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European Biophysics Journal: EBJ

Vratislav Cmiel, Josef Skopalik, Katerina Polakova, Jan Solar, Marketa Havrdova, David Milde, Ivan Justan, Massimiliano Magro, Zenon Starcuk, Ivo Provaznik
In the last few years, magnetically labeled cells have been intensively explored, and non-invasive cell tracking and magnetic manipulation methods have been tested in preclinical studies focused on cell transplantation. For clinical applications, it is desirable to know the intracellular pathway of nanoparticles, which can predict their biocompatibility with cells and the long-term imaging properties of labeled cells. Here, we quantified labeling efficiency, localization, and fluorescence properties of Rhodamine derivatized superparamagnetic maghemite nanoparticles (SAMN-R) in mesenchymal stromal cells (MSC)...
November 26, 2016: European Biophysics Journal: EBJ
Zhuoyang Lu, Hua Li, Chen Hou, Yunhua Peng, Jiangang Long, Jiankang Liu
Amyloid-β (Aβ) is widely recognized as toxic to neuronal cells. Its deposition on plasma and intracellular membranes and aggregation into amyloid plaques can disturb the composition and physiological function of neurons. Whether a physical property of cells, such as stiffness, is altered by endogenously overexpressed Aβ has not yet been investigated. In this study, we used human neuroblastoma cells stably overexpressing amyloid precursor protein (APP) and its Swedish mutant form (APPswe) to measure the changes in cell stiffness...
November 16, 2016: European Biophysics Journal: EBJ
O Dunne, M Weidenhaupt, P Callow, A Martel, M Moulin, S J Perkins, M Haertlein, V T Forsyth
Small-angle neutron scattering (SANS) is a powerful technique for the characterisation of macromolecular structures and interactions. Its main advantage over other solution state approaches is the ability to use D2O/H2O solvent contrast variation to selectively match out specific parts of a multi-component system. While proteins, nucleic acids, and lipids are readily distinguished in this way, it is not possible to locate different parts of a protein-protein system without the introduction of additional contrast by selective deuteration...
November 14, 2016: European Biophysics Journal: EBJ
Patrizia Iavicoli, François Rossi, Baptiste Lamarre, Angelo Bella, Maxim G Ryadnov, Luigi Calzolai
Peptide-lipid interactions support a variety of biological functions. Of particular interest are those that underpin fundamental mechanisms of innate immunity that are programmed in host defense or antimicrobial peptide sequences found virtually in all multicellular organisms. Here we synthetically modulate antimicrobial peptide-lipid interactions using an archetypal helical antimicrobial peptide and synthetic membranes mimicking bacterial and mammalian membranes in solution. We probe these interactions as a function of membrane-induced folding, membrane stability and peptide-lipid ratios using a correlative approach encompassing light scattering and spectroscopy measurements such as circular dichroism spectroscopy, fluorescence and nuclear magnetic resonance spectroscopy...
November 10, 2016: European Biophysics Journal: EBJ
Juan J Dominguez Pardo, Jonas M Dörr, Aditya Iyer, Ruud C Cox, Stefan Scheidelaar, Martijn C Koorengevel, Vinod Subramaniam, J Antoinette Killian
A promising tool in membrane research is the use of the styrene-maleic acid (SMA) copolymer to solubilize membranes in the form of nanodiscs. Since membranes are heterogeneous in composition, it is important to know whether SMA thereby has a preference for solubilization of either specific types of lipids or specific bilayer phases. Here, we investigated this by performing partial solubilization of model membranes and analyzing the lipid composition of the solubilized fraction. We found that SMA displays no significant lipid preference in homogeneous binary lipid mixtures in the fluid phase, even when using lipids that by themselves show very different solubilization kinetics...
November 4, 2016: European Biophysics Journal: EBJ
Anatoliy I Dragan, Christopher M Read, Colyn Crane-Robinson
Structural modifications to interacting systems frequently lead to changes in both the enthalpy (heat) and entropy of the process that compensate each other, so that the Gibbs free energy is little changed: a major barrier to the development of lead compounds in drug discovery. The conventional explanation for such enthalpy-entropy compensation (EEC) is that tighter contacts lead to a more negative enthalpy but increased molecular constraints, i.e., a compensating conformational entropy reduction. Changes in solvation can also contribute to EEC but this contribution is infrequently discussed...
October 28, 2016: European Biophysics Journal: EBJ
Benedikt Fels, Nikolaj Nielsen, Albrecht Schwab
No abstract text is available yet for this article.
October 27, 2016: European Biophysics Journal: EBJ
Wallance Moreira Pazin, Danilo da Silva Olivier, Neus Vilanova, Ana Paula Ramos, Ilja Karina Voets, Ademilson Espencer Egea Soares, Amando Siuiti Ito
Green propolis, a mixture of beeswax and resinous compounds processed by Apis mellifera, displays several pharmacological properties. Artepillin C, the major compound in green propolis, consists of two prenylated groups bound to a phenyl group. Several studies have focused on the therapeutic effects of Artepillin C, but there is no evidence that it interacts with amphiphilic aggregates to mimic cell membranes. We have experimentally and computationally examined the interaction between Artepillin C and model membranes composed of dimyristoylphosphatidylcholine (DMPC) because phosphatidylcholine (PC) is one of the most abundant phospholipids in eukaryotic cell membranes...
October 26, 2016: European Biophysics Journal: EBJ
Anna Mularski, Jonathan Wilksch, Eric Hanssen, Jian Li, Takehiro Tomita, Sacha James Pidot, Tim Stinear, Frances Separovic, Dick Strugnell
Atomic force microscopy measurements of capsule thickness revealed that that the wild-type Klebsiella pneumoniae AJ218 capsular polysaccharides were rearranged by exposure to colistin. The increase in capsule thickness measured near minimum inhibitory/bactericidal concentration (MIC/MBC) is consistent with the idea that colistin displaces the divalent cations that cross-bridge adjacent lipopolysaccharide (LPS) molecules through the capsule network. Cryo-electron microscopy demonstrated that the measured capsule thickness at near MIC/MBC of 1...
October 17, 2016: European Biophysics Journal: EBJ
Annick Renevey, Sereina Riniker
Polytheonamide B (pTB), a highly cytotoxic peptide produced by a symbiotic bacterium of the marine sponge Theonella swinhoei, forms a transmembrane pore consisting of 49 residues. More than half of its residues are posttranslationally modified. Epimerizations result in alternating L- and D-amino acids that allow the peptide to adopt a [Formula: see text]-helical conformation. Unusually, the wide [Formula: see text]-helix of pTB is stable in a polar environment, which is in contrast to gramicidin A, an antibiotic with similar function and structure...
October 15, 2016: European Biophysics Journal: EBJ
Apolinary Sobieszek
In early studies on smooth muscle, I described a crude myosin fraction (CMF) in which self-assembly of myosin filaments was observed. For the first time, the 14-nm periodicity stemming from regular arrangement of myosin heads on the filament surface was observed (Sobieszek in J Mol Biol 70:741-744, 1972). In this fraction, we also observed formation of long ribbon-shaped aggregates exhibiting a 5.6-nm periodicity, characteristic of tropomyosin (TM) paracrystals (Sobieszek and Small in Phil Trans R Soc Lond B 265:203-212, 1973)...
September 27, 2016: European Biophysics Journal: EBJ
MohammadMahdi Sahebifard, Alireza Shahidi, Saeed Ziaei-Rad
In the current article, the dynamic evolution of two-phase vesicles is presented as an extension to a previous stationary model and based on an equilibrium of local forces. In the simplified model, ignoring the effects of membrane inertia, a dynamic equilibrium between the membrane bending potential and local fluid friction is considered in each phase. The equilibrium equations at the domain borders are completed by extended introduction of membrane section reactions. We show that in some cases, the results of stationary and evolutionary models are in agreement with each other and also with experimental observations, while in others the two models differ markedly...
September 23, 2016: European Biophysics Journal: EBJ
Carmela Rianna, Manfred Radmacher
We used atomic force microscopy (AFM) technique to measure the viscoelastic response of cancer and normal thyroid cells on different stiffness polyacrylamide gels. After applying a step in contact we recorded the stress relaxation of cells in order to measure their viscous and elastic properties. With the help of an extended version of the Hertz model, we could quantify for the first time by AFM the elastic modulus and the dynamic viscosity of cells on substrates with different stiffnesses. We have cultured anaplastic carcinoma and normal thyroid cells on three different substrates: polyacrylamide gels with elastic modulus in a range of 3-5 and 30-40 kPa and "infinitely" stiff Petri dishes...
September 19, 2016: European Biophysics Journal: EBJ
Dariusz Man, Ryszard Olchawa
The effect of the surface layer of model membranes on their physical properties was discussed in this paper. The research involved a physical ESR experiment with the use of spin probes and computer simulation based on the Monte Carlo technique. Liposomes formed during the process of sonication of lecithin were scanned in an ESR spectrometer. The membrane surface layer model, represented by the system of electric dipoles arranged in rectangular or hexagonal matrices, was studied. The final states of computer simulations were presented as textures...
September 17, 2016: European Biophysics Journal: EBJ
Natalia A Koubassova, Sergey Y Bershitsky, Michael A Ferenczi, Theyencheri Narayanan, Andrey K Tsaturyan
Contraction of skeletal and cardiac muscle is controlled by Ca(2+) ions via regulatory proteins, troponin (Tn) and tropomyosin (Tpm) associated with the thin actin filaments in sarcomeres. In the absence of Ca(2+), Tn-C binds actin and shifts the Tpm strand to a position where it blocks myosin binding to actin, keeping muscle relaxed. According to the three-state model (McKillop and Geeves Biophys J 65:693-701, 1993), upon Ca(2+) binding to Tn, Tpm rotates about the filament axis to a 'closed state' where some myosin heads can bind actin...
September 17, 2016: European Biophysics Journal: EBJ
Eamonn F Healy, Luis Cervantes
Superoxide dismutase [Cu-Zn], or SOD1, is a homo-dimeric protein that functions as an antioxidant by scavenging for superoxides. A wide range of SOD1 variants are linked to inherited, or familial, amyotrophic lateral sclerosis, a progressive and fatal neurodegenerative disease. Aberrant SOD1 oligomerization has been strongly implicated in disease causation, even for sporadic ALS, or SALS, which accounts for ~90 % of ALS cases. Small heat shock proteins (sHSP) have been shown to protect against amyloid fibril formation in vitro, and the sHSP αB-crystallin suppresses in vitro aggregation of SOD1...
December 2016: European Biophysics Journal: EBJ
Haiyang Yu, Samya Chakravorty, Weihua Song, Michael A Ferenczi
Phosphorylation of the regulatory light chain (RLC) of myosin modulates cellular functions such as muscle contraction, mitosis, and cytokinesis. Phosphorylation defects are implicated in a number of diseases. Here we focus on striated muscle where changes in RLC phosphorylation relate to diseases such as hypertrophic cardiomyopathy and muscular dystrophy, or age-related changes. RLC phosphorylation in smooth muscle and non-muscle cells are covered briefly where relevant. There is much scientific interest in controlling the phosphorylation levels of RLC in vivo and in vitro in order to understand its physiological function in striated muscles...
December 2016: European Biophysics Journal: EBJ
Benedikt Fels, Nikolaj Nielsen, Albrecht Schwab
The tumor environment contributes importantly to tumor cell behavior and cancer progression. Aside from biochemical constituents, physical factors of the environment also influence the tumor. Growing evidence suggests that mechanics [e.g., tumor (stroma) elasticity, tissue pressure] are critical players of cancer progression. Underlying mechanobiological mechanisms involve among others the regulation of focal adhesion molecules, cytoskeletal modifications, and mechanosensitive (MS) ion channels of cancer- and tumor-associated cells...
October 2016: European Biophysics Journal: EBJ
Nahit Rizaner, Rustem Onkal, Scott P Fraser, Alessandro Pristerá, Kenji Okuse, Mustafa B A Djamgoz
The possible association of intracellular Ca(2+) with metastasis in human cancer cells is poorly understood. We have studied Ca(2+) signaling in human prostate and breast cancer cell lines of strongly versus weakly metastatic potential in a comparative approach. Intracellular free Ca(2+) was measured using a membrane-permeant fluorescent Ca(2+)-indicator dye (Fluo-4 AM) and confocal microscopy. Spontaneous Ca(2+) oscillations were observed in a proportion of strongly metastatic human prostate and breast cancer cells (PC-3M and MDA-MB-231, respectively)...
October 2016: European Biophysics Journal: EBJ
Oksana Iamshanova, Pascal Mariot, V'yacheslav Lehen'kyi, Natalia Prevarskaya
Sodium (Na(+)) ions are known to regulate many signaling pathways involved in both physiological and pathological conditions. In particular, alterations in intracellular concentrations of Na(+) and corresponding changes in membrane potential are known to be major actors of cancer progression to metastatic phenotype. Though the functionality of Na(+) channels and the corresponding Na(+) currents can be investigated using the patch-clamp technique, the latter is rather invasive and a technically difficult method to study intracellular Na(+) transients compared to Na(+) fluorescence imaging...
October 2016: European Biophysics Journal: EBJ
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