Predicting cadmium fractions in agricultural soils using proximal sensing techniques.

Cadmium (Cd) accumulation in agricultural systems has caused global environmental and health concerns. Application of phosphate fertiliser to sustain plant production unintentionally accumulated Cd in agricultural soils over time. Rapid and cost-effective Cd monitoring in these soils will help to inform Cd management practices. Compared to total Cd analysis, examining chemical fractions by sequential extraction methods can provide information on the origin, availability, and mobility of soil Cd, and to assess the potential plant Cd uptake. A total of 87 air-dried topsoil (0-15 cm) samples from pastoral farms with a history of long-term application of phosphate fertiliser were analysed using wet chemistry methods for total Cd and Cd forms in exchangeable, acid soluble, metal oxides bound, organic matter bound, and residual fractions. The data acquired using three proximal sensing techniques, visible-near-infrared (vis-NIR), mid-infrared (MIR), and portable X-ray fluorescence (pXRF) spectroscopy were used as input for partial least squares regression to develop models predicting total Cd and Cd fractions. The average total Cd concentration was 0.58 mg Cd/kg soil. For total Cd, cross-validation (cv) results of models using individual vis-NIR, MIR, and pXRF data performed with normalised root mean squared error (nRMSEcv) of 26%, 30%, and 31% and concordance correlation coefficient (CCCcv) of 0.85, 0.77, and 0.75, respectively. For exchangeable Cd, model using MIR data performed with nRMSEcv of 40% and CCCcv of 0.57. For acid soluble and organic matter bound Cd, models using vis-NIR data performed with nRMSEcv of 11% and 33% and CCCcv of 0.97 and 0.84, respectively. Reflectance spectroscopy techniques could potentially be applied as complementary tools to estimate total Cd and plant available and potentially available Cd fractions for effective implementation of Cd monitoring programmes.

H-Gly-His psi (NHCO)Lys-OH, partially modified retro-inverso analogue of the growth factor glycyl-L-histidyl-L-lysine with enhanced enzymatic stability.

A partially retro-inverso analogue of the natural growth factor GHK was synthesized, in which the -CONH- bond between histidine and lysine was modified as -NHCO-. This modification is not expected to perturb the spatial distribution of the side-chains, and therefore the binding processes, compared to the native peptide. In the synthesis of the analogue two possible systems for deblocking of N pi-Bom group of histidine have been applied and compared. An alternative method is also described for the incorporation of malonyllysine into the peptide chain. When evaluated with respect to resistance toward degradation by human plasma in vitro, the new peptide analogue showed approximately a ten-fold increase in stability versus the parent peptide.

Protonation equilibria of quinolone antibacterials.

The acid-base properties of seven antibacterial 7-piperazinyl fluoroquinolone derivatives were studied by potentiometry and UV and NMR spectroscopy. These molecules contain two proton-binding sites of similar basicity, namely, the piperazine amino and the carboxylate groups, as proven by 1H NMR spectroscopy. The basicities are quantitated at the molecular level in terms of macroconstants, and also at the submolecular level in terms of microconstants. The microconstants are then used to calculate the concentration of the positive, zwitterionic, neutral, and negatively charged species (microspeciation). The zwitterionic forms always predominate over their neutral protonation isomers, but the zwitterionic:neutral concentration ratio is considerably different for the examined fluoroquinolone derivatives.