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et al. / A novel water-soluble fluorescent probe Mass spectrometry. (5-I3C)-Retinal: m/z 285 (M + ); I3C incorporation calcd. from the mass spectra: 85%; exact mass calcd. for '3C,,'3CH,,0: 258.2174; found: 285.2164. ( 18-'3C)-Retinal: m/z 285 ( M + ) ; I3C incorporation calcd. from the mass spectra: 92.4%.from the Netherlands Organization for the Advancement of Pure Research (ZWO). The authors wich to hank Drs. C. Erkelens and Mr. F. Lefeber for recording the NMR spectra and Mr. J . J. van Houte for recording the mass spectra. The manuscript was reviewed by Miss S. Amadio.Abstract. The reaction of the 3,3',5,5'-tetramethyI-2,2'-pyrromethen-1,l '-BF, complex with chlorosulfonic acid and its subsequent neutralisation with sodium bicarbonate yields the titled compound 1, which, in addition to appropriate thermal and photochemical stability, possesses excellent fluorescent properties. As a preliminary assay of its potential usefulness as a fluorescent probe in medical and biological research, the chemical was administered intravenously to rats and possible signs of toxicity were recorded. The rats showed no apparent detrimental effects and excreted the compound in the urine within three hours. In tests in which Salmonella and E. coli strains were used as indicators of genotoxicity, no mutagenic effects were observed.

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A series o f Pseudomonas species -the so-called fluorescent group -produces peptidic sidero phores when grown in an iron-deficient medium. They all contain (1 S)-5-amino-2,3-dihydro-8,9-dihydroxy-1 H-pyrimido[ 1,2-a]quinoline-1 -carboxylic acid (la) [3] or its dihydro derivative as a chrom o phore. The amino group is amidically bound to a small dicarboxylic acid (usually several pyoverdins differing only in the nature of the latter can be found to co-occur) while the carboxylic group is linked to a peptide residue (not necessarily via its N-terminus). Pyoverdins produced by the various Pseudomonas species or even subspecies usually differ in the peptidic part of the molecule. By now the isolation o f about 20 pyoverdins with different peptidic portions has been described [5], but for only six of them (not counting variations in the na ture of the dicarboxylic acid) the structure has been determined by spectroscopic and chemical methods (three from Ps. sp. [6][7][8]