Search results for "upramolecular aggregate"
showing 8 items of 8 documents
Supramolecular Aggregates in Vacuum: Positively Mono-Charged Sodium Alkanesulfonate Clusters
2010
The formation and structural features of positively mono-charged aggregates of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium methane—(MetS), butane—(ButS) and octane—(OctS) sulfonate molecules in the gas phase have been investigated by electrospray ionization mass spectrometry, energy-resolved mass spectrometry and density functional theory (DFT) calculations. The experimental results show that the center-of-mass collision energy required to dissociate 50% of these mono-charged aggregates scantly depends on the length of the alkyl chain as well as on the aggregation number. This, together with the large predominance of mono-charged species in the mass spectra, was rationalized i…
Polyaspartylhydrazide Copolymer-Based Supramolecular Vesicular Aggregates as Delivery Devices for Anticancer Drugs
2008
In this paper we report on three different hydrophilic copolymers based on alpha,beta-polyaspartylhydrazide (PAHy) bearing butyric groups in the side chain (C 4) (PAHy-C 4) or a combination of butyric groups and positive charged residues ((carboxypropyl)trimethylammonium chloride, CPTACl) (PAHy-C 4-CPTA) that were synthesized and used for the preparation of new supramolecular vesicular aggregates (SVAs) containing gemcitabine as an antitumor drug. Gemcitabine-loaded SVAs containing synthesized PAHy derivatives were characterized from the physicochemical and technological point of view and the in vitro toxicity and anticancer activity on two different human cancer cell lines, i.e., CaCo-2 (h…
ION MOBILITY STUDIES ON SODIUM-BIS (2- ETHYLHEXIL)SULFOSUCCINATE (AOTNa) AGGREGATES
2012
The supramolecular charged aggregates formed during ESI ionization of AOTNa solutions under critical micelle concentration have been studied thorough ion mobility experiments. In particular, positively charged clusters with several charge states, ranging from +1 to +4, have been investigated. It has been found that, despite to previous investigations (Siuzdak et al. 1995, Nohara et al. 1998), specific ionic aggregates with a peculiar cross section are observed. Indeed a single drift time is observed for each charged aggregate. Using both calculated cross section and experimental calibration curves the experimental cross section of the observed cation has been determined. It is worth noting …
Degrees of freedom effect on fragmentation in tandem mass spectrometry of singly charged supramolecular aggregates of sodium sulfonates
2012
The characteristic collision energy (CCE) to obtain 50% fragmentation of positively and negatively single charged noncovalent clusters has been measured. CCE was found to increase linearly with the degrees of freedom (DoF) of the precursor ion, analogously to that observed for synthetic polymers. This suggests that fragmentation behavior (e.g. energy randomization) in covalent molecules and clusters are similar. Analysis of the slope of CCE with molecular size (DoF) indicates that activation energy of fragmentation of these clusters (loss of a monomer unit) is similar to that of the lowest energy fragmentation of protonated leucine-enkephalin. Positively and negatively charged aggregates be…
Structure, stability, and fragmentation of sodium bis(2-ethylhexyl)sulfosuccinate negatively charged aggregates in vacuo by MD simulations.
2014
Negatively charged supramolecular aggregates formed in vacuo by n bis(2-ethylhexyl)sulfosuccinate (AOT(-)) anions and n + n(c) sodium counterions (i.e., [AOT(n) Na(n+nc)](nc)) have been investigated by molecular dynamics (MD) simulations for n = 1 to 20 and n(c) = -1 to -5. By comparing the maximum excess charge values of negatively and positively charged AOTNa aggregates, it is found that the charge storage capability is higher for the latter systems, the difference decreasing as the aggregation number increases. Statistical analysis of physical properties like gyration radii and moment of inertia tensors of aggregates provides detailed information on their structural properties. Even for …
Aggregation in aqueous media of tri-block copolymers tuned by the molecular selectivity of cyclodextrins
2009
The water + cyclodextrin + poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) mixtures have been investigated to explore the temperature effect on the aggregation of the copolymer in the presence of cyclodextrins (CDs). The CDs with different cavity sizes were chosen because they may include either the hydrophilic poly(ethylene oxides) block or both kinds of blocks. The differential scanning calorimetry and viscosity experiments straightforwardly evidenced that the critical micellar temperature is shifted to larger values by adding a CD which is able to include the middle poly(propylene oxide) block while it is not influenced by the presence of CD which is selective to the poly…
Electrospray ion mobility mass spectrometry of positively charged sodium bis[2-ethythexyl)sulfosuccinate aggregates.
2014
Collision cross-sections (CCS) of positively singly and multiply charged aggregates of the surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) in the gas phase have been measured by quadrupole ion mobility time-of-flight mass spectrometry. Calibration of the observed drift times to the CCS of the AOTNa non-covalent aggregates was achieved by collecting, under the same experimental conditions, the drift times of a range of singly and multiply charged polyalanine peptides whose CCS had been obtained by conventional ion mobility spectrometry. Together with an obvious increase of the aggregate cross-section with the aggregation number, it was found that the aggregate cross-section increa…
Charged supramolecular assemblies of surfactant molecules in gas phase
2016
The aim of this review is to critically analyze recent literature on charged supramolecular assemblies formed by surfactant molecules in gas phase. Apart our specific interest on this research area, the stimuli to undertake the task arise from the widespread theoretical and applicative benefits emerging from a comprehensive view of this topic. In fact, the study of the formation, stability, and physicochemical peculiarities of non-covalent assemblies of surfactant molecules in gas phase allows to unveil interesting aspects such as the role of attractive, repulsive, and steric intermolecular interactions as driving force of supramolecular organization in absence of interactions with surround…