Design, synthesis and characterisation of a fluorescently labelled CyPLOS ionophore.
A novel fluorescently labelled synthetic ionophore, based on a cyclic phosphate-linked disaccharide (CyPLOS) backbone and decorated with four tetraethylene glycol tails carrying dansyl units, has been synthesised in 12 steps in 26% overall yield. The key intermediate in the synthetic strategy is a novel glucoside building block, serving through its 2- and 3-hydroxy groups as the anchor point for flexible tetraethylene glycol tentacles with reactive azido moieties at their ends. To test the versatility of this glucoside scaffold, it was preliminarily functionalised with a set of diverse probes--as fluorescent, redox-active or hydrophobic tags--either by reduction of the azides followed by condensation with activated carboxylic acid derivatives, or by a direct coupling with a terminal alkyne in a Cu(I)-promoted 1,3-dipolar cycloaddition. Tagging of the monomeric building block with dansyl residues allowed us to prepare a fluorescent, amphiphilic macrocycle, which was investigated for its propensity to self-aggregate in CDCl(3)--studied by means of concentration-dependent (31)P NMR spectroscopy experiments--and in aqueous solution, in which combined dynamic light scattering (DLS) and small-angle neutron scattering (SANS) measurements provided a detailed physico-chemical analysis of the self-assembled systems, mainly organised in the form of large vesicles. Its ion-transport properties through phospholipid bilayers, determined by HPTS fluorescence assays, showed this compound to be more active than the previously synthesised CyPLOS congeners. Solvent-dependent fluorescence changes for the labelled ionophore in liposome suspension established that the dansyl moieties are dispersed in environments with polarity intermediate between those of CH(2)Cl(2) and propan-2-ol, suggesting that the CyPLOS tentacles infiltrate the mid-polar region of the membranes.
Department of Organic Chemistry and Biochemistry, University Federico II of Napoli, Via Cintia, 4, 80126 Napoli, Italy.
Cinzia
C
Coppola
Antonio
A
Paciello
Gaetano
G
Mangiapia
Sabina
S
Licen
Mariangela
M
Boccalon
Lorenzo
L
De Napoli
Luigi
L
Paduano
Paolo
P
Tecilla
Daniela
D
Montesarchio
D005456:Fluorescent Dyes / Q000737:chemistry*; D017136:Ion Transport; D007476:Ionophores / Q000737:chemistry* / Q000378:metabolism; D047028:Macrocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D005456:Fluorescent Dyes; D007476:Ionophores; D047028:Macrocyclic Compounds; D009844:Oligosaccharides; D014867:Water