Stress‐Induced Domain Wall Motion in a Ferroelastic Mn3+ Spin Crossover Complex

Domain wall motion is detected for the first time during the transition to a ferroelastic and spin state ordered phase of a spin crossover complex. Single‐crystal X‐ray diffraction and resonant ultrasound spectroscopy (RUS) revealed two distinct symmetry‐breaking phase transitions in the mononuclear Mn³⁺ compound [Mn(3,5‐diBr‐sal₂(323))]BPh₄, 1. The first at 250 K, involves the space group change Cc→Pc and is thermodynamically continuous, while the second, Pc→P1 at 85 K, is discontinuous and related to spin crossover and spin state ordering. Stress‐induced domain wall mobility was interpreted on the basis of a steep increase in acoustic loss immediately below the the Pc‐P1 transition     

Alkaline Phosphatase-based Electrochemical Analysis for Point-of-Care Testing

Point-of-care testing (POCT) devices have evolved to provide beneficial information about an individual's health whenever needed. Enzyme-based analytical devices have facilitated the highly selective detection of numerous biological molecules and ions. Enzymes are commonly used as the tags of recognition components, such as antibodies, to generate and amplify detection signals. Particularly, alkaline phosphatase (ALP) is one of the most widely used enzymes because of its high turnover number and low cost. Rapid response time and the incorporation of many sensors fabricated by micro/nano processing technologies are the advantages in using electrochemical devices as analytical tools. Therefore, ALP-based electrochemical devices have potential applications for more practical POCT platforms. This review summarizes recent research progress of ALP-based electrochemical devices for POCT. In addition to ALP substrates, the application of ALP-based immunosensors, aptasensors, and DNAzyme sensors are discussed.     

A Ligand That Targets CUG Trinucleotide Repeats

The development of small molecules that can recognize specific RNA secondary and tertiary structures is currently an important research topic for developing tools to modulate gene expression and therapeutic drugs. Expanded CUG trinucleotide repeats, known as toxic RNA, capture the splicing factor MBNL1 and are causative of neurological disorder myotonic dystrophy type 1 (DM1). Herein, the rational molecular design, synthesis, and binding analysis of 2,9‐diaminoalkyl‐substituted 1,10‐phenanthroline (DAP), which bound to CUG trinucleotide repeats, is described. The results of melting temperature (T_m) analyses, surface plasmon resonance (SPR) assay, and electrospray spray ionization time‐of‐flight (ESI‐TOF) mass spectrometry showed that DAP bound to r(CUG)₉ but not to r(CAG)₉ and r(CGG)₉. The dual luciferase assay clearly indicated DAP bound to the r(CUG)_n repeat by affecting the translation in vitro.     

Moisture driven aging mechanism of LiFePO4 subjected to air exposure

The impact of air exposure on LiFePO₄–C nanocomposites has been investigated at moderate temperature. We show here that the storage in 120 °C hot air for 30 days leads not only to the material delithiation but also to the formation of an amorphous ferric phosphate side-phase, accounting for 38% of the total iron. The formed phase is found to be partially hydrated, suggesting a water-driven aging mechanism and a proposed hypothetic formula: Li_xFePO₄(OH)_x. The side-phase displays new electrochemical activity but poor cyclability and the overall battery performance is thus deteriorated. The regeneration of pristine structure, together with the performance recovery can be achieved by a simple thermal treatment under inert atmosphere.     

Fluorometric determination of fluoride ion by reagent tablets containing 3-hydroxy-2'-sulfoflavone and zirconium(IV) ethylenediamine tetraacetate

A reagent tablet for determination of fluoride ion has been prepared using ethylenediamine-N,N,N′,N′-tetraacetate complex of zirconium (Zr-EDTA), 3-hydroxy-2′-flavone (FS) and an appropriate pH buffer. Dissolving of the tablet into water exhibits an intense blue fluorescence (λ_max = 460 nm) upon excitation at 377 nm and the fluorescence intensity decreases with the presence of fluoride ion. Hence, a simple fluorescent detection procedure for fluoride ion in aqueous media was successfully constructed with this tablet. The principle of this detection system is the ligand exchange reaction of FS bound to Zr-EDTA with fluoride ion. The present system provides an easy, rapid and selective determination method of fluoride ion ranging from 5 × 10⁻⁶ to 1 × 10⁻³ mol dm⁻³. The measurement of real samples with this tablet showed the similar results as those by the common method with the Alfusone reagent.     

Structure and photochemical properties of (mu-alkoxo)bis(mu-carboxylato)diruthenium complexes with naphthylacetate ligands

Two new dinuclear Ru(III) complexes containing naphthalene moieties, K[Ru2(dhpta)(mu-O2CCH2-1-naph)2] (1) and K[Ru2(dhpta)(mu-O2CCH2-2-naph)2] (2) (H5dhpta = 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, naph-1-CH2CO2H = 1-naphthylacetic acid, naph-2-CH2CO2H = 2-naphthylacetic acid), were synthesized. Complex 2 crystallized as an orthorhombic system having a space group of Pbca with unit cell parameters a = 10.6200(5) A, b = 20.270(1) A, c = 35.530(2) A, and Z = 8. EXAFS analysis of 1 and 2 in the solid states and in solution clarified that the dinuclear structures of 1 and 2 were kept in DMSO solutions. Variable-temperature magnetic susceptibility data indicated that the two Ru(III) centers are strongly antiferromagnetically coupled as shown by the large coupling constants, J = -581 cm(-1) (1) and -378 cm(-1) (2). In the cyclic voltammograms of 1 and 2, one oxidation peak and two reduction peaks which were assigned to the redox reaction of the ruthenium moieties were observed in DMF. The large conproportionation constants estimated from the reduction potentials of Ru(III)Ru(III) and Ru(III)Ru(II) indicated the great stability of the mixed-valent state. The mixed-valent species [Ru(III)Ru(II)(dhpta)(mu-O2CCH2-R)2](2-) (R = 1-naph (6) and R = 2-naph (7)) were prepared by controlled potential electrolysis of 1 and 2 in DMF. The electronic absorption spectra of 6 and 7 were similar to that of [Ru(III)Ru(II) (dhpta)(mu-O2CCH3)2](2-) which is a typical Class II type mixed-valent complex. The fluorescence decay of 1 and 2 indicated that there are two quenching processes which come from the excimer and monomer states. The short excimer lifetimes of 1 and 2 were ascribed to the energy transfer from the naphthyl moieties to the Ru centers. The different excimer ratio between 1 and 2 suggested that the excimer formation is affected by the conformation of the naphthyl moieties in the diruthenium(III) complexes.     

Rapid and simultaneous determination of nonsteroidal anti-inflammatory drugs in human plasma by LC–MS with solid-phase extraction

A rapid, selective and sensitive analytical method for the simultaneous determination of 16 nonsteroidal anti-inflammatory drugs (NSAIDs) in human plasma was carried out using Oasis HLB solid-phase extraction (SPE), followed by reversed-phase high-performance liquid chromatography and quadrupole mass spectrometry with electrospray ionization operated in the negative ion mode. The recoveries of NSAIDs from human plasma by SPE were greater than 76.7%. The use of a short column packed with small particles enabled rapid and simultaneous determination within 7 min. The detection limits for the NSAIDs were 0.01–0.9 μg/ml using the selected ion monitoring mode.     

Comparative studies of carbohydrate-binding proteins from Xenopus laevis skin and eggs. Sugar-binding specificities and affinity purification

Salt and detergent extracts of acetone-dried powder of Xenopus laevis skin and eggs were fractionated on sugar-Sepharose columns, to which lactose, melibiose, galactose, rhamnose and mannose had been covalently linked, by successive elution with chelating reagent and specific sugars, resulting in separation of the different Ca2(+)-dependent and Ca2(+)-independent carbohydrate-binding proteins. The skin of X. laevis contains a salt-extractable Ca2(+)-dependent lactose-binding lectin of 30 kilodalton (kDa) and the eggs a similar lectin of 43 kDa, but they both lack Ca2(+)-dependent galactose-binding lectins. The 30 kDa lactose-binding lectin which agglutinates human A erythrocytes was isolated by successive affinity chromatography on two linked sugar-Sepharose columns, i.e., a galactose-Sepharose-lactose-Sepharose (GL) column system. Since the 30 kDa lectin was not recovered in the Ca2(+)-dependent lactose-binding protein fraction from the GL column system under the dithiothreitol (DDT)-free conditions, it was concluded that the lectin requires the presence of DTT and calcium for binding to the lactose-Sepharose column.