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  • 1.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Eriksson, Emma K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Ubiquinone-10 alters mechanical properties and increases stability of phospholipid membranes2015In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1848, no 10, p. 2233-2243Article in journal (Refereed)
    Abstract [en]

    Abstract Ubiquinone-10 is mostly known for its role as an electron and proton carrier in aerobic cellular respiration and its function as a powerful antioxidant. Accumulating evidence suggest, however, that this well studied membrane component could have several other important functions in living cells. The current study reports on a previously undocumented ability of ubiquinone-10 to modulate the mechanical strength and permeability of lipid membranes. Investigations of DPH fluorescence anisotropy, spontaneous and surfactant induced leakage of carboxyfluorescein, and interactions with hydrophobic and hydrophilic surfaces were used to probe the effects caused by inclusion of ubiquinone-10 in the membrane of phospholipid liposomes. The results show that ubiquinone in concentrations as low as 2 mol.% increases the lipid packing order and condenses the membrane. The altered physicochemical properties result in a slower rate of release of hydrophilic components, and render the membrane more resistant towards rupture. As judged from comparative experiments using the polyisoprenoid alcohol solanesol, the quinone moiety is essential for the membrane stabilizing effects to occur. Our findings imply that the influence of ubiquinone-10 on the permeability and mechanical properties of phospholipid membranes is similar to that of cholesterol. The reported data indicate, however, that the molecular mechanisms are different in the two cases.

  • 2.
    Agmo Hernandez, Victor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hermes, Michael
    Milchev, Alexander
    Scholz, Fritz
    The overall adhesion-spreading process of liposomes on a mercury electrode is controlled by a mixed diffusion and reaction kinetics mechanism2009In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, no 4, p. 639-649Article in journal (Refereed)
    Abstract [en]

    Using high-resolution chronoamperometric measurements, with sampling each 1.333 micro s, the initial step of the adhesion-spreading of liposomes on a mercury electrode was studied. These measurements allow getting a deeper insight into the first interaction of the liposomes with the mercury electrode, and they show that the overall adhesion-spreading process at different potentials is partially controlled by a fast but weak interaction equilibrium resulting in a mixed diffusion- and reaction-kinetics-controlled mechanism of the overall reaction.

  • 3.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Intrinsic Heterogeneity in Liposome Suspensions Caused by the Dynamic Spontaneous Formation of Hydrophobic Active Sites in Lipid Membranes2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, p. 4873-4883Article in journal (Refereed)
    Abstract [en]

    The spontaneous, dynamic formation of hydrophobic active sites in lipid bilayer membranes is studied and characterized. It is shown that the rates of formation and consumption of these active sites control at least two important properties of liposomes: their affinity for hydrophobic surfaces and the rate by which they spontaneously release encapsulated molecules. The adhesion and spreading of liposomes onto hydrophobic polystyrene nanoparticles and the spontaneous leakage of an encapsulated fluorescent dye were monitored for different liposome compositions employing Cryo-TEM, DLS, and fluorescence measurements. It was observed that an apparently homogeneous, monodisperse liposome suspension behaves as if composed by two different populations: a fast leaking population that presents affinity for the hydrophobic substrate employed, and a slow leaking population that does not attach immediately to it. The results reported here suggest that the proportion of liposomes in each population changes over time until a dynamic equilibrium is reached. It is shown that this phenomenom can lead to irreproducibility in, for example, spontaneous leakage experiments, as extruded liposomes leak much faster just after preparation than 24 h afterward. Our findings account for discrepancies in several experimental results reported in the literature. To our knowledge, this is the first systematic study addressing the issue of an existing intrinsic heterogeneity of liposome suspensions.

  • 4.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lendeckel, Uwe
    Institut für Medizinische Biochemie und Molekularbiologie, Universitätsmedizin Greifswald, Germany.
    Scholz, Fritz
    Institut für Biochemie, Universität Greifswald, Germany.
    Electrochemistry of Adhesion and Spreading of Lipid Vesicles on Electrodes2013In: Applications of Electrochemistry in Medicine / [ed] Schlesinger, Mordechay, Springer US , 2013, Vol. 56, p. 189-247Chapter in book (Other academic)
    Abstract [en]

    Biological membranes have developed to separate different compartments of organisms and cells. There is a large number of rather different functions which membranes have to fulfil: (1) they control the material and energy fluxes of metabolic processes, (2) they provide a wrapping protecting the compartments from chemical and physical attacks of the environment, (3) they provide interfaces at which specific biochemical machineries can operate (e.g., membrane bound enzymes), (4) they are equipped for signal transduction, (5) they possess the necessary stability and flexibility to allow cell division, and endo- and exocytosis as well as migration, (6) they present anchoring structures that enable cell-to-cell and cell-to-matrix physical interactions and intercellular communication. These are certainly not all functions of membranes as new functionalities are continuously reported. Since the biological membranes separate essentially aqueous solutions, such separating borders—if they should possess a reasonable stability and also flexibility combined with selective permeability—have to be built up of hydrophobic molecules exposing to both sides a similar interface. It was one of the most crucial and most lucky circumstances for the development and existence of life that certain amphiphilic molecules are able to assemble in bilayer structures (membranes), which—on one side—possess a rather high physical and chemical stability, and—on the other side—are able to incorporate foreign molecules for modifying both the physical properties as well as the permeability of the membranes for defined chemical species. The importance of the chemical function of membranes and all its constituents, e.g., ion channels, pore peptides, transport peptides, etc., is generally accepted. The fluid-mosaic model proposed by Singer and Nicolson [1] is still the basis to understand the biological, chemical, and physical properties of biological membranes. The importance of the purely mechanical properties of membranes came much later into the focus of research. The reasons are probably the dominance of biochemical thinking and biochemical models among biologists and medical researchers, as well as a certain lack of appropriate methods to probe mechanical properties of membranes. The last decades have changed that situation due to the development of techniques like the Atomic Force Microscopy, Fluorescence Microscopy, Micropipette Aspiration, Raman Microspectroscopy, advanced Calorimetry, etc. This chapter is aimed at elucidating how the properties of membranes can be investigated by studying the interaction of vesicles with a very hydrophobic surface, i.e., with the surface of a mercury electrode. This interaction is unique as it results in a complete disintegration of the bilayer membrane of the vesicles and the formation of an island of adsorbed lipid molecules, i.e., a monolayer island. This process can be followed by current-time measurements (chronoamperometry), which allow studying the complete disintegration process in all its details: the different steps of that disintegration can be resolved on the time scale and the activation parameters can be determined. Most interestingly, the kinetics of vesicle disintegration on mercury share important features with the process of vesicle fusion and, thus, sheds light also on mechanisms of endocytosis and exocytosis. Most importantly, not only artificial vesicles (liposomes) can be studied with this approach, but also reconstituted plasma membrane vesicles and even intact mitochondria. Hence, one can expect that the method may provide in future studies also information on the membrane properties of various other vesicles, including exosomes, and may allow investigating various aspects of drug action in relation to membrane properties (transmembrane transport, tissue targeting, bioavailability, etc.), and also the impact of pathophysiological conditions (e.g., oxidative modification) on membrane properties, on a hitherto not or only hardly accessible level.

  • 5.
    Agmo Hernandez, Victor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Milchev, Alexander
    Scholz, Fritz
    Study of the temporal distribution of the adhesion-spreading events of liposomes on a mercury electrode2009In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, no 7, p. 1111-1114Article in journal (Refereed)
    Abstract [en]

    The formal analysis of the mechanism of adhesion spreading of liposomes at mercury electrodes shares several characteristics with the mechanism of metal nucleation at electrodes. It is shown that the description of the temporal distribution of the adhesion-spreading events is similar to that of the temporal distribution of metal clusters. Both processes are stochastic in nature and can be described by the Poisson distribution. Using this approach, a previously proposed model for the overall adhesion-spreading mechanism, considering the formation of active sites on the liposome and the actual attachment of the liposomes to the mercury surface, is validated.

  • 6.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Reijmar, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Label-Free Characterization of Peptide-Lipid Interactions Using Immobilized Lipodisks2013In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 85, no 15, p. 7377-7384Article in journal (Refereed)
    Abstract [en]

    Lipodisks, planar lipid bilayer structures stabilized by PEG-ylated lipids, were in the present study covalently bound and immobilized onto sensors for quartz crystal microbalance with dissipation monitoring (QCM-D) studies. It is shown that the modified sensors can be used to characterize the interaction of lipodisks with α-helical amphiphilic peptides with an accuracy similar to that obtained with well established fluorimetric approximations. The method presented has the great advantage that it can be used with peptides in their native form even if no fluorescent residues are present. The potential of the method is illustrated by determining the parameters describing the association of melittin, mastoparan X, and mastoparan with immobilized lipodisks. Both thermodynamic and kinetic analyses are possible. The presented method constitutes a useful tool for fundamental studies of peptide–membrane interactions and can also be applied to optimize the design of lipodisks, for example, for sustained release of antimicrobial peptides in therapeutic applications.

  • 7.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Samuelsson, Jörgen
    Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Forssén, Patrik
    Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Enhanced interpretation of adsorption data generated by liquid chromatography and by modern biosensors2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1317, no SI, p. 22-31Article in journal (Refereed)
    Abstract [en]

    In this study we demonstrate the importance of proper data processing in adsorption isotherm estimations. This was done by investigating and reprocessing data from five cases on two closely related platforms: liquid chromatography (LC) and biosensors. The previously acquired adsorption data were reevaluated and reprocessed using a three-step numerical procedure: (i) preprocessing of adsorption data, (ii) adsorption data analysis and (iii) final rival model fit. For each case, we will discuss what we really measure and what additional information can be obtained by numerical processing of the data. These cases clearly demonstrate that numerical processing of LC and biosensor data can be used to gain deeper understanding of molecular interactions with adsorption media. This is important because adsorption data, especially from biosensors, is often processed using old and simplified methods.

  • 8.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    The theory of metal electronucleation applied to the study of fundamental properties of liposomes2013In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 17, no 2 (SI), p. 299-305Article, review/survey (Refereed)
    Abstract [en]

    This short review describes how the theory of electrochemical metal nucleation considering non-stationary effects due to the activation of latent nucleation sites has been successfully translated and applied to describe phenomena observed on lipid membranes. This rather unexpected connection is merely formal, but has resulted in a completely new approach in liposome research. It has been proposed that hydrophobic active sites spontaneously and constantly appear and disappear on lipid membranes. These sites control the affinity of liposomes for hydrophobic surfaces and determine the permeability of the lipid membrane to small hydrophilic molecules. Thus, the kinetic models for liposome adhesion on hydrophobic substrates and for the spontaneous leakage of liposomal content are identical to that of non-stationary nucleation mentioned above. Therefore, the broad scope of the available work on metal nucleation has facilitated the interpretation of the data obtained in liposome research. Future applications of the nucleation model in the realm of liposomes are also discussed.

  • 9.
    Agmo Hernández, Víctor
    et al.
    Institut für Biochemie, Universität Greifswald.
    Scholz, Fritz
    The electrochemistry of liposomes2008In: Israel Journal of Chemistry, ISSN 0021-2148, Vol. 48, p. 169-184Article, book review (Refereed)
  • 10.
    Agmo Hernández, Víctor
    et al.
    Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany.
    Scholz, Fritz
    Universität Greifswald .
    The lipid composition determines the kinetics of adhesion and spreading of liposomes on mercury electrodes2008In: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 74, no 1, p. 149-156Article in journal (Refereed)
    Abstract [en]

    The dependence of membrane properties on their composition was studied by following the adhesion and spreading of unilamellar and multilamellar liposomes on static mercury electrodes with the help of chronoamperometry. The analysis of the peak-shaped signals allows determining the kinetic parameters of the three-step adhesion-spreading process. The presence of cholesterol in the membrane stabilizes the bilayer in the liquid-crystal line phase, and destabilizes the gel phase. The kinetic parameters also show the effect of superlattice formation in the DMPC-cholesterol system. The detergent triton X-100 is only incorporated in the liquid-crystalline DMPC membranes, and it is expelled to the solution when the membrane is transformed to the gel phase. In the liquid-crystalline membrane, it enhances the adhesion-spreading of liposomes on mercury. The lyric peptides mastoparan X and melittin affect the adhesion-spreading in a similar manner. For the rupture-spreading step, their effect is explained by pore formation. The results obtained with lecithins of different length suggest that the bilayer opening process has much in common with flip-flop translocations. For this process the activation energies were found to be independent of the chain length of the lecithin molecules, while the preexponential factor in the Arthenius equation decreases drastically for longer chains.

  • 11.
    Duong-Thi, Minh-Dao
    et al.
    Linnaeus University, Department of Chemistry and Biomedical Sciences, SE-39182 Kalmar, Sweden.
    Bergström, Maria
    Linnaeus University, Department of Chemistry and Biomedical Sciences, SE-39182 Kalmar, Sweden.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Eriksson, Jonny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Ohlson, Sten
    Nanyang Technological University, School of Biological Sciences, Singapore 637551, Republic of Singapore.
    To Yiu Ying, Janet
    Nanyang Technological University, School of Biological Sciences, Singapore 637551, Republic of Singapore.
    Torres, Jaume
    Nanyang Technological University, School of Biological Sciences, Singapore 637551, Republic of Singapore.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lipodisks integrated with weak affinity chromatography enable fragment screening of integral membrane proteins2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 3, p. 981-988Article in journal (Refereed)
    Abstract [en]

    Membrane proteins constitute the largest class of drug targets but they present many challenges in drug discovery. Importantly, the discovery of potential drug candidates is hampered by the limited availability of efficient methods for screening drug-protein interactions. In this work we present a novel strategy for rapid identification of molecules capable of binding to a selected membrane protein. An integral membrane protein (human aquaporin-1) was incorporated into planar lipid bilayer disks (lipodisks), which were subsequently covalently coupled to porous derivatized silica and packed into HPLC columns. The obtained affinity columns were used in a typical protocol for fragment screening by weak affinity chromatography (WAC), in which one hit was identified out of a 200 compound collection. The lipodisk-based strategy, which ensures a stable and native-like lipid environment for the protein, is expected to work also with other membrane proteins and screening procedures.

  • 12.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Bartsch, Maik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Bergström Lind, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    On-target titanium dioxide-based enrichment for characterization of phosphorylations in the Adenovirus pIIIa protein2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1317, no SI, p. 105-109Article in journal (Refereed)
    Abstract [en]

    A recently developed titanium dioxide (TiO2) based on-target method for phosphopeptide enrichment and matrix assisted laser desorption-ionization mass spectrometry (MALDI MS) analysis was used to investigate phosphorylations in the Adenovirus type 2 structural protein pIIIa. Lysates of purified virus particles were separated on 1-D SDS-PAGE and the band for the pIIIa protein was excised for tryptic digestion into peptides that were enriched with the on-target method. The enrichment provided by the method clearly improved the detectability of phosphorylated peptides and the results show for the first time evidence for multi-phosphorylated peptides in pIIIa. Moreover, three novel phosphorylations were identified in the protein sequence, even though the precise positions could not be determined. These results illustrate the potential of the method for the characterization of novel phosphoproteomes in biological samples of medical relevance.

  • 13.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Malmström, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Optimized Protocol for On-Target Phosphopeptide Enrichment Prior to Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry Using Mesoporous Titanium Dioxide2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 11, p. 4577-4583Article in journal (Refereed)
    Abstract [en]

    A novel on-target phosphopeptide enrichment method is presented that allows specific enrichment and direct analysis by matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS) of phosphorylated peptides. Spots consisting of a thin film of anatase titanium dioxide are sintered onto a conductive glass surface. Enrichment and analysis can be performed on the modified target with minimal sample handling. The protocol leads to an enrichment efficiency that is superior to what has been reported before for similar methods. The method was tested using beta-casein as a model phosphorylated protein as well as with a custom peptide mixed with its phosphorylated form. A very low detection limit, a significantly improved phosphoprofiling capability, and a simple experimental approach provide a powerful tool for the enrichment, detection, and analysis of phosphopeptides.

  • 14.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Malmström, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Hernandez, Victor Agmo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Mesoporous TiO2-Based Experimental Layout for On-Target Enrichment and Separation of Multi- and Monophosphorylated Peptides Prior to Analysis with Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 3, p. 761-766Article in journal (Refereed)
    Abstract [en]

    A simple method for on-target enrichment and subsequent separation and analysis of phosphorylated peptides is presented. The tryptic digest of a phosphorylated protein, in this case beta-casein, is loaded onto a spot on a thin stripe made of mesoporous TiO2 sintered onto a conductive glass surface. After washing with a salicylic buffer in order to remove the nonphosphorylated peptides, the stripe is placed in an elution chamber containing a phosphate solution. In a way analogous to thin layer chromatography (TLC), the phosphate solution acts as an eluent, clearly separating multi- and monophosphorylated peptides. By performing matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS) along the stripe, the detection of all phosphorylated peptides present in the digest is facilitated, as they are isolated from each other. The method was also tested on commercial drinking milk, achieving successful separation between multi- and monophosphorylated peptides, as well as a detection limit in the femtomole range. As the enrichment, separation, and analysis take place in the same substrate, sample handling and risk of contamination and sample loss is minimized. The results obtained suggest that the method, once optimized, may successfully provide a complete phosphoproteome.

  • 15.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Cooperative adsorption behavior of phosphopeptides on TiO2 leads to biased enrichment, detection and quantification2015In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, no 1, p. 303-312Article in journal (Refereed)
    Abstract [en]

    The adsorption behavior of phosphopeptides onto TiO2 surfaces was studied using the quartz crystal microbalance with dissipation monitoring (QCM-D) as the main experimental technique. The main focus is the characterization of the emergence of positive cooperativity under conditions where the peptides have a positively charged C-term. It is shown that when carrying no net charge, small water-soluble peptides as a rule develop positive cooperativity. The impact of the adsorption mechanism on the outcome of TiO2 based enrichment methods was investigated with the help of matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS). The data presented illustrate how the phosphopeptide profile in the enriched material may deviate from that in the native sample, as cooperative phosphopeptides are overrepresented in the former. Furthermore, commonly employed washing and elution solutions may facilitate preferential release of certain peptides, leading to further bias in the recovered sample. Taken together, the results of the present study demonstrate that thorough understanding of the mechanisms behind the adsorption of phosphopeptides on the enrichment material is necessary in order to develop reliable qualitative and quantitative methods for phosphoproteomics.

  • 16.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Physicochemical Characterization of Phosphopeptide/Titanium Dioxide Interactions Employing the Quartz Crystal Microbalance Technique2013In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 7, p. 2019-2025Article in journal (Refereed)
    Abstract [en]

    The rapidly growing field of phosphoproteomics has led to a strong demand for procedures enabling fast and reliable isolation and enrichment of phosphorylated proteins and peptides. During the past decade, several novel phosphopeptide enrichment methods based on the affinity of phosphoryl groups for titanium dioxide (TiO2) have been developed and tested. The ultimate goal of obtaining comprehensive phosphoproteomes has, however, been found difficult to achieve and the obtained results often vary, dependent on the enrichment method and protocol used. In the present study, the physical chemistry of the phosphopeptide binding to TiO2 is investigated by means of measurements using a quartz crystal microbalance with dissipation monitoring (QCM-D). Special emphasis is put on the effect of the degree of phosphorylation of the phosphopeptide, the impact of the primary amino acid structure, and the role of electrostatic interactions. The results show that, in general, adsorption of phosphopeptides follows the Langmuir model and that the affinity for the TiO2 surface increases in a nonlinear fashion with increasing degree of phosphorylation. An exception was detected, however, where positive cooperativity between the peptides existed and the Langmuir model no longer applied. The source behind the cooperativity could be traced back to the primary amino acid structure and, more specifically, the presence of positively charged amino acids in positions that enable electrostatic interaction with phosphoryl groups on neighboring peptides. Regardless of the net peptide charge, the TiO2–phosphopeptide interaction was for all phosphopeptides investigated found to be mainly of electrostatic origin. This study highlights and explains some of the most common problems with the TiO2-based enrichment methods used today.

  • 17.
    Eriksson, Emma K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Agmo Hernandez, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Effect of ubiquinone-10 on the stability of biomimetic membranes of relevance for the inner mitochondrial membrane.2018In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1860, no 5, p. 1205-1215Article in journal (Refereed)
    Abstract [en]

    Ubiquinone-10 (Q10) plays a pivotal role as electron-carrier in the mitochondrial respiratory chain, and is also well known for its powerful antioxidant properties. Recent findings suggest moreover that Q10 could have an important membrane stabilizing function. In line with this, we showed in a previous study that Q10 decreases the permeability to carboxyfluorescein (CF) and increases the mechanical strength of 1-palmitoyl-2-oleyl-sn-glycero-phosphocholine (POPC) membranes. In the current study we report on the effects exerted by Q10 in membranes having a more complex lipid composition designed to mimic that of the inner mitochondrial membrane (IMM). Results from DPH fluorescence anisotropy and permeability measurements, as well as investigations probing the interaction of liposomes with silica surfaces, corroborate a membrane stabilizing effect of Q10 also in the IMM-mimicking membranes. Comparative investigations examining the effect of Q10 and the polyisoprenoid alcohol solanesol on the IMM model and on membranes composed of individual IMM components suggest, moreover, that Q10 improves the membrane barrier properties via different mechanisms depending on the lipid composition of the membrane. Thus, whereas Q10's inhibitory effect on CF release from pure POPC membranes appears to be directly and solely related to Q10's lipid ordering and condensing effect, a mechanism linked to Q10's ability to amplify intrinsic curvature elastic stress dominates in case of membranes containing high proportions of palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE).

  • 18.
    Eriksson, Emma K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Grad, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Gedda, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Agmo Hernandez, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Osmoprotective effect of ubiquinone in lipid vesicles modelling the E. coli plasma membrane2019In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, no 7, p. 1388-1396Article in journal (Refereed)
  • 19.
    Hellberg, D
    et al.
    Universität Greifswald.
    Scholz, Fritz
    Universität Greifswald.
    Schubert, F
    Lovric, M
    Omanovic, D
    Agmo Hernandez, Victor
    Thede, R
    Kinetics of liposome adhesion on a mercury electrode2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, p. 14715-14726Article in journal (Refereed)
    Abstract [en]

    The adhesion of liposomes on a mercury electrode leads to capacitive signals due to the formation of islands of lecithin monolayers. Integration of the current-time transients gives charge-time transients that can be fitted by the empirical equation Q(t) = Q(0) + Q(1)(1 - exp(-t/tau(1))) + Q(2)(1 - exp(-t/tau(2))), where the first term on the right side is caused by the docking of the liposome on the mercury surface, the second term is caused by the opening of the liposome, and the third term is caused by the spreading of the lecithin island on the mercury surface. The temperature dependence of the two time constants tau(1) and tau(2) and the temperature dependence of the overall adhesion rate allow determination of the activation energies of the opening, the spreading, and the overall adhesion process both for gel-phase 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and for liquid-crystalline-phase DMPC liposomes. In all cases, the spreading is the rate-determining process. Negative apparent activation energies for the spreading and overall adhesion process of liquid-crystalline-phase DMPC liposomes can be explained by taking into account the weak adsorption equilibria of the intact liposomes and the opened but not yet spread liposomes. A formal kinetic analysis of the reaction scheme supports the empirical equation used for fitting the charge-time transients. The developed kinetic model of liposome adhesion on mercury is similar to kinetic models published earlier to describe the fusion of liposomes. The new approach can be used to probe the stability of liposome membranes.

  • 20.
    Hernandez, Victor Agmo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Intrinsic Heterogeneity in Liposome Suspensions Caused by the Dynamic Spontaneous Formation of Hydrophobic Active Sites in Lipid Membranes2012Conference paper (Refereed)
  • 21. Hernandez, Victor Agmo
    et al.
    Niessen, Juliane
    Harnisch, Falk
    Block, Stephan
    Greinacher, Andreas
    Kroemer, Heyo K.
    Helm, Christiane A.
    Scholz, Fritz
    The adhesion and spreading of thrombocyte vesicles on electrode surfaces2008In: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 74, p. 210-216Article in journal (Refereed)
    Abstract [en]

    The interaction of thrombocyte vesicles with the surface of metal electrodes, i.e., mercury, gold and gold electrodes modified with self assembled monolayers (SAM), was studied with the help of chronoamperometry, atomic force microscopy, and quartz crystal microbalance measurements. The experimental results show that the interaction of the thrombocyte vesicles with the surface of the electrodes depends on the hydrophobicity of the latter: whereas on very hydrophobic surfaces (mercury and gold functionalized with SAM) the thrombocyte vesicles disintegrate and form a monolayer of lipids. on the less hydrophobic gold surface a bilayer is formed. The chronoamperometric measurements indicate the possibility of future applications to probe membrane properties of thrombocytes. (C) 2008 Elsevier B.V. All rights reserved.

  • 22. Hernandez, Victor Agmo
    et al.
    Scholz, Fritz
    Kinetics of the adhesion of DMPC liposomes on a mercury electrode. Effect of lamellarity, phase composition, size and curvature of liposomes, and presence of the pore forming peptide Mastoparan X2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, p. 10723-10731Article in journal (Refereed)
    Abstract [en]

    Liposomes suspended in aqueous electrolyte solutions can adhere at mercury electrodes. The adhesion is a complex process that starts with the docking and opening and leads to a spreading, finally resulting in the formation of islands of adsorbed lecithin molecules. The adhesion process can be followed by chronoamperometry, and a detailed analysis of the macroscopic and microscopic kinetics can be performed yielding rate constants and activation parameters. By using giant unilamellar liposomes and multilamellar liposomes, the effect of lamellarity and liposome size could be elucidated for liposomes in the liquid crystalline, gel, and superlattice phase states. Below the phase transition temperature, the time constant of opening of the liposomes (i.e., the irreversible binding of the lecithin molecules on the preliminary contact interface liposome vertical bar mercury and the therewith associated disintegration of the liposome membrane on that spot) is shown to be strongly size dependent. The activation energy, however, of that process is size independent with the exception of very small liposomes. That size dependence of time constants is a result of the size dependence of the initial contact area. The time constant and the activation energies of the spreading step exhibit a strong size dependence, which could be shown to be due to the size dependence of rate and activation energy of pore formation. Pore formation is necessary to release the solution included in the liposomes. This understanding was corroborated by addition of the pore inducing peptide Mastoparan X to the liposome suspension. The obtained results show that electrochemical studies of liposome adhesion on mercury electrodes can be used as a biomimetic tool to understand the effect of membrane properties on vesicle fusion.

  • 23. Hernandez, Victor Agmo
    et al.
    Scholz, Fritz
    One redox probe (dmfc) can drive the transfer of anions and cations across the aqueous electrolyte ionic liquid interface2006In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 8, p. 967-972Article in journal (Refereed)
    Abstract [en]

    Three-phase electrodes consisting of droplets of 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate containing decamethylferrocenium (dmfc(+)) cations, immobilized on the surface of graphite electrodes and immersed in aqueous electrolyte solutions have been employed to study the redox driven transfer of anions and cations. Very surprisingly, it has been observed that anions as well as cations can be transferred with one redox probe (dmfc/dmfc(+)) because the Gibbs energies of ion transfer of the different ions are rather similar. (C) 2006 Elsevier B.V. All rights reserved.

  • 24. Hernandez, Victor Agmo
    et al.
    Scholz, Fritz
    Reply to the comment on kinetics of the adhesion of DMPC liposomes on a mercury electrode. Effect of lamellarity, phase composition, size and curvature of liposomes, and presence of the pore forming peptide mastoparan X2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23Article in journal (Refereed)
  • 25. Lundsten, S.
    et al.
    Spiegelberg, D.
    Agmo Hernandez, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Brown, C.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lane, D.
    Nestor, M.
    Radioiodination Of Small Stapled Peptides For p53 Therapy2017Conference paper (Refereed)
  • 26.
    Meiby, Elinor
    et al.
    Department of Chemistry and Biomedical Sciences, Linnaeus University, Kalmar.
    Morin Zetterberg, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Ohlson, Sten
    Department of Chemistry and Biomedical Sciences, Linnaeus University, Kalmar Sweden AND School of Biological Sciences, Nanyang Technological University, Singapore.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Immobilized lipodisks as model membranes in high-throughput HPLC-MS analysis2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 14, p. 4859-4869Article in journal (Refereed)
    Abstract [en]

    Lipodisks, also referred to as polyethylene glycol (PEG)-stabilized bilayer disks, have previously been demonstrated to hold great potential as model membranes in drug partition studies. In this study, an HPLC-MS system with stably immobilized lipodisks is presented. Functionalized lipodisks were immobilized on two different HPLC support materials either covalently by reductive amination or by streptavidin-biotin binding. An analytical HPLC column with immobilized lipodisks was evaluated by analysis of mixtures containing 15 different drug compounds. The efficiency, reproducibility, and stability of the system were found to be excellent. In situ incorporation of cyclooxygenase-1 (COX-1) in immobilized lipodisks on a column was also achieved. Specific binding of COX-1 to the immobilized lipodisks was validated by interaction studies with QCM-D. These results, taken together, open up the possibility of studying ligand interactions with membrane proteins by weak affinity chromatography.

  • 27.
    Mårtensson, Christoffer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Agmo Hernández, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Ubiquinone-10 in gold-immobilized lipid membrane structures acts as a sensor for acetylcholine and other tetraalkylammonium cations2012In: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 88, p. 171-180Article in journal (Refereed)
    Abstract [en]

    It is reported that the reduction of ubiquinone incorporated into supported lipid bilayers and into immobilized liposome layers on gold electrodes is kinetically and thermodynamically enhanced by the presence of acetylcholine and tetrabutylammonium (TBA+) in solution. The reduction peak and the mid-peak potentials of the redox reactions, determined by cyclic voltammetry, are displaced towards more positive potentials by approximately 500 and 250 mV, respectively, in the case of TBA+; and by approximately 750 and 530 mV, respectively, in the case of acetylcholine. The intensity of the signal varies with the cation concentration, allowing for quantitative determinations in the millimolar range. It is proposed that the enhanced reduction of ubiquinone arises from the formation of tetraalkylammonium cation–ubiquinone radical anion ion-pairs. Electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) measurements confirmed that the potential shift and the intensity of the redox signal are coupled with the adsorption of the tetraalkylammonium cations on the lipid membrane. The Langmuir adsorption equilibrium constant (K) of TBA+ on lipid membranes at physiological pH is determined. In supported lipid bilayers K = 440.7 ± 160 M− 1, while in an immobilized liposome layer K = 35.53 ± 3.53 M− 1.

  • 28.
    Norling, Karin
    et al.
    Division of Biological Physics, Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Bernasconi, Valentina
    Mucosal Immunobiology and Vaccine Center (MIVAC), Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, 405 30 Gothenburg, Sweden.
    Agmo Hernandez, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Parveen, Nagma
    Division of Biological Physics, Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lycke, Nils Y
    Mucosal Immunobiology and Vaccine Center (MIVAC), Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, 405 30 Gothenburg, Sweden.
    Höök, Fredrik
    Division of Biological Physics, Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Bally, Marta
    Section of Virology, Department of Clinical Microbiology, Umeå University, 901 85 Umeå, Sweden; Wallenberg Centre for Molecular Medicine, Umeå University, 901 85 Umeå, Sweden.
    Gel Phase 1,2-Distearoyl-sn-glycero-3-phosphocholine-Based Liposomes Are Superior to Fluid Phase Liposomes at Augmenting Both Antigen Presentation on Major Histocompatibility Complex Class II and Costimulatory Molecule Display by Dendritic Cells in Vitro2019In: ACS infectious diseases, ISSN 2373-8227, Vol. 5, no 11, p. 1867-1878Article in journal (Refereed)
    Abstract [en]

    Lipid-based nanoparticles have in recent years attracted increasing attention as pharmaceutical carriers. In particular, reports of them having inherent adjuvant properties combined with their ability to protect antigen from degradation make them suitable as vaccine vectors. However, the physicochemical profile of an ideal nanoparticle for vaccine delivery is still poorly defined. Here, we used an in vitro dendritic cell assay to assess the immunogenicity of a variety of liposome formulations as vaccine carriers and adjuvants. Using flow cytometry, we investigated liposome-assisted antigen presentation as well as the expression of relevant costimulatory molecules on the cell surface. Cytokine secretion was further evaluated with an enzyme-linked immunosorbent assay (ELISA). We show that liposomes can successfully enhance antigen presentation and maturation of dendritic cells, as compared to vaccine fusion protein (CTA1-3Eα-DD) administered alone. In particular, the lipid phase state of the membrane was found to greatly influence the vaccine antigen processing by dendritic cells. As compared to their fluid phase counterparts, gel phase liposomes were more efficient at improving antigen presentation. They were also superior at upregulating the costimulatory molecules CD80 and CD86 as well as increasing the release of the cytokines IL-6 and IL-1β. Taken together, we demonstrate that gel phase liposomes, while nonimmunogenic on their own, significantly enhance the antigen-presenting ability of dendritic cells and appear to be a promising way forward to improve vaccine immunogenicity.

  • 29. Quentel, Francois
    et al.
    Elleouet, Catherine
    Mirceski, Valentin
    Hernandez, Victor Agmo
    L’Her, Maurice
    Lovric, Milivoj
    Komorsky-Lovric, Sebojka
    Scholz, Fritz
    Studying ion transfers across a room temperature ionic liquid vertical bar aqueous electrolyte interface driven by redox reactions of lutetium bis(tetra-tert-butylphthalocyaninato)2007In: JOURNAL OF ELECTROANALYTICAL CHEMISTRY, ISSN 1572-6657, Vol. 611, p. 192-200Article in journal (Refereed)
    Abstract [en]

    Ion transfer reactions across the interface between an aqueous electrolyte solution and the room temperature ionic liquid (RTIL) 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([hmim][fap]) were studied with the help of three-phase electrodes. The electrode assembly comprised an edge plane pyrolytic graphite electrode modified with a thin layer of [hmim][fap] containing lutetium bis(tetra-tert-butylphthalocyaninato) (Lu[tBu(4)Pc](2)) as redox probe. Lu[tBu(4)Pc]2 can be oxidized and reduced to a stable hydrophobic monovalent cation and anion, respectively, hence allowing investigation of the transfer of cations and anions in one and the same voltammetric experiment. In spite of the strong hydrophobicity of the salt [hmim][fap], the electrode reactions of he redox probe studied in contact with various inorganic aqueous electrolytes, were frequently accompanied by expulsion of ions constituting the RTIL into the aqueous phase. Using ion chromatography it was found that the distribution of ions in the aqueous electrolyte/RTIL biphasic system is strongly determined by ion exchange reactions. The affinity of the ions of the RTIL for the aqueous phase was assessed using the water-nitrobenzene (W-NB) system, and the following Gibbs energies of ion transfer were found: Delta(W–>NB) G([hmim]+)(circle minus) = -16.6 +/- 0.9 kJ mol(-1) and Delta(W-NB) G([fap]-)(circle minus) 22.4 +/- 0.3 kJ mol(-1). (C) 2007 Elsevier B.V. All rights reserved.

  • 30.
    Reijmar, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Andersson, Karl
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. Ridgeview Instruments AB, Skillsta 4, 740 20 Vänge, Sweden.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Characterizing and controlling the loading and release of cationic amphiphilic peptides onto and from PEG-stabilized lipodisks2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 46, p. 12091-12099Article in journal (Refereed)
    Abstract [en]

    Recent studies have identified PEG-stabilized lipid nanodisks (lipodisks) as promising carriers for cationic amphiphilic peptides with antimicrobial and anticancer activity. Using fluorimetric and nanogravimetric methods, we have in this work characterized the parameters describing and controlling the binding of three selected peptides (melittin, LL37, and magainin 2) onto lipodisks. It was found that the affinity of melittin for lipodisks is independent of the disk size and rim charge. On the other hand, the number of binding sites is strongly dependent on both parameters, with the highest loading being obtained for small disks with a negatively charged rim. An optimized composition of the lipodisks was utilized to study the loading of antimicrobial peptides magainin 2 and human LL37. It was observed that although magainin 2 can be loaded in large amounts, it is released very fast upon dilution, which limits future therapeutic applications. In contrast, LL37 can be loaded at relevant concentrations and the formulation is stable. This opens up for applications of LL37-loaded lipodisks as antibiotics and in anticancer treatments.

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