PubMed · 526550
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P Thiyagarajan, P K Ponnuswamy. 1979. Solvent accessibility study on tRNAPhe.. https://doi.org/10.1002/bip.1979.360180911
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We report a series of experiments and a theoretical model designed to systematically define and evaluate the relative importance of nanoparticle, oligonucleotide, and environmental variables that contribute to the observed sharp melting transitions associated with DNA-linked nanoparticle structures. These variables include the size of the nanoparticles, the surface density of the oligonucleotides on the nanoparticles, the dielectric constant of the surrounding medium, target concentration, and the position of the nanoparticles with respect to one another within the aggregate. The experimental data may be understood in terms of a thermodynamic model that attributes the sharp melting to a cooperative mechanism that results from two key factors: the presence of multiple DNA linkers between each pair of nanoparticles and a decrease in the melting temperature as DNA strands melt due to a concomitant reduction in local salt concentration. The cooperative melting effect, originating from short-range duplex-to-duplex interactions, is independent of DNA base sequences studied and should be universal for any type of nanostructured probe that is heavily functionalized with oligonucleotides. Understanding the fundamental origins of the melting properties of DNA-linked nanoparticle aggregates (or monolayers) is of paramount importance because these properties directly impact one's ability to formulate high sensitivity and selectivity DNA detection systems and construct materials from these novel nanoparticle materials.
The mechanical and physical properties of glycerol-plasticized wheat gluten films dried at different temperatures (20, 50, and 80 degrees C) and relative humidities (35 and 70% RH) were investigated. Dispersion of wheat gluten was prepared at pH 11 in aqueous solution. Films were obtained by casting the wheat gluten suspension, followed by solvent evaporation in a temperature and relative humidity controlled chamber. Decreasing relative humidity altered most of the mechanical properties. At 35% RH, tensile strength increased when drying temperature increased. However, at 70% RH, tensile strength decreased when temperature increased. Thickness of the films decreased by increasing temperature. Hypothetical coating strength increased with increasing drying temperature at 35% RH. However, at 70% RH, a maximum value was observed at 50 degrees C. Films produced at 80 degrees C exhibited low solubility in aqueous solution. Addition of 1.5% (w/v) sodium dodecyl sulfate increased solubility of all of the films except the film dried at 50 degrees C and 70% RH. Overall, drying temperature and relative humidity affected mechanical and physical properties of the wheat gluten films. However, the effect of drying temperature was more pronounced than the effect of relative humidity.
The D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) was used to increase the aqueous solubility and dissolution rate of furosemide. The solid dispersion of furosemide with TPGS was prepared by solvent method using methanol. The aqueous solubility and the dissolution rate of furosemide were rapid and markedly enhanced from the 1:2 furosemide-TPGS solid dispersion. The X-ray diffractometry showed that pure furosemide and furosemide contained within the physical mixture were crystalline in nature, whereas furosemide in the solid dispersion was not in crystalline form. The infrared spectroscopic analysis showed that an interaction, in the solid dispersion, such as an association between the functional groups of furosemide and TPGS might occur in the molecular level. The infrared spectroscopy and differential thermal analysis showed the physicochemical modifications of the furosemide from the solid dispersion. The solid dispersion technique with TPGS provides a promising way to increase the solubility and dissolution rate of poorly soluble drugs.