carbocyanines and betadex

Ternary lipid compositions in model membranes segregate into large-scale liquid-ordered (L(o)) and liquid-disordered (L(d)) phases. Here, we show mum-sized lipid domain separation leading to vesicle formation in unperturbed human HaCaT keratinocytes. Budding vesicles in the apical portion of the plasma membrane were predominantly labelled with L(d) markers 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, 1,1'-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, 1,1'-didodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate and weakly stained by L(o) marker fluorescein-labeled cholera toxin B subunit which labels ganglioside GM(1) enriched plasma membrane rafts. Cholesterol depletion with methyl-beta-cyclodextrin enhanced DiI vesiculation, GM(1)/DiI domain separation and was accompanied by a detachment of the subcortical cytoskeleton from the plasma membrane. Based on these observations we describe the energetic requirements for plasma membrane vesiculation. We propose that the decrease in total 'L(o)/L(d)' boundary line tension arising from the coalescence of smaller L(d)-like domains makes it energetically favourable for L(d)-like domains to bend from flat mum-sized surfaces to cap-like budding vesicles. Thus living cells may utilize membrane line tension energies as a control mechanism of exocytic events.

Topics: Adhesiveness; beta-Cyclodextrins; Biophysical Phenomena; Carbocyanines; Cell Line; Cell Survival; Cytoplasmic Vesicles; Cytoskeleton; Exocytosis; Humans; Keratinocytes; Lipids

Several subphthalocyanine derivatives that contain an alkoxo substituent as an axial ligand (RO-Subpc, R = 9-anthracenemethyl, benzyl, phenyl, 3,5-dimethylbenzyl, 3,5-dimethylphenyl, 4-methylbenzyl, and 4-methylphenyl) were synthesized. The formation of inclusion complexes of RO-Subpc with beta-CD in DMSO and at the toluene/water interface was investigated by UV/Vis absorption spectroscopy, induced circular dichroism (ICD), and nuclear magnetic resonance (NMR) measurements. Interfacial tension measurements suggested that beta-CD adsorbed as a monolayer at the toluene/water interface and probably orientated towards the toluene phase with its primary face. The 1:1 composition of beta-CD.RO-Subpc inclusion complexes was confirmed in DMSO and at the toluene/water interface for BzO-Subpc, PhO-Subpc, MeBzO-Subpc, and MePhO-Subpc. A 2:1 inclusion complex of AnO-Subpc formed in DMSO. The observed ICD spectra of beta-CDRO-Subpc inclusion complexes are discussed with respect to molecular modeling and the simulation based on Tinoco-Kirkwood theory. Interestingly, the ICD spectra of beta-CD.BzO-Subpc and beta-CD.MeBzO-Subpc inclusion complexes exhibited a negative sign in DMSO and a positive sign at the toluene/water interface. This reversal of the ICD sign strongly suggests a difference in the structure of the inclusion complexes: beta-CD at the interface formed the inclusion complex with its primary face, whereas the secondary face of beta-CD bound favorably to RO-Subpc in DMSO.

Topics: beta-Cyclodextrins; Carbocyanines; Circular Dichroism; Dimethyl Sulfoxide; Molecular Structure; Optics and Photonics; Stereoisomerism; Toluene; Water