Heterogeneous Nucleation of Protein Crystals on Fluorinated Layered Silicate

Here, we describe an improved system for protein crystallization based on heterogeneous nucleation using fluorinated layered silicate. In addition, we also investigated the mechanism of nucleation on the silicate surface. Crystallization of lysozyme using silicates with different chemical compositions indicated that fluorosilicates promoted nucleation whereas the silicates without fluorine did not. The use of synthesized saponites for lysozyme crystallization confirmed that the substitution of hydroxyl groups contained in the lamellae structure for fluorine atoms is responsible for the nucleation-inducing property of the nucleant. Crystallization of twelve proteins with a wide range of pI values revealed that the nucleation promoting effect of the saponites tended to increase with increased substitution rate. Furthermore, the saponite with the highest fluorine content promoted nucleation in all the test proteins regardless of their overall net charge. Adsorption experiments of proteins on the saponites confirmed that the density of adsorbed molecules increased according to the substitution rate, thereby explaining the heterogeneous nucleation on the silicate surface

STM imaging of a model surface of Ru(4,4'-dicarboxy-2,2'-bipyridine)_2(NCS)_2 dye-sensitized TiO_2 photoelectrodes

A TiO_2(1 1 0)-(1 × 1) surface was prepared in an ultra-high vacuum, transported in laboratory air, and observed with a scanning tunneling microscope (STM) operated in a vacuum of 10^ Pa. Empty state images showed atomically flat terraces separated by single-height steps, on which 5-fold-coordinated surface Ti atoms were observed as spots arranged in a rectangular lattice. The Ru(4,4′-dicarboxy-2,2′-bipyridine)_2(NCS)_2 (N3) dye was adsorbed on the TiO_2 surface by immersing the TiO_2 wafer into an acetonitrile solution of the dye. In the empty state images, individual N3 molecules were observed as oval particles protruding by 0.6 nm from the TiO_2 surface. The oval shape elongated to the [11^^-0] directions was attributed to electron tunneling from tip to unoccupied states localized at the two carboxyl groups bound to the TiO_2 surface

Nuclide production cross sections in proton-induced reactions on Bi at GeV energies

Proton-induced nuclide production cross sections for Bi at incident energies of 0.4, 1.5, and 3.0 GeV are measured with the activation method using the proton beams accelerated from the Rapid-Cycling Synchrotron of the Japan Proton Accelerator Research Complex (J-PARC). A total of 127 cross-section data are obtained. The measured data are compared with two types of Monte Carlo-based spallation models (i.e. INCL++ coupled with ABLA07 and INCL4.6 coupled with GEM), and the evaluated nuclear data library, JENDL/HE-2007. The result showed that INCL++/ABLA07 overall agrees with the experimental data, whereas INCL4.6/GEM underestimates the production of fission fragments

Inversion of Circularly Polarized Luminescence in Phenylethynyl-substituted Binaphthol Derivatives

An inversion in the sign of circularly polarized luminescence (CPL) was achieved by strategically varying the substitution positions of phenylethynyl (PE) groups on the binaphthyl backbone while maintaining consistent axial chirality. Theoretical investigations indicated that the substitution position of PE groups on binaphthyl significantly influence the orientation of the transition dipole moments in the excited state, resulting in the sign inversion of CPL in 7-PEn compared with other substrates