A family of amphiphilic cyclodextrins (6, 7) has been prepared through 6-S-alkylation (alkyl=n-dodecyl and n-hexadecyl) of the primary side and 2-O-PEGylation of the secondary side of alpha-, beta-, and gamma-cyclodextrins (PEG=poly(ethylene glycol)). These cyclodextrins form nonionic bilayer vesicles in aqueous solution. The bilayer vesicles were characterized by transmission electron microscopy, dynamic light scattering, dye encapsulation, and capillary electrophoresis. The molecular packing of the amphiphilic cyclodextrins was investigated by using small-angle X-ray diffraction of bilayers deposited on glass and pressure-area isotherms obtained from Langmuir monolayers on the air-water interface. The bilayer thickness is dependent on the chain length, whereas the average molecular surface area scales with the cyclodextrin ring size. The alkyl chains of the cyclodextrins in the bilayer are deeply interdigitated. Molecular recognition of a hydrophobic anion (adamantane carboxylate) by the cyclodextrin vesicles was investigated by using capillary electrophoresis, thereby exploiting the increase in electrophoretic mobility that occurs when the hydrophobic anions bind to the nonionic cyclodextrin vesicles. It was found that in spite of the presence of oligo(ethylene glycol) substituents, the beta-cyclodextrin vesicles retain their characteristic affinity for adamantane carboxylate (association constant K(a)=7.1 x 10(3) M(-1)), whereas gamma-cyclodextrin vesicles have less affinity (K(a)=3.2 x 10(3) M(-1)), and alpha-cyclodextrin or non-cyclodextrin, nonionic vesicles have very little affinity (K(a) approximately 100 M(-1)). Specific binding of the adamantane carboxylate to beta-cyclodextrin vesicles was also evident in competition experiments with beta-cyclodextrin in solution. Hence, the cyclodextrin vesicles can function as host bilayer membranes that recognize small guest molecules by specific noncovalent interaction.

We report that the efflux of 5(6)-carboxyfluorescein anions from neutral egg yolk phosphatidylcholine vesicles is mediated by oligo/polyarginines only in the presence of activating amphiphilic anions. Screening of anion activators reveals best synergism for amphiphilic carboxylates (fullerene > calix[4]arene approximately coronene > pyrene > calix[6]arene > alkyl), whereas amphiphilic sulfates show less satisfactory activation despite often lower effective concentrations. The analogous alcohols and one calix[4]arene diphosphate were inactive. These results are discussed in the context of a tentative anion carrier mechanism, where interactions with bilayer (interface-directed translocation) and carrier (arene-templated carboxylate-guanidinium pairing) contribute to activator efficiencies. Applied to HeLa cells, pyrenebutyrate is shown to significantly increase the uptake of a fluorescently labeled octaarginine in a concentration-dependent manner.

Abstract:Three water-soluble tetracationic quadrupolar chromophores comprising two three-coordinate boron -acceptor groups bridged by thiophene-containing moieties were synthesised for biological imaging applications. The derivative 3 containing the bulkier 5-(3,5-Me2C6H2)-2,2′-(C4H2S)2-5′-(3,5-Me2C6H2) bridge is stable over a long period of time, exhibits a high fluorescence quantum yield and strong one-(OPA) and two-photon absorption (TPA), with a TPA cross-section of 268 GM at 800 nm in water. Confocal laser scanning fluorescence microscopy studies in live cells indicate localisation of the chromophore at the mitochondria; moreover, cytotoxicity measurements prove biocompatibilty. Thus, chromophore 3 has excellent potential for one-and two-photon excited fluorescence imaging of mitochondrial function in cells.

Although cholesterol has been involved in the pathophysiology of Alzheimer disease (AD), its distribution in the cerebral cortex over the course of AD is unknown. We describe an original method to quantify cholesterol distribution using time-of-flight secondary ion mass spectrometry imaging. Cholesterol was unevenly distributed along the cortical thickness, being more abundant close to the white matter, in both control and AD cases. However, the mean cholesterol signal was significantly higher in the lower half of the cortex in AD samples compared to controls. This increase, when converted into cortical layers, was statistically significant for layers III and IV and did not reach significance in layers V + VI, the variability being too high at the interface between grey and white matter. The density of neurofibrillary tangles and of senile plaques was not statistically linked to the abundance of cholesterol. Cholesterol overload thus appears a new and independent alteration of AD cerebral cortex. The structure in which cholesterol accumulates and the mechanism of this accumulation remain to be elucidated.

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The core of the SP is made of aggregated amyloid-␤ (A ␤ ) peptide. A ␤ peptide is cleaved from a type 1 transmembrane protein, the amyloid protein precursor (APP), by the sequential activities of the ␤ and ␥ secretases. Special staining of microscopic sections from brain samples of AD patients has long suggested that SPs were enriched in lipids ( 5 ). The presence of cholesterol among those lipids is plausible since apolipoprotein E (apoE), a transporter of cholesterol, has been found in the SPs by immunohistochemistry ( 6, 7 ). The apo 4 allele is currently considered as the risk factor best associated with AD ( 8 ). Although the role of cholesterol has remained elusive, a much debated meta-analysis has shown that the use of statins, which inhibit cholesterol synthesis, was associated with a decreased prevalence of AD ( 9, 10 ). In cell cultures, the interaction between APP and cholesterol metabolism has been found so intricate that APP has been considered a sensor modulating the cholesterol content of the cell membrane ( 11 ).Histological studies have apparently confi rmed the cholesterol enrichment of the SPs in transgenic mice and AD patients ( 12 ). Two methods have been used. 1 ) Filipin, a well-known fl uorescent probe of membrane cholesterol, labels the SPs and subsequently resists the photobleaching that rapidly decreases the fl uorescence of the surrounding tissue. 2 ) An enzymatic technique based upon cholesterol oxidase activity was initially devised (and commercialized) for colorometric cholesterol assay (not for histochemistry). It is based on the oxidation of Amplex Red ® (10-acetyl-3,7-dihydroxyphenoxazine) into brightly fl uorescent resorufi n. Press, September 18, 2009 DOI 10.1194 Abbreviations: A ␤ , amyloid-␤ peptide; AD, Alzheimer's disease; apoE, apolipoprotein E; APP, amyloid protein precursor; LCM, laser capture microdissection; LC-MS, liquid chromatography coupled with mass spectrometry; LRP, low density lipoprotein receptor-related protein; SP, senile plaque. Published, JLR Papers in