Nature of magnetic impurity induced superparamagnetism and anomalous Hall effect in β-FeSi2 single crystals

The magnetic properties of β-FeSi₂ single crystals were investigated using magnetization and anomalous Hall effect measurements. These measurements clearly show the appearance of superparamagnetism, the origin of which is attributed to defect-induced magnetic aggregates. Unlike previous reports, based on our combined analysis using magnetization and the anomalous Hall effect, we found that two kinds of aggregates, which are magnetically distinct, exist in our samples. Among the two types found, one gives an anomalous Hall term, which follows a side-jump mechanism while the other is a completely new kind, suggesting that magnetic properties of β-FeSi₂ are very unconventional. The sizes of the aggregates were estimated from our experimental data.     

An Efficient Synthesis of Sulfo Lewis X Analog Containing 1-Deoxynojirimycin 1

Abstract

Sulfo Lewis^x analog containing 1-deoxynojirimycin (13) has been efficiently synthesized. Glycosidation of ethyl 2,3,4-tri-O-benzyl-1-thio-β-D-fucopyranoside (5) with O-2,6-di-O-benzoyl-3,4-isopropylidene-β-D-galactopyranosyl)-(1→4)-2,6-di-O-benzoyl-N-benzyloxycarbonyl-1,5-dideoxy-1,5-imino-D-glucitol (4), prepared from O-β-D-galactopyranosyl-(1→4)-1,5-dideoxy-1,5-imino-D-glucitol (1) via 3 steps, and subsequent acid hydrolysis of the isopropylidene group gave the desired trisaccharide diol derivative (7) in good yield. Compound 7 was easily converted into 3′-O-sulfo Lewis^x analog (13) via 6 steps in high yield.

     

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.     

Indoline derivatives I: synthesis and factor Xa (FXa) inhibitory activities

A series of bisamidine derivatives each having a ring structure in the center of the molecule was synthesized and their Factor Xa (FXa) inhibitory activities were evaluated. Among them, some indoline derivatives showed potent inhibitory activities in vitro. In particular, (R)-18a having an (R)-configuration at the 2-position of the indoline ring exhibited the most potent FXa inhibitory activity in vitro, more potent than DX-9065a. Furthermore, (R)-18a exhibited more potent anticoagulant activity than DX-9065a. We also succeeded in obtaining an X-ray crystal structure of FXa bound with (R)-18a.     

One-step isolation and identification of hydroxylamino-dinitrotoluenes, unstable products from 2,4,6-trinitrotoluene metabolites, with thin-layer chromatography and laser time-of-flight mass spectrometry

Two kinds of hydroxylamino-dinitrotoluenes (HADNTs), 2-hydroxylamino-4,6-dinitrotoluene (2HADNT) and 4-hydroxylamino-2,6-dinitrotoluene (4HADNT), are known to be major metabolites produced from 2,4,6-trinitrotoluene (TNT) by bacteria. These chemicals could not be identified as TNT metabolites produced by Pseudomonas sp. strain TM15 because the mass spectra of these chemicals could not be obtained by liquid chromatography-mass spectrometry (MS) or gas chromatography-MS, which are the classic methods for identifying the metabolites of xenobiotics. However, these problems are overcome by isolating 2HADNT and 4HADNT from TNT metabolites with one-step thin-layer chromatography using dichloromethane as the developing solvent, and individually extracting them into acetonitrile by collecting spots of 2HADNT and 4HADNT. The purity of each HADNT was approximately 98%, based on the results of high-performance liquid chromatographic analyses. 2HADNT and 4HADNT are identified by obtaining their mass spectra with laser time-of-flight MS. 2HADNT and 4HADNT dissolve in distilled water and are spontaneously broken down with time. Also, heat treatment (increasing temperatures) and dissolved oxygen accelerate the destruction of HADNTs. This technique may be applicable for the identification and exact quantitative analysis of unstable and fragile compounds such as HADNTs.     

Light-scattering study of polyelectrolyte complex formation between anionic and cationic nanogels in an aqueous salt-free system

We studied complex formation in an aqueous salt-free system (pH approximately 3 and at 25 degrees C) between nanogel particles having opposite charges. Anionic gel (AG) and cationic gel (CG) particles consist of lightly cross-linked N-isopropylacrylamide (NIPA) copolymers with 2-acrylamido-2-methylpropane sulfonic acid and with 1-vinylimidazole, respectively. The number of charges per particle was -4490 for AG and +20 300 for CG, as estimated from their molar masses (3.33 MD for AG and 11.7 MD for CG) by static light scattering (SLS) and their charge densities (1.35 mmol/g for AG and 1.74 mmol/g for CG) by potentiometric titration. The complexes were formed through the addition of AG to CG and vice versa using a turbidimetric titration technique. At the endpoint of the titration, the aggregate formed was a complex based upon stoichiometric charge neutralization: CG(n)()(+) + xAG(m)()(-) --> CG(n)()(+) (AG(m)()(-))(x)() where x = (n)()/(m)(). At different stages of the titration before the endpoint, the resulting complexes were examined in detail using dynamic light scattering, SLS, and electrophoretic light scattering (ELS). The main results are summarized as follows: (i) When AG with a hydrodynamic radius (R(h)) of 119 nm is added to CG (R(h) approximately 156 nm), the (R(h)) of the complex size decreases from 156 to 80 nm. (ii) In contrast to this (R(h)) change, the molar mass increases from 11.7 MD to 24 MD with increasing amounts of added AG. (iii) Upon addition of CG to AG, the complex formed has the same size ((R(h)) approximately 80 nm) and the same molar mass (55 +/- 2.5 MD) until 55 +/- 5% of AG has been consumed in the complexation. To understand these results, we used the following two models: the random model (RM), in which the added AG particles uniformly bind to all of the CG particles in the system via a strong electrostatic attraction, and the all-or-none model (AONM), in which part of the AG particles in the system preferably bind to the added CG particles to neutralize their electric charges but the other AG particles are uncomplexed and remain in the system. The complex formations upon addition of AG to CG and CG to AG were elucidated in terms of RM and AONM, respectively.     

Polymer microarrays for cellular adhesion

Microarray screening of polymer libraries for cellular adhesion was developed utilising a thin film of agarose to allow unsurpassed localisation of cell binding onto the array substrate and the discovery of cell specific polymers.     

Hydrophilic polymer supported nanoparticles prepared from samarium trichloride and lanthanum trichloride in liquid-phase

Nanoparticles were obtained by the reaction of SmCl₃·6H₂O with sodium borohydride (NaBH₄) in the presence of sodium polyacrylate (PAA) with average molecular weight of 5,100 as a capping polymer. The resulting colloidal solution was placed on a Cu grid and characterized by transmission electron microscope (TEM) measurement, which clearly indicated the generation of nanoparticles. The reaction of LaCl₃ with NaBH₄ in the presence of PAA led to preparation of lanthanum nanoparticles, similarly as samarium nanoparticles.     

Photodynamic Activity of C70 Caged within Surface‐Cross‐Linked Liposomes

[70]Fullerene (C₇₀) encapsulated into a surface‐cross‐linked liposome, a so‐called cerasome, was prepared by an exchange reaction incorporating C₇₀?γ‐cyclodextrin complexes into lipid membranes. Fullerene exchange in a cerasome‐incorporated C₇₀ (CIC₇₀), as well as in a lipid‐membrane‐incorporated C₇₀ (LMIC₇₀), was completed within 1 min with stirring at 25 °C. CIC₇₀ was more resistant to lysis than LMIC₇₀ towards lysing agents such as surfactants. Furthermore, the photodynamic activity of CIC₇₀ in HeLa cells was similar to that of LMIC₇₀, indicating that C₇₀ can act as a photosensitizing drug (PS) without release from cerasome membranes. Thus, in contrast with general drug‐delivery systems (DDSs), which require the drug to be released from the interior of liposomes, carriers for PSs for use in photodynamic therapy (PDT) do not necessarily need to release the drug. These results indicate that DDSs with high morphological stability can increase the residence time in blood and achieves tumor‐selective drug delivery by the enhanced permeability and retention (EPR) effect.