Tunable Fusion and Aggregation of Liposomes Triggered by Multifunctional Surface-Cross-Linked Micelles

Water-soluble organic nanoparticles were prepared by cross-linking the micelles of a tripropargylated cationic surfactant by a diazide cross-linker in the presence of Cu(I) catalysts. The nanoparticles were decorated with hydrophilic ligands of different lengths on the surface. By interacting with negatively charged liposomes through tunable electrostatic interactions, these nanoparticles induced fusion and leakage of large unilamellar vesicles (LUVs). Fusion or aggregation of the membranes was highly sensitive to the rigidity and phase structures of the membranes, enabling thermally gated fusion to occur within a very narrow window of temperature change

Protection/Deprotection of Surface Activity and Its Applications in the Controlled Release of Liposomal Contents

The micelles of two tripropargylammonium-functionalized cationic surfactants were cross-linked by a disulfide-containing diazido cross-linker in the presence of Cu(I) catalysts. With multiple residual alkyne groups on the surface, the resulting surface cross-linked micelles (SCMs) were postfunctionalized by reaction with 2-azidoethanol and an azido-terminated poly(ethylene glycol), respectively, via the alkyne–azide click reaction. The water-soluble nanoparticles obtained had low surface activity due to the buried hydrophobic tails. Cleavage of the disulfide cross-links by dithiothreitol (DTT) exposed the hydrophobic tails and resumed surface activity of the “caged” surfactants within 2 min after DTT addition. The controlled breakage of the SCMs was used to lower the surface tension of aqueous solutions and trigger the release of liposomal contents on demand

Absolute Configuration of 2,2\u27,3,3\u27,6-Pentachlorinatedbiphenyl (PCB 84) Atropisomers

Nineteen polychlorinated biphenyl (PCB) congeners, such as 2,2′,3,3′,6-pentachlorobiphenyl (PCB 84), display axial chirality because they form stable rotational isomers, or atropisomers, that are non-superimposable mirror images of each other. Although chiral PCBs undergo atropselective biotransformation and atropselectively alter biological processes, the absolute structure of only a few PCB atropisomers has been determined experimentally. To help close this knowledge gap, pure PCB 84 atropisomers were obtained by semi-preparative liquid chromatography with two serially connected Nucleodex β-PM columns. The absolute configuration of both atropisomers was determined by X-ray single-crystal diffraction. The PCB 84 atropisomer eluting first and second on the Nucleodex β-PM column correspond to (aR)-(−)-PCB 84 and (aS)-(+)-PCB 84, respectively. Enantioselective gas chromatographic analysis with the β-cyclodextrin-based CP-Chirasil-Dex CB gas chromatography column showed the same elution order as the Nucleodex β-PM column. Based on earlier reports, the atropisomers eluting first and second on the BGB-172 gas chromatography column are (aR)-(−)-PCB 84 and (aS)-(+)-PCB 84, respectively. An inversion of the elution order is observed on the Cyclosil-B gas chromatography and Cellulose-3 liquid chromatography columns. These results advance the interpretation of environmental and human biomonitoring as well as toxicological studies

Enhancing Binding Affinity by the Cooperativity between Host Conformation and Host–Guest Interactions

Glutamate-functionalized oligocholate foldamers bound Zn(OAc)2, guanidine, and even amine compounds with surprisingly high affinities. The conformational change of the hosts during binding was crucial to the enhanced binding affinity. The strongest cooperativity between the conformation and guest-binding occurred when the hosts were unfolded but near the folding–unfolding transition. These results suggest that high binding affinity in molecular recognition may be more easily obtained from large hosts capable of strong cooperative conformational changes instead of those with rigid, preorganized structures

Biphenyl-4-yl 2,2,2-trichloro­ethyl sulfate

The mol­ecular structure of the title compound, C14H11Cl3O4S, displays a biphenyl dihedral angle of 4.9 (2)° between the benzene rings, which is significantly smaller than the calculated dihedral angle of 41.2° of biphenyl derivatives without ortho substituents. The CAr—O bond length of 1.432 (4) Å is comparable with other sulfuric acid biphenyl-4-yl ester 2,2,2-trichloro­ether ester derivatives without electronegative substituents in the sulfated phenyl ring

3′,4′-Dichloro­biphenyl-4-yl 2,2,2-trichloro­ethyl sulfate

The four independent mol­ecules in the asymmetric unit of the title compound, C14H9Cl5O4S, are related by pseudo-inversion centres. The mol­ecules have Caromatic—O bond lengths ranging from 1.426 (10) to 1.449 (9) Å and biphenyl-4-yl sulfate ester bond lengths ranging from 1.563 (6) to 1.586 (6) Å, which is comparable to structurally related sulfuric acid diesters. The dihedral angles between the benzene rings range from 22.5 (4) to 29.1 (4)° and are significantly smaller than the calculated dihedral angle of 41.2°

4′-Chloro­biphenyl-3-yl 2,2,2-trichloro­ethyl sulfate

The title compound, C14H10Cl4O4S, is a 2,2,2-trichloro­ethyl-protected precursor of 4′-chloro­biphenyl-3-yl sulfate, a sulfuric acid ester of 4′-chloro­biphenyl-3-ol. The Caromatic—O and O—S bond lengths of the Caromatic—O—S unit are comparable to those in structurally analogous biphenyl-4-yl 2,2,2-trichloro­ethyl sulfates with no electro­negative chlorine substituent in the benzene ring with the sulfate ester group. The dihedral angle between the aromatic rings is 27.47 (6)°

4′-Chloro­biphenyl-4-yl 2,2,2-trichloro­ethyl sulfate

The title compound, C14H10Cl4O4S, is an inter­mediate in the synthesis of the PCB sulfate monoester of 4′-chloro-biphenyl-4-ol. Both the sulfate monoester and 4′-chloro-biphenyl-4-ol are metabolites of PCB 3 (4-chloro­biphen­yl). There are two mol­ecules with different conformations in the asymmetric unit. The solid state dihedral angles between the benzene rings are 18.52 (10) and 41.84 (16)° in the two mol­ecules, whereas the dihedral angles between the least-squares plane of the sulfated benzene ring and O—S (Ar—C—O—S) are 66.2 (3) and 89.3 (3)°. The crystal was an inversion twin with a refined component fraction of 0.44 (7)

Electron ionization mass spectral fragmentation study of sulfation derivatives of polychlorinated biphenyls

<p>Abstract</p> <p>Background</p> <p>Polychlorinated biphenyls are persistent organic pollutants that can be metabolized via hydroxylated PCBs to PCB sulfate metabolites. The sensitive and selective analysis of PCB sulfate monoesters by gas chromatography-mass spectrometry (GC-MS) requires their derivatization, for example, as PCB 2,2,2-trichloroethyl (TCE) sulfate monoesters. To aid in the identification of unknown PCB sulfate metabolites isolated from biological samples, the electron impact MS fragmentation pathways of selected PCB TCE sulfate diesters were analyzed and compared to the fragmentation pathways of the corresponding methoxylated PCBs.</p> <p>Results</p> <p>The most abundant and characteristic fragment ions of PCB TCE sulfate diesters were formed by releasing CHCCl₃, SO₃, HCl₂and/or CCl₃from the TCE sulfate moiety and Cl₂, HCl, ethyne and chloroethyne from an intermediate phenylcyclopentadienyl cation. The fragmentation pattern depended on the degree of chlorination and the position of the TCE sulfate moiety (i.e., <it>ortho </it>vs. <it>meta/para </it>to the second phenyl ring), but were independent of the chlorine substitution pattern. These fragmentation pathways are similar to the fragmentation pathways of structurally related methoxylated PCBs.</p> <p>Conclusion</p> <p>Knowledge of the fragmentation patterns of PCB TCE sulfate diesters will greatly aid in determining the position of sulfate moiety (<it>ortho </it>vs. <it>meta/para</it>) of unknown PCB sulfate metabolites isolated from environmental or laboratory samples.</p