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Biophysical Chemistry

F Stellato, Z Fusco, R Chiaraluce, V Consalvi, S Dinarelli, E Placidi, M Petrosino, G C Rossi, V Minicozzi, S Morante
Far-UV Circular Dichroism experiments and Atomic Force Microscopy tomography are employed to assess the impact of β-sheet breakers on the Aβ1-40 peptide aggregation process in the presence of Cu(2+) or Zn(2+) transition metals. In this work we focus on two specific 5-amino acids long β-sheet breakers, namely the LPFFD Soto peptide, already known in the literature, and the LPFFN peptide recently designed and studied by our team. We provide evidence that both β-sheet breakers are effective in reducing the Aβ1-40 aggregation propensity, even in the presence of metal ions...
May 15, 2017: Biophysical Chemistry
Sylvia L Hanna, Jenny L Huang, Alana J Swinton, Gregory A Caputo, Timothy D Vaden
Ionic liquids (ILs) have been investigated for potential antibacterial and antibiotic applications due to their ability to destabilize and permeabilize the lipid bilayers in cell membranes. Bacterial assays have shown that combining ILs with antibiotics can provide a synergistic enhancement of their antibacterial activities. We have characterized the mechanism by which the conventional ILs 1-butyl-3-methylimidazolium chloride (BMICl) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4) enhance the lipid membrane permeabilization of the well-known antibiotic polymyxin B (PMB)...
May 11, 2017: Biophysical Chemistry
Aura M Jiménez Garduño, Leon J Juárez-Hernández, María J Polanco, Laura Tosatto, Daniela Michelatti, Daniele Arosio, Manuela Basso, Maria Pennuto, Carlo Musio
Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy's disease, is a motor neuron disease caused by the expansion of a polymorphic CAG tandem repeat encoding a polyglutamine (polyQ) tract in the androgen receptor (AR) gene. SBMA is triggered by the binding of mutant AR to its natural ligands, testosterone and dihydrotestosterone (DHT). To investigate the neuronal alterations of motor neuron cell models of SBMA, we applied patch-clamp methods to verify how polyQ expansions in the AR alter cell ionic currents...
May 10, 2017: Biophysical Chemistry
Laura Colombo, Alessio Gamba, Laura Cantù, Mario Salmona, Fabrizio Tagliavini, Valeria Rondelli, Elena Del Favero, Paola Brocca
We investigated the effects of punctual A-to-V and A-to-T mutations in the amyloid precursor protein APP, corresponding to position 2 of Aβ1-42. Those mutations had opposite effects on the onset and progression of Alzheimer disease, the former inducing early AD pathology and the latter protecting against the onset of the disease. We applied Static and Dynamic Light Scattering and Circular Dichroism, to study the different mutants in the early stages of the aggregation process, essential for the disease. Comparative results showed that the aggregation pathways differ in the kinetics and extent of the process, in the size of the aggregates and in the evolution of the secondary structure, resulting in fibrils of different morphology, as seen by AFM...
May 6, 2017: Biophysical Chemistry
Toru Shigematsu, Naho Furukawa, Ryo Takaoka, Mayumi Hayashi, Shoji Sasao, Shigeaki Ueno, Kanako Nakajima, Miyuki Kido, Kazuki Nomura, Akinori Iguchi
We analyzed the effect of high hydrostatic pressure (HHP) treatment on reducing sugar production in the tuberous root of sweet potato (Ipomoea batatas), based on pressure-gelatinization of starch and subsequent saccharification by internal amylases. HHP treatment at up to 600MPa at ambient temperature for 10min did not apparently affect the reducing sugar concentration in tuberous root. However, HHP treatment at 100 to 500MPa and 60°C or 70°C for 10min increased reducing sugar concentration as both the pressure and temperature increased...
May 1, 2017: Biophysical Chemistry
J Somkuti, Z Török, F Pfalzgraf, L Smeller
The concentration of macromolecules inside a cell is very high, which can affect the behavior of the enzymes, and consequently influence vital biological processes. This is called macromolecular crowding. Since the most important effect of macromolecular crowding is the excluded volume, we performed pressure experiments, where the volume (as conjugate parameter to the pressure) is the crucial factor. We measured the temperature and pressure stability of bovine serum albumin and lysozyme with various concentrations of crowding agents, dextran, Ficoll™ and lysozyme itself...
May 1, 2017: Biophysical Chemistry
Valeria Rondelli, Paola Brocca, Nicola Tranquilli, Giovanna Fragneto, Elena Del Favero, Laura Cantù
The preparation and investigation of model membranes is deserving growing interest both for the physics of complex systems, and for biology. The need of simplified models should preserve mimicking the qualifying characteristics of biological membranes, and keep non-invasive and detailed description. As a main feature, biological membranes are non-homogeneous in the disposition of components, both in the lateral and in the transverse direction. We prepared asymmetric supported membranes containing GM1 ganglioside in biomimetic proportion according to different protocols...
April 29, 2017: Biophysical Chemistry
Alessandro Roncador, Aura Matilde Jimenez-Garduño, Laura Pasquardini, Giovanni Giusti, Nicola Cornella, Lorenzo Lunelli, Cristina Potrich, Ruben Bartali, Lucrezia Aversa, Roberto Verucchi, Mauro Dalla Serra, Silvia Caponi, Salvatore Iannotta, Paolo Macchi, Carlo Musio
We report a comprehensive study of the biocompatibility and neurocompatibility of titanium dioxide films (TiO2) prepared by Pulsed Microplasma Cluster Source (PMCS). This technique uses supersonic pulsed beams seeded by clusters of the metal oxide synthesized in a plasma discharge. The final stoichiometry of the TiO2 thin films is tuned changing the gas mixture, achieving stoichiometric or oxygen overstoichiometric films. All the films showed consistent biocompatibility and a spontaneous absorption of poly-d-lysine (PDL) that favors the adhesion and growth of murine cortical neurons...
April 26, 2017: Biophysical Chemistry
G C Santini, C Potrich, L Lunelli, L Vanzetti, S L Marasso, M Cocuzza, F C Pirri, C Pederzolli
A reliable clinical assay based on circulating microRNAs (miRNAs) as biomarkers is highly required. Microdevices offer an attractive solution as a fast and inexpensive way of concentrating these biomarkers from a low sample volume. A previously developed polydimethylsiloxane (PDMS) microdevice able to purify and detect circulating miRNAs was here optimized. The optimization of the morphological and chemical surface properties by nanopatterning and functionalization is presented. Surfaces were firstly characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), fluorescamine assay and s-SDTB (sulphosuccinimidyl-4-o-(4,4-dimethoxytrityl) butyrate) assay and subsequently tested for their capacity to adsorb a fluorescent miRNA...
April 26, 2017: Biophysical Chemistry
Kazuyuki Akasaka, Akihiro Maeno, Akira Yamazaki
A bacterial spore protects itself with an unusually high concentration (~10% in dry weight of spore) of dipicolinic acid (DPA), the release of which is considered the crucial step for inactivating it under mild pressure and temperature conditions. However, the process of how the spore releases DPA in response to pressure remains obscure. Here we apply (1)H high-resolution high-pressure NMR spectroscopy, for the first time, to the spore suspension of Bacillus subtilis natto and monitor directly and in real-time the leaking process of DPA in response to pressure of 200MPa at 20°C...
April 19, 2017: Biophysical Chemistry
Kehinde Onwochei Okonjo
Thirteen histidines and the α-chain terminal amino group (ACTA) make all of the contributions to the Bohr effect of human hemoglobin. The pKas of the 13 histidines in carbonmonoxy- and deoxyhemoglobin are known from (1)H NMR studies. Those of ACTA are not so precisely known. We employed the Wyman equation and the 13 histidine pairs of pKas to determine the pKas of ACTA by curve-fitting to hemoglobin Bohr effect data. Using all 14 pairs of pKas as preliminary data, we employed the Wyman equation to fit the Bohr data for hemoglobin chemically modified at Cys93β with cystamine, cystine and iodoacetamide...
April 18, 2017: Biophysical Chemistry
Shubhatam Sen, Monojit Chakraborty, Snigdha Goley, Swagata Dasgupta, Sunando DasGupta
The effect of oscillation induced by a frequency-dependent alternating current (AC) electric field to dissociate preformed amyloid fibrils has been investigated. An electrowetting-on-dielectric type setup has been used to apply the AC field of varying frequencies on preformed fibrils of human serum albumin (HSA). The disintegration potency has been monitored by a combination of spectroscopic and microscopic techniques. The experimental results suggest that the frequency of the applied AC field plays a crucial role in the disruption of preformed HSA fibrils...
April 13, 2017: Biophysical Chemistry
Liina Kangur, Michael R Jones, Arvi Freiberg
Using the native bacteriochlorophyll a pigment cofactors as local probes, we investigated the response to external hydrostatic high pressure of reaction center membrane protein complexes from the photosynthetic bacterium Rhodobacter sphaeroides. Wild-type and engineered complexes were used with a varied number (0, 1 or 2) of hydrogen bonds that bind the reaction center primary donor bacteriochlorophyll cofactors to the surrounding protein scaffold. A pressure-induced breakage of hydrogen bonds was established for both detergent-purified and membrane-embedded reaction centers, but at rather different pressures: between 0...
April 7, 2017: Biophysical Chemistry
Carlos Henrique Dumard, Shana P C Barroso, Ana Clara V Santos, Nathalia S Alves, José Nelson S S Couceiro, Andre M O Gomes, Patricia S Santos, Jerson L Silva, Andréa C Oliveira
BACKGROUND: Avian influenza A viruses can cross naturally into mammals and cause severe diseases, as observed for H5N1. The high lethality of human infections causes major concerns about the real risk of a possible pandemic of severe diseases to which human susceptibility may be high and universal. High hydrostatic pressure (HHP) is a valuable tool for studies regarding the folding of proteins and the assembly of macromolecular structures such as viruses; furthermore, HHP has already been demonstrated to promote viral inactivation...
April 6, 2017: Biophysical Chemistry
Paola Cardiano, Francesco Crea, Claudia Foti, Ottavia Giuffrè, Silvio Sammartano
A potentiometric, UV and (1)H NMR study on Cu(2+)-ampicillin [(2S,5R,6R)-6-([(2R)-2-amino-2-phenylacetyl]amino)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid] and -amoxicillin [(2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid] systems in NaCl aqueous solution at I=0.15molL(-1) and t=25°C is reported. On the basis of potentiometric results two speciation models were proposed for each system. It was found that spectrophotometric and (1)H NMR measurements are essential for selecting the most reliable speciation models...
April 4, 2017: Biophysical Chemistry
Indu Sharma, Sudip K Pattanayek
The surface energy, a macroscopic property, depends on the chemical functionality and micro- and macroscopic roughness of the surface. The adsorption of two widely used proteins bovine serum albumin (BSA) and lysozyme on surfaces of four different chemical functionalities were done to find out the interrelation between macroscopic and microscopic properties. We have observed the secondary structure of protein after its adsorption. In addition, we observed the variation of surface energy of proteins due to variation in adsorption time, change in protein concentration and effect of a mixture of proteins...
April 1, 2017: Biophysical Chemistry
Masayoshi Nishiyama
High-pressure microscopy is one of the powerful techniques to visualize the effects of hydrostatic pressures on research targets. It could be used for monitoring the pressure-induced changes in the structure and function of molecular machines in vitro and in vivo. This review focuses on the dynamic properties of the assemblies and machines, analyzed by means of high-pressure microscopy measurement. We developed a high-pressure microscope that is optimized both for the best image formation and for the stability to hydrostatic pressure up to 150 MPa...
March 30, 2017: Biophysical Chemistry
Masaki Goto, Yuya Aoki, Nobutake Tamai, Hitoshi Matsuki
The phase transitions of N-methylated di-O-hexadecylphosphatidylethanolamines (DHPE, DH-N-methyl-PE (DHMePE) and DH-N,N-dimethyl-PE (DHMe2PE)) were observed by differential scanning calorimetry (DSC) and fluorometry under atmospheric pressure and by light-transmittance measurements under high pressure. The DSC thermograms showed that the N-methylated DHPE bilayers underwent the phase transition from the gel phase to the liquid crystalline (Lα) phase under atmospheric pressure. The gel phase was identified by fluorometry as the lamellar gel (Lβ) phase, and not interdigitated gel (LβI) phase...
March 30, 2017: Biophysical Chemistry
Matthias Karl, Michael Spoerner, Thuy-Vy Pham, Sunilkumar Puthenpurackal Narayanan, Werner Kremer, Hans Robert Kalbitzer
High pressure NMR spectroscopy is a powerful method for identifying rare conformational states of proteins from the pressure response of their chemical shifts. Many proteins have bound adenine nucleotides at their active centers, in most cases in a complex with Mg(2+)-ions. The (31)P NMR signals of phosphate groups of the nucleotides can be used as probes for conformational transitions in the proteins themselves. For distinguishing protein specific pressure effects from trivial pressure responses not due to the protein interaction, data of the pressure response of the free nucleotides must be available...
March 30, 2017: Biophysical Chemistry
Marzieh Saeedi, Alexander P Lyubartsev, Seifollah Jalili
To provide insight into the molecular mechanisms of local anesthetic action, we have carried out an extensive investigation of two amide type local anesthetics, lidocaine and articaine in both charged and uncharged forms, interacting with DMPC lipid membrane. We have applied both standard molecular dynamics simulations and metadynamics simulations to provide a detailed description of the free energy landscape of anesthetics embedded in the lipid bilayer. The global minimum of the free energy surface (equilibrium position of anesthetics in the lipid membrane) occurred around 1nm of the bilayer center...
March 29, 2017: Biophysical Chemistry
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