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Different Solubility (different + solubility)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Combined 13C NMR and DFT/GIAO studies of the polyketides Aurasperone A and Fonsecinone A

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2008
Sergio de Lazaro
Abstract Structural characterization by NMR spectroscopy and DFT calculations was performed for two dimeric naphtho-,-pyrones, the polyketides Aurasperone A and Fonsecinone A. Experimental data (13C NMR chemical shifts and interatomic geometries) were found to be in reasonable agreement with theoretical ones, obtained at B3LYP level for three different basis sets (6-31G/6-31G(d)/6-31G(d,p)). Additionally, the dipolar moments calculation allowed explaining the different solubility for these molecules. The 13C NMR theoretical chemical shifts were calculated with the GIAO method and the solvent effects were taken into account by means of the PCM approximation. In this work, the DFT/GIAO methodology shows to be a reliable tool in the assignment of experimental NMR chemical shifts of similar molecules. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]

Thermogravimetric investigation of the hydration behaviour of hydrophilic matrices

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2010
Lorena Segale
Abstract This article proposes thermogravimetric analysis (TGA) as a useful method to investigate the hydration behaviour of hydrophilic matrix tablets containing hydroxypropylmethylcellulose (HPMC), sodium carboxymethylcellulose (NaCMC) or a mixture of these two polymers and four drugs with different solubility. The hydration behaviour of matrix systems was studied as a function of the formulation composition and of the dissolution medium pH. TGA results suggest that the hydration of matrices containing HPMC is pH-independent and not affected by the characteristics of the loaded drug; this confirms HPMC as a good polymer to formulate controlled drug delivery systems. On the other hand, the performances of NaCMC matrix tablets are significantly affected by the medium pH and the hydration and swelling of this ionic polymer is influenced by the loaded drug. For systems containing the two polymers, HPMC plays a dominant role in the hydration/dissolution process at acidic pH, while at near neutral pH both the cellulose derivatives exert a significant influence on the hydration performance of systems. The results of this work show that TGA is able to give quantitative highlights on the hydration behaviour of polymeric materials; thus this technique could be a helpful tool to support conventional hydration/swelling/dissolution studies. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2070,2079, 2010 [source]

Encapsulation and/or Release Behavior of Bovine Serum Albumin within and from Polylactide-Grafted Dextran Microspheres

MACROMOLECULAR BIOSCIENCE, Issue 4 2004
Tatsuro Ouchi
Abstract Summary: Polylactide (PLA)-grafted dextran (Dex- graft -PLA) of various contents of sugar units was synthesized by anionic polymerization of L -lactide (L -LA) using the alkoxide of partially trimethylsilylated dextran (TMSDex) and subsequently removing the trimethylsilyl (TMS) groups. The copolymer showed different solubility from L -LA homopolymer with increasing the content of sugar units. We prepared bovine serum albumin (BSA)-loaded microspheres (MS)s according to a water-in-oil-in-water emulsion-solvent evaporation/extraction method using methylene chloride/DMSO as an organic cosolvent. MSs prepared from Dex- graft -PLA [MS(Dex- graft -PLA)s] exhibited higher loading efficiency of BSA than MSs prepared from PLLA [MS(PLLA)s]. The in vitro release rate of BSA from MS(Dex- graft -PLA) was faster than that from MS(PLLA). BSA released from MS(Dex- graft -PLA) maintained the secondary structure of native BSA to a great extent, compared with BSA released from MS(PLLA). Confocal fluorescence images of the differential interference micrographs over the fluorescence images of MS(PLLA) and MS(Dex- graft -PLA). [source]

Nanoscale Structural and Electronic Properties of Ultrathin Blends of Two Polyaromatic Molecules: A Kelvin Probe Force Microscopy Investigation

CHEMPHYSCHEM, Issue 4 2006
Vincenzo Palermo Dr.
Abstract We describe a Kelvin Probe Force Microscopy (KPFM) study on the morphological and electronic properties of complex mono and bi-molecular ultrathin films self-assembled on mica. These architectures are made up from an electron-donor (D), a synthetic all-benzenoid polycyclic aromatic hydrocarbon, and an electron-acceptor (A), perylene-bis-dicarboximide. The former molecule self-assembles into fibers in single component films, while the latter molecule forms discontinuous layers. Taking advantage of the different solubility and self-organizing properties of the A and D molecules, multicomponent ultrathin films characterized by nanoscale phase segregated fibers of D embedded in a discontinuous layer of A are formed. The direct estimation of the surface potential, and consequently the local workfunction from KPFM images allow a comparison of the local electronic properties of the blend with those of the monocomponent films. A change in the average workfunction values of the A and D nanostructures in the blend occurs which is primarily caused by the intimate contact between the two components and the molecular order within the nanostructure self-assembled at the surface. Additional roles can be ascribed to the molecular packing density, to the presence of defects in the film, to the different conformation of the aliphatic peripheral chains that might cover the conjugated core and to the long-range nature of the electrostatic interactions employed to map the surface by KPFM limiting the spatial and potential resolution. The local workfunction studies of heterojunctions can be of help to tune the electronic properties of active multicomponent films, which is crucial for the fabrication of efficient organic electronic devices as solar cells. [source]