Spontaneous Formation Of Aggregates Research Articles

Spontaneous Vesicle Formation of Monododecenyl Phosphonic Acid in Water.

We report the synthesis of amphiphilic dodecenyl phosphonic acid PC12 from vinylphosphonic acid, a reactive phosphonic acid intermediate. The trans-P-C=C moiety enabled PC12 to disperse well in water. Surface tension and dynamic light scattering measurements revealed that PC12 exhibited high surface activity and reduced the surface tension of water from 72.0 to 23.6 mN/m, thereby resulting in the spontaneous formation of aggregates even in a dilute aqueous solution (critical aggregation concentration (CAC) = 4.8 × 10-4 M). In contrast to modern lipids with double-tailed structures, the PC12 of simple singletailed structure spontaneously formed bilayered vesicles, without an external energy supply. Compared with the strength of hydrogen bonds formed by the long, saturated alkyl chain of dodecyl phosphonic acid (DPA), the strength of PC12 intermolecular hydrogen bonds was weaker. The melting point of PC12 was approximately 20°C lower than that of DPA. These results indicate that the trans-P-C=C moiety was considerably important for spontaneous vesicle formation in water. Preliminary modeling of the morphological transitions of the closed bilayer structures in the vesicles was then conducted, by varying the pH and adding an α-helical peptide scaffold.

Ex vivo modelling of the formation of inflammatory platelet-leucocyte aggregates and their adhesion on endothelial cells, an early event in sepsis

Septicaemia is an acute inflammatory reaction in the bloodstream to the presence of pathogen-associated molecular patterns. Whole blood stimulation assays capture endotoxin-induced formation of aggregates between platelets and leucocytes using flow cytometry. We wanted to assess extent of spontaneous aggregate formation in whole blood stimulation assays and compare the effects of endotoxin and heat-killed, clinically relevant, bacterial pathogens on aggregate formation and then on adhesion of aggregates to TNFα-stimulated endothelial cells. We found that endotoxin (from Escherichia coli or Salmonella enteritidis) was not a suitable stimulus to provoke platelet-leucocyte aggregates in vitro, as it did not further increase the extent of aggregates formed spontaneously in stasis of hirudin-anticoagulated blood. Specifically, whole blood samples stimulated with or without LPS produced aggregates with a mean surface area of 140.97 and 117.68 μm2, respectively. By contrast, incubation of whole blood with heat-killed Klebsiella pneumoniae or Staphylococcus aureus produced significantly enhanced and complex cellular aggregates (with a mean surface area of 470.61 and 518.39 μm2, respectively) which adhered more frequently to TNFα (and free fatty acid)-stimulated endothelial cells. These were reliably captured by scanning electron microscopy. Adhesion of cellular aggregates could be blocked by incubation of endothelial cells with a commercial P-selectin antibody and an angiopoietin-2 ligand trap. In conclusion, we have developed an in vitro method that models the acute inflammatory reaction in whole blood in the presence of sepsis-relevant bacterial pathogen surfaces.

ChemInform Abstract: Organized Molecular Systems as Reaction Media

AbstractReview: 63 refs.

Organized molecular systems as reaction media

Abstract Media are among the most important factors to be considered for organic synthesis in soft and non-polluting conditions satisfying the conditions for sustainable development. Organized Molecular Systems (OMS) are very useful when efforts are being made to apply the twelve green chemistry principles, more precisely to replace organic solvents, to carry out reactions in water, to employ catalysis and biocatalysis, to economize molecules (and, of course, of atoms) and to work with low-energy conditions. These OMS posses a number of advantages: solubilization of substances that are not normally soluble in the continuous phase of OMS, localization of reactants and products, and selective orientation and stabilization of the various entities in the various stages of the reaction. Rapid and selective reactions of preparative amounts of substrate can be carried out in such media, which are also very suitable for mechanistic studies. First, we performed organic photoreactions in microemulsions (macroscopically homogeneous and transparent media). Thus, we were able to confirm the interfacial localization of the processes by means of chemical internal sensors and infrared spectroscopy; to propose a formulation strategy for diminishing the number of substrates in the medium (molecular economy principle); and to use high interfacial concentration to carry out reactions in the liquid phase although they are generally only possible in the solid state. The most important scientific point was the demonstration of the generalization of the amphiphilicity concept, by using polar non-aqueous solvents. 1986 saw the end of a controversy concerning the use of formamide in place of water. With this type of solvent, we have been able to perform important reactions: the Wacker process, Diels-Alder reactions, and olefin amidations. Then we postulated the formation of aggregates without surfactants if differential solvations were operative. All organic reactions can be influenced by the spontaneous formation of aggregates. To finish, with such systems, it is possible to orientate the reactivity of competitive reactions (e.g. cyclization and polymerization) and help to protect the environment, for example in the synthesis of clean surfactants in clean conditions. With the extension of these observations and results to the use of rigid objects (similar to rigid micelles) we were able to obtain very high enantioselective excess in chiral processes.

Aggregate Formation in Aqueous Solutions of Carboxymethylcellulose and Cationic Surfactants

The addition of cationic surfactants to an aqueous solution of an anionic polymer, carboxymethylcellulose (carboxyMC), causes the spontaneous formation of aggregates in a certain range of concentrations. Here we studied two surfactants, dodecyl and hexadecyl trimethylammonium bromide (DTAB and CTAB, respectively). Using different techniques (light scattering, potentiometry, viscosimetry, and zetametry), we found that a simple lengthening of the surfactant tail length by four CH2 groups drastically changes the aggregate morphology, size, and charge. We explored in detail how the surfactant and polymer concentrations act on these systems.

A Bioremediation Method Based on Self-Immobilization of Cells in Shallow Layer of Soil.

We proposed a novel bioremediation method, bioremediation by the self-immobilization system (BSIS), for application to treat pollution of soil spreading over a wide area. In this method, cells are immobilized by spontaneous formation of aggregates and retained in soil. We selected B. subtilis IFO3335 strain, which secretes viscous filaments and forms strong aggregates, as one of strains suitable for this bioremediation method based on self-immobilization, and studied their behavior in soil. These cells could be retained at a shallow layer under soil for a long period.