheimer's disease. In light of the increasing number of proteins reported to retard Aβ fibril formation, we investigated the influence of small hydrophilic model proteins of different charge on Aβ aggregation kinetics and their interaction with Aβ. We followed the amyloid fibril formation of Aβ40 and Aβ42 using thioflavin T fluorescence in the presence of six charge variants of calbindin D9k and single-chain monellin. The formation of fibrils was verified with transmission electron microscopy. We observe retardation of the aggregation process from proteins with net charge +8, +2, -2, and -4, whereas no effect is observed for proteins with net charge of -6 and -8. The single-chain monellin mutant with the highest net charge, scMN+8, has the largest retarding effect on the amyloid fibril formation process, which is noticeably delayed at as low as a 0.01:1 scMN+8 to Aβ40 molar ratio. scMN+8 is also the mutant with the fastest association to Aβ40 as detected by surface plasmon resonance, although all retarding variants of calbindin D9k and single-chain monellin bind to Aβ40.

  • 4.
    Assarsson, Anna
    et al.
    Lund University.
    Linse, Sara
    Lund University.
    Cabaleiro-Lago, Celia
    Lund University.
    Effects of polyamino acids and polyelectrolytes on amyloid β fibril formation2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 29, p. 8812-8Article in journal (Refereed)
    Abstract [en]

    The fibril formation of the neurodegenerative peptide amyloid β (Aβ42) is sensitive to solution conditions, and several proteins and peptides have been found to retard the process. Aβ42 fibril formation was followed with ThT fluorescence in the presence of polyamino acids (poly-glutamic acid, poly-lysine, and poly-threonine) and other polymers (poly(acrylic acid), poly(ethylenimine), and poly(diallyldimethylammonium chloride). An accelerating effect on the Aβ42 aggregation process is observed from all positively charged polymers, while no effect is seen from the negative or neutral polymers. The accelerating effect is dependent on the concentration of positive polymer in a highly reproducible manner. Acceleration is observed from a 1:500 polymer to Aβ42 weight ratio and up. Polyamino acids and the other polymers exert quantitatively the same effect at the same concentrations based on weight. Fibrils are formed in all cases as verified by transmission electron microscopy. The concentrations of polymers required for acceleration are too low to affect the Aβ42 aggregation process through increased ionic strength or molecular crowding effects. Instead, the acceleration seems to arise from the locally increased Aβ42 concentration near the polymers, which favors association and affects the electrostatic environment of the peptide.

  • 5.
    Assarsson, Anna
    et al.
    Lund University.
    Pastoriza-Santos, Isabel
    Spain.
    Cabaleiro-Lago, Celia
    Lund University.
    Inactivation and adsorption of human carbonic anhydrase II by nanoparticles2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 31, p. 9448-56Article in journal (Refereed)
    Abstract [en]

    The enzymatic activity of human carbonic anhydrase II (HCAII) was studied in the presence of nanoparticles of different nature and charge. Negatively charged nanoparticles inhibit HCAII whereas no effect is seen for positively charged particles. The kinetic effects were correlated with the strength of binding of the enzyme to the particle surface as measured by ITC and adsorption assays. Moreover, conformational changes upon adsorption were observed by circular dichroism. The main initial driving force for the adsorption of HCAII to nanoparticles is of electrostatic nature whereas the hydrophobic effect is not strong enough to drive the initial binding. This is corroborated by the fact that HCAII do not adsorb on positively charged hydrophobic polystyrene nanoparticles. Furthermore, the dehydration of the particle and protein surface seems to play an important role in the inactivation of HCAII by carboxyl-modified polystyrene nanoparticles. On the other hand, the inactivation by unmodified polystyrene nanoparticles is mainly driven by intramolecular interactions established between the protein and the nanoparticle surface upon conformational changes in the protein.

  • 6.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    Garcia-Rio, L.
    Spanien.
    Hervella, P.
    Spanien.
    The effect of changing the microstructure of a microemulsion on chemical reactivity2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 19, p. 9586-9595Article in journal (Refereed)
    Abstract [en]

    A kinetic study was carried out on various solvolytic reactions in water/NH4OT/isooctane microemulsions. The NH4OT surfactant is a derivative of the sodium salt of bis(2-ethylhexyl) sulfosuccinate (NaOT or AOT), where the Na+ counterion has been replaced by NH4+. The counterion substitution effects the phase diagram of the system, and therefore, NH4OT-based microemulsions with high water content reaching values of W = 350 (W = [H2O]/[NH4OT]) can be obtained. The presence of high W values suggests a transition in the microemulsion microstructure from water-in-oil (w/o) to oil-in-water (o/w), as was confirmed by conductivity and H-1 NMR self-diffusion measurements. The interpretation of the kinetic studies in terms of pseudophase formalism allows us to analyze the effect of the microemulsion on chemical reactivity, regardless of its microstructure. It has been confirmed that the values of the solvolytic rate constants at the interphase of oil-in-water microemulsions are similar to those obtained for aqueous SDS systems, showing that the hydration degree of the interphase of the oil-in-water microemulsions is independent of W. The influence of the surfactant counterion on the solvolytic rate constants was analyzed by comparing HOT-, NaOT-, and NH4OT-based microemulsions. An important influence on the rate constants caused by the changes in the structural properties of water has been observed as was confirmed by the water H-1 NMR signals.

  • 7.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    Garcia-Rio, L.
    Spanien.
    Herves, P.
    Spanien.
    Mejuto, J. C.
    Spanien.
    Perez-Juste, J.
    Spanien.
    In search of fully uncomplexed cyclodextrin in the presence of micellar aggregates2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 32, p. 15831-15838Article in journal (Refereed)
    Abstract [en]

    The chemical behavior of beta-cyclodextrin/nonionic surfactant mixed systems has been investigated using the basic hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide as a chemical probe. The experimental results prove that at the cmc, there are significant quantities of uncomplexed beta-CD in equilibrium with the micellar aggregates. In contrast to the expected situation, the percentage of uncomplexed beta-CD in equilibrium with the micellar system increases on increasing the hydrophobicity of the surfactant molecule. This behavior is due to the existence of two simultaneous processes: complexation of surfactant monomers by cyclodextrin and the process of self-assembly to form micellar aggregates. The autoaggregation of surfactant monomers is expected to be more important than the complexation process in this mixed system. Varying the hydrophobicity of the surfactant monomer enabled us to determine that the percentages of uncomplexed cyclodextrin in equilibrium with the micellar system were in the range of 5-95%.

  • 8.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    Garcia-Rio, L
    Spanien.
    Herves, P
    Spanien.
    Perez-Juste, J
    Spanien.
    Effects of zwitterionic vesicles on the reactivity of benzoyl chlorides2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 16, p. 8524-8530Article in journal (Refereed)
    Abstract [en]

    A systematic study on the solvolysis reaction of substituted benzoyl chlorides in the presence of zwitterionic vesicles of dipalmitoyl phosphatidylcholine (DPPC) has been performed. Size, shape, surface charge, and polarity of the interface of the vesicular aggregates were determined using various techniques. The application of the pseudophase formalism allowed us to obtain the thermodynamic and kinetic coefficients characteristic of the reaction. The effects of vesicular aggregates on the solvolysis of benzoyl chlorides, which are known to be sensitive to the physical properties of the medium, depend on the nature of the substrate. For benzoyl chlorides with electron-donating groups, which react predominantly through a dissociative mechanism which is strongly affected by medium properties, the rate constant decreases as the vesicle concentration increases. On the other hand, for benzoyl chlorides with electron-withdrawing groups, which react mainly via an associative pathway, DPPC vesicles catalyze the solvolysis reaction.

  • 9.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    Garcia-Rio, L
    Spanien.
    Herves, P
    Spanien.
    Perez-Juste, J
    Spanien.
    Reactivity of benzoyl chlorides in nonionic microemulsions: Potential application as indicators of system properties2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 47, p. 22614-22622Article in journal (Refereed)
    Abstract [en]

    The solvolysis reactivity of benzoyl chlorides entails a high sensitivity on medium properties. A systematic study of the reaction of a series of these substrates, varying the electron-withdrawing character of the substituent, has been performed in nonionic microemulsions. The kinetic effects due to variation of microemulsion compositions can be assigned to modifications in system properties, to be precise, to modifications in interface properties. Microemulsion properties that are obtained from kinetic analysis of solvolysis show a good agreement with the characterization of the microemulsion that was made via H-1 NMR and solvatochromic fluorescence probes. Benzoyl chlorides with electron-donating groups react through a dissociative mechanism, whereas electron-withdrawing groups favor an associative mechanism. A comparative analysis of reactivity between the different substrates at the interface shows a variation in the contributions of both reaction pathways, associative and dissociative, to the whole reaction mechanism. The confined media shift the point where the mechanism changes from an associative to a dissociative pathway, far away from the turning point in water. Furthermore, the change in mechanism can be modulated by modification of the microemulsion composition.

  • 10.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    Garcia-Rio, L.
    Spanien.
    Herves, P.
    Spanien.
    Perez-Juste, J.
    Spanien.
    Spectrophotometric study of metal-ligand reactions in isooctane/Brij30/water nonionic microemulsions2007In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 295, no 1-3, p. 49-54Article in journal (Refereed)
    Abstract [en]

    The complexation between Ni2+ and pyridine-2-azo-p-dimethylaniline (PADA) was studied in isooctane/polyoxyethylenglycol dodecyl ether (Brij30)/water microemulsions at 25 degrees C. The apparent complexation constant depends on microemulsion composition. The proposed model, which takes into account the heterogeneity of the system at the microscopic scale, allows us to determine the distribution constants of both reactants and the complexation constant at the interface. The complex is less stable in microemulsion than in water due to a more efficient hydration of the nickel hexahydrate coordination complex that arises from the interaction between the polar head group of the surfactant and the interfacial water. (c) 2006 Elsevier B.V. All rights reserved.

  • 11.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    Garcia-Rio, Luis
    Spanien.
    Herves, Pablo
    Spanien.
    Mejuto, Juan C.
    Spanien.
    Perez-Juste, Jorge
    Spanien.
    Characterization of alkane diol-CD complexes. Acid denitrosation of N-methyl-N-nitroso-p-toluenesulphonamide as a chemical probe2006In: JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY, ISSN 1388-3127, Vol. 54, no 3-4, p. 209-216Article in journal (Refereed)
    Abstract [en]

    A study was carried out on the acid denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in mixed systems made up of linear (geminal and terminal) alkyl diols and beta-cyclodextrin (CD). The alkyl diols used allowed us to vary the length of the hydrocarbon chain from 2 to 6 carbon atoms. The observed rate constant, k(obs), decreases in the presence of CD. The inhibition profile decreases as the as the number of carbons in the chain is increased. This behaviour can be interpreted as a consequence of a balance between the complexation processes of MNTS and the alkyl diols by the CD. At a constant CD concentration and increase in the diols concentration decreases the concentration of free cyclodextrin available to complex with MNTS molecules and therefore produces an increases in the observed rate constant. The results were interpreted in terms of two different models; trough the presupposition and non-presupposition of a stoichiometry for the CD-diols complex. Both models agreed quite well and allow us to determine the uncomplexed cyclodextrin concentration in each case as well as the stoichiometry of the complexes. The binding constant for both types of alkane diols increase with increasing the number of carbon in the chain. Besides, the binding constant of the alpha,beta-alkane diols is higher than for the analog alpha,beta-alkane diols. One of the main consequences of this study is that the acid denitrosation of MNTS can be use to obtain the stochiometry of the CD-diol complexes and to monitor the free cyclodextrin concentration.

  • 12.
    Cabaleiro-Lago, Celia
    et al.
    Spanien.
    García-Río, L
    Spanien.
    Hervés, P
    Spanien.
    Pérez-Juste, J
    Spanien.
    Fully uncomplexed cyclodextrin in mixed systems of vesicle-cyclodextrin: solvolysis of benzoyl chlorides.2009In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, no 19, p. 6749-6755Article in journal (Refereed)
    Abstract [en]

    In this contribution the influence of beta-cyclodextrin (CD) on the behavior of aqueous systems containing vesicles of dipalmitoyl phosphatidyl choline (DPPC) has been studied by determining the kinetics of the solvolysis reaction of substituted benzoyl chlorides whose solvolysis reactivity entails a high sensitivity on media properties. The application of the pseudophase formalism allowed us to obtain the thermodynamic and kinetic coefficients characteristic of the reaction, which are essentially independent of the concentration of CD. We were able to determine the percentages of uncomplexed cyclodextrin in equilibrium with the vesicular system which were in all cases compatible with 100%. The obtained results led us to conclude that the properties of DPPC vesicles are not affected by the presence of CD in the medium and there is no type of interaction between the CD and the vesicular surfactant monomers and, therefore, all cyclodextrin is present in the mixed system as uncomplexed cyclodextrin.

  • 13.
    Cabaleiro-Lago, Celia
    et al.
    Irland.
    Lynch, I
    Irland.
    Dawson, K A
    Irland.
    Linse, S
    Lunds universitet.
    Inhibition of IAPP and IAPP(20-29) fibrillation by polymeric nanoparticles2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 5, p. 3453-3461Article in journal (Refereed)
    Abstract [en]

    The fibrillation process of the islet amyloid polypeptide (IAPP) and its fragment (IAPP(20-29)) was studied by means of Thioflavin T (ThT) fluorescence and transmission electron microscopy in the absence and presence of N-isopropylacrylamide:N-tert-butylacrylamide (NiPAM:BAM) copolymeric nanoparticles. The process was found to be strongly affected by the presence of the nanoparticles, which retard protein fibrillation as a function of the chemical surface properties of the nanoparticles. The NiPAM:BAM ratio was varied from 50:50 to 100:0. The nanoparticles with higher fraction of NiPAM imposed the strongest retardation of IAPP and IAPP(20-29) fibrillation. These particles have the strongest hydrogen bonding capacity due to the less bulky N-isopropyl group and thus less steric hindrance of the hydrogen-bonding groups of the nanoparticle polymer backbone. Kinetic fibrillation data, as monitored by ThT fluorescence and supported by surface plasmon resonance experiments, suggest that the peptide is strongly absorbed onto the surface of the nanoparticles. This interaction reduces the concentration of peptide free in solution available to proceed to fibrillation which results in an increased lag time of fibrillation, observed as a delayed onset of ThT fluorescence increase, plus a reduction of the amount of fibrils formed as indicated by the equilibrium values at the end of the fibrillation reaction. For the fragment (IAPP(20-29)), the presence of nanoparticles changes the mechanism of association from monomers to fibrils, by interfering with early oligomeric species along the fibrillation pathway.

  • 14.
    Cabaleiro-Lago, Celia
    et al.
    Lunds universitet.
    Nilsson, Markus
    Lunds universitet.
    Soderman, Olle
    Lunds universitet.
    Self-diffusion NMR studies of the host-guest interaction between beta-cyclodextrin and alkyltrimethylammonium bromide surfactants2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 25, p. 11637-11644Article in journal (Refereed)
    Abstract [en]

    Diffusion measurements by nuclear magnetic resonance (NMR) spectroscopy were used to investigate the host-guest association between beta-cyclodextrin (CD) and alkyltrimethylammonium bromide surfactants with different chain lengths, ranging from 6 up to 16 carbons. The scope and limitations of the method in the study of formation of inclusion complexes are discussed. The influences of the presence of CD in the micellization process have been studied, and the apparent critical micellar concentration and the self-diffusion coefficients of the species present in the systems have been calculated. The stoichiometries of the different complexes have been determined. Evidence for the formation of a 2:1 complex in the case Of C(16)TAB has been found.

  • 15.
    Cabaleiro-Lago, Celia
    et al.
    Lunds universitet.
    Nilsson, Markus
    Lunds universitet.
    Valente, Artur J. M.
    Portugal.
    Bonini, Massimo
    Italien.
    Soderman, Olle
    Lunds universitet.
    NMR diffusometry and conductometry study of the host-guest association between beta-cyclodextrin and dodecane 1,12-bis(trimethylammonium bromide)2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 300, no 2, p. 782-787Article in journal (Refereed)
    Abstract [en]

    Surfactants form association complexes with cyclodextrins. In the present investigation we have used NMR-diffusometry and electrical conductivity to follow the interactions which take place between ss-cyclodextrm and a bolaform surfactant: dodecane 1, 1 2-bis(trimethylammonium bromide). Both H-1 NMR self-diffusion and conductometry data indicate the formation of a 1: 1 inclusion complex. Assuming this stoichiometry, it was possible to calculate the association constant; from the analysis of the self-diffusion coefficients of free ss-cyclodextrin and the bolaform surfactant an association constant K = 3 x 10(3) Mb(-1) was obtained while the analysis of conductivity data gave a comparable value of K = 2.5 x 10(3) M-1. (c) 2006 Elsevier Inc. All rights reserved.

  • 16.
    Cabaleiro-Lago, Celia
    et al.
    Irland.
    Quinlan-Pluck, Fiona
    Irland.
    Lynch, Iseult
    Irland.
    Dawson, Kenneth A
    Irland.
    Linse, Sara
    Lund University.
    Dual effect of amino modified polystyrene nanoparticles on amyloid β protein fibrillation2010In: ACS Chemical Neuroscience, E-ISSN 1948-7193, Vol. 1, no 4, p. 279-87Article in journal (Refereed)
    Abstract [en]

    The fibrillation kinetics of the amyloid β peptide is analyzed in presence of cationic polystyrene nanoparticles of different size. The results highlight the importance of the ratio between the peptide and particle concentration. Depending on the specific ratio, the kinetic effects vary from acceleration of the fibrillation process by reducing the lag phase at low particle surface area in solution to inhibition of the fibrillation process at high particle surface area. The kinetic behavior can be explained if we assume a balance between two different pathways: first fibrillation of free monomer in solution and second nucleation and fibrillation promoted at the particle surface. The overall rate of fibrillation will depend on the interplay between these two pathways, and the predominance of one mechanism over the other will be determined by the relative equilibrium and rate constants.

  • 17.
    Cabaleiro-Lago, Celia
    et al.
    Irland.
    Quinlan-Pluck, Fiona
    Irland.
    Lynch, Iseult
    Irland.
    Lindman, Stina
    Lund University.
    Minogue, Aedin M
    Irland.
    Thulin, Eva
    Lund University.
    Walsh, Dominic M
    Irland.
    Dawson, Kenneth A
    Irland.
    Linse, Sara
    Lund University.
    Inhibition of amyloid beta protein fibrillation by polymeric nanoparticles2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 46, p. 15437-43Article in journal (Refereed)
    Abstract [en]

    Copolymeric NiPAM:BAM nanoparticles of varying hydrophobicity were found to retard fibrillation of the Alzheimer's disease-associated amyloid beta protein (Abeta). We found that these nanoparticles affect mainly the nucleation step of Abeta fibrillation. The elongation step is largely unaffected by the particles, and once the Abeta is nucleated, the fibrillation process occurs with the same rate as in the absence of nanoparticles. The extension of the lag phase for fibrillation of Abeta is strongly dependent on both the amount and surface character of the nanoparticles. Surface plasmon resonance studies show that Abeta binds to the nanoparticles and provide rate and equilibrium constants for the interaction. Numerical analysis of the kinetic data for fibrillation suggests that binding of monomeric Abeta and prefibrillar oligomers to the nanoparticles prevents fibrillation. Moreover, we find that fibrillation of Abeta initiated in the absence of nanoparticles can be reversed by addition of nanoparticles up to a particular time point before mature fibrils appear.

  • 18.
    Cabaleiro-Lago, Celia
    et al.
    Lunds universitet.
    Szczepankiewicz, Olga
    Lunds universitet.
    Linse, Sara
    Lunds universitet.
    The effect of nanoparticles on amyloid aggregation depends on the protein stability and intrinsic aggregation rate.2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 3, p. 1852-1857Article in journal (Refereed)
    Abstract [en]

    Nanoparticles interfere with protein amyloid formation. Catalysis of the process may occur due to increased local protein concentration and nucleation on the nanoparticle surface, whereas tight binding or a large particle/protein surface area may lead to inhibition of protein aggregation. Here we show a clear correlation between the intrinsic protein stability and the nanoparticle effect on the aggregation rate. The results were reached for a series of five mutants of single-chain monellin differing in intrinsic stability toward denaturation, for which a correlation between protein stability and aggregation propensity has been previously documented by Szczepankiewicz et al. [Mol. Biosyst.20107 (2), 521-532]. The aggregation process was monitored by thioflavin T fluorescence in the absence and presence of copolymeric nanoparticles with different hydrophobic characters. For mutants with a high intrinsic stability and low intrinsic aggregation rate, we find that amyloid fibril formation is accelerated by nanoparticles. For mutants with a low intrinsic stability and high intrinsic aggregation rate, we find the opposite--a retardation of amyloid fibril formation by nanoparticles. Moreover, both catalytic and inhibitory effects are most pronounced with the least hydrophobic nanoparticles, which have a larger surface accessibility of hydrogen-bonding groups in the polymer backbone.

  • 19.
    Campos-Rey, P
    et al.
    Spanien.
    Cabaleiro-Lago, Celia
    Spanien.
    Hervés, P
    Spanien.
    Promoting mechanistic changes: solvolysis of benzoyl halides in nonionic microemulsions.2009In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, no 35, p. 11921-11927Article in journal (Refereed)
    Abstract [en]

    Solvolysis of benzoyl halides has been studied in nonionic isooctane/Brij30/water microemulsions. The reaction takes place only at the microemulsion interface due to the low solubility of benzoyl halides. The variation of the properties (water content and hydration water nucleophilic character) of the microemulsion interface as the amount of water in the system decreases favors mechanistic changes in the solvolytic reaction. The true rate and equilibrium constants at the interface were obtained by means of the formalism of the pseudophase. Rate constant values at the interface change as the water content of the microemulsion is modified. The changes are consistent with a shift of mechanism from dissociative toward associative. The predominance of either dissociative or associative mechanism is dependent on the characteristics of the leaving group. The associative character decreases as the salient group of the benzoyl halides improves. Moreover, the associative pathway is strongly favored in the microemulsion system studied.

  • 20.
    Campos-Rey, P
    et al.
    Spanien.
    Cabaleiro-Lago, Celia
    Lunds universitet.
    Hervés, P
    Spanien.
    Solvolysis of substituted benzoyl chlorides in nonionic and mixed micellar solutions.2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 44, p. 14004-14011Article in journal (Refereed)
    Abstract [en]

    The solvolysis of substituted benzoyl chlorides is sensitive both to substituent electronic effects and to medium effects. The solvolysis reactions of substituted benzoyl chlorides have been analyzed in the presence of nonionic micelles. The reaction is inhibited or catalyzed depending on the reaction mechanism, dissociative or associative, respectively. The micellar effects observed can be related to the low water content and low polarity of the interface as well as an increase of the nucleophilic character of the interfacial water. Moreover, the effect of the micellar surface charge on the solvolysis mechanism with high associative character was systematically studied. Mixed micelles of nonionic-ionic surfactants with a variable ionic content were prepared and characterized regarding charge and polarity. A correlation between the net charge of the micelles and the rate constants at the micellar interface was observed. The results suggest that the transient state for this mechanism is highly stabilized in a positively charged environment while the negative surface given by anionic micelles strongly inhibit the solvolysis reaction.

  • 21.
    Holm, Sandra
    et al.
    Kristianstad University, Faculty of Education.
    Jönsson Ahlbin, Mimmie
    Kristianstad University, Faculty of Education.
    Naturvetenskap och estetik i förskolan: fysikaliska förändringar och upptäckande av vätskor med barn i förskolan2020Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Det här examensarbetet fokuserar på hur man kan kombinera två innehållsaspekter i undervisning med barn i förskolan. Innehållet som bearbetas är naturvetenskap och estetik. Naturvetenskapsdelen i arbetet innefattar kemiska reaktioner och den estetiska delen innefattar drama. Dramat kommer att användas som ett verktyg för att lära om naturvetenskap med fokus på kemiska reaktioner. Studiens insamlingsmetod innefattar filmning och ljudinspelning. Resultatet i studien visar att barnens perspektiv blir synligt genom att barnen får berätta sina tankar om kemiska vätskor. Studiens resultat visar även att ett intresse har väckts bland barnen kring kemiska vätskor och detta lägger en grund för förskollärare att arbeta vidare med och utgå från barnens intresse.

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    Naturvetenskap och estetik i förskolan - fysikaliska förändringar och upptäckande av vätskor med barn i förskolan
  • 22.
    Linse, Sara
    et al.
    Irland.
    Cabaleiro-Lago, Celia
    Irland.
    Xue, Wei-Feng
    England.
    Lynch, Iseult
    Irland.
    Lindman, Stina
    Lunds universitet.
    Thulin, Eva
    Lunds universitet.
    Radford, Sheena E.
    England.
    Dawson, Kenneth A.
    Irland.
    Nucleation of protein fibrillation by nanoparticles2007In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 104, no 21, p. 8691-8696Article in journal (Refereed)
    Abstract [en]

    Nanoparticles present enormous surface areas and are found to enhance the rate of protein fibrillation by decreasing the lag time for nucleation. Protein fibrillation is involved in many human diseases, including Alzheimer's, Creutzfeld-Jacob disease, and dialysis-related amyloidosis. Fibril formation occurs by nucleation-dependent kinetics, wherein formation of a critical nucleus is the key rate-determining step, after which fibrillation proceeds rapidly. We show that nanoparticles (copolymer particles, cerium oxide particles, quantum dots, and carbon nanotubes) enhance the probability of appearance of a critical nucleus for nucleation of protein fibrils from human beta(2)-microglobulin. The observed shorter lag (nucleation) phase depends on the amount and nature of particle surface. There is an exchange of protein between solution and nanoparticle surface, and beta(2)-Microglobulin forms multiple layers on the particle surface, providing a locally increased protein concentration promoting oligomer formation. This and the shortened lag phase suggest a mechanism involving surf ace-assisted nucleation that may increase the risk for toxic cluster and amyloid formation. It also opens the door to new routes for the controlled self-assembly of proteins and peptides into novel nanomaterials.

  • 23.
    Lundqvist, Martin
    et al.
    Lund University.
    Cabaleiro-Lago, Celia
    Lund University.
    Buffer formulation affects the interaction between lysozyme and polymeric nanoparticles2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 504, p. 78-85Article in journal (Refereed)
    Abstract [en]

    The effect of the buffer formulation in terms of buffer identity and ionic strength on the interaction between chicken egg lysozyme and carboxyl-modified polystyrene nanoparticles has been systematically studied. The time evolution of the fluorescence of a reporter molecule shows that lysozyme interacts with the nanoparticles in all the studied conditions. The interaction results in changes in protein conformation and decrease of the colloidal stability of nanoparticles. In absence of a background salt the rate of adsorption is affected mainly by the ionic strength of the buffer solution, although, specific buffer effects may contribute to a certain extent. The identity of the different buffer components does not significantly alter the dynamics of the process in presence of salt at constant ionic strength. However, an increase of ionic strength leads to slower processes indicating that the adsorption is affected by the presence of increasing number of ions in solution.

  • 24.
    Lynch, Iseult
    et al.
    Irland.
    Cedervall, Tommy
    Irland.
    Lundqvist, Martin
    Irland.
    Cabaleiro-Lago, Celia
    Irland.
    Linse, Sara
    Lunds universitet.
    Dawson, Kenneth A.
    Irland.
    The nanoparticle - protein complex as a biological entity; a complex fluids and surface science challenge for the 21st century2007In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 134-35, p. 167-174Article in journal (Refereed)
    Abstract [en]

    The major aim of our current work is to develop a deep understanding of biological effects of nanoparticles and how these effects are mediated by proteins that are adsorbed on the nanoparticles under different biological circumstances. Due to their small size, nanoparticles have distinct properties compared to the bulk form of the same materials, and these properties are rapidly revolutionizing many areas of medicine and technology. However, relatively little is known about the interaction of nanoscale objects with biological systems, as this requires quite different concepts from more established nanoscience. Thus, we have argued that in a biological fluid, proteins associate with nanoparticles, and it is the amount and presentation of the proteins on the surface rather than the particles themselves that are the cause of numerous biological responses. It is this outer layer of proteins that is seen by the biological cells, and leads to their responses. We are developing novel techniques to identify and quantify the proteins that are consistently associated with nanoparticles, as a function of the nanoparticle size, shape, and surface properties, and to correlate the adsorbed protein identities with their association and dissociation rates to and from the nanoparticles. We also seek to understand the degree of conformational change that they undergo upon adsorption to the nanoparticles. In essence, we wish to create "epitope maps" of the protein corona that surrounds nanoparticles in biological solutions, as it is the particle-protein complex that is the biologically active entity. (c) 2007 Elsevier B.V. All rights reserved.

  • 25.
    Nasir, Irem
    et al.
    Lund University.
    Lundqvist, Martin
    Lund University.
    Cabaleiro-Lago, Celia
    Lund University.
    Size and surface chemistry of nanoparticles lead to a variant behavior in the unfolding dynamics of human carbonic anhydrase2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 41, p. 17504-15Article in journal (Refereed)
    Abstract [en]

    The adsorption induced conformational changes of human carbonic anhydrase I (HCAi) and pseudo wild type human carbonic anhydrase II truncated at the 17th residue at the N-terminus (trHCAii) were studied in presence of nanoparticles of different sizes and polarities. Isothermal titration calorimetry (ITC) studies showed that the binding to apolar surfaces is affected by the nanoparticle size in combination with the inherent protein stability. 8-Anilino-1-naphthalenesulfonic acid (ANS) fluorescence revealed that HCAs adsorb to both hydrophilic and hydrophobic surfaces, however the dynamics of the unfolding at the nanoparticle surfaces drastically vary with the polarity. The size of the nanoparticles has opposite effects depending on the polarity of the nanoparticle surface. The apolar nanoparticles induce seconds timescale structural rearrangements whereas polar nanoparticles induce hours timescale structural rearrangements on the same charged HCA variant. Here, a simple model is proposed where the difference in the timescales of adsorption is correlated with the energy barriers for initial docking and structural rearrangements which are firmly regulated by the surface polarity. Near-UV circular dichorism (CD) further supports that both protein variants undergo structural rearrangements at the nanoparticle surfaces regardless of being "hard" or "soft". However, the conformational changes induced by the apolar surfaces differ for each HCA isoform and diverge from the previously reported effect of silica nanoparticles.

  • 26.
    Nilsson, Markus
    et al.
    Lunds universitet.
    Cabaleiro-Lago, Celia
    Lunds universitet.
    Valente, Artur J. M.
    Portugal.
    Soderman, Olle
    Lunds universitet.
    Interactions between gemini surfactants, 12-s-12, and beta-cyclodextrin as investigated by NMR diffusometry and electric conductometry2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 21, p. 8663-8669Article in journal (Refereed)
    Abstract [en]

    The interaction between beta-cyclodextrin (CD) and gemini surfactant of the type alkyl-alpha,omega-bis(dodecyldimethyl-ammonium bromide) with different spacer lengths of 2, 8, and 10 carbons has been investigated by means of electric conductivity (EC) and proton self-diffusion NMR at 298 K. The formation of a 2: 1 (CD: gemini) complex in a two-step mechanism is observed with the first association constant (K-11) higher than the second one (K-21), but both relatively small in comparison with single C-12-tailed surfactant. The value of the association constants increased with spacer length both for the first and second associated CD, which indicates that the available space on the gemini molecule is important. The magnitudes of the association constant both for the first and second complexation are discussed. The first association constant is small ( when compared with the homologous single-chain surfactant) due to hydrophobic interaction between the hydrocarbon tails within the gemini molecule, while the second association constant shows no cooperativity and its magnitude is discussed in terms of steric constrains.

  • 27. Rispens, T
    et al.
    Cabaleiro-Lago, Celia
    Nederländerna.
    Engberts, J B F N
    Kinetics of hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in binary water-cosolvent mixtures; the role of solvent activity and solute-solute interactions2005In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 3, no 4, p. 597-602Article in journal (Refereed)
    Abstract [en]

    Rate constants are reported for the pH-independent hydrolysis of 4-methoxyphenyl-2,2-dichloroethanoate in aqueous solution as a function of the concentration of added cyanomethane ( acetonitrile), polyethylene glycol ( PEG 400) and tetrahydrofuran ( THF). The concentration of water was varied between ca. 25 and 55.5 M. It was found that the variation in water activity yields only a minor contribution to the observed variation in rate constants. Interestingly, for both cyanomethane and PEG 400 log(k) varies approximately linearly with the molar concentration of water. Medium effects in highly aqueous solutions ( [ H2O] > 50 M) of ethanol, 1-propanol, 2-propanol, 1-butanol and 2-methyl-2-propanol have also been determined. Unexpectedly, in this concentration range the alcohols induce significantly smaller effects per unit volume than cyanomethane. The present results are discussed in terms of pairwise interaction parameters. Isobaric activation parameters have been determined and reveal remarkable differences in the nature of the induced medium effects.

  • 28.
    Sanagavarapu, Kalyani
    et al.
    Lund University.
    Nüske, Elisabeth
    Germany.
    Nasir, Irem
    USA.
    Meisl, Georg
    England.
    Immink, Jasper N
    Lund University.
    Sormanni, Pietro
    England.
    Vendruscolo, Michele
    England.
    Knowles, Tuomas P J
    England.
    Malmendal, Anders
    Lund University.
    Cabaleiro-Lago, Celia
    Kristianstad University, Faculty of Natural Science, Avdelningen för miljö- och biovetenskap. Kristianstad University, Faculty of Natural Science, Research environment Man & Biosphere Health (MABH). Lund University.
    Linse, Sara
    Lund University.
    A method of predicting the in vitro fibril formation propensity of Aβ40 mutants based on their inclusion body levels in E. coli2019In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, no 1Article in journal (Refereed)
    Abstract [en]

    Overexpression of recombinant proteins in bacteria may lead to their aggregation and deposition in inclusion bodies. Since the conformational properties of proteins in inclusion bodies exhibit many of the characteristics typical of amyloid fibrils. Based on these findings, we hypothesize that the rate at which proteins form amyloid fibrils may be predicted from their propensity to form inclusion bodies. To establish a method based on this concept, we first measured by SDS-PAGE and confocal microscopy the level of inclusion bodies in E. coli cells overexpressing the 40-residue amyloid-beta peptide, Aβ40, wild-type and 24 charge mutants. We then compared these results with a number of existing computational aggregation propensity predictors as well as the rates of aggregation measured in vitro for selected mutants. Our results show a strong correlation between the level of inclusion body formation and aggregation propensity, thus demonstrating the power of this approach and its value in identifying factors modulating aggregation kinetics.

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