Synthesis and characterization of biodiesel fuel based of esters of tall oil fatty acids

Synthesis of esters from tall oil fatty acids and lower aliphatic alcohols is studied, and characteristics of the products as substitutes or components of diesel fuel are determined.     

A quantum chemical study of the formation of 2-hydroperoxy-coelenterazine in the Ca<Superscript>2+</Superscript>-regulated photoprotein obelin

The Ca²⁺-regulated photoprotein obelin determines the luminescence of the marine hydroid Obelia longissima. Bioluminescence is initiated by calcium and appears as a result of the oxidative decarboxylation related to the coelenterazine substrate. The luciferase of the luminescent marine coral Renilla muelleri (RM) also uses coelenterazine as a substrate. However, three proteins are involved in the in vivo bioluminescence of these animals: luciferase, green fluorescent protein, and Ca²⁺-regulated coelenterazine-binding protein (CBP). In fact, CBP that contains one strongly bound coelenterazine molecule is the RM luciferase substrate in the in vivo bioluminescent reaction. Coelenterazine becomes available for oxygen and the reaction with luciferase only after binding CBP with calcium ions. Unlike Ca²⁺-regulated photoproteins, the coelenterazine molecule is not activated by oxygen in the CBP molecule. In this work, by means of quantum chemical methods the behavior of substrates in these proteins is analyzed. It is shown that coelenterazine can form different tautomers: CLZ(2H) and CLZ(7H). The formation of 2-hydroperoxy-coelenterazine is studied. According to the obtained data, these proteins use different forms of the substrates for the reaction. In obelin, the substrate is in the CLZ(2H) form that affords hydrogen peroxide. In RM, coelenterazine is in the CLZ(7H) form, and therefore, CBP is not activated by oxygen.     

Investigation of the protonation state of novel cationic lipids designed for gene transfection

In order to be used in versatile DNA delivery systems, novel cationic lipids were synthesized. The head groups of the new compounds represented by monoamines or oligoamines can be charged or uncharged depending on the environmental pH. Since their pK values are unknown, the protonation properties of these lipids have been studied in a wide pH range. In our experiments, the amphiphilic molecules were organized as a Langmuir monolayer at the air-water interface. Total reflection X-ray fluorescence (TRXF) was used to determine the 2D concentration of bromide counterions bound to a positively charged (protonated) Langmuir monolayer. The protonation rate of the novel cationic lipids was estimated by comparing the fluorescence intensity with that of dioctadecyldimethylammonium bromide monolayers as a reference. TRXF investigations were supplemented with results of film-balance measurements, grazing incidence X-ray diffraction, and X-ray reflectivity data. The results obtained display that the monolayers of all studied compounds are completely uncharged at pH values above 10. In the investigated pH region, the highest protonation rate of the monolayers is observed at pH 3. The influence of the monolayer packing density on the protonation properties is clearly shown.     

Physicochemical investigation of a lipid with a new core structure for gene transfection: 2-amino-3-hexadecyloxy-2-(hexadecyloxymethyl)propan-1-ol

Cationic liposomes/DNA complexes can be used as nonviral vectors for direct delivery of DNA-based biopharmaceuticals to damaged cells and tissues. In order to obtain more effective and safer liposome-based gene transfection systems, the new cationic lipid 2-amino-3-hexadecyloxy-2-(hexadecyloxymethyl)propan-1-ol (AHHP) was synthesized. In this paper we report on the synthesis of AHHP and investigations of its physical-chemical properties. Langmuir monolayers of AHHP were studied at the air/buffer interface by film balance measurements, grazing incidence X-ray diffraction (GIXD), and infrared reflection absorption spectroscopy (IRRAS). Structure and thermotropic phase behavior of AHHP in aqueous dispersion were examined by small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). The results show clear differences in structure and phase behavior of AHHP, both in the monolayer system and in aqueous dispersions, in dependence on the subphase pH due to protonation or deprotonation of the primary amine in the lipid head group. Thermodynamic data derived from pi-A isotherms provide information about the critical temperature (Tc), which is in rough agreement with the temperature of the lipid phase transition from gel to fluid state (Tm) found by X-ray and calorimetry studies of AHHP aqueous dispersions. The packing properties of the molecules in mono- and bilayer systems are very similar. DNA couples to the monolayer of the new lipid at low as well as at high pH but in different amounts. The DNA coupling leads to an alignment of adsorbed DNA strands indicated by the appearance of a Bragg peak. The distance between aligned DNA strands does not change much with increasing monolayer pressure.     

Polymeric Multilayer Capsules in Drug Delivery

Recent advances in medicine and biotechnology have prompted the need to develop nanoengineered delivery systems that can encapsulate a wide variety of novel therapeutics such as proteins, chemotherapeutics, and nucleic acids. Moreover, these delivery systems should be “intelligent”, such that they can deliver their payload at a well‐defined time, place, or after a specific stimulus. Polymeric multilayer capsules, made by layer‐by‐layer (LbL) coating of a sacrificial template followed by dissolution of the template, allow the design of microcapsules in aqueous conditions by using simple building blocks and assembly procedures, and provide a previously unmet control over the functionality of the microcapsules. Polymeric multilayer capsules have recently received increased interest from the life science community, and many interesting systems have appeared in the literature with biodegradable components and biospecific functionalities. In this Review we give an overview of the recent breakthroughs in their application for drug delivery.     

Liquid-vapor equilibrium in the system acetone-methanol-<Emphasis Type="Italic">N</Emphasis>-butylpyridinium hexafluorophosphate

The liquid-vapor equilibrium in the system acetone-methanol-N-butylpyridinium hexafluorophosphate was studied at 313.15 K.     

Kinetic stability of water-dispersed oil droplets encapsulated in a polyelectrolyte multilayer shell

The original theoretical model of polyelectrolyte adsorption onto water-dispersed colloid particles is extended to the system of polydisperse droplets of sunflower oil. Polycation (poly(allylamine hydrochloride)) and polyanion (poly(sodium 4-styrenesulfonate)) are taken in the theoretically projected concentrations to perform Layer-by-Layer assembly of a multilayer shell on the surface of oil droplets preliminary stabilized with a protein emulsifier (bovine serum albumin). The velocity of gravitational separation in suspension of encapsulated oil droplets is theoretically predicted and experimentally measured depending on the coating shell's thickness, aiming to clarify the mechanism to control over the separation process. Combining the theory and experimental data, the mass density of a polyelectrolyte multilayer shell assembled in a Layer-by-Layer fashion is obtained. Polyelectrolyte multilayer coated oil droplets are characterized by means of ζ-potential, and particle size measurements, and visualized by scanning electron microscopy.