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Fibroblast growth factor 20 (FGF20) is a member of the FGF family with potential for use in several different therapeutic categories. In this work, we provide the first structural characterization of FGF20 using a wide variety of approaches. Like other members of the FGF family, FGF20 appears to possess a beta-trefoil structure. The effect of pH on the conformation and thermal stability of FGF20 is evaluated using far-UV circular dichroism (CD), intrinsic and ANS fluorescence, and high-resolution derivative UV absorption spectroscopy. Empirical phase diagrams are constructed to describe the solution behavior of FGF20 over a wide pH and temperature range. The protein appears to be unstable at pH <5, with aggregation and precipitation observed during dialysis. A major heat-induced conformational change also causes aggregation and precipitation of FGF20 at elevated temperatures. The highest thermal stability is observed near neutral pH (Tm ~55 degrees C at pH 7). The effect of several high- and low-molecular mass polyanions on the thermal stability of FGF20 is also examined using CD, intrinsic fluorescence, and DSC analysis. Among these ligands, heparin exhibits the greatest stabilizing effect on FGF20, increasing the Tm by more than 10 degrees C.

Comparisons of the reflection and diffraction of thermal energy beams of 3He, 4He, H2, and D2 from the (001) surface of LiF are reported. Intense diffracted beams, including those of the second order, result from a freshly cleaved LiF surface without heating, and large exposures of H2O vapor do not reveal any measurable change in either the intensity, normalized to constant incident beam intensity, or location of such beams. The intensity and location of the individual beams are examined, taking into account the influence of adjacent beams. The locations of beams not so influenced display good agreement with the predictions of simple diffraction theory. The shapes and intensities of the diffracted beams are compared for the four gases with reference to possible inelastic effects. The decreasing intensities of diffracted beams for the same incident de Broglie wavelength are found to be in the order 4He, H2, and D2, i.e., in the order of increasing rotational energy coupling with the surface; 3He diffracted beams have intensities approximately the same as for 4He. The order of decreasing specular intensity, on the other hand, changes, depending on angle of incidence, but 3He is consistently more intense than for 4He, implying a mass collisional dependence. Preferentially scattered beams, similar to those reported for the heavier rare gases, are also evident although the presence of these beams only becomes apparent when conditions are such that the influence of other beams (diffracted and specular) is small. Selective adsorption studies reveal the presence of one or more bound energy states for each of the gases. The energy states for 3He and 4He are found to be significantly different, which is consistent with the results for the adsorption of these gases on charcoal. The energy states for H2 and D2 are identical, within the experimental error, and considerably greater in magnitude than for either 3He or 4He.