Scanning ion conductance microscopy for imaging biological samples in liquid: a comparative study with atomic force microscopy and scanning electron microscopy

The present study was designed to show the applicability of scanning ion conductance microscopy (SICM) for imaging different types of biological samples. For this purpose, we first applied SICM to image collagen fibrils and showed the usefulness of the approach-retract scanning (ARS)/hopping mode for such samples with steep slopes. Comparison of SICM images with those obtained by AFM revealed that the ARS/hopping SICM mode can probe the surface topography of collagen fibrils and chromosomes at nanoscale resolution under liquid conditions. In addition, we successfully imaged cultured HeLa cells, with 15 μm in height by ARS/hopping SICM mode. Because SICM can obtain non-contact (or force-free) images, delicate cellular projections were visualized on the surface of the fixed cell. SICM imaging of live HeLa cells further demonstrated its applicability to study the morphological dynamics associated with biological processes on the time scale of minutes under liquid conditions. We further applied SICM for imaging the luminal surface of the trachea and succeeded in visualizing the surface of both ciliated and non-ciliated cells. These SICM images were comparable with those obtained by scanning electron microscopy. Although the dynamic mode of AFM provides better resolution than the ARS/hopping mode of SICM in some samples, only the latter can obtain contact-free images of samples with steep slopes, rendering it an important tool for observing live cells as well as unfixed or fixed soft samples with complicated shapes. Taken together, we demonstrate that SICM imaging, especially using an ARS/hopping mode, is a useful technique with unique capabilities for imaging the three-dimensional topography of a range of biological samples under physiologically relevant aqueous conditions.     

Electrooptics of beta-FeOOH particle in aqueous media 2. Field-strength dependence of decay and steady-state birefringence, and the hydrodynamic and electrooptic properties

Steady-state and decay birefringence, expressed in terms of the optical phase retardation per cell length delta/d, was measured on beta-FeOOH in aqueous ionic media at 633 nm and at 25 degrees C by an electric square-pulse technique over a wide range of field strength E to ca. 6 kV/cm. The field-strength dependence of both delta/d and field-free rotational relaxation time tau was determined at the sample concentrations between 0.0011 and 0.055 g/L and in the 0.02-2.0 mM NaCl concentration range. Extrapolation of both delta/d and tau values to infinitely high fields (E(2)-->infinity) could yield birefringence- and weight-average quantities, respectively. Observed tau values were decreased at weak fields but leveled off to ca. 0.3 ms at very high fields due to a slight polydispersity regarding the length and volume of particles. The weight-average relaxation time tau(w) was calculated with Perrin's expressions theoretically from the length, width, and volume of beta-FeOOH particles estimated in the dried state from electron micrograph. These quantities were variously averaged. The size distribution was discussed in terms of observed discrete histogram and theoretical (Weibull and Lansing-Kraemer) distribution functions. The sign of observed delta/d value was always positive. The infinitely high-field (delta/d)(infinity) values and the reduced optical anisotropy factor Delta g/n were evaluated by fitting to theoretical orientation functions. The intrinsic birefringence (n3-n1) could be estimated with the mean refractive index n(p) reported in the literature. For the spindle-shaped particle with an axial ratio of ca. 4, the sign of Delta g/n is always positive, whereas the quantity (n3-n1) was either negative (n(p) > 2.35) or positive (n(p) < 2.05) in sign or nearly zero (ca. n(p) = 2.26), depending critically on the n(p) values.     

Raman scattering studies of the Ba2MnWO6 and Sr2MnWO6 double perovskites

Polycrystalline Ba2MnWO6 (BMW) and Sr2MnWO6 (SMW) samples were studied between 80 and 1200 K by Raman scattering spectroscopy. In the case of BMW (space group Fmm), four Raman active vibrational modes, predicted by factor group analysis, were identified. Raman scattering studies with different wavelengths revealed a resonant bands between 300 and 800 cm-1. The origin of these bands was related to the Franck-Condon process. Line broadening versus temperature and phonon frequency were studied, and a qualitative explanation was proposed. SMW samples had considerably more complex Raman spectra. It was found that SMW transformed from tetragonal (room-temperature space group P42/n) to the cubic phase between 670 and 690 K; the phase transition temperature was dependent on sample preparation conditions, and it was considerably lower than in the case of large grain size powders. The role of grain size in phase transition is discussed. Mn ions were found to have a crucial role in the lattice dynamics of both materials.     

C3-symmetric trisimidazoline-catalyzed enantioselective bromolactonization of internal alkenoic acids

A method for conducting enantioselective bromolactonization reactions of trisubstituted alkenoic acids, using the C(3)-symmetric trisimidazoline 1 and 1,3-dibromo-5,5-dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ-lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)-olefins rather than (E)-olefins are favorable substrates for the process. The method is not only applicable to acyclic olefin reactants but can also be employed to transform cyclic trisubstituted olefins into chiral spirocyclic lactones. Finally, the synthetic utility of the newly developed process is demonstrated by its application to a concise synthesis of tanikolide, an antifungal marine natural product.     

Polymerization of methyl methacrylate by the binary system of the copper–amine complex type resin and carbon tetrachloride

The polymerization of vinyl monomers initiated by binary initiator systems composed of a copper–amine complex type resin and organic halides has been studied. These binary systems initiated the polymerization of various vinyl monomers. A kinetic study of the polymerization of methyl methacrylate initiated by the copper–amine complex resin–CCl₄ system was carried out, and it was found that the polymerization proceeds by way of a radical mechanism. This fact was also supported by the copolymerization of methyl methacrylate with styrene. The overall activation energy of the polymerization of methyl methacrylate was estimated as 8.4 kcal/mole. The activity of the initiator systems was greatly dependent upon the dissociation energy of carbon–halogen bonds in the organic halides. A possible initiation mechanism with the binary systems is proposed and discussed.     

Conformational and Intermolecular Interaction Dynamics of Photolyase/Cryptochrome Proteins Monitored by the Time‐Resolved Diffusion Technique

Cryptochrome (CRY), a blue light sensor protein, possesses a similar domain structure to photolyase (PHR) that, upon absorption of light, repairs DNA damage. In this review, we compare the reaction dynamics of these systems by monitoring the reaction kinetics of conformational change and intermolecular interaction change based on time‐dependent diffusion coefficient measurements obtained by using the pulsed laser‐induced transient grating technique. Using this method, time‐dependent biomolecular interactions, such as transient dissociation reactions in solution, have been successfully detected in real time. Conformational change in (6‐4) PHR has not been detected after the photoexcitation by monitoring the diffusion coefficient. However, the repaired DNA dissociates from PHR with a time constant of 50 μs, which must relate to a minor conformational change. However, CRY exhibits a considerable diffusion change with a time constant of 400 ms, which indicates that the protein–solvent interaction is changed by the conformational change. The C‐terminal domain of CRY is shown to be responsible for this change.     

Concise procedure for the synthesis of cardiolipins having different fatty acid combinations

Production of a wide variety of cardiolipin (CL) analogues is critical for studying molecular mechanism of diverse biological functions of CL in mitochondria. We describe a concise procedure for the synthesis of CL using a phosphoramidite approach, which allows for the production of diverse CL analogues bearing linoleic acid(s) at any position on the glycerol backbone.     

Formation of Supramolecular Nanostructures through in Situ Self-Assembly and Post-Assembly Modification of a Biocatalytically Constructed Dipeptide Hydrazide**

Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.