Fullerenes Enclosed in Bridged Calix[5]arenes

Host systems that bind C ₇₀ preferentially to C ₆₀ are found in the bridged calix[5]arenes 1 (X= alkyne bridge). The complexation-induced shifts of the bound fullerene guests provide valuable information on the structure and dynamics of the supramolecular complex.     

Detection and grading for esophageal varices in patients with chronic liver damage: comparison of gadolinium-enhanced and unenhanced steady-state coherent MR images

The purpose of this study was to compare observer interpreted steady-state coherent coronal images and gadolinium-enhanced axial images in terms of the detection and grading of esophageal varices. Magnetic resonance imaging (MRI) and gastrointestinal endoscopy were performed within 2 weeks in 90 patients with chronic liver damage, including 55 with untreated esophageal varices, for periodic screening purposes. Two blinded readers retrospectively reviewed T1- and T2-weighted images with gadolinium-enhanced (gadolinium image set) and steady-state coherent (coherent image set) images. Sensitivity for the detection of esophageal varices was higher (P<.001) in the gadolinium image set (76%) than in the coherent image set (35%); on the other hand, specificity was higher (P<.001) in the coherent image set (91%) than in the gadolinium image set (66%). Furthermore, area under the ROC curve was higher for the gadolinium image set (Az=0.823) than the coherent image set (Az=0.761) (P=.48). Moderate and weak positive correlations with endoscopic grades were found for the gadolinium image (r=0.48, P<.01) and coherent image sets (r=0.34, P=.018). The addition of steady-state coherent imaging to the current routine liver imaging protocol did not improve the detection or grading of esophageal varices, whereas gadolinium-enhanced imaging was found to be potentially valuable. Nevertheless, endoscopy was confirmed to be mandatory in patients with esophageal varices suspected by MRI of the liver.     

Molecular weight characterization of poly[(R)-3-hydroxybutyrate] synthesized by genetically engineered strains of Escherichia coli

This study investigated the relationship of growth conditions, host strains and molecular weights of poly[(R)-3-hydroxybutyrate] [P(3HB)] synthesized by genetically engineered Escherichia coli. Various PHA synthases belonging to types I-IV enzymes were expressed in E. coli JM109 under the same experimental conditions, and the molecular weights of the polymers were characterized by gel permeation chromatography. The results demonstrate that P(3HB) polymers have varied molecular weights and polydispersities dependent on the characteristics of the individual PHA synthase employed. P(3HB) with high number-average molecular weights (M_n) [(1.5-4.0) × 10⁶] and narrow polydispersities (1.6-1.8) were synthesized by PHA synthases from Ralstonia eutropha (type I), Delftia acidovorans (type I) and Allochromatium vinosum (type III). Contrary to these, P(3HB) with relatively low M_n [(0.17-0.79) × 10⁶] and broad polydispersities (2.2-9.0) were synthesized by PHA synthases from Aeromonas caviae (type I), Pseudomonas sp. 61-3 (type II) and Bacillus sp. INT005 (type IV). Furthermore, the molecular weights of P(3HB) synthesized under various culture conditions, in various hosts of E. coli and by mutants of PHA synthase were characterized. It was found that, in addition to culture pH [Kusaka et al. Appl Microbiol Biotechnol 1997;47:140], other variances such as culture temperature, host strain and use of mutants are effective in changing polymer molecular weight.     

Modified Synthesis and Supramolecular Polymerization of Rim-to-Rim Connected Bisresorcinarenes

The acid-catalyzed condensation reaction of resorcinol and bisdimethoxyacetals gave rise to rim-to-rim connected bisresorcinarenes in good yields. In the presence of ethanol, the homoditopic bisresorcinarenes assembled to form supramolecular polymers via hydrogen bonding interactions. The fibrous morphologies of the supramolecular polymers were confirmed by atomic force microscopy and scanning electron microscopy.     

Molecular Recognition of Hydrocarbon Guests by a Supramolecular Capsule Formed by the 4:4 Self-Assembly of Tris(Zn2+–Cyclen) and Trithiocyanurate in Aqueous Solution

We have previously reported that the trimeric Zn²⁺–cyclen complex (tris(Zn²⁺–cyclen), [Zn₃L¹]⁶⁺) and the trianion of trithiocyanuric acid (TCA³⁻) assembled in a 4:4 ratio to form a cuboctahedral supramolecular cage, [(Zn₃L¹)₄(TCA³⁻)₄]¹²⁺ (hereafter referred to as a Zn–cage), in neutral aqueous solution (cyclen=1,4,7,10-tetraazacyclododecane). Herein, we examined the molecular recognition of C₁–C₁₂ hydrocarbons (C_nH_(2n+2) (n≈1–12)), cyclopentane, cyclododecane, cis-decalin, and trans-decalin by the Zn–cage under normal atmospheric pressure. This cage complex was also able to encapsulate guest molecules that had larger volumes than that of the inner cavity of the Zn–cage, thereby suggesting that the inner shape of the Zn–cage was flexible. Computational simulations of Zn–cage–guest complexes provided support for this conclusion. Moreover, the solvent-accessible surface areas (SASA) of the Zn–cage host, guest molecules, and the Zn–cage-guest complexes were calculated and the data were used to explain the order of stability determined by the guest-replacement experiments. The storage of volatile molecules in aqueous solution by the Zn–cage is also discussed.     

Coherent storage of photoexcited triplet states using 29Si nuclear spins in silicon

Pulsed electron paramagnetic resonance spectroscopy of the photoexcited, metastable triplet state of the oxygen-vacancy center in silicon reveals that the lifetime of the m(s)=±1 sublevels differs significantly from that of the m(s)=0 state. We exploit this significant difference in decay rates to the ground singlet state to achieve nearly ~100% electron-spin polarization within the triplet. We further demonstrate the transfer of a coherent state of the triplet electron spin to, and from, a hyperfine-coupled, nearest-neighbor (29)Si nuclear spin. We measure the coherence time of the (29)Si nuclear spin employed in this operation and find it to be unaffected by the presence of the triplet electron spin and equal to the bulk value measured by nuclear magnetic resonance.     

Fluorescence imaging of potassium ions in living cells using a fluorescent probe based on a thrombin binding aptamer-peptide conjugate

When a biotinylated FRET probe based on a peptide-thrombin binding aptamer conjugate was introduced together with streptavidin and biotinylated nuclear export signal peptide into HeLa cells, the resulting ternary complex enabled visualization of K(+) concentration changes in the cell.     

In-situ monitoring of degradation of C/C composites and coatings in an inductively coupled plasma by a spectroCCD camera

Spatially and spectrally resolved profiles of atomic emission around the surface of C/C composites with double layer coatings in an inductively coupled plasma (ICP) have been measured by means of a spectroCCD camera. The plasma temperature around the sample disk was measured with the two-line method using atomic lines of iron, and found to be higher under oxidizing conditions because of combustion heat. This is a good measure of reflecting that the degradation is more significant under the oxidizing condition. The degradation procedure of the C/C composites with the double layer coatings has also been measured by a multi-channel spectrometer. The degradation of the sealant and the following attack of the plasma on a SiC layer were observed by the temporal change in emission intensity.     

Relationship between physicochemical properties and chemical stability of muramyldipeptide derivative B30-MDP in liposomal solutions

The muramyldipeptide derivative B30-MDP has immunoadjuvant activity and vesicle-forming ability in aqueous environments. It is therefore important to evaluate the relationship between its physicochemical properties and chemical stability for use as a vaccine adjuvant. We studied the effects of octyl--D-glucoside (O.G.) incorporation on the physicochemical properties and chemical stability in aqueous solution at pH 7.4. The changes in particle size and in the membrane fluidity of B30-MDP liposomes, which were induced by the addition of O.G., were measured to confirm the transition from micelle phase to vesicle phase. The degradation of B30-MDP in both liposomal and mixed micellar solutions was measured by reverse-phase high-performance liquid chromatography. This degradation occurred by a pseudo first-order reaction at 313, 323 and 333 K. The shelf-life of the B30-MDP solution supplemented with O.G. was approximately one-seventh of that of B30-MDP alone in the liposomal solution. The changes in thek _obs values of B30-MDP correlated well with those in membrane fluidity induced by O.G. incorporation. These results indicate that an increase in membrane fluidity labilizes B30-MDP in liposomal solution.     

Diels-alder reactions of cyclohexadienes derived from decarboxylation of photo[4 + 2]cycloadducts between 4,6-dimethyl-2-pyrone and cyclic olefins

Labile photo [4 + 2] adducts between 4,6-dimethyl-2-pyrone and cyclic olefins reacted with second olefins to give cross adducts, and with acetylenes to afford both bis-adducts and benzene derivatives with the concurrent decarboxylation, respectively. The reaction mechanism of the latter was considered.