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Human placental factor XI11 (F XIII), purified from a commercial source and activated by calcium, was used to enzymatically cross-link individual whey proteins (a-lactalbumin, @-lactoglobulin, bovine serum albumin) and a mixture of total caseins and bovine serum albumin. Polymerization of DTTreduced a-lactalbumin and @-lactoglobulin was incomplete. Saturation of the response was reached in the time range 2-3 h and the substrate concentration range 10-20 mg/mL. A heat treatment had no effect on the polymerization of a-lactalbumin by F XIII,, whereas @-lactoglobulin gelled. A nonenzymatic gelation of both reduced proteins was observed above 50 mg/mL in the presence of calcium. Analysis of reaction products between BSA and caseins indicated that both proteins were polymerized, in the absence of DTT, through the formation of intermolecular cross-links. In contrast, polymerization of BSA required this reductant.

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We developed a method for the quantitative determination of sodium fluoride (NaF), sodium monofluorophosphate (SMFP) and amine fluoride (AmF) in toothpastes on the Belgian market. Samples were suspended in water and the determination was made using anion chromatography with conductivity detection after chemical suppression. The described ion chromatographic method is an easy and reliable isocratic high-performance liquid chromatography method for the determination of total soluble fluoride content in toothpastes. The analytical repeatability and reproducibility, the matrix effects and the method's decision limit of three different toothpastes containing NaF, SMFP and AmF at a concentration close to the permitted one of 0.15 g % total F are determined. All the samples analysed are in conformity with the Cosmetics Directive 76/768/EC; none exceeds the limit of 0.15 g %.

Dynorphin A, which displays a wide variety of physiological effects, binds to opioid receptors preferentially at the kappa receptor type. kappa-selective antagonists would be very useful as pharmacological and biochemical probes to study and better understand the action of dynorphin A at its preferred receptor. However, the development of such molecules has been elusive, and very few are known at this time. Taking these features into account, we have synthesized by the solid-phase procedure several analogues of dynorphin A containing various D-amino acid substitutions. The binding properties of the peptides have been examined at three main opioid binding sites (mu, delta, and kappa) and their kappa selectivity determined. Their biological activities have been tested in three specific pharmacological assays for agonist and/or antagonist properties. Introduction of D-Trp substitution leads to analogues, in particular [D- Trp2,8,D-Pro10]-, [D-Trp5,8,D-Pro10]-, and [D-Trp2,4,8,D-Pro10]dynorphin(1-11), showing antagonist properties in the isolated rabbit vas deferens preparation, a kappa specific bioassay. The antagonism against dynorphin A is weak, as indicated by the observed Ke values (433, 199, and 293 nM, respectively), and not very selective (kappa vs. mu). Such peptide analogues derived from the endogenous ligand and endowed with antagonist properties are the first ones reported to date and could open a promising way in designing more potent and selective kappa opioid antagonists.

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