Sensitive and selective DNA probe based on “turn-on” photoluminescence of C-dots@RGO

In this study, highly hydrophilic and photoluminescent sheets of reduced graphene oxide decorated with carbon dots (C-dots@RGO), methylene blue (MB), and a probe DNA have been used for the detection of DNA. The photoluminescence of C-dots@RGO is quenched by MB, which is restored in the presence of a target DNA. The combination of the C-dots@RGO, MB, and a DNA probe is selective for perfectly matched DNA over mismatched DNA, mainly because relative to single-stranded DNA, double-stranded DNA intercalates more strongly with MB, but interacts more weakly with RGO. In the presence of a target DNA, MB intercalates with the as-formed double-stranded DNA and is released from the surface of C-dots@RGO, leading to “turn-on” photoluminescence. The practicality of this assay has been validated by the determination of tumor suppressor gene BRCA1, with linearity over the concentration range from 25 to 250 nM and a limit of detection (LOD, at a signal-to-noise ratio of 3) of 14.6 nM. The C-dots@RGO probe provides higher specificity towards target DNA than towards common salts, carbohydrates, amino acids, and proteins found in real samples. Having the advantages of simplicity, cost-effectiveness, selectivity, and sensitivity, the DNA-P/C-dots@RGO–MB probe on microwells has been successfully employed for the detection of DNA, suggesting its potential for multiple analyses of DNA targets when various DNA probes are employed.     

“On–off–on” pyrene-based fluorescent chemosensor for the selective recognition of Cu2+ and S2− ions and its utilization in live cell imaging

A new “on–off–on” fluorescence chemosensor (DPD) was designed, synthesized, and characterized based on pyrene and benzothiozole hydrazide. The probe DPD shows high affinity towards Cu²⁺ ions and the DPD-Cu²⁺ ensemble shows high sensitivity towards S²⁻ ions through the displacement method in the presence of other interfering ions. The detection limits of DPD for Cu²⁺ and S²⁻ ions were found to be 0.73 and 0.87 nM, respectively. Furthermore, the receptor was effectively applied to recognize Cu²⁺ and S²⁻ ions in real samples and live A549 cells through imaging studies.     

Expired pharmaceutical compounds as potential inhibitors for cast iron corrosion in acidic medium

The inhibition potential of some expired waste pharmaceutical drugs, namely cefpodoxime (CF), levofloxacin (LV), ofloxacin (OX) and linezolid (LZ) on cast iron corrosion in 1 M HCl has been tested for the first time by chemical (weight loss) and electrochemical (Tafel polarization and impedance spectroscopy) methods. At a constant acid concentration (1 M HCl), the inhibition efficiency (IE%) increased with the increase of the inhibitors’ concentration. At optimum inhibitor concentration, the CF exhibited the highest inhibition efficiency (95.2%). Inhibitors were adsorbed on the cast iron surface through the Langmuir adsorption isotherm at all concentrations and temperatures studied. Antagonism and synergism arising between the halide ions and the inhibitors were also explained. Thermodynamic parameters have been calculated and are discussed. Tafel polarization curves pointed to all inhibitors acting as mixed-type. Corrosion inhibition properties of the inhibitors have been inferred from FT-IR spectra, UV–Vis spectra, surface morphological analysis and wide-angle X-ray diffraction studies.     

Encapsulation of dicinnamalacetone in β-cyclodextrin: A physicochemical evaluation and molecular modeling approach on 1:2 inclusion complex

The aim of this research is to prepare and characterize the inclusion complex between Dicinnamalacetone (DCA) and β-CD. The inclusion complex of Dicinnamalacetone [DCA] and Beta-cyclodextrin [β-CD] was characterized both in solution and solid state by UV-visible spectroscopy, Fluorescence spectroscopy, Nano second time resolved fluorescence study, Fourier Transform Infra-red spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Powder X-ray diffractometry (XRD), Atomic Force Microscopy (AFM) and molecular modeling test. The 1:2 soichiometry of inclusion complex and binding constant values were determined by Benesi-Hildebrand plot and confirmed by Job's continuous variation method. FT-IR study indicated that the aromatic rings of the Dicinnamalacetone molecule were included in the β-CD cavities. The nano second time resolved fluorescence study revealed that DCA exhibits single exponential decay in aqueous medium and bi-exponential decay in β-CD medium indicating the formation of inclusion complex. From the DSC study it is observed that the thermal stability of the inclusion complex was significantly enhanced when compared with the pure compound due to strong interaction between DCA and β-CD. Furthermore, implementation of molecular modeling test confirmed that the complexation could reduce the energy of the system. The experimental studies revealed that the most predominant structure of 1:2 inclusion complex is the one in which the two aromatic ends of DCA were inserted into the cavities of two β-CD molecules.     

Molecular interaction studies of acrylic esters with 1-alcohols

Hydrogen bonding between 1-alcohols and acrylic esters in n-heptane has been studied by FTIR spectroscopic method. The formation constant of the 1:1 complexes has been calculated using Nash method. The values of formation constant and free energy change vary with alcohol and ester chain length, which suggests that the strengths of the intermolecular O-H...O=C bonds are shown to be dependent on the alkyl group of acrylic esters and the 1-alcohols and the results shows that the proton donating ability of 1-alcohols is in the order: 1-propanol<1-butanol<1-pentanol and the accepting ability of acrylic esters is in the order: methyl methacrylate相似文献   

Recent developments in monitoring calcium and protein interactions in cells using fluorescence lifetime microscopy

Time-resolved fluorescence lifetime microscopy (TRFLM) allows the combination of the sensitivity of fluorescence lifetime to environmental parameters to be monitored in a spatial manner in single living cells, as well as providing more accurate, sensitive, and specific diagnosis of certain clinical diseases and chemical analyses. Here we discuss two applications of TRFLM: (1) the use of nonratiometric probes such as Calcium Crimson, for measuring Ca²⁺; and (2) quantification of protein interaction in living cells using green and blue fluorescent protein (GFP and BFP, respectively) expressing constructs in combination with fluorescence resonance energy transfer microscopy (FRET). With respect to measuring Ca²⁺ in biological samples, we demonstrate thatintensity-based measurements of Ca²⁺ with single-wavelength Ca²⁺ probes such as Calcium Crimson may falsely report the actual Ca²⁺ concentration. This is due to effects of hydrophobicity of the local environment on the emission of Calcium Crimson as well as interaction of Calcium Crimson with proteins, both of which are overcome by the use of TRFLM. The recent availability of BFP (P4-3) and GFP (S65T) (which can serve as donor and acceptor, respectively) DNA sequences which can be attached to the carboxy-or amino-terminal DNA sequence of specific proteins allows the dual expression and interaction of proteins conjugated to BFP and GFP to be monitored in individual cells using FRET. Both of these applications of TRFLM are expected to enhance substantially the information available regarding both the normal and the abnormal physiology of cells and tissues.     

Electroluminescence of liquid dye solutions in a waveguide cell

Luminescence from dye molecules is observed when a liquid dye solution is subjected to a high electric field. The structure and geometry of the electrodes and the refractive index of the dye solution make the cell a waveguide. The radiation pattern of the electroluminescence and the spectral dispersion of the emission are explained.     

Dielectric relaxation of butyl acrylate—alcohol mixtures using time domain reflectometry

Dielectric relaxation measurements of butyl acrylate—alcohol mixtures at different concentrations and temperatures within the frequency range of 10 MHz to 10 GHz have been carried out using time domain reflectometry. Parameters such as the static permittivity, dielectric relaxation time, the Kirkwood correlation factor, the excess inverse relaxation time, and thermodynamic functions were determined and discussed to yield information on the molecular structure and dynamics of the mixture. The value of the dielectric properties decreases with increasing butyl acrylate concentration in alcohol and systematically varies with the length of alcohol alkyl chain. Negative values of the excess inverse relaxation time found for all concentrations and at all temperatures studied may indicate that the effective dipoles rotate slowly.     

Molecular interaction of alcohols with acrylic esters in non-polar solvents

The molecular interaction between alcohols (1-propanol, 1-pentanol, 1-heptanol, and 1-octanol) and acrylic esters (methyl methacrylate (MMA), ethyl methacrylate (EMA) and butyl methacrylate (BMA)) have been studied in carbon tetrachloride and benzene at 298 K using dielectric and FTIR spectroscopic methods. The result shows that, 1:1 complex is predominant in these systems. The strength of hydrogen bond (O–H:C=O) formation shows a significant dependence of on alkyl chain length of both alcohols and acrylic esters and the nature of the solvent used. To cite this article: K. Dharmalingam, et al., C. R. Chimie 9 (2006).