Shift Of Absorption Wavelength Research Articles

Characterizing the binding interaction between antimalarial artemether (AMT) and bovine serum albumin (BSA): Spectroscopic and molecular docking methods

Artemether (AMT), a peroxide sesquiterpenoides, has been widely used as an antimalarial for the treatment of multiple drug-resistant strains of plasmodium falciparum malaria. In this work, the binding interaction of AMT with bovine serum albumin (BSA) under the imitated physiological conditions (pH7.4) was investigated by UV spectroscopy, fluorescence emission spectroscopy, synchronous fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD), three-dimensional fluorescence spectroscopy and molecular docking methods. The experimental results indicated that there was a change in UV absorption of BSA along with a slight red shift of absorption wavelength, indicating that the interaction of AMT with BSA occurred. The intrinsic fluorescence of BSA was quenched by AMT due to the formation of AMT–BSA complex. The number of binding sites (n) and binding constant of AMT–BSA complex were about 1 and 2.63×103M−1 at 298K, respectively, suggesting that there was stronger binding interaction of AMT with BSA. Based on the analysis of the signs and magnitudes of the free energy change (ΔG0), enthalpic change (ΔH0) and entropic change (ΔS0) in the binding process, it can be concluded that the binding of AMT with BSA was enthalpy-driven process due to |ΔH°|>|TΔS°|. The results of experiment and molecular docking confirmed the main interaction forces between AMT and BSA were van der Waals force. And, there was a slight change in the BSA conformation after binding AMT but BSA still retains its secondary structure α-helicity. However, it had been confirmed that AMT binds on the interface between sub-domain IIA and IIB of BSA.

Thermo‐Optical Properties of Amino Acid Modified ZnO‐PVA Colloidal Suspension Under CW Laser Illumination

SummaryIn this paper, we present synthesis of amino acids (l‐arginine and l‐alanine) assisted surface modification of ZnO nanoparticles (NPs) using chemical precipitation method. Study emphasizes the utility of l‐arginine over l‐alanine in the synthesis process and ZnO NPs with average particle size of 18 nm have been successfully obtained using l‐arginine. Structural properties were evaluated using powder X‐ray diffraction (XRD) pattern, energy dispersive X‐ray spectroscopy (EDAX) and transmission electron microscopy (TEM) that confirmed the purity, surface morphology and hexagonal wurtzite crystal structure of ZnO NPs. Linear optical studies using ultraviolet‐visible (UV‐vis) spectroscopy and Fourier transform infra‐red (FT‐IR) spectroscopy indicated the blue shift of excitons absorption wavelength and surface modification by amino acids. Blue shifting is more prominent for l‐arginine and optical band gap of 3.48 eV has been achieved in the present case. Third order nonlinearity (nonlinear refraction and absorption) of ZnO NPs embedded in polyvinyl alcohol (ZnO‐PVA colloidal suspension) was studied by Z‐scan technique at wavelength 632.8 nm in continuous wavelength regime which shows negative nonlinearity with self‐defocusing effect. Large value of n2 and β were obtained in case of ZnO NPs passivated by l‐arginine and effect was attributed to thermal lensing. Thermally stimulated third order nonlinear susceptibility (x(3)) for ZnO‐PVA colloids have also been calculated and presented.

Synthesis, crystal structure and conjugation properties of iminopyridine copper(I) phosphine complexes

Some copper(I) complexes with imonopyridine ligands [Cu(L1)(PPh3)2]X (X=Cl (1a), ClO4 (2a), BF4 (3a), PF6 (4a)) and [Cu(L2)(PPh3)2]X (X=Cl (1b), ClO4 (2b), BF4 (3b), PF6 (4b)) [Where L1=N-(2-pyridylmethylene)-4-(bromo)aniline, L2=N-(2-pyridylmethylene)-4-(ethynyl)aniline; PPh3=triphenylphosphine] have been synthesized and characterized on the basis of their elemental analyses, IR, 1H NMR and 31P NMR spectral studies. The representative complexes [Cu(L1)(PPh3)2]ClO4 (2a) and [Cu(L2)(PPh3)2]PF6 (4b) were characterized by single crystal X-ray analysis which reveals a distorted tetrahedral geometry around each copper(I) center. Quasireversible redox behavior is accounted for all complexes corresponding to Cu(II)/Cu(I) couple. Photophysical properties of all complexes indicate that the insertion of ethynyl (CCH) functionality on iminopyridine induces pronounced red shift in absorption and emission wavelength of copper(I) complexes.

DNA binding ability of histone-like protein HPhA is negatively affected by interaction with Pb2+.

The histone-like protein (HPhA) is highly homologous to the eukaryotic histones and has the ability to bind to the DNA molecules. In this study, we tested divalent metal ions Mg(2+), Ca(2+), Zn(2+), Pb(2+) for their effect on the recombinant HPhA (rHPhA)-DNA binding. We found that only Pb(2+) was able to reduce the formation of rHPhA-DNA complex using gel mobility shift assays. Equilibrium dialysis showed that Pb(2+) bound to rHPhA by a 2:1 ratio. The interaction of Pb(2+) and rHPhA was further studied by spectroscopic method including fluorescence, ultraviolet visible (UV-Vis) absorption, and circular dichroism (CD) spectroscopies. Fluorescent spectroscopy results suggested that Pb(2+) and rHPhA formed a complex that caused internal quenching of the fluorescence of the protein at the ground state, and the quenching is predominately static and mixed with dynamic quenching. UV-Vis absorption spectrum results showed Pb(2+) caused a slightly blue shift of the maximum absorption wavelength of rHPhA which indicated the reduction of the protein's hydrophobicity. The CD spectrum further indicated that a reduction of the α-helix content of rHPhA occurred upon binding to Pb(2+). Synchronous fluorescence spectrometry analysis revealed that Pb(2+) was able to affect the polarity of the amino acids that near the Trp and Tyr residues. These results together showed that Pb(2+) interact with the recombinant rHPhA and this interaction negatively affect the ability of rHPhA to form complex with DNA molecules.

Synthesis and characterization of water-soluble polythiophene derivatives for cell imaging.

In this work, four water-soluble polythiophene derivatives (PT, PT-DDA, PT-ADA, and PT-ADA-PPR) with different pendant moieties were synthesized via oxidative copolymerization by FeCl3. By increasing the hydrophobic ability of side chain moieties, there is a gradually blue shift for the maximum absorption wavelength and red shift for the maximum emission wavelength, a reducing trend for fluorescence quantum yields, a growing trend for Stokes shift, and an increasing trend for the mean sizes in the order of PT, PT-ADA, and PT-DDA. All the synthesized polymers show low toxicity and good photostability and accumulate in the lysosomes of A549 cells. Furthermore, the introduction of porphyrin group to PT-ADA side chain (PT-ADA-PPR) broadens the absorption and emission ranges of PT-ADA. PT-ADA-PPR could be excited at two different excitation wavelengths (488 nm and 559 nm) and exhibits two emission pathways, and dual-color fluorescence images (orange and red) of PT-ADA-PPR accumulated in A549 cells are observed. Thus, PT-ADA-PPR could be used as an excellent dual-color fluorescent and lysosome-specific imaging material.

Preparation of Fe-doped TiO2 nanotube arrays and their room-temperature ferromagnetic properties.

Fe-doped titania nanotube arrays (NTs) were fabricated by electrochemical anodization on a Ti foil using Fe(NO3)3 · 2H2O as iron source. Their morphology, structure and optical properties were investigated by field emission scanning electron microscopy, X-ray diffraction, UV-visible absorption spectroscopy and photoluminescence spectroscopy. The UV-visible reflection spectrum of the Fe-doped TiO2 NTs showed a red shift in wavelength of absorption and greater reflectivity compared with the undoped sample due to the Fe ion incorportion in TiO2 lattices. The photoluminescence spectrum of the Fe-doped TiO2 NTs shows two strong new peaks centered at 388 nm and 694 nm, besides the UV emission peak owing to the electronic transition mediated by the defect levels such as oxygen vacancies in the band gap. The magnetic property of the Fe-doped TiO2 NTs exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.146 x 10(-2) emu/cm3 and a coercive field of 60 Oe. And the cause of the magnetic properties has been discussed in detail.

Synthesis of Zinc Phthalocyanine and its Dimerization in DMF

Zinc phthalocyanine was prepared with improved method with high yields and characterized by XRD and FT-IR analysis. The SEM analysis was also conducted to demonstrate the apparent morphology of the synthesized compound. Dimerization of the zinc phthalocyanine was measured by UV-Vis spectroscopy in N, N-dimethyl formamide (DMF). The red–shift of maximum absorption wavelength and deviation from Lambert-Beer law was observed with increasing the concentration.

Controllable synthesis and characterization of highly fluorescent silver nanoparticles

Highly fluorescent silver nanoparticles (AgFNPs) have been prepared by microemulsion method and the sizes of AgFNPs were controlled by altering the molar ratio (ω) of water-to-surfactant in the water-in-oil microemulsion. The results were shown that the AgFNPs sizes increased with incremental molar ratio (ω) of water-to-surfactant. The AgFNPs have been characterized by transmission electron microscopy, dynamic light scattering, fluorescence and absorption spectroscopy, and fluorescence lifetime study. Study of the spectral characteristics was shown that the absorbance of AgFNPs increased significantly with the ω, and linear relationship between absorbance and the size of AgFNPs was observed. The increase of AgFNPs size caused a red shift of maximum absorption wavelength in the UV–Vis spectra, and the relationship between maximum absorption wavelength and AgFNPs size appeared linear dependence. The maximum fluorescence emission wavelength did not shift with the change of particles size, but the emission intensity increases with the ω. The results were shown that the other factors to affect the fluorescence properties of AgFNPs were the surface properties and microstructure, except the AgFNPs size. These surface properties depend upon the stabilizing agent, reactant concentration, and solvents and so on.

Study of the photocatalytic activity of nanocrystalline S, N-codoped TiO2 thin films and powders under visible and sun light irradiation

Homogeneous and transparent sulfur and nitrogen (S, N)-codoped TiO2 nanocrystalline thin films were deposited on glass substrates by sol gel dip coating method using thiourea (Tu) as a source of sulfur and nitrogen. The surface structure of the films was modified by addition of different concentrations of polyethylene glycol (PEG) into the TiO2 sol. The equal powders of pure and modified TiO2 were also prepared to compare of their photocatalytic activity with films.The films and powders were characterized by different techniques like diffuse reflectance UV–Vis spectroscopy (DRS), X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX).DRS exhibited a shift in optical absorption wavelength to visible region and XRD analysis showed that only the anatase TiO2 formed in both of film and powder. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) as a model. The modified TiO2 films and powders showed excellent visible-light photocatalytic ability for the degradation of MO under both irradiation of visible and sun light. So that, up to 96% MO can be decomposed in sun light only within 3h in the presence of a modified TiO2 film consist of Tu/TiO2 molar ratio of 0.45 and 0.9g PEG. On the other hand, MO solution was discolored completely under sun light in 75min in the presence of the modified TiO2 powder.

Magnetic and Optical Properties of Mn Doped ZnO Nanocrystalline Films

We have investigated the properties of Mn-doped ZnO nanocrystalline film growing on zinc foil by the hydrothermal method. X-ray photoelectron spectroscopy shows that the manganese ions exist as Mn2+ in the film. From UV-vis spectra, we observe a red shift in wavelength of absorption and greater reflectivity due to the Mn ion incorporation in ZnO lattices. The photoluminescence spectrum of the Mn-doped ZnO film shows two strong new blue peaks centered at 424 nm and 443 nm, besides the UV emission peak owing to the band gap of ZnO semiconductor. The magnetic property of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902 x 10(-3) emu/cm3 and a coercive field of 47 Oe. We suggest that the blue emission of the Mn-doped ZnO film corresponds to the electron transition from the level of interstitial Zn and Mn to the valence band. The defects brought about by Mn ion incorporation are the main cause of the room temperature ferromagnetic property.

Imparting conductivity and chromic behavior on polyester fibers by means of poly(3‐methylthiophene) nanocoating

AbstractPoly(3‐methylthiophene) (P3MT)‐coated polyester fabric is a conductive textile with specific electrical and optical properties; for instance, color change under external stimulus (chromic behavior) was successfully prepared by chemical polymerization with continuous, speed stirring technique. To investigate the striking effect of some variable conditions of polymerization process, the effect of reaction time, temperature, and oxidant concentration on conductivity of the P3MT‐coated fabric was studied. Scanning electron microscopy confirmed that the surface of fabric has entirely been coated with P3MT particles. The further characterizations were investigated using Fourier transform infrared spectroscopy to provide evidence of forming particles onto the fabric, UV–vis absorption spectroscopy, electrical surface resistivity, and pressure dependence visible reflectance spectrophotometer measurements and X‐ray diffraction analysis. The blue shift in wavelength of maximum absorption of about 95 nm to a longer wavelength from that observed in the reflectance spectra of coated polyester fabric; under high‐pressure P3MT‐coated polyester fabric demonstrated piezochromism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Bonding Nature and Electron Delocalization of An(COT)2, An = Th, Pa, U

A systematic study of a series of An(COT)(2) compounds, where An = Th, Pa, U, and COT represents cyclooctatetraene, has been performed using relativistic density functional theory. The ZORA Hamiltonian was applied for the inclusion of relativistic effects, taking into account all of the electrons for the optimization and explicitly including spin-orbit coupling effects. Time-dependent density functional theory (TDDFT) was used to calculate the excitation energies with the GGA SAOP functional, and the electronic transitions were analyzed using double group irreducible representations. The calculated excitation energies are in perfect correlation with the increment of the ring delocalization as it increases along the actinide series. These results are sufficient to ensure that, for these complexes, the increment in delocalization, as indicated by ELF bifurcation and NICS analysis, leads to a shift in the maximum wavelength of absorption in the visible region. Also, delocalization in the COT ring increases along the actinide series, so the systems become more aromatic because of a modulation induced by the actinides.

Voltammetric and spectroscopic studies on the interaction of tilmicosin with bovine serum albumin at different pHs

In this study, the voltammetric behavior of the interaction between tilmicosin (TIM) and bovine serum albumin (BSA) was investigated using voltammetry and UV–Vis spectroscopy techniques. In the presence of BSA, the main reductive signal of TIM gradually decreased without the appearance of new peaks. The formation of a 1:1 complex between TIM and BSA were determined at different pHs (3, 7.4 and 11). This interaction was also supported by ultraviolet spectroscopy. After the addition of TIM into the BSA solution, at pH 3 and 7.4, the absorption band of BSA at 217 nm decreased, shifted to smaller wavelengths, and narrowed. However, at pH 11, the absorbance of BSA at 217 nm decreased without the shift of maximum absorption wavelength. The interaction between TIM and BSA was mainly sourced from electrostatic or hydrophobic (intercalation) interactions.

Surface plasmon resonance scattering and absorption sensing of Concanavalin A using glycoconjugated gold nanoparticles

Glycoconjugated gold nanoparticles (AuNPs) are of great interest as probes for detecting carbohydrate–protein interactions. Three sensing methods – absorption, light scattering and wavelength-ratiometric scattering – were used to detect polyvalent interactions between mannose-conjugated AuNPs and Concanavalin A (Con A). Nanoparticle aggregation was induced by protein–carbohydrate interaction, which shifted the plasmon absorption to longer wavelengths and increased the intensity of plasmon light scattering. The plasmon absorption wavelength shift and scattering light intensity enhancement were proportional to the concentration of Con A in the range 5.7–20.2 nM and 3.8–36.7 nM, respectively, and the corresponding limits of detection were 3.4 and 2.3 nM, respectively. The wavelength-ratiometric scattering method showed the lowest detection limits (1.9 nM) for Con A, at 5–40 times lower than those obtained using existing glycoconjugated AuNPs.

Optical properties of TiO 2 thin films after Ag ion implantation

Metal plasma ion implantation has being successfully developed for improving the electronic and optical properties of semiconductor materials. Prior to deposition, a TiO 2 colloidal suspension was synthesized by microwave-induced thermal hydrolysis of the titanium tetrachloride aqueous solution. The TiO 2 thin film was optimized to obtain a high-purity crystalline anatase phase by calcinations at 550 °C. The TiO 2 coating was uniform without aggregation, which provided good photo conversion efficiency. Ag ion implantation into the as-calcined TiO 2 thin films was conducted with 1 × 10 15 ~ 1 × 10 16 ions/cm 2 at 40 keV. The peak position and intensity of the photoluminescence and UV–Vis absorption spectra are quite sensitive to Ag doping. The optical characterization showed a shift in optical absorption wavelength towards infrared ray side, which was correlated with the structure variation of the Ag + implanted TiO 2. Due to the strong capability of forming compounds between the energetic silver ions and TiO 2, the photoluminescence emission and UV–Vis absorption efficiencies were improved.

Prediction of the Bandgap of a Core-Shell Microsphere via Light Intensity Fluctuations

It has been experimentally observed that in the case of microspheres irradiated by light, the absorption wavelength shift occurs, known as the blueshift, with changing shell materials (i.e., by decreasing the refractive index of the shell). In the present investigation, we want to demonstrate it numerically by using the boundary element method. The material used for the simulation is a core-shell (SiO2and another material of a larger refractive index) microsphere and it is irradiated by unpolarized monochromatic light wave. This paper intends to demonstrate that it is possible to predict the bandgap of a core-shell microsphere resulting from two different bandgap materials and that the numerical simulation employed produces the blueshift.

Synthesis and biological evaluation of novel pyridazine analogues (3-aldehyde-1-phenylpyridazine derivatives)

Five new pyridazine compounds were synthesized. The usefulness of IR, 1HNMR and 13CNMR spectroscopy for the structural analysis of the new compounds is well established. The differences in molecular structure between one absorbing compound and another affected a shift in absorption wavelength (.max). The structure-activity relationship among the pyridazine derivatives was measured against some pathogens. Compound 3e was found to be a more active drug than the standard antibiotic, streptomycin SO4. © 2010 International Formulae Group. All rights reserved.Keywords: Biological evaluation, novel, pyridazine derivatives, antimicrobial agents.

Colorimetric sensing of Cu(ii): Cu(ii) induced deprotonation of an amide responsible for color changes

9,10-Anthraquinone-based chemosensor 1 indicates the presence of Cu(II) ions among other transition metal ions with high selectivity by a color change from yellow to dark red. Chemosensor 2 shows binding toward Cu(II), Ni(II) and Co(II) with color changes from yellow to dark red, red and pale green, respectively. Especially, Co(II) binding with chemosensor 2 causes significantly green fluorescence. On addition of Cu(II), 1 and 2 exhibit 76 and 80 nm red shifts in absorption wavelength (pH 7.0). The effect on pH by the formation of these 1-Cu(II) and 2-Cu(II) complexes was determined by UV-vis spectroscopic pH titration. In the pH range of 6-7.5, a maximum absorption was observed at 473 nm and exhibited the formation of deprotonated 1-Cu(II) and 2-Cu(II) complexes.

Effect of Alkyl Substitution on the Electronic Structure and Spectrum of Rhodamine

The structures of eight kinds of rhodamine compounds,substituted by different alkyls at different positions,were optimized using the density functional theory (DFT) at the B3LYP level. On the basis of these optimized structures,the influence of the substituting group on the electronic structures and spectral properties as well as frontier molecular orbitals of rhodamine were analyzed using the singlet configuration interaction (CIS) method and time dependent density functional theory (TD-DFT). Results indicate that the frontier molecular orbitals are mainly distributed in the xanthene ring of rhodamine when only one H atom of the two N-ends in the rhodamine molecule is substituted by alkyls. The distribution of the highest occupied molecular orbital (HOMO) is the greatest in the main conjugate ring and the difference in the distribution ratio between the HOMO and the the lowest unoccupied molecular orbital (LUMO) is small. When the four H atoms of the two N-ends in the rhodamine molecules are substituted by methyl,the bandgap is found to be the narrowest and the red shift in the gas maximum absorption wavelength is the largest. When the four H atoms of the two N-ends in rhodamine molecules are substituted by ethyl,the gas fluorescence maximum emission wavelength is the longest.

Vanadia–titania thin films for photocatalytic degradation of formaldehyde in sunlight

Thin films of vanadia–titania with good adhesion to the substrates have been deposited on various substrates such as glass slides, glass helix and silica raschig rings by simple sol–gel dip coating process using vanadium and titanium peroxide gel. The optimum concentration of vanadia in titania for obtaining good uniform viscous gel was found to be 0.5–4 wt% beyond which the vanadia particles disturb the gel network, resulting in the formation of a gelatinous precipitate. The films of vanadia–titania as well as the dried powder of the bulk gel were characterized by different characterization techniques. Optical characterization by UV–vis spectrophotometer showed a shift in optical absorption wavelength to the visible region that may be due to the incorporation of vanadia into titania structure. The XRD revealed the formation of anatase phase in pure titania as well as titania with up to 2% vanadia loading, whereas formation of rutile as minor phase along with anatase as major phase was observed at higher vanadia loading. The XRD did not show any peaks of vanadia phase up to 5% vanadia loading indicating either incorporation of vanadia into titania structure or high dispersion of amorphous vanadia on titania support. The pure and vanadia doped TiO 2 thin films were evaluated for their photocatalytic activity for degradation of methylene blue as a model pollutant under sunlight. Doping of V 2O 5 in TiO 2 showed an increase in the photo-degradation rate of methylene blue by a factor of 3–6.6 times compared to pure TiO 2. The highest rate has been obtained for 4% V 2O 5-doped TiO 2 films. Vanadia doped TiO 2 thin films were also found to be very active for photocatalytic degradation of formaldehyde from aqueous solution in sunlight.