Reconstitution of bacterial photosynthetic unit in a lipid bilayer studied by single-molecule spectroscopy at 5 K

As a model of photosynthetic unit (PSU), self-assembled aggregates of pigment-protein complexes from photosynthetic bacteria were prepared in a lipid bilayer by reconstitution of the light-harvesting 2 (LH2) complex and light-harvesting 1-reaction center (LH1-RC) complex through detergent removal of their micelles in the presence of lipids. By performing polarization-controlled fluorescence and fluorescence-excitation spectroscopy on single aggregates at a temperature of 5 K, the composition of individual aggregates was determined and excitation energy transfer (EET) between constituent complexes was observed. LH2 and LH1-RC from a bacterium, Rhodobacter (Rb.) sphaeroides, were found to form a trimeric aggregate in which EET takes place from one LH2 to two LH1-RCs. In contrast, a heterodimer of LH2 and LH1-RC in which EET works was found to assemble from a combination of complexes of different bacterial species, that is, LH2 from Rb. sphaeroides and LH1-RC from Rhodopseudomonas (Rps.) palustris.     

Crystallization, transformation and microstructures of polymorphic fats in colloidal dispersion states

This article reviews new information about polymorphic structures, kinetic and microscopic properties of fat crystals in colloidal dispersion states such as aggregates (spherulite), oil-in-water (O/W) emulsion and water-in-oil (W/O) emulsion. The kinetic processes of fat crystallization under external factors such as different cooling rates, shear and ultrasound irradiation are reviewed. Microstructures of fats revealed by synchrotron radiation microbeam X-ray diffraction techniques in bulk and emulsion states are also reviewed for the first time.     

Synthetic protocol for diarylethenes through Suzuki-Miyaura coupling

The synthesis of a variety of diarylethenes through the Suzuki-Miyaura coupling reaction of 1,2-dichlorohexafluorocyclopentene with arylboronic acids and esters has been developed. Thiophenes with various substituents such as cyano and ester functionalities can be incorporated.     

Ruthenium Trichloride-Catalyzed Allyl Ether Formation

Ruthenium complexes are well known to catalyze the oxidation of alcohols,¹ where a ruthenium alkoxide has been assumed as a key intermediate. The formation of symmetrical ethers from certain carbinols is also catalyzed by ruthenium in a similar manner.² We now wish to report that the mixed etherification of allyl alcohols is catalyzed by RuCl₃, which acts as a Lewis acid to cleave the allylic carbon—oxygen bond.     

Energy Transfer between Flavin and Cytochrome c

Energy transfer between photoexcited flavin and cytochrome c has been investigated in order to estimate intermolecular forces between flavin and cytochrome c. The quenching of the fluorescence of flavin by cytochrome c excited at 372 nm was found to be much greater than that excited at 465 nm. This dependence of the quenching on the exciting wavelength is considered to be due to the “prerelaxational” fast energy transfer. From the analysis of the quenching of the fluorescence of FMN and lumiflavin by cytochrome c excited at 465 nm, it was concluded that 1) the quenching is mainly controlled by resonance energy transfer, and 2) the heterogeneous dispersion state of molecules due to electrostatic forces makes the critical transfer distance, R ₀, of the resonance process longer than the real distance. For the quenching of the fluorescence of flavodoxin by cytochrome c, it was found that complex formation is a dominant process and is controlled to a great extent by electrostatic forces. Furthermore, fluorescence decay curves were measured by a single-photon counting method in order to estimate the dynamic processes of flavin fluorescence. The results also showed that the resonance process exists in the energy transfer between flavin and cytochrome c.     

Optimizing coverage of metal oxide nanoparticle prepared by pulsed laser deposition on nonenzymatic glucose detection

Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(0 0 1) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode.     

Expanding family of π-conjugated trinuclear dithiolenes: the cases of group 8 (Ru(II)) and 10 (Ni(II) and Pt(II)) metals

New π-conjugated trinuclear dithiolenes with group 8 (6, Ru(II)) and 10 (7 and 8, Ni(II) and Pt(II)) metals were synthesized. Compounds 6 and 7 exhibited intense electronic communication through the phenylene bridge among the three dithiolene moieties during oxidation of the metalladithiolene rings, which has not been confirmed in the analogous family of group 9 metals, 1-5. Compound 8 exhibited an intense absorption band across the visible and near-IR regions, which was assigned as a charge transfer to the diimine and was red-shifted and broadened compared to the corresponding band of the mononuclear complex.     

Formation of PtRu alloy nanoparticle catalyst by radiolytic process assisted by addition of <Emphasis Type="SmallCaps">dl</Emphasis>-tartaric acid and its enhanced methanol oxidation activity

PtRu nanoparticle catalysts with 2-nm size supported on carbon were synthesized by a radiolytic process, assisted with the addition of dl-tartaric acid. Gradual alloying with the addition was confirmed by structural analyses with techniques of the X-ray diffraction and the X-ray absorption fine structure. Their methanol oxidation activities evaluated by the linear sweep voltammetry were higher than that of the commercial one, and found to be enhanced in accordance with the gradual change in the bimetallic structure from the Pt-core/Ru-shell to the random alloy. A good correlation was found between the catalytic activity and the indicators, which stands for the occurring frequency of the Pt–Ru bonds, calculated from the coordination numbers determined by the extended X-ray absorption fine structure analysis. It was confirmed that the addition of dl-tartaric acid in the radiolytic process certainly promoted the random alloy formation of PtRu bimetallic nanoparticles and enhanced their methanol oxidation activity.     

Prominent signal intensity of T1/T2 prolongation in subcortical white matter of the anterior temporal region on conventional screening MRI of late preterm infants with normal development

Purpose

This study discusses prominent signal intensity of T₁/T₂ prolongation of subcortical white matter within the anterior temporal region in premature infant brains that radiologists may encounter when interpreting conventional screening MRIs.

Materials and Methods

T₁- and T₂-weighted images of 69 preterm and term infants with no neurological abnormalities or developmental delays were evaluated retrospectively for areas of prominent signal intensity of T₁/T₂ prolongation in white matter. We measured signal intensities of anterior temporal white matter, deep temporal white matter, frontopolar white matter and subcortical white matter of the precentral gyrus. We accessed chronological changes in signal intensity in the anterior and deep temporal white matter. We also analyzed variance tests among the signal intensity ratios to the ipsilateral thalamus of white matter areas by gestational age.

Results

There was high frequency of prominent signal intensity of T₁/T₂ prolongation in the temporal tip, particularly at a gestational age of 36–38 weeks. Signal intensity ratio of the anterior temporal white matter was lower on T₁-weighted images and higher on T₂-weighted images, and the finding became less prominent with increasing gestational age. The signal intensity ratios of anterior temporal white matter at a gestational age of 36–37 weeks and 38–39 weeks were significantly different from other regions.

Conclusion

Prominent signal intensity of T₁/T₂ prolongation of subcortical white matter of the anterior temporal region is seen in normal premature infants, especially those at 36–39 gestational weeks. Although it is a prominent finding, radiologists should understand that these findings do not represent a pathological condition.     

Visible fluorescence spectroscopy of single proteins at liquid-helium temperature

Fluorescence spectroscopy of single proteins at liquid-helium temperatures reveals a relation between structural dynamics and biological functions of the proteins. The technical difficulties in detecting visible fluorescence are chromatic aberration and optical background. They were overcome by a new optical design using reflective optics and employing two-photon excitation. The fluorescence spectrum of single green-fluorescent proteins taken at a temperature of 1.5 K makes a distinction between different metastable conformations that last for tens of seconds.