Reference

Fluorescent probes for opioid receptors

Fluorescent probes for opioid receptors. Kolb, Vera M.; Koman, Ahmet; Terenius, Lars (Dep. Chem. Biochem., South. Illinois Univ., Carbondale, IL 62901, USA). Life Sci., 33(Suppl. 1), 423-6 (English) 1983. CODEN: LIFSAK. ISSN: 0024-3205. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) Naloxone, naltrexone and oxymorphone were labeled in position 6 with fluorescein by coupling their hydrazone analogs with fluorescein isothiocyanate [3326-32-7]. Naloxone was also coupled in a similar way with rhodamine-B [72001-55-9]. The compds. thus obtained were: 1-(N)-fluoresceinylnaloxone thiosemicarbazone (6-FN) [88641-41-2], 1-(N)-fluoresceinylnaltrexone thiosemicarbazone [88641-43-4], 1-(N)-fluoresceinyloxymorphone thiosemicarbazone [88641-42-3]; 1-(N)-tetramethylrhodaminyl-B naloxone thiosemicarbazone [88646-65-5]. These compds. 72001-55-9 and 88646-65-5 are also in the experiment. were tested for opioid receptor binding in rat brain synaptosomal plasma membranes and for biol. activity on the guinea pig ileum. All compds. retained activity, showing some changes in affinity and binding profile compared to their parent compds. 6-FN, for example, showed decreased (~10x) affinity compared to naloxone in opiate displacement anal. but retained potency in displacement of opioid peptides. Antagonist activity of 6-FN in the guinea pig ileum bioassay was about ten-fold less than that of naloxone. .

The thiourea group modulates the fluorescence emission decay of fluorescein-labeled molecules

The thiourea group modulates the fluorescence emission decay of fluorescein-labeled molecules. Klonis, Nectarios; Sawyer, William H. (Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Australia). Photochemistry and Photobiology, 77(5), 502-509 (English) 2003 American Society for Photobiology. CODEN: PHCBAP. ISSN: 0031-8655. DOCUMENT TYPE: Journal CA Section: 9 (Biochemical Methods) We have investigated the spectral properties and emission characteristics of fluorescein-5-thiocarbamoyl-N,N'-caproate (FITC-ACA) to examine the origin of the complex emission decay often obsd. in fluorescein-labeled mols. 60-32-2 and 3326-32-7 which are cas registry numbers are also used here. The covalent attachment of fluorescein to e-amino-n-caproic acid does not perturb the prototropic transitions of the chromophore or the general fluorescence characteristics of the various prototropic forms. However, both the monoanion and dianion forms of FITC-ACA are quenched relative to free fluorescein and exhibit a complex emission decay that is described by two discrete lifetimes. The thiourea group that links the chromophore to the caproic acid is shown to modulate the emission properties of the FITC-ACA. We show that the emission decay can also be analyzed using the asym. distribution model of Alcala et al. In this anal., the tL and tu parameters that represent the lower and upper lifetime limits of the distribution reflect the quenched (0 ns) and unquenched lifetimes, resp. The b parameter that describes the distribution of lifetimes between the two limiting states can be related to the quenching efficiency of the thiourea group and to the structure and dynamics of the FITC-ACA mol. .