Eighty-eight Pseudomonas aenrginosa isolates, most of them from the Collection of Bacterial Strains of the lnstitut Pasteur, Paris, were analysed for their pyoverdine-mediated iron incorporation system by different methods, including pyoverdine isoelectrofocusing analysis, pyoverdine-mediated growth stimulation, immunoblot detection of (ferri)pyoverdine outer-membrane receptor and pyoverdine-facilitated iron uptake. The same grouping of the strains was reached by each of these methods, resulting in the classification of the P. aenrginosa isolates, even those which were devoid of pyoverdine production, into three different siderophore types. Forty-two percent of the strains were identified with the --strain P. aeruginosa ATCC 15692 (group I), 42% were identical with the second type-strain P. aenrginosa ATCC 27853 (group II) and 16% reacted identically with the clinical isolate P. aenrginosa Pa6, whose pyoverdine was recognized in this study to be identical in structure to the pyoverdine produced by a natural isolate, P. aeruginosa strain R. No new pyoverdine species was detected among these strains.

Alzheimer's disease, Huntington's disease and prion diseases are part of a growing list of diseases associated with formation of beta-sheet containing fibrils. In a previous publication, we demonstrated that the self-association of the Alzheimer's beta-amyloid (Abeta) peptide is inhibited by peptides homologous to the central core domain of Abeta, but containing N-methyl amino acids at alternate positions. When these inhibitor peptides are arrayed in an extended, beta-strand conformation, the alternating position of N-methyl amino acids gives the peptide two distinct faces, one exhibiting a normal pattern of peptide backbone hydrogen bonds, but the other face having limited hydrogen-bonding capabilities due to the replacement of the amide protons by N-methyl groups. Here, we demonstrate, through two-dimensional NMR and circular dichroic spectroscopy, that a pentapeptide with two N-methyl amino acids, Abeta16-20m or Ac-K(Me)LV(Me)FF-NH2, does indeed have the intended structure of an extended beta-strand. This structure is remarkably stable to changes in solvent conditions and resists denaturation by heating, changes in pH (from 2.5 to 10.5), and addition of denaturants such as urea and guanindine-HCl. We also show that this peptide, despite its hydrophobic composition, is highly water soluble, to concentrations > 30 mm, in contrast to the nonmethylated congener, Abeta16-20 (Ac-KLVFF-NH2). The striking water solubility, in combination with the hydrophobic composition of the peptide, suggested that the peptide might be able to pass spontaneously through cell membranes and model phospholipid bilayers such as unilamellar vesicles. Thus, we also demonstrate that this peptide is indeed able to pass spontaneously through both synthetic phospholipid bilayer vesicles and cell membranes. Characterization of the biophysical properties of the Abeta16-20m peptide may facilitate the application of this strategy to other systems as diverse as the HIV protease and chemokines, in which there is dimerization through beta-strand domains.

Two pyoverdin-ampicillin conjugates were synthesized and their structures were confirmed by mass spectrometry and NMR spectroscopy. In contrast to ampicillin, the conjugates exhibited high antibacterial activity against Pseudomonas aeruginosa ATCC 15692 and ATCC 27853, effective only against the strain which is using the parent pyoverdin for iron uptake. This suggests that the conjugates enter the bacterial cell via the ferripyoverdin uptake pathway. Growth stimulation studies with conjugates hydrolysed

The aim of this study was (I) to define the scope and limitations of the Sharpless asymmetric dihydroxylation (AD) for polymer-bound olefins of different structural types and (II) to elaborate HRMAS NMR methods for the direct on-bead monitoring of the asymmetric dihydroxylation, including the on-bead determination of enantiomeric excess (ee). (I) 2-Methoxy-4-(2-propenyl)phenol (eugenol, E), 10-undecenoic acid (U), and (E)-4-hydroxystilbene (S) were bound to Wang-resin or TentaGel S-OH. These olefins gave low (E, 32%), intermediate (U, 88%), and very high enantiomeric excesses (S, >99%) when treated with AD mix β in solution. When bound to the polymers, the trend of the enantioselectivities remained the same [S (97%) > U (20-45%) > E (0-3%)]. However, the absolute ee values demonstrate that only the most selective types of substrates in homogeneous solution have practical potential for enantioselective AD on solid phase. (II) HRMAS NMR was successfully used for on-bead monitoring and for the first time for the ee measurement of the polymer-bound dihydroxylation product. As an example, the full assignment of all resonances of polymerbound 10-undecenoic acid (U) and its dihydroxylation product is presented. For the ee measurement, the polymer-bound dihydroxylation product was derivatized with Mosher's acid. The integration of seven different pairs of resonances in the 13 C HRMAS NMR of the diastereomeric Mosher esters gave (in each case) an ee value that agreed within <1% with that determined by chiral HPLC after cleavage of the AD product.

From ferribactins which accompany pyoverdins in iron deficient cultures of fluorescent pseudomonads a subunit has been obtained formed by condensation of D-tyrosin with L-2,4-diaminobutyric acid to give 2-(1-R-amino-2-p-hydroxyphenylethyl)-1,4,5,6-tetrahydropyrimidine-4-S′-carboxylic acid (1). Evidence is presented that 1 is the precur or of the typical pyoverdin chromophore 7 a.