A highly specific polyclonal antiserum to the environmental contaminant 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (p,p′-DDT)

A very selective polyclonal antiserum against 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (p,p′-DDT) was obtained by a careful choice of the haptenic structure (2,2-bis(4-chlorophenyl)-ethanol hemisuccinate). This hapten was conjugated to BSA to prepare the immunogen. The effects of different types of solid phases on the equilibrium reaction between the hapten on solid phase and the polyclonal antiserum were evaluated to obtain a fine tuning of the antiserum performances in terms of specificity for p,p′-DDT and sensitivity to low levels of this pesticide. The calibration curves obtained show that it is possible to set up a sensitive assay for p,p′-DDT, employing a p,p′-dichlorodiphenylacetic acid-based solid phase, with a detection limit of 0.12 ng/mL and a working range of about 0.21–40 ng/mL. Selectivity towards several p,p′-DDT-related substances was good (o,p-DDT 17%, p,p′-DDD 1.2% o,p-DDD 6.3%, p,p′-DDE 6.7%). Received: 4 November 1996 / Revised: 9 June 1997 / Accepted: 16 June 1997     

Chronic Low-Dose UVA Irradiation Induces Local Suppression of Contact Hypersensitivity, Langerhans Cell Depletion and Suppressor Cell Activation in C3H/HeJ Mice

Abstract— It has previously been demonstrated that chronic low-dose solar-simulated UV radiation could induce both local and systemic immunosuppression as well as tolerance to a topically applied hapten. In this study, we have used a chronic low-dose UV-irradiation protocol to investigate the effects of UVA on the skin immune system of C3H/HeJ mice. Irradiation with UVA+B significantly suppressed the local and systemic primary contact hypersensitivity (CHS) response to the hapten 2,4,6-trinitrochlo-robenzene. Furthermore UVA+B reduced Langerhans cell (LC) and dendritic epidermal T cell (DETC) densities in chronically UV-irradiated mice. Ultraviolet A irradiation induced local, but not systemic, immunosuppression and reduced LC (32%) but not DETC from the epidermis compared to the shaved control animals. Treatment of mice with both UVA+B and UVA radiation also induced an impaired secondary CHS response, and this tolerance was transferable with spleen cells. These results suggest that depletion of LC, but not DETC, may be involved in UVA-induced local immunosuppression in our model, and that tolerance was induced in the presence of normal numbers of DETC. Hence exposure of C3H/HeJ mice 5 days per week for 4 weeks with UVA can induce local immunosuppression and tolerance.     

High-temperature thermal behaviour of Cr-Doped LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> spinels synthesized by the sucrose-aided combustion method

Chromium doped spinels LiCr_YMn_2−YO₄ (0.2≤Y≤0.8) has been synthesized by the sucrose-aided combustion procedure. The thermal behaviour, phase homogeneity and structural characteristics of the samples were studied by thermal analysis, coupled mass spectrometry, and room-and high-temperature X-ray diffraction methods. It was found that the ‘as prepared’ samples contained residual organic impurities undetectable for X-ray diffraction, that burn out completely at 400°C. Samples treated between 400 and 750°C are single phase spinels, whose crystallites size increase from 10 to 50 nm on increasing the temperature. Cr-doping enhances the thermal stability of the spinels, which augments on increasing the Cr content Y. The enhanced thermal stability of the spinels has been accounted for based on the high excess stabilization energy of Cr³⁺ in octahedral ligand field.     

Recent discoveries on the structure of iodine(iii) reagents and their use in cross-nucleophile coupling

This perspective article discusses structural features of iodine(iii) compounds as a prelude to presenting their use as umpolung reagents, in particular as pertains to their ability to promote the selective coupling of two nucleophilic species via 2e⁻ oxidation.

This perspective article discusses structural features of iodine(iii) compounds as a prelude to presenting their use as umpolung reagents, to promote the selective coupling of two nucleophilic species via 2e⁻ oxidation.     

Glycosylation site analysis of human alpha-1-acid glycoprotein (AGP) by capillary liquid chromatography-electrospray mass spectrometry

A new anionic surfactant (RapiGest SF) was successfully used for site-specific analysis of glycosylation in human alpha-1-acid glycoprotein (AGP). By means of this analytical approach combined with capillary HPLC-mass spectrometry (and tandem mass spectrometry), the N-linked glycosylation pattern of AGP was explored. On the basis of mass matching and MS/MS experiments ca 80 different AGP-derived glycopeptides were identified. Glycosylation shows a markedly different pattern for the various glycosylation sites. At sites I and II, triantennary complex-type oligosaccharides predominate and at sites III, IV and V, tetra-antennary complex-type oligosaccharides predominate. Sites IV and V show the presence of additional N-acetyl lactosamine (Gal-GlcNAc) units (even higher degree of branching and/or longer antennae are also present).     

Rapid trace analysis of alachlor in water and vegetable samples

The use of a rapid and specific (cross-reactivity<4%) enzyme-linked immunosorbent assay (ELISA) for the determination of alachlor residues in water and vegetable samples is addressed. The analytical method consists of a fast extraction procedure followed by an optimised ELISA. The detection limit was 0.44 microg l(-1), with a linear range from 0.89 to 143.2 microg l(-1). For alachlor extraction from water samples, different solid-phase cartridges (C, Ph, C8 and C2) were assayed using MeOH as eluent. Extracts were diluted (1:4) with distilled water before ELISA. This procedure gave recoveries close to 100% with RSDs<14%. For vegetable samples, alachlor was extracted directly with MeOH and the extracts diluted 1:40 (v/v) with saline buffer prior to ELISA. The results obtained by the proposed procedure correlate well with the reference method (multiresidue extraction-GC-MS) for vegetable samples (r>0.85).     

The direct detection of a hydrogen bond in the solid state by NMR through the observation of a hydrogen-bond mediated (15)N [bond] (15)N J coupling

A new method for detecting hydrogen bonds in the solid state is presented. Using two-dimensional NMR correlation experiments, it is shown that a hydrogen-bond mediated J coupling can be observed in a powder under magic-angle spinning conditions, even though the J coupling is 2 orders of magnitude smaller than the dominant anisotropic interactions encountered in solid-state NMR. Specifically, the observation of a pair of peaks in a two-dimensional 15N-15N solid-state INADEQUATE experiment due to two nitrogens that have no covalent connectivity is attributed to the presence of a J coupling across a linking hydrogen bond.     

Photoinduced electroreduction of chlorophyllide on alkanethiol-coated mercury

Monolayers of n-alkanethiols of chain length from C12 to C18 were self-assembled on a hanging mercury drop electrode, and a film of chlorophyllide (Chlide) was adsorbed on top of them. The reduction photocurrents following illumination of the Chlide film were measured over the potential range in which the Chlide is electroinactive in the dark, and their action spectra were determined. Plotting the derivative of the photocurrents with respect to the applied potential against potential yields bell-shaped curves that can be fitted to a Gaussian. The potential of the Gaussian maximum was used to determine the reorganization energy lambda for the Chlide electroreduction process. An increase in the thiol chain length causes lambda to decrease regularly and the photocurrent to decay exponentially with the monolayer thickness, with a decay constant beta of about 0.17 A(-1).     

Purification of human leucocyte pyruvate kinase

The M2 form of pyruvate kinase (M2-PK) was purified from human leucocytes by a new method involving a succession of two different Dyematrex agarose chromatographies. The main step consisted of an orange dye affinity column with elution by fructose-1,6-diphosphate. This purification procedure allowed us to obtain M2-PK with a specific activity of 433 I.U./mg of protein, i.e. a 188-fold purification with an overall yield of 33%. The homogeneity of this preparation was verified by sodium dodecyl sulphate polyacrylamide gel electrophoresis and double immunodiffusion in Ouchterlony plates. Anti-M2-PK antibodies obtained from rabbit neutralized the enzyme activity. Their specificity with regard to other types of PK showed that anti-M2-PK also reacted with M1-PK but not with R-PK.     

Selective determination of trimethylamine in air by liquid chromatography using solid phase extraction cartridges for sampling

The selective determination of trimethylamine (TMA) in air by liquid chromatography is reported. Sampling is effected by flushing air through C18-packed solid-phase extraction (SPE) cartridges at a flow rate of 15 mL/min for 15 min. Next, TMA is desorbed from the cartridges and injected into the chromatographic system. The analyte is then selectively retained on a precolumn (20 mm x 2.1 mm i.d., packed with 30 microm, Hypersil C18 phase), and derivatized on-line by injecting 9-fluorenylmethyl chloroformate (FMOC). Finally, the TMA-FMOC derivative is transferred to the analytical column (125 mm x 4 mm i.d., LiChrospher 100 RP18, 5 microm), and monitored at 262 nm. The method was applied to the measurement of TMA in air in the 0.25-2.5 microg interval (equivalent to concentrations of TMA of 1.1-11 mg/m3), providing good linearity, reproducibility and accuracy. The mean recovery of TMA was (96 +/- 7%) (n = 12), and the limit of detection was 0.05 microg. The proposed procedure allows the selective determination of TMA in the presence of other primary and secondary short-chain aliphatic amines.