Near infrared studies of styrene-sodium methacrylate ionomers

Near Infrared (NIR) spectroscopy coupled with chemometrics techniques were utilized to study the composition and properties of styrene-sodium methacrylate ionomers. Predictive models were obtained for mol % ionic content, as well as for the ionic cluster glass transition temperature, storage modulus, and tan δ peak parameters. The results illustrate the feasibility of using NIR and chemometrics algorithms as a property predictive tool, as well as the potential for the development of full calibration models. The chemometric parameters are discussed based on correlations with ionomer NIR spectral features and the role water molecules play as a probe for the associated structure of the ionomer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2877–2886, 1998     

Exploiting Incommensurate Symmetry Numbers: Rational Design and Assembly of M2M3′L6 Supramolecular Clusters with C3h Symmetry

Mixed-metal mesocates [M₂Pd₃Br₆L₆]⁴⁻ (M=Ti^IV, Sn^IV; L=4-diphenylphosphanyl-catecholate) have been synthesized, in which the two incommensurate symmetry elements generated by the different metal ions are linked by a rigid, bifunctional ligand to generate a C_3h-symmetrical cluster (see picture).     

Triple Helicate—Tetrahedral Cluster Interconversion Controlled by Host–Guest Interactions

A unique ligand design allows the formation of both an M₂L₃ triple helicate and an M₄L₆ tetrahedron (M=Ti, Ga; L=ligand based on 2,6-diaminoanthracene). Although the tetrahedron is entropically disfavored, a strong host–guest interaction with Me₄N⁺ is enough to drive the equilibrium towards the tetrahedron. Remarkably, the helicate can be quantitatively converted into the tetrahedron simply by addition of Me₄N⁺ (shown schematically).     

Terthienyl-Based Redox-Switchable Hemilabile Ligands: Transition Metal Polymeric Complexes with Electrochemically Tunable or Switchable Coordination Environments?

By controlling the extent of oxidation of the polymeric forms of the new class of isolable, polymerizable terthienyl Ru^II complexes 1 , one can modulate both the binding strength of the polymer backbone for Ru^II and the electronic nature of the bound metal centers.     

Remarkably large remote-stereocenter-induced chromatographic differences: azulenyl 1,5-diols

A series of four new azulene-1,5-diol diastereomers were prepared and found to exhibit large differences (ΔR_f 0.22–0.46) in silica TLC mobilities despite having stereocenters four bonds apart. The stereoisomers were identified by X-ray crystallography, and in all cases the RR/SS diastereomers were less strongly retained than the RS/SR diastereomers. The crystal structures suggested that this is due to a conformational preference for the CF₃ groups to be nearly perpendicular to the plane of the azulene ring, which caused the dihedral angle between the OH groups to be larger (in the RR/SS diastereomers) or smaller (in the RS/SR diastereomers). The smaller dihedral angles allow the RS/SR diastereomers to simultaneously bind to a silica surface and thus be more strongly retained. Two similar benzene derivatives and several cycloalkanediols with more proximate stereocenters showed little or no difference in mobilities between diastereomers, though the NMR differences were greater. Thus, the azulene ring is an important factor in enforcing the conformational preferences, either through steric interactions with the 4/8 substituents (H or methyl) or its significant dipole moment, or both.     

Thermal decomposition of some biologically active complexes of ruthenium (III) with quinolone derivatives

A series of new complexes with mixed ligands of the type RuL₂(DMSO) _m Cl₃·nH₂O ((1) L: norfloxacin (nf), m = 1, n = 1; (2) L: ciprofloxacin (cp), m = 2, n = 2; (3) L: ofloxacin (of), m = 1, n = 1; (4) L: enrofloxacin (enro), m = 0.5, n = 4; DMSO: dimethylsulfoxide) were synthesised and characterised by chemical analysis and IR data. In all complexes both fluoroquinolone derivative and DMSO act as unidentate. The thermal behaviour steps were investigated in synthetic air flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, quinolone derivative and DMSO degradation respectively. The final product of decomposition is ruthenium (IV) oxide.     

Monitoring erythrocytes in a microchip channel that narrows uniformly: towards an improved microfluidic-based mimic of the microcirculation

The release of adenosine triphosphate (ATP) from red blood cells (RBCs) flowing through PDMS microchannels has been determined as a function of channel cross-sectional area using a design containing a channel that narrows uniformly. ATP, released from the RBCs in response to the mechanical deformation of their cell membranes, increased as the channel cross-section decreased. One sample of rabbit RBCs released 1.16 +/- 0.11, 1.92 +/- 0.14 and 2.09 +/- 0.10 microM ATP as the median cross-sectional area decreased from 4314 to 3192 to 2052 microm(2), respectively. Numerous samples (n = 6) displayed the same trend. Incubating a sample of RBCs with diamide, a substance known to stiffen cell membranes without harming the cell cytosol, provided evidence that no cell lysis occurred in the microchip device. This novel use of lab-on-a-chip technology allows for channel designs that enable an in vitro study of physiological events that occur in the microcirculation.     

Photodynamic treatment (ALA-PDT) suppresses the expression of the oncogenic Bcr-Abl kinase and affects the cytoskeleton organization in K562 cells

K562 is the chronic myelogenous leukemia (CML)-derived cell line that expresses high levels of chimeric oncoprotein Bcr-Abl. The deregulated (permanent) kinase activity of Bcr-Abl leads to continuous proliferation of K562 cells and their resistance to the apoptosis promotion by conventional drugs. The photodynamic treatment (PDT) based on the application of 5-aminolevulinic acid (ALA) and irradiation with blue light (ALA-PDT) resulted in the suppression of K562 cells proliferation. It was followed by a necrosis-like cell death [K. Kuzelová, D. Grebenová, M. Pluskalová, I. Marinov, Z. Hrkal, J. Photochem. Photobiol. B 73 (2004) 67-78]. ALA-PDT led to the perturbation of the Hsp90/p23 multichaperone complex of which the Bcr-Abl is the client protein. Bcr-Abl protein was suppressed whereas the bcr-abl mRNA level was not affected. Further on, we observed several changes in the cytoskeleton organization. We detected ALA-PDT-mediated disruption of filamental actin structure using FITC-Phalloidin staining. In connection with this we uncovered certain cytoskeleton organizing proteins involved in the cell response to the treatment. Among these proteins, Septin2, which plays a role in maintaining actin bundles, was suppressed. Another one, PDZ-LIM domain protein 1 (CLP36) was altered. This protein acts as an adaptor molecule for LIM-kinase which phosphorylates and thus inactivates cofilin. Cofilin was indeed dephosphorylated and could thus be activated and operate as an actin-depolymerizing factor. We propose the scheme of molecular response of K562 cells to ALA-PDT.     

Improved synthesis of C4α- and C4β-methyl analogues of 2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate

An efficient and divergent synthesis of C4α- and C4β-methyl-substituted analogues of 2-aminobicyclo[3.1.0]hexane 2,6-dicarboxylate, which are important tools in the study of metabotropic glutamate receptor function, has been achieved. By taking advantage of an unanticipated facial selectivity of the bicyclo[3.1.0]hexane ring system, either the C4α- or C4β-methyl substituent was introduced in a highly stereoselective and high-yielding manner.