PubMed · 14333048
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R N MEALS. 1965-05-28. SILICONES.. https://doi.org/10.1111/j.1749-6632.1965.tb45384.x
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In the present study, the permeation characteristics of a hydrophilic basic compound (HBC) in a bio-mimetic parallel artificial membrane permeability assay (bio-mimetic PAMPA) were investigated in detail. The bio-mimetic PAMPA membrane was constructed on a hydrophobic filter by impregnating a lipid solution consisting of phosphatidylcholine (0.8%, w/w), phosphatidylethanolamine (0.8%, w/w), phosphatidylserine (0.2%, w/w), phosphatidylinositol (0.2%, w/w), cholesterol (1.0%, w/w), and 1,7-octadiene (97.0%, w/w). The pH-permeability curve (pH 3-10), the effect of lipid composition, concentration dependency (0.02-2.00 mM), and inhibition by other cationic compounds, were investigated for several HBCs. Ketoprofen and methylchlorpromazine were also employed as an acidic and a quaternary ammonium compound, respectively. At pH 3-6, the permeability of timolol, a HBC, was higher than expected from the pH-partition hypothesis, especially in the PI-containing membrane, whereas the pH-permeability curve of ketoprofen followed the pH-partition hypothesis. Permeation of HBC was saturable and inhibited by basic and quaternary ammonium compounds. Similar results were also found for methylchlorpromazine. The permeation characteristics of HBC observed in the present study are not usually expected in a passive permeation process across an artificial membrane. The participation of facilitated permeation of cationic species was suggested, in addition to a simple passive diffusion of un-dissociated species. Ion pair transport was suggested as a possible permeation mechanism of cationic species. However, further investigation is necessary to clarify the reason for the permeation characteristics of HBC.
A series of 5'-linked stilbene-DNA conjugates with different substituents in the distal aromatic ring of the stilbene was prepared, and the effect of the modifications on duplex stability was determined via UV-melting curves. A trimethoxystilbene derivative as a 5'-substituent increases duplex melting points by up to 12.2 degrees C per modification. With this alkoxystilbene substituent, terminal mismatches in DNA duplexes lower the melting point by up to 23.4 degrees C over the perfectly matched control, whereas terminal mismatches in unmodified DNA cause melting point depressions of no more than 6.1 degrees C. An aminomethylstilbene substituent linked to an oligopyrrolamide minor groove binder increases the melting point of an all-A/T decamer by up to 32.7 degrees C, thus shifting the melting point into a range typical for duplexes with statistical G/C-content. An affinity- and selectivity-enhancing effect was also observed when the trimethoxystilbene cap was employed on a small DNA microarray. The phosphoramidite of the trimethoxystilbene can be readily employed in automatic DNA synthesis, facilitating the generation of DNA chips with improved fidelity.
In this work, the effects of fluorination of polyimide thin films on surface and dielectric characteristics were studied using X-ray photoelectron spectroscopy (XPS) and dielectric spectrometry, respectively. The thermal and mechanical properties of the film were characterized by thermogravimetric analysis (TGA) and tensile strengths, respectively. The fluorine content of the polyimide thin film was increased with increasing treatment concentration, resulting in decreasing dielectric constant of the film. It was found that the replacement of fluorine led to the decrease of the local electronic polarizability of polyimide, or to the increase of the free volume, which can be attributed to the relatively large size of fluorine. Nevertheless, the fluorination did not significantly affect thermal or mechanical properties of the polyimide film under mild conditions in this system.