Monospecific antibodies were raised against a synthetic peptide K159 (SQGVVESMNKELKKIIGQVRDQAEHLKTA) reproducing the segment 147–175 of HIV‐1 integrase (IN). Synthesis of substituted and truncated analogs of K159 led us to identify the functional epitope reacting with antibodies within the C‐terminal portion 163–175 of K159. Conformational studies combining secondary structure predictions, CD and NMR spectroscopy together with ELISA assays, showed that the greater is the propensity of the epitope for helix formation the higher is the recognition by anti‐K159. Both the antibodies and the antigenic peptide K159 exhibited inhibitory activities against IN. In contrast, neither P159, a Pro‐containing analog of K159 that presents a kink around proline but with intact epitope conformation, nor the truncated analogs encompassing the epitope, were inhibitors of IN. While the activity of antibodies is restricted to recognition of the sole epitope portion, that of the antigenic K159 likely requires interactions of the peptide with the whole 147–175 segment in the protein [Sourgen F., Maroun, R.G., Frère, V., Bouziane, A., Auclair, C., Troalen, F. & Fermandjian, S. (1996) Eur. J. Biochem. 240, 765–773 ]. Actually, of all tested peptides only K159 was found to fulfill conditions of minimal number of helical heptads to achieve the formation of a stable coiled‐coil structure with the IN 147–175 segment. The binding of antibodies and of the antigenic peptide to this segment of IN hampers the binding of IN to its DNA substrates in filter‐binding assays. This appears to be the main effect leading to inhibition of integration. Quantitative analysis of filter‐binding assay curves indicates that two antibody molecules react with IN implying that the enzyme is dimeric within these experimental conditions. Together, present data provide an insight into the structure–function relationship for the 147–175 peptide domain of the enzyme. They also strongly suggest that the functional enzyme is dimeric. Results could help to assess models for binding of peptide fragments to IN and to develop stronger inhibitors. Moreover, K159 antibodies when expressed in vivo might exhibit useful inhibitory properties.

Water-soluble cadmium telluride (CdTe) quantum dots (QDs) were synthesized using thioglycolic acid as capping agent; this reaction was carried out at pH = 10.2 and refluxed at 100°C for 18 h. The CdTe QDs prepared at various reflux times from 1 to 18 h were coated on the glass substrates to obtain thin films of the CdTe QDs with the same thickness. The CdTe thin films were characterized by X-ray diffraction, ultraviolet-vis spectroscopy, and photoluminescence spectroscopy. The absorption thresholds of the CdTe thin films are blueshifted by about 0.65 eV with respect to the bulk value (1.5 eV), due to the quantum size effect as expected from the nanocrystalline nature of the CdTe QDs. X-ray diffraction showed that the films consisted of small CdTe nanocrystallites, 2.91 to 3.57 nm in size, showing quantum size effects. The effects of temperature on the electrical properties of the films were studied in detail. Electrical resistivity measurements were carried out for different films in the temperature range from 343 to 463 K. It is shown that activation energy increases by increasing the reflux time.

Summary The secondary ion mass spectrometry (SIMS) microscope is able to map chemical elements in tissue sections. Although absolute quantification of an element remains difficult, a relative quantitative approach is possible for soft tissue by using carbon (12C) as an internal reference present at large homogeneous and constant concentration in specimen and embedding resin. In this study, this approach is used to standardize the signal of an SIMS microscope for the quantification of halogens (19F—, 35Cl— and 79Br—) and calcium (40Ca+). Standard preparation was determined based on homogeneity and stability criteria by molecular incorporation (halogens) or mixing (calcium) in methacrylate resin. Standard measurements were performed by depth analysis on areas of 8 μm (halogens) and 150 μm (calcium) in diameter for 10–30 min, under Cs+ (halogens) or O2+ (calcium) bombardment. Results obtained from 100–120 measurements for each standard dilution show that the relationship between the signal intensity measured and the elemental concentration (μg/mg of wet tissue or mm) is linear in the range of biological concentrations. This quantitative approach was applied firstly to bromine of the 5‐bromo‐2′‐deoxyuridine (BrdU) used as nuclear marker of rat hepatocytes in proliferation. The second model concerns depletion of calcium concentration in cortical compartment in Paramecium tetraurelia during exocytosis. Then signal standardization in SIMS microscopy allows us to correlate quantitative results with those obtained from other methods.

In this work, a novel biosensor was fabricated for detection of DNA damage induced by 4-nonylphenol (NP) and also determination of NP. To achieve this goal, a glassy carbon electrode (GCE) was modified with chitosan (Chit), gold nanoparticles (Au NPs) and DNA-multiwalled carbon nanotubes (DNA-MWCNTs). Then, the DNA-MWCNTs/ Au NPs/Chit/GCE was incubated with methylene blue (MB) to obtain MB-DNA-MWCNTs/Au NPs/Chit/GCE in which MB was used as the redox indicator. The modifications applied to the GCE were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopic (EDS) and theoretical evidence. MB is a derivative of anthraquinone which can intercalate into double helix structure of DNA. By treating MB-DNA-MWCNTs/Au NPs/Chit/GCE with NP, a higher R ct was observed because the insertion of the NP may result in a more negative charge environment on the DNA surface which hinders accessibility of [Fe(CN) 6 ] 3-/4anion to the electrode surface. Change in the EIS response of the biosensor in the presence of NP was used to develop a novel system for monitoring the DNA damage induced by NP. The EIS technique was also used to develop a sensitive electroanalytical method for determination of NP.