A new triclinic crystal form of human serum albumin (HSA), derived either from pool plasma (pHSA) or from a Pichia pastoris expression system (rHSA), was obtained from polyethylene glycol 4000 solution. Three-dimensional structures of pHSA and rHSA were determined at 2.5 A resolution from the new triclinic crystal form by molecular replacement, using atomic coordinates derived from a multiple isomorphous replacement work with a known tetragonal crystal form. The structures of pHSA and rHSA are virtually identical, with an r.m. s. deviation of 0.24 A for all Calpha atoms. The two HSA molecules involved in the asymmetric unit are related by a strict local twofold symmetry such that the Calpha atoms of the two molecules can be superimposed with an r.m.s. deviation of 0.28 A in pHSA. Cys34 is the only cysteine with a free sulfhydryl group which does not participate in a disulfide linkage with any external ligand. Domains II and III both have a pocket formed mostly of hydrophobic and positively charged residues and in which a very wide range of compounds may be accommodated. Three tentative binding sites for long-chain fatty acids, each with different surroundings, are located at the surface of each domain.
We demonstrated the generation of vortex beams using a GaAs-based ring-shaped Bragg reflector waveguide functioning as a highly dispersive angular diffraction element for potential applications in integrated mode-multiplexing in a multimode fiber. The polarization measurement of far-field patterns shows the formation of a radially polarized vortex beam. A tunable ring-shaped far-field pattern was demonstrated by tuning the wavelength of coupled light. We also integrated multi-ring vortex beam emitters, demonstrating the possibility of the creation and multiplexing of vortex beams with different orbital momentums.
The total synthesis of paclitaxel (Taxol) is described. Double Rubottom oxidation of the bis(silyl enol ether) derived from a tricarbocyclic diketone effectively installed a bridgehead olefin and C-5/ C-13 hydroxy groups in a one-step operation. The novel Ag-promoted oxetane formation smoothly constructed the tetracyclic framework of paclitaxel.
We developed a frequency-modulation atomic force microscopy (FM-AFM) system combined with Kelvin probe force microscopy (KFM) and scanning capacitance force microscopy (SCFM). Using the developed system, we investigated the surface structure and electrical characteristics of a bulk heterojunction (BHJ) sample consisting of a mixture of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly(3-hexylthiophene) (P3HT). The BHJ structure consisted of PCBM and P3HT molecules. These materials are often used as the active and charge transport layers in an organic solar cell, respectively. The results suggest that we succeeded in visualizing the phase separation in the BHJ sample using SCFM measurements. We illustrated the energy band diagrams from the KFM results and showed that band bending occurs from the organic material side at the interface with the indium–tin oxide substrate. Furthermore, the KFM and SCFM results suggested that charge separation occurs in the BHJ structure.
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