Metabolomics approach for determining growth-specific metabolites based on Fourier transform ion cyclotron resonance mass spectrometry

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) is the best MS technology for obtaining exact mass measurements owing to its great resolution and accuracy, and several outstanding FT-ICR/MS-based metabolomics approaches have been reported. A reliable annotation scheme is needed to deal with direct-infusion FT-ICR/MS metabolic profiling. Correlation analyses can help us not only uncover relations between the ions but also annotate the ions originated from identical metabolites (metabolite derivative ions). In the present study, we propose a procedure for metabolite annotation on direct-infusion FT-ICR/MS by taking into consideration the classification of metabolite-derived ions using correlation analyses. Integrated analysis based on information of isotope relations, fragmentation patterns by MS/MS analysis, co-occurring metabolites, and database searches (KNApSAcK and KEGG) can make it possible to annotate ions as metabolites and estimate cellular conditions based on metabolite composition. A total of 220 detected ions were classified into 174 metabolite derivative groups and 72 ions were assigned to candidate metabolites in the present work. Finally, metabolic profiling has been able to distinguish between the growth stages with the aid of PCA. The constructed model using PLS regression for OD₆₀₀ values as a function of metabolic profiles is very useful for identifying to what degree the ions contribute to the growth stages. Ten phospholipids which largely influence the constructed model are highly abundant in the cells. Our analyses reveal that global modification of those phospholipids occurs as E. coli enters the stationary phase. Thus, the integrated approach involving correlation analyses, metabolic profiling, and database searching is efficient for high-throughput metabolomics. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

1,17‐Hepta­decane­diol

In the title compound, C₁₇H₃₆O₂, one of the hydroxyl groups has a gauche conformation with respect to the hydro­carbon skeleton, which is all‐trans, whereas the other has a trans conformation. The molecular shape is rod‐like and the compound has a rotator phase in which mol­ecules are assured greater motional freedom, as in liquid crystals. In addition, the mol­ecules arranged along the longest axis, b, form layers which are very similar to those of the smectic A liquid crystals.     

New Synthesis of Mono-Halogenated Adamantanes

A variety of direct halogenations on the adamantane skeleton have been reported. For example, bromination of adamantane with bromine, which is considered to proceed through an ionic mechanism, gives high yield of 1-broinoadamsntane. In contrast to the ionic bromination of adamantane, chlorinations are much less selective^2,3,4,5. Photochloroadamantane of adamantane gives l-chloroadamntane and 2-chloroadamantane. Chlorination with t-butyl chloride in the presence of A1C1₃ gives rise to a mixture of 1-chloroadamantane and 1,3-dichloroadamantane.     

Electrorheological Effect and Electro‐Optical Properties of Side‐on Liquid Crystalline Polysiloxane in a Nematic Solvent

The electrorheological (ER) effect and the electro‐optical properties of a ′′side‐on′′ liquid crystalline polysiloxane (PS) are investigated. A large ER effect is observed and the response to the shear stress of neat PS in the nematic phase is shown to be affected by the shear rate. PS is also mixed with a low‐molar nematic liquid crystal (5CB) in order to improve the response behavior to the applied electric field. The rheological properties of such mixtures are highly dependent on the concentration of 5CB. The composites respond faster to the applied electric field and have improved electro‐optical properties. This study offers a new perspective on the development of liquid crystal materials for the ER effect.     

Temperature dependence of the work function of Bi2Sr2CaCu2O8 single crystal cleaved at low temperature

We measured the anomalous change in the work function of Bi₂Sr₂CaCu₂O₈ around a critical temperature (T_c ≈ 85 K). The work function becomes a minimum at T_c; the work function decreases in a normal-conductive state and then increases in a superconductive state as the temperature decreases. An increase in the work function for a transition from a normal-conductive state to a superconductive state at 0 K is about 9 meV. The contribution of the chemical potential and the surface dipole barrier to the work function are discussed.     

1,15‐Penta­decane­diol

In the title compound, C₁₅H₃₂O₂, one of the terminal hydroxyl groups has a gauche conformation with respect to the hydro­carbon skeleton, while the other is trans. The mol­ecules lie parallel to the longest axis and form layers similar to those of the smectic A structure of liquid crystals. These features are similar to those of the homologues with an odd number of C atoms, but different from those with an even number.     

Magnetic sponge prepared with an alkanedithiol-bridged network of nanomagnets

The magnetic dipole-dipole interaction between nanomagnets having huge magnetic moments can have a strength comparable to that of the van der Waals interaction between them, and it can be manipulated by applying an external magnetic field of conventional strength. Therefore, the cooperation between the dipole-dipole interaction and the applied magnetic field allows the magnetic moments of nanomagnets to be aligned and organized in an ordered manner. In this work, a network of magnetic nanoparticles connected with flexible long-alkyl-chain linkers was designed to develop a "magnetic sponge" capable of absorbing and desorbing guest molecules with changes in the applied magnetic field. The magnetization of the sponge with long-alkyl-chain bridges (30 C atoms) exhibited a 500% increase after cooling in the presence of an applied field of 7 T relative to that in the absence of a magnetic field. Cooling in a magnetic field leads to anisotropic stretching in the sponge due to reorganization of the nanomagnets along the applied field, in contrast to the isotropic organization under zero-field conditions. Such magnetic-responsive organization and reorganization of the magnetic particle network significantly influences the gas absorption capacity of the nanopores inside the material. The absorption and desorption of guests in an applied magnetic field at low temperature can be regarded as a fascinating "breathing feature" of our magnetic sponge.     

Freeze-fracture electron microscopic and calorimetric studies on microscopic states of surface-modified liposomes with poly(ethylene glycol) chains

The differential scanning calorimetry (DSC) and the freeze-fracture electron microscopy of dipalmitoyl phosphatidylcholine (DPPC) liposomes containing distearoyl-N-monomethoxy poly(ethylene glycol)-succinyl-phosphatidylethanolamines (PEG-DSPE) were carried out. The DSC peak of DPPC liposomes containing PEG-DSPE had a shoulder. The main phase transition temperature of DPPC bilayer membranes containing PEG-DSPE whose molecular weight of PEG is less than 3000 was slightly shifted to a higher temperature, while that containing PEG-DSPE whose molecular weight of PEG is more than 5000 was slightly shifted to a lower temperature. The electron micrographs of freeze-fracture replicas of DPPC liposomes containing PEG-DSPE quenched from 37±2°C exhibited banded and planar textures, suggesting the lateral phase separation in the bilayer membranes.     

Carboxyfluorescein leakage from poly(ethylene glycol)-grafted liposomes induced by the interaction with serum

The effects of fetal bovine serum (FBS) on carboxyfluorescein (CF) leakage from poly(ethylene glycol)-grafted liposomes (PEG-liposomes) were investigated. PEG-liposomes were prepared from dipalmitoylphosphatidylcholine (DPPC) and distearoyl-N-monomethoxy poly(ethylene glycol)-succinyl-phosphatidylethanolamines (DSPE-PEG) having PEG molecular weights of 1000, 2000, 3000 and 5000. The presence of FBS dramatically increased CF leakage from liposomes near the gel-liquid crystalline phase transition temperature, but had little effect at lower and higher temperatures. The CF leakage from PEG-liposomes whose molecular weight in PEG units was above 2000 was suppressed compared with that of liposomes without PEG. And, there was hardly any difference in the effect of the PEG molecular weight of the PEG-lipids on CF leakage from PEG-liposomes with FBS when PEG-lipids with a molecular weight in PEG units above 2000 were used. On the other hand, the leakage of CF from liposomes containing 0.145 mol fractions of DSPE-PEG1000 was larger than that of liposomes without PEG. Furthermore, the effects of FBS on the cooperative units of lipid molecules during the gel-liquid crystalline phase transition of liposomes were examined. However, the cooperative units of liposomes with FBS had little change compared with that of liposomes without FBS.     

Pseudorotaxane structure of a fullerene derivative--cyclodextrin 1:2 complex

X-Ray crystallography revealed that the C(60) derivative·γ-cyclodextrin (γ-CDx) complex has a pseudorotaxane structure and the structure of the crystal clarified the importance of multi-point hydrogen bonds between two γ-CDxs for stabilising the 3·γ-CDx complex.