Synthesis and characterization of a series of highly fluorogenic substrates for glutathione transferases, a general strategy

Glutathione transferases (GSTs) are used in biotechnology applications as fusion partners for facile purification and are also overexpressed in certain tumors. Consequently, there is a need for sensitive detection of the enzymes. Here we describe a general strategy for the synthesis and characterization of novel fluorogenic substrates for GSTs. The substrates were synthesized by introducing an electrophilic sulfonamide linkage to fluorescent molecules containing an amino group [e.g., 2,4-dinitrobenzenesulfonamide (DNs) derivatives of coumarin, cresyl violet, and rhodamine]. The derivatives were essentially nonfluorescent, and upon GST catalyzed cleavage of the dinitrobenzenesulfonamide, free fluorophore is released (and 1-glutathionyl-2,4-dinitrobenzene + SO(2)). All the coumarin-, cresyl violet- and rhodamine-based fluorogenic probes turned out to be good substrates for most GSTs, especially for GSTA(1-1), in terms of strong fluorescence increases (71-1200-fold), high k(cat)/K(m) values (10(4)-10(7) M(-1) s(-1)) and significant rate enhancements (10(6)-10(9)-fold). The substrates were successfully applied to quantitate very low levels of GST activity in cell extracts and DNs-cresyl violet was also successfully applied to the imaging of microsomal MGST(1) activity in living cells. The cresyl violet stained cells retained their fluorescence after fixation, which is a very useful property. In summary, we describe a general and versatile strategy to generate fluorogenic GST substrates, some of them providing the most sensitive assays so far described for GSTs.     

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.     

Spectroscopic detection of the most stable carbonic acid, cis-cis H2CO3

Carbonic acid had not been detected by any spectroscopic means for a long period. Recently, we have reported the detection of its second most stable conformer, cis-trans H(2)CO(3), as the first spectroscopic detection of the isolated carbonic acid molecule. In the present work, the most stable conformer of carbonic acid, cis-cis H(2)CO(3), in the gas phase has been successfully produced in a supersonic jet using a pulsed discharge nozzle, and pure rotational transitions of this molecule have been observed by a Fourier-transform microwave spectrometer. In addition to cis-cis H(2)CO(3), its deuterated isotopologue, cis-cis D2CO3, has been observed, yielding the r(0) structure of the cis-cis conformer. Furthermore, hyperfine constants of the deuterated cis-trans conformers were also determined. The two structures for the stable isolated carbonic acid molecule, those of the cis-cis and cis-trans conformers, are considered to provide basic information for the understanding of chemical reactions involving carbonic acid The present result is accurate enough to be used in radio astronomical observations, where the ortho∕para ratio of cis-cis H(2)CO(3) may be used as an important probe of interstellar chemistry.     

A Montel Type Result for Super-Polyharmonic Functions on R<Superscript><Emphasis Type="Italic">N</Emphasis></Superscript>

Our aim in this paper is to discuss a Montel type result for a family F{\mathcal F} of super-polyharmonic functions on R ^N . We give a condition on spherical means to assure that F{\mathcal F} contains a sequence converging outside a set of capacity zero.     

Covariance tapering for prediction of large spatial data sets in transformed random fields

The best linear unbiased predictor (BLUP) is called a kriging predictor and has been widely used to interpolate a spatially correlated random process in scientific areas such as geostatistics. However, if an underlying random field is not Gaussian, the optimality of the BLUP in the mean squared error (MSE) sense is unclear because it is not always identical with the conditional expectation. Moreover, in many cases, data sets in spatial problems are often so large that a kriging predictor is impractically time-consuming. To reduce the computational complexity, covariance tapering has been developed for large spatial data sets. In this paper, we consider covariance tapering in a class of transformed Gaussian models for random fields and show that the BLUP using covariance tapering, the BLUP and the optimal predictor are asymptotically equivalent in the MSE sense if the underlying Gaussian random field has the Matérn covariance function.     

Two kinds of positive holes in YBa2Cu3O7-δ around Tc through the analysis of the hall effect in weak field

Abstract

To obtain information about the mechanism of high T_c superconductivity in YBa₂Cu₃O_7-δ (YBCO) the dependence of Hall coefficient R_H and electrical resistivity ρ on the temperature were studied in range from 77 to 300K. An inflexion point θ was found to exist around 130K in R_H(T) and ρ(T) curves. Both the mobility μ and the concentration of the holes were evaluated above and below θ, separately. The μ of the holes dominant below θ was ten times greater than that above θ. The concentration of the heavy holes above θ was, however, one hundred times larger than that below θ. A discussion will be given in terms of the transport process of the holes drifting through P_[sgrave]- and P_σ-orbits on the CuO₂ planes in YBCO.     

Neutron Magnetic Scattering of Intercalation Compounds Fex TiS2

Abstract

Neutron magnetic scattering of intercalation compounds Fe^xTiS² has been measured systematically as a function of Fe concentration x. In the x = 0.15 and 1/4 samples, so-called small-angle scattering was observed associated with a spin-glass transition. In the x = 1/2 sample, clear magnetic Bragg reflections were observed. The position of the magnetic peak with the smallest Q number was not commensurate with the nuclear lattice-unit. The magnetic structure of Fe^1/2TiS² was found not to be a simple ferromagnetic structure as was ever suggested but a long-period magnetic structure. In the x = 1/3 sample, broad magnetic diffuse peak whose Q number was also not commensurate with the nuclear lattice-unit was observed. The origin of the magnetism of Fe^1/3TiS², what is called a cluster-glass, seems the short-range ordered magnetic-clusters with a long-period magnetic structure.     

Controlled Stacking and Unstacking of Peripheral Chlorophyll Units Drives the Spring‐Like Contraction and Expansion of a Semi‐Artificial Helical Polymer

Developing new strategies for controlling polymer conformations through precise molecular recognition can potentially generate a machine‐like motion that is dependent on molecular information—an important process for the preparation of new intelligent nanomaterials (e.g., polymer‐based nanomachines) in the field bordering between polymer chemistry and conventional supramolecular sciences. Herein, we propose a strategy to endow a helical polymer chain with dynamic spring‐like (contraction/expansion) motion through the one‐dimensional self‐assembly (aggregation/disaggregation) of peripheral amphiphilic molecules. In this developing system, we employed a semi‐artificial helical polysaccharide presenting peripheral amphiphilic chlorophyll units as a power device that undergoes contractive motion in aqueous media, driven by strong π–π interactions of its chlorophyll units or by cooperative molecular recognition of bipyridyl‐type ligands through pairs of chlorophyll units, thereby converting molecular information into the regulated motion of a spring. In addition, this system also undergoes expansive motion through coordination of pyridine. We anticipate that this strategy will be applicable (when combined with the established wrapping chemistry of the helical polysaccharide) to the development of, for example, drug carriers (e.g., nano‐syringes), actuators (stimuli‐responsive films), and directional transporters (nano‐railways), thereby extending the frontiers of supramolecular science.