Effective long-range attraction between protein molecules in solutions studied by small angle neutron scattering

Small angle neutron scattering intensity distributions taken from cytochrome C and lysozyme protein solutions show a rising intensity at a very small wave vector Q, which can be interpreted in terms of the presence of a weak long-range attraction between protein molecules. This interaction has a range several times that of the diameter of the protein molecule, much greater than the range of the screened electrostatic repulsion. We show evidence that this long-range attraction is closely related to the type of anion present and ion concentration in the solution.     

A Study on the Luminescence and Energy Transfer of Single-Phase and Color-Tunable KCaY(PO(4))(2):Eu(2+),Mn(2+) Phosphor for Application in White-Light LEDs

Novel single-phased white light-emitting KCaY(PO(4))(2):Eu(2+),Mn(2+) phosphors for light-emitting diode (LED) applications were synthesized by conventional solid-state reaction. The emission hue could be controlled by tuning the Eu(2+)/Mn(2+) ratio via the energy transfer; the the emission hue of KCaY(PO(4))(2):Eu(2+),Mn(2+) varied from blue (0.1853, 0.2627) to white-light (0.3350, 0.3203) and eventually to purple (0.3919, 0.2867). The mechanism of energy transfer from a sensitizer Eu(2+) to an activator Mn(2+) in KCaY(PO(4))(2):Eu(2+),Mn(2+) phosphors was demonstrated to be an electric dipole-quadrupole interaction. Combining a NUV 405-nm chip and a white-emitting KCaY(PO(4))(2):1%Eu(2+),4%Mn(2+) phosphor produced a white-light NUV LED, demonstrating CIE chromaticity coordinates of (0.314, 0.329) and a color temperature of 6507 K.     

Incorporating intermicellar interactions in the fitting of SANS data from cationic wormlike micelles

Small-angle neutron scattering (SANS) from cationic wormlike micellar solutions composed of hexadecyltrimethylammonium bromide (CTABr) and hexadecylpyridinium bromide (CPyBr) in deuterated water was studied at 40 degrees C as a function of surfactant and salt concentrations. Two scattering functions of semiflexible chains incorporating excluded volume effects, with and without the intermicellar interactions, were used in SANS data model fitting. Two needed changes were made in the well-accepted models. Extensive and systematic SANS data analysis suggests the robustness of these corrected scattering functions when the intermicellar interactions are included. The influence of the headgroups and ionic strength on the contour length and micellar flexibility of these two systems was demonstrated on the basis of the quantitative structural information obtained from the model fitting. Micellar flexibility was found to depend on surfactant concentration, even when intermicellar interactions were taken into account, despite predictions to the contrary.     

Distinguishing the monomer to cluster phase transition in concentrated lysozyme solutions by studying the temperature dependence of the short-time dynamics

Recent combined experiments by small angle neutron scattering (SANS) and neutron spin echo (NSE) have demonstrated that dynamic clusters can form in concentrated lysozyme solutions when the right combination of a short-ranged attraction and a long-ranged electrostatic repulsion exists. In this paper, we investigate the temperature effect on the dynamic cluster formation and try to pinpoint the transition concentration from a monomeric protein phase to a cluster phase. Interestingly, even at a relatively high concentration (10% mass fraction), despite the significant change in the SANS patterns that are associated with the change of the short-ranged attraction among proteins, the normalized short-time self-diffusion coefficient is not affected between 5 and 40?°C. This is interpreted as a lack of cluster formation in this condition. However, at larger concentrations such as 17.5% and 22.5% mass fraction, we show that the average hydrodynamic radius increases significantly and causes a large decrease of the normalized self-diffusion coefficient as a result of cluster formation when the temperature is changed from 25 to 5?°C.     

SBA-15负载Mo、Co对稻壳与废轮胎共热解油的影响

在500℃下将不同比例的稻壳与轮胎混合物在SBA-15,Mo/SBA-15和Co/SBA-15三种催化剂下共热解,研究了不同催化剂及不同比例稻壳与轮胎的混合物对热解油产率、热值和比重等的影响,并对热解油元素组成进行分析.结果表明,随着轮胎比例的增大,热解油比重和粘度有所降低;当稻壳与轮胎比例为75:25时,Co/SBA-15对油中氧含量的降低和氢含量的提高表现出较好的效果.