Evidence of HIV-1 gp120/V3 — CCR5 peptide complex organization in vitro

The V3-loop of the HIV-1 envelope glycoprotein gp120 interacts with the chemokine receptor CCR5 on the surface of the target cell. Electrostatic interactions between the electropositive V3-loop and the strongly electronegative CCR5 appear to play a prominent role in this process. In the present study we showed by dynamic light scattering that a 3:2 mixture of a linear V3 peptide and CCR5 N-terminal peptide with sulphated tyrosines gave a shift of the relaxation times and the appearance of second peak at longer times, characteristic of complex formation, with dimensions of the order of 1000 nm. The strong interactions between the cationic V3 peptide and the anionic CCR5 N-terminal peptide are manifested in the distinct CW-EPR spectra of the mixture as compared to the separate peptides.     

Protein interactions in concentrated ribonuclease solutions

To investigate the protein interactions involved in the crystallization process of ribonuclease A, dynamic light scattering (DLS) and small angle X-ray scattering experiments (SAXS) were performed on concentrated solutions. Whereas the translational diffusion coefficient obtained from DLS is sensitive to thermodynamic and hydrodynamic interactions and permits to calculate an interaction parameter, the shape of the SAXS curves is related to the type of interaction (attractive or repulsive). We compared the effect of pH on protein interactions in the case of two types of crystallizing agents: a mixture of salts (3 M sodium chloride plus 0.2 M ammonium sulfate) and an organic solvent (ethanol). The results show that in the presence of ethanol, as in low salt, protein interactions become more attractive as the pH increases from 4 to 8 and approaches the isoelectric point. In contrast, a reverse effect is observed in high salt conditions: the strength of attractive interactions decreases as the pH increases. The range of the pH effect can be related to ionization of histidine residues, particularly those located in the active site of the protein. The present observations point out the important role played by localized charges in crystallization conditions, whatever the precipitating agent.     

Production and Study of Silver Nanoparticles by 532 nm Laser Pulse Ablation in NaCl Solution

In this experimental research, silver nanoparticles are produced in NaCl solution by the laser ablation method. Our aim was to investigate the effect of the amount of NaCl in the ablation medium on the characteristics of nanoparticles. A 7 ns pulsed Neodymium YAG laser (Nd:YAG) at 5 J/cm2 fluence and 532 nm wavelength was employed to produce Ag nanoparticles in distilled water with four different concentrations of NaCl. The optical properties, size distribution, and agglomeration of nanoparticles were investigated by several diagnostics. The UV–Visible absorption spectra of the Ag nanoparticles exhibit absorptions in the UV region because of surface plasmon resonance. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the size distribution and morphology of nanoparticles. Dynamic light scattering (DLS) was employed to measure the hydrodynamic size of nanoparticles in suspensions. With X-ray diffraction (XRD) pattern, the lattice structure of nanoparticles was studied. Fourier transform infrared (FTIR), photoluminescence (PL) spectra were obtained to observe the molecular structure and atomic energy levels of particles.     

Hydrothermal synthesis of organic hybrid BaTiO3 nanoparticles using a supercritical continuous flow reaction system

Barium titanate (BaTiO₃: BT) nanoparticles were synthesized by the hydrothermal method in the presence of dispersants using a continuous supercritical flow reaction system. The reactants of TiO₂ sol/Ba(NO₃)₂ mixed solution and KOH solution were used as starting materials and that was heated quickly up to 400 °C under the pressure of 30 MPa for 8 ms as reaction time. The dispersant solution such as polyacrylic acid (PAA) and polyoxyethylene(20) sorbitan monooleate (Tween 80) was injected in the cooling process after the reaction. The crystal phase of the obtained particles was identified as perovskite cubic BaTiO₃ by X-ray diffractometry (XRD) and Raman spectroscopy. Raman spectra and thermogravimetric data revealed that PAA and Tween 80 fabricated hybrid BT nanoparicles. Primarily particle size of the BaTiO₃ nanoparticle was determined by means of BET surface area, as small as less than 10 nm irrespective of dispersants. In contrast, dispersed particle size in solution measured by dynamic light scattering (DLS) technique decreased from 282 nm to less than 100 nm depending on the dispersant. Aggregation of BaTiO₃ nanoparticles might be depressed in the presence of dispersants, especially PAA is the most effective among the dispersants examined.     

Complexes of poly-N-vinylpyrrolidone with sulfonated tetraphenylporphins

The interaction of sulfonated tetraphenylporphins H₂ TPPS₄(HCl)₂ and in CuTPPS₄ with poly-N-vinylpyrrolidone (PVP) is studied using small-angle neutron scattering, dynamic light scattering, visible spectrophotometry, and viscometry. It is shown that porphyrin molecules form complexes with PVP, thus charging the polymeric chain.     

Molecular Organization of Porphyrin-Metal Complexes

Abstract

Tetraethyltetramethylporphyrin substituted at two facing meso positions by N-methylimidazolyl groupings and its metal complexes were prepared. The absorption spectra of Zn and Mg complexes showed a characteristic splitting of Soret band and red-shifts of Q-bands indicating the exciton interaction of porphyrins in a slipped cofacial arrangement, where each imidazolyl group in one metal porphyrin is coordinated to metals in the other porphyrin skeleton. Typical upfield shifts in the ¹H NMR spectra arising from such the stacking structure elucidated Zn and Mg complexes as a dimer and an oligomeric mixture, respectively. Bis(imidazolyl)substituted tetraethyltetramethyl-porphyrin was also prepared. It suggested the hydrogen bonded oligomer formation through imidazolyl-imidazolyl interactions in a columnar orientation.

Electric conductivities of films prepared from these compounds werecharacterized. In a same line with behaviors in solution, samples capable of π-stacking interaction with adjacent porphyrins via ligand-to-metal coordination or hydrogen bonding exhibited higher conductivities as well as lower activation energies for the thermal conduction. These behaviors are understood as due to the overlap of π-systems of one porphyrin with neighboring porphyrins.     

Advanced in Development IR Modulators of Ferroelectric Liquid Crystals Utilizing Transient Light Scattering Effects

Abstract

The highly efficient IR-modulation has been achieved using LC electro-optic elements. Experimental infrared modulator elements have been fabricated and demonstrated utilizing the transient light scattering effect of ferroelectric liquid crystal with asymmetric waveform voltage drive. The new elements performed 80%, 50%, 40% and 25% modulation degree in the 632.8nm, 2, 3-5 and 8-12 μm region. And we observed micro domain structure under the scattering state by a polarizing microscope to understand the mechanism of the domain switching. In addition, we evaluated properties of the scattering angular and temperature dependence quite important for the design of optics for the application in the infrared range.     

Spectroscopy of Charge Transfer Complexes of Aniline Blue

Charge transfer (CT) complexes of aniline blue (AB) were prepared with standard organic acceptors such as TCNQ, TCNE, DDQ, and chloranil and studied with UV-VIS-NIR spectra showing σ→π* and π→π* transitions along with free-carrier absorption due to scattering of light particles which has been found involving phonon–photon, electron–photon, and electron–electron scattering. Infrared spectra contain half power beta density due to hopping conduction and an asymmetric band corresponding to A(k) = A₀k exp(?bk) as absorption associated with diffraction of IR light from the crystalline particles.     

Liquid crystalline G phase of self assembled donor-acceptor molecules by intermolecular hydrogen bonding

The interaction with donor p-n-alkylbenzoic acid and acceptor nonyl-p-hydroxy benzoate molecules was studied. The likely association of these molecules to complexes is studied by intermolecular hydrogen bonding. The textures are observed by polarizing optical microscope with corresponding transitions confirmed by differential scanning calorimetry. The molecular complexes exhibited enantiotropic crystal G phases in both heating and cooling cycles. The relevant functional groups C═O, C-O and OH in formation of molecular complexes are attributed with spectral shifts in infrared spectra and further with absorption studies. The proton NMR studies convinced the structural aspects of hydrogen bonded structure. Crystal parameters were studied with powdered X-ray diffraction. The results show that constituent molecules self organize through intermolecular hydrogen bonding in the formation of crystal G phase.     

Dynamic Scattering with Storage in Smectics C and Nematics with Smectic C Ordering

Stored dynamic scattering and stored domain structure were observed in smectic C and in nematic phases of p-n-heptyloxybenzoic acid (HOBA). The sdtored texture can easily be erased with a high frequency electric field. The smallest frequency for erasure decreases with the decreasing temperature. Stored scattering centers and stored domain structure in S₁ solid phase of HOBA were also observed.     

Synthesis and characterization of semiconductor metal sulfide nanocrystals using microemulsion technique

The semiconductor nanocrystals ZnS, PbS, CdS and CuS were synthesized via microemulsion technique involving metal acetate, reducing agent (Na₂S) and Triton X‐100 as surfactant. Nanocrystals were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of ZnS, PbS, CdS and CuS nanocrystals were found to be 5.6 nm, 13.3 nm, 11.4 nm and 6.2 nm, respectively. Different parameters like surfactant (Triton X‐100) concentration, water‐to‐surfactant ratio (ω), precursor concentration [zinc acetate, (Zn(AC)₂], reducing agent concentration [sodium sulphide, (Na₂S)] were optimized to synthesize ZnS quantum dots.     

Liquid crystal biomimetic nanosystems loaded with vegetal extracts

Abstract

This article is aimed to design new antioxidant phyto-nanosystems based on liposomes and vegetal extracts of sage (Salvia officinalis L.) and mint (Mentha piperita L.). The lipid vesicles were obtained by thin film hydration method, and vegetal extracts of sage or mint were incorporated both in hydrophobic and in aqueous compartments of these lipid systems. The obtained phyto-containing liposomes were characterized by UV–Vis absorption and dynamic light scattering (DLS) measurements, and their antioxidant activity was assessed through chemiluminescence technique. The obtained artificial lipid bilayers loaded with phyto-extracts exhibited impressive antioxidant properties.     

Defect structure and light‐induced scattering of Zr‐doped near‐stoichiometric Mn:Fe:LiNbO3 crystals grown by TSSG method

Near‐stoichiometric Mn:Fe:LiNbO₃ crystals doped with various concentration of ZrO₂ were grown by top seed solution growth (TSSG) method in the air atmosphere. The Zr concentration in the crystal was determined by inductively coupled plasma optical emission spectrometer. The defect structures were analyzed by means of ultraviolet‐visible and infrared transmittance spectra. The appearance of vibration peak at 3466 cm^‐1 in infrared spectra manifested that Li/Nb ratio in crystals approached to stoichiometric proportion. The fundamental absorption edge represented continuous red‐shift which was discrepancy with congruent doped LiNbO₃ crystals showed that doping ions possessed different location mechanism. The light‐induced scattering of the doped stoichiometric LiNbO₃crystals were quantitatively scaled via incident exposure energy. The results demonstrated that Zr(2 mol%):Mn:Fe:LiNbO₃ crystal had the weakest light‐induced scattering and the mechanism related to their defect structures was discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of P2O5 content on the structure of SiO2-Na2O-CaO-P2O5 bioglasses by Si and P MAS-NMR

²⁹Si and ³¹P MAS-NMR has been used in order to study the influence of P₂O₅ content on the structure of SiO₂-Na₂O-CaO-P₂O₅ bioglasses. The ²⁹Si NMR spectra show many Q_Siⁿ entities co-existing in the same glass. For all the glasses, the Q_Siⁿ species are associated with Ca²⁺ and Na⁺. The glass network becomes more and more polymerized when the P₂O₅ content increases. The ³¹P NMR spectra show that the phosphorus is present as monophosphate with or without diphosphate complexes associated with both Ca²⁺ and Na⁺. The increase in phosphorus content modifies the relative abundance of phosphate complexes and leads to changes in the chemical environment around phosphate indicating that the distribution of cations is not homogeneous. Indeed most phosphate complexes attract calcium. The percentage of diphosphate complexes increases with the P₂O₅ content as the silicate network repolymerizes.     

A facile approach towards synthesis,characterization, single crystal structure,and DFT study of 5-bromosalicylalcohol

5-Bromosalicylalcohol was prepared by the interaction of NaBH₄ and 5-bromosalicylaldehyde. The use of sodium borohydride makes the reaction easy, facile, economic and does not require any toxic catalyst. The compound is characterized by FTIR, ¹H NMR, ¹³C NMR, TEM and ESI-mass spectra. Crystal structure is determined by single crystal X-ray analysis. Quantum mechanical calculations of geometries, energies and thermodynamic parameters are carried out using density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data.     

Characterization of oligomerization of a peptide from the ebola virus glycoprotein by small-angle neutron scattering

Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) studies showed that model peptides QNALVCGLRQ (G33) and QNALVCGLRG (G31) corresponding to region 551–560 of the GP protein of the Sudan Ebola virus are prone to oligomerization in solution. Both peptides can form amyloid-like fibrills. The G33 peptide forms fibrils within one day of incubation, whereas the fibrillogenesis of the G31 peptide is observed only after incubation for several months. The possible role of the observed processes in the pathogenesis and the possibility of applying a combination of the TEM and SANS techniques to search for new compounds that are able to influence the protein oligomerization are discussed.     

Light scattering dynamic study of the gelation process

Light scattering is a choice method for studying the dynamic properties of fractal structures and growth processes. We present preliminary light scattering measurements to characterize the formation of small silica particles prepared in highly basic TMOS/methanol/water sols and the transformation of sol into gel employing digital clipped autocorrelation spectroscopy. The light scattering is due to gel clusters.     

Specific physical and chemical properties of two modifications of poly(N-vinylcaprolcatam)

Two modifications of poly(N-vinylcaprolactam)—PVCL25 and PVCL40 (drying of a PVCL solution at 25 and 40°С, respectively)—as powdered films and their solutions were systematically investigated for the first time. Powders were studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, low-temperature krypton adsorption, and differential scanning calorimetry. Solutions were studied by smallangle X-ray scattering and dynamic light scattering. It was demonstrated that powders of PVCL25 and PVCL40 differ in the characteristics of the sub- and microstructure and in the water content and the solutions differ in the particle size. The relationships between the characteristics of the systems in the solid and liquid state and between the hydrodynamic diameter of PVCL particles in solution and their coagulation time were found.     

3-Aryloxypropiononitriles Intermediates: Crystal and Molecular Structure of 2- and 4-(2-Bromoethoxy)diphenylmethanes

The crystal structure of 2- and 4-(2-bromoethoxy)diphenylmethanes ( I and II respectively), intermediates in a novel synthesis of substituted 3-aryloxypropiononitriles, have been determined by single crystal X-ray diffraction at room temperature (r.t.) and at 150K. No significant changes in the crystal structure of I and II have been observed in going from r.t. to 150K. In both compounds the bromoethoxy group presents a gauche conformation and shows a short Br.O intramolecular interaction that allows to explain the very good reaction yields obtained in the novel synthesis. The three-dimensional structure of I is stabilized by two intermolecular hydrogen bonds and that of II by six. This difference in the crystal packing of I and II explains the variation in the m.p. The analysis of ¹H and ¹³C NMR spectra suggests that the molecular conformations in solution are similar to those found in solid state.     

Synthesis and Characterisation of Macrocyclic Liquid Crystalline Ligands and their Metal Complexes

Abstract

Four macrocyclic liquid crystalline ligands derived from 1,8 dihydroxy ethyl 1,3,6,8,10,13 hexa aza cyclotetradecane(DHAT) and trans-4-n-alkoxy cinnamoyl chloride have been synthesised and their metal complexes using Cu(II),Ni(II),Pb(II), V(V) and U(VI) metal ions have been isolated. The ligands and their metal complexes were characterised by elemental analysis, FTIR,NMR,X-Ray and DSC studies. Polarising microscope was used to identify mesomorphic textures of the ligands and the complexes.

The transition temperature and mesophase textures of the ligands and complexes have been compared. The effect of presence of different metal ions on mesomorphic properties has been discussed.