Interaction of small amounts of bovine serum albumin with phospholipid monolayers investigated by surface pressure and atomic force microscopy

The influence of small amounts of bovine serum albumin (BSA) (nM concentration) on the lateral organization of phospholipid monolayers at the air-water interface and transferred onto solid substrates as one-layer Langmuir-Blodgett (LB) films was investigated. The kinetics of adsorption of BSA onto the phospholipid monolayers was monitored with surface pressure isotherms in a Langmuir trough, for the zwitterionic dipalmitoylphosphatidyl ethanolamine (N,N-dimethyl-PE) and the anionic dimyristoylphosphatidic acid (DMPA). A monolayer of N,N-dimethyl-PE or DMPA incorporating BSA was transferred onto a solid substrate using the Langmuir-Blodgett technique. Atomic force microscopy (AFM) images of one-layer LB films displayed protein-phospholipid domains, whose morphology was characterized using dynamic scaling theories to calculate roughness exponents. For DMPA-BSA films the surface is characteristic of self-affine fractals, which may be described with the Kardar-Parisi-Zhang (KPZ) equation. On the other hand, for N,N-dimethyl-PE-BSA films, the results indicate a relatively flat surface within the globule. The height profile and the number and size of globules varied with the type of phospholipid. The overall results, from kinetics of adsorption on Langmuir monolayers and surface morphology in LB films, could be interpreted in terms of the higher affinity of BSA to the anionic DMPA than to the zwitterionic N,N-dimethyl-PE. Furthermore, the effects from such small amounts of BSA in the monolayer point to a cooperative response of DMPA and N,N-dimethyl-PE monolayers to the protein.     

Synthesis,crystal structure and studies on the interaction with albumin of a new silver(I) complex based on 2‐(4‐nitrobenzenesulfonamido)benzoic acid

In the present work, the two‐dimensional (2D) polymer poly[[μ₄‐2‐(4‐nitrobenzenesulfonamido)benzoato‐κ⁴O¹:O¹:O^1′:N⁶]silver(I)] (AgL), [Ag(C₁₃H₉N₂O₆S)]_n, was obtained from 2‐(4‐nitrobenzenesulfonamido)benzoic acid (HL), C₁₃H₁₀N₂O₆S. FT–IR, ¹H and ¹³C{¹H} NMR spectroscopic analyses were used to characterize both compounds. The crystal structures of HL and AgL were determined by single‐crystal X‐ray diffraction. In the structure of HL, O—H…O hydrogen bonds between neighbouring molecules result in the formation of dimers, while the silver(I) complex shows polymerization associated with the O atoms of three distinct deprotonated ligands (L^?). Thus, the structure of the Ag complex can be considered as a coordination polymer consisting of a one‐dimensional linear chain, constructed by carboxylate bridging groups, running parallel to the b axis. Neighbouring polymeric chains are further bridged by Ag—C monohapto contacts, resulting in a 2D framework. Fingerprint analysis of the Hirshfeld surfaces show that O…H/H…O hydrogen bonds are responsible for the most significant contacts in the crystal packing of HL and AgL, followed by the H…H and O…C/C…O interactions. The Ag…Ag, Ag…O/O…Ag and Ag…C/C…Ag interactions in the Hirshfeld surface represent 12.1% of the total interactions in the crystal packing. Studies of the interactions of the compounds with human serum albumin (HSA) indicated that both HL and AgL interact with HSA.     

Fano resonance in heavily doped porous silicon

Unexpectedly, the Fano resonance caused by the interference of continuum electron excitations with the longitudinal optical (LO) phonons was observed in random porous Si by Raman scattering. The analysis of the experimental data shows that the electron states trapped at the Si SiO₂ interface dominate in the observed Raman scattering. The gap energy associated with the interface states was determined. Copyright © 2011 John Wiley & Sons, Ltd.     

On positive solutions for a class of singular quasilinear elliptic systems

We study through the lower and upper-solution method, the existence of positive weak solution to the quasilinear elliptic system with weights

     

Are metabolites of Fusarium oxysporum responsible for fungal skin invasion? A morphological and Raman spectroscopy monitoring

Fusarium is an emerging pathogen with high levels of morbidity and mortality. A significant tissue response is observed in infected patients, and the condition has been associated with the production of toxic metabolites. The aim of the present study was to identify a major fraction of crude metabolic extract of Fusarium oxysporum and investigate its effects on the skin of healthy rats. Fraction F1 was obtained from the cultivation of F. oxysporum in Czapek–Dox. In the treatment groups, fraction F1 (0.05 mg/ ml) was injected intradermally, while (50 µl) 0.9% of saline solution was injected in the control groups. The animals were killed 3, 6, 12, and 24 h after inoculation. The skin was fixed for inclusion in paraffin to obtain histological sections and stained with hematoxylin and eosin, Sirius red, and terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling. Samples were analyzed using Fourier transform Raman spectroscopy. The tissue reactions were classified and compared over time and by treatment. In the treatment group, inflammatory reaction peaked at 6 h, being classified as moderate, with infiltrate composed mainly of neutrophils. terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling staining was negative. The area occupied by types I and III collagen in the treatment group increased over time. There was a change in the area occupied by amide I and the ratios of the –CH₂ and –CH₃ molecules. It can be argued that the fraction F1 contains elements that contribute to the invasion of Fusarium in the skin, destructurizing the organization of the extracellular matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermal stability of P3HT and P3HT:PCBM blends in the molten state

The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investigated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including thermogravimetric analysis (TGA), rotational rheometry, infrared spectroscopy (FTIR-ATR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), gel permeation chromatography (GPC), UV-Vis and fluorescence spectroscopy. The results obtained strongly suggest that the processing of P3HT in its molten state is possible, without noticeable degradation, if carried out under nitrogen atmosphere and if the processing (residence) times are relatively short. Conversely, as expected, in a normal air atmosphere P3HT degrades rapidly at temperatures above its melting point. The effect of PCBM on the thermal stability of P3HT:PCBM blends in the molten state was also studied using TGA, and in air atmosphere PCBM is shown to delay oxidation.     

Three 2,5‐dialkoxy‐1,4‐diethynylbenzene derivatives

2,5‐Diethoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene, C₂₀H₃₀O₂Si₂, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5‐dialkoxy‐1,4‐bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu‐catalysed cross‐coupling. 2,5‐Diethoxy‐1,4‐diethynylbenzene, C₁₄H₁₄O₂, (II), results from protodesilylation of (I). 1,4‐Diethynyl‐2,5‐bis(heptyloxy)benzene, C₂₄H₃₄O₂, (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)–(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C—H...π interactions between the methylene H atoms and the acetylenic C atom. Compound (II) shows π–π interactions between the acetylenic C atoms, complemented by C—H...π interactions between the methyl H atoms and the acetylenic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen‐bond‐type interactions between the acetylenic H atoms and the ether O atoms.     

Binary and ternary inclusion complexes of dapsone in cyclodextrins and polymers: preparation, characterization and evaluation

Dapsone (DAP) is a synthetic sulfone drug with bacteriostatic activity, mainly against Mycobacterium leprae. In this study we have investigated the interactions of DAP with cyclodextrins, 2-hydroxypropyl-β-cyclodextrin (HPβCD) and β-cyclodextrin (βCD), in the presence and absence of water-soluble polymers, in order to improve its solubility and bioavailability. Solid systems DAP/HPβCD and DAP/βCD, in the presence or absence of polyvinylpyrrolidone (PVP K30) or hydroxypropyl methylcellulose (HPMC), were prepared. The binary and ternary systems were evaluated and characterized by SEM, DSC, XRD and NMR analysis as well as phase solubility assays, in order to investigate the interactions between DAP and the excipients in aqueous solution. This study revealed that inclusion complexes of DAP and cyclodextrins (HPβCD and βCD) can be produced in order to improve DAP solubility and bioavailability in the presence or absence of polymers (PVP K30 and HPMC). The more stable inclusion complex was obtained with HPβCD, and consequently HPβCD was more efficient in improving DAP solubility than βCD, and the addition of polymers had no influence on DAP solubility or on the stability of the DAP/CDs complexes.