Crystalline-ionic conductors of lithium ions have been investigated since 1970s. They showed lower conductivity than silver and copper ones. Recently, new super lithium ionic conductor, LGPS system was designed and developed. This material showed quite high conductivity, 12 mS/cm, but, its structure was completely new and unknown. By the assistance of crystallographic software using an ab initio method, the unknown structure was solved from multi-probe powder diffraction data. That type of software is really necessary on the material searching field.
This series of the tutorial articles of SHELXL are mainly for the general users in the X-ray structure analyses of the small molecules. The first lesson includes the overall features of the SHELXL, the process of the refinement using ins and res files, and the concept of the constraints and restraints, the generation and treatment of the H atoms in the refinement, and the determination of the absolute structure.
Cas9 is an RNA-guided DNA endonuclease and is implicated in the bacterial CRISPR-Cas adaptive immune system. Cas9 binds dual guide RNAs or single-guide RNA, and the Cas9-RNA complex recognizes and cleaves target double-stranded DNA via RNA-DNA complementarity. To understand this unprecedented, RNA-guided DNA cleavage mechanism, we solved the crystal structure of Cas9 in complex with guide RNA and target DNA. The ternary complex structure provides insights into the RNA-guided DNA cleavage mechanism, and paves the way for the rational design of new, Cas9-based tools.
For efficient use of sunlight, the light-harvesting core antenna (LH1) and the reaction center (RC) form a supramolecular complex (LH1-RC) in photosynthetic bacteria. We determined the crystal structure of a LH1-RC complex from a purple bacterium, Thermochromatium tepidum. The structure reveals that the RC is completely surrounded by 16 αβ-heterodimers. Calcium ions are bound at the periplasmic side of LH1. 32 bacteriochlorophyll and 16 spirilloxanthin molecules form an elliptical assembly in LH1. The pigment geometry involved in the absorption characteristics and excitation energy transfer is determined. In addition, ubiquinone channels and lipid molecules are observed in the complex.
Recent developments of luminescent copper(I) complexes are remarkable and some copper(I) complexes exhibit interesting chromic behaviors of luminescence in response to outer stimuli such as temperature, vapor, and mechanical force. In this article, recent progress of luminescent chromic copper(I) complexes is introduced. Tetranuclear copper(I) clusters with the cubanetype [Cu4I4] core present good examples of luminescence thermochromism, vapochromism, and mechanochromism. In addition, some unique chromic systems are found recently: A dinuclear copper(I) complex, [Cu2(μ-I)2(dmso)2(PPh3)2](dmso = dimethyl sulfoxide) exhibits unique photochromic luminescence on the basis of the flip and release of dmso. Highly luminescent mononuclear copper(I) complexes with ternary ligand systems, [CuI(PPh3)2(L)](L = N-heteroaromatic compounds) are generated by the mechanical grinding.
Cage-type mesoporous silicas display rich structural diversity. Among them, cage-type mesoporous silicas with tetrahedrally close-packed (TCP) structures can be described by four types of polyhedron, 512, 51262, 51263, and 51264. We have investigated (i) the Fm3m-Fd3m type intergrowth and (ii) several types of stacking fault in the Fd3m structure using transmission electron microscopy (TEM). The stacking faults can be explained by the stacking of three kinds of layer based on a description of the polyhedra. We have also observed that (iii) one of new stacking sequences, with a large repeating unit, contains these three layers and bears a close resemblance to one of the Frank-Kasper phases with rhombohedral symmetry known as μ-phase.
We report a method of femtosecond crystallography for determining radiation damage-free crystal structures of large proteins at atomic resolution. The name of the method is ʻserial femtosecond rotation crystallographyʼ (SF-ROX). Here, we demonstrate experimental details of SF-ROX and 1.9-Å radiation damage-free structure analysis of bovine cytochrome c oxidase, a large (420-kDa), highly radiation-sensitive membrane protein.