Solvent-free direct regioselective ring opening of epoxides with imidazoles

The reaction of different epoxides with commercially available imidazole at 60 °C leads to the formation of the corresponding 1-(β-hydroxyalkyl)imidazoles in a regioselective manner. When the reaction is applied to a chiral epoxide [(R)-styrene oxide], the expected chiral alcohol is isolated with the same enantiomeric excess. The use of benzimidazole as the heterocyclic component in the same process also allows the simple preparation of the corresponding 1-(β-hydroxyalkyl)benzimidazoles.     

Indene and pseudoazulene discotic liquid crystals: a synthetic and structural study

Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic structure. Although the molecules have rigid aromatic cores, they lack terminal tails and instead the polarizable atoms (S, halogens) or polar groups (CN, CO) act as unusual soft parts. On the basis of many structurally related materials, we conclude that for this type of compound molecular stacking in the solid state is a prerequisite for the appearance of a columnar mesophase, although other intermolecular interactions within the layers are also important in establishing liquid-crystalline order. The behavior reported for these mesomorphic molecules opens up new possibilities in the search for related molecular interactions that might be useful for the construction of supramolecular architectures with particular properties.     

Totally selective ring-opening of amino epoxides with ketones: a general entry to enantiopure (2R,3S)- and (2S,3S)-3-aminoalkano-1,2-diols

[Reaction: see text] Transformation of enantiopure diastereoisomers (2R,1'S)- and (2S,1'S)-2-(1-aminoalkyl)epoxides into the corresponding 4-(1-aminoalkyl)-1,3-dioxolanes is achieved by reaction with different ketones in the presence of BF3.Et2O. The conversion takes place in very high yields, total selectivity, and without epimerization. A mechanism to explain this transformation is proposed. The obtained 1,3-dioxolanes can be deprotected, and (2R,3S)- and (2S,3S)-3-aminoalkano-1,2-diols were isolated.     

Interfacial characteristics of β-casein spread films at the air–water interface

Casein is well known to be a good protein emulsifier and β-casein is the major component of casein and commercial sodium caseinate. This work studies the behaviour of β-casein at the interface. The interfacial characteristics (structure and stability) of β-casein spread films have been examined at the air–water interface in a Langmuir-type film balance, as a function of temperature (5–40°C) and aqueous phase pH (pH 5 and 7). From surface pressure–area isotherms (π–A isotherms) as a function of temperature we can draw a phase diagram. β-Casein spread films present two structures and the collapse phase. That is, there is a critical surface pressure and a surface concentration at which the film properties change significantly. This transition depends on the temperature and the aqueous phase pH. The film structure was observed to be more condensed and β-casein interfacial density was higher at pH 5. β-Casein films were stable at surface pressures lower than equilibrium surface pressure. In fact, no hysteresis was observed in π–A isotherms after continuous compression-expansion cycles or over time. The relative area relaxation at constant surface pressure (10 or 20 mN m⁻¹) and the surface pressure relaxation at constant area near the monolayer collapse, can be fitted by two exponential equations. The characteristic relaxation times in β-casein films can be associated with conformation–organization changes, hydrophilic group hydration and/or surface rheology, as a function of pH.     

Do charge-remote fragmentations occur under matrix-assisted laser desorption ionization post-source decompositions and matrix-assisted laser desorption ionization collisionally activated decompositions?

The precursor ions of tetraphenylporphyrins that are substituted with fatty acids can be introduced into the gas phase by matrix-assisted laser desorption ionization (MALDI) and undergo post-source and collisionally activated decompositions (CAD) in a time-of-flight mass spectrometer. The goal of the research is to obtain a better understanding of post-source decompositions (PSD); specifically, we asked the question of whether ions undergoing PSD have sufficient energy to give charge-remote fragmentations along an alkyl chain. We chose the porphyrin macrocycle because we expected it to act as an inert "support," allowing the molecule to be desorbed by MALDI and to be amenable to charge-remote fragmentation. MALDI-PSD and MALDI-CAD spectra are similar to high-energy CAD spectra and considerably more informative than low-energy CAD spectra, showing that charge-remote fragmentations of the fatty acid moieties do occur upon MALDI-PSD and MALDI-CAD.     

A Mesoionic Diselenolene Anion and the Corresponding Radical Dianion

Dichalcogenolenes are archetypal redox non-innocent ligands with numerous applications. Herein, a diselenolene ligand with fundamentally different electronic properties is described. A mesoionic diselenolene was prepared by selenation of a C2-protected imidazolium salt. This ligand is diamagnetic, which is in contrast to the paramagnetic nature of standard dichalcogenolene monoanions. The new ligand is also redox-active, as demonstrated by isolation of a stable diselenolene radical dianion. The unique electronic properties of the new ligand give rise to unusual coordination chemistry. Thus, preparation of a hexacoordinate aluminum tris(diselenolene) complex and a Lewis acidic aluminate complex with two ligand-centered unpaired electrons was achieved.     

Suppression of Liquid-Liquid Phase Separation and Aggregation of Antibodies by Modest Pressure Application

The high colloidal stability of antibody (immunoglobulin) solutions is important for pharmaceutical applications. Inert cosolutes, excipients, are generally used in therapeutic protein formulations to minimize physical instabilities, such as liquid–liquid phase separation (LLPS), aggregation and precipitation, which are often encountered during manufacturing and storage. Despite their widespread use, a detailed understanding of how excipients modulate the specific protein-protein interactions responsible for these instabilities is still lacking. In this work, we demonstrate the high sensitivity to pressure of globulin condensates as a suitable means to suppress LLPS and subsequent aggregation of concentrated antibody solutions. The addition of excipients has only a minor effect. The high pressure sensitivity observed is due to the fact that these flexible Y-shaped molecules create a considerable amount of void volume in the condensed phase, leading to an overall decrease in the volume of the system upon dissociation of the droplet phase by pressure already at a few tens of to hundred bar. Moreover, we show that immunoglobulin molecules themselves are highly resistant to unfolding under pressure, and can even sustain pressures up to about 6 kbar without conformational changes. This implies that immunoglobulins are resistant to the pressure treatment of foods, such as milk, in high-pressure food-processing technologies, thereby preserving their immunological activity.     

Selected Species of the Cucurbitaceae Family Used in Mexico for the Treatment of Diabetes Mellitus

In Mexico, Diabetes mellitus (DM) is a serious health problem, and although the current pharmacological treatments for DM such as insulin and oral hypoglycemics are available, the Mexican population continues to use medicinal plants in the treatment of DM. The antidiabetic properties of the plant species that belong to the Cucurbitaceae family has already been recognized worldwide. Since Mexico is one of the most important centers of diversity of Cucurbitaceae, the present work contributes to the review of the most used species of Cucurbitaceae in the treatment of DM in Mexico. The reviewed species (Cucurbita ficifolia, C. maxima, C. moschata, C. pepo, Ibervillea sonorae, Sechium edule, Citrullus lanatus, Cucumis melo, and C. sativus) revealed that the antidiabetic effects exerted are effective in a number of mechanisms involved in the complex pathogenesis of DM: hypoglycemic, antioxidant, anti-inflammatory, anti-obesity, protective effects on diverse organs and cells, as well as in the control of dyslipidemias; furthermore, the select species of the Cucurbitaceae family could also be essential components of diets for the control of DM in patients with the disease. Thus, the Cucurbitaceae species selected in the present work represent a source of antidiabetic agents that perhaps establish the bases for novel clinical treatments.