Thermally induced structural transformation of polytriazoleimide to polyindoleimide

A new kind of polytriazoleimide containing bisphenyl-l,2,3-triazole（BPT） was synthesized by copper-catalyzed 1,3-dipolar cycloaddition of azides and alkynes（CuAAC） and polycondensation.The thermal stability and degradation mechanism of the polytriazoleimide were investigated.The results show that the structure of BPT in polytriazoleimide transforms to phenylindole after thermal treatment,accompanying the release of N₂.     

Thermally induced structural transformation in a hydrogen-bonded supramolecular single-crystal

The thermally induced structural transformation of a hydrogen-bonded crystal formed from an amphoteric molecule of 6-[2-methoxy-4-(pyridylazo)phenoxy]hexanoic acid MeO was studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction measurement (XRD). Crystal form of the hydrogen-bonded crystal was measured by single crystal four circle diffractometer (Mo-K_α radiation). As a result, the crystal of MeO was stabilized by many C–H⋅⋅⋅O hydrogen bonds, and the C–H⋅⋅⋅O hydrogen bonds were broken by thermal energy reversibly. After transformation the supramolecular architecture was composed of supramolecular polymer including free-rotation pentamethylene main chains.     

Thermally induced defluorination during a mer to fac transformation of a blue-green phosphorescent cyclometalated iridium(III) complex

The new homoleptic tris-cyclometalated [Ir(C^N)(3)] complexes mer-8, fac-8, and fac-9 incorporating γ-carboline ligands are reported. Reaction of 3-(2,4-difluorophenyl)-5-(2-ethylhexyl)-pyrido[4,3-b]indole 6 with iridium(III) chloride under standard cyclometalating conditions gave the homoleptic complex mer-8 in 63% yield. The X-ray crystal structure of mer-8 is described. The Ir-C and Ir-N bonds show the expected bond length alternations for the differing trans influence of phenyl and pyridyl ligands. mer-8 quantitatively isomerized to fac-8 upon irradiation with UV light. However, heating mer-8 at 290 °C in glycerol led to an unusual regioselective loss of one fluorine atom from each of the ligands, yielding fac-9 in 58% yield. fac-8 is thermally very stable: no decomposition was observed when fac-8 was heated in glycerol at 290 °C for 48 h. The γ-carboline system of fac-8 enhances thermal stability compared to the pyridyl analogue fac-Ir(46dfppy)(3)10, which decomposes extensively upon being heated in glycerol at 290 °C for 2 h. Complexes mer-8, fac-8, and fac-9 are emitters of blue-green light (λ(max)(em) = 477, 476, and 494 nm, respectively). The triplet lifetimes for fac-8 and fac-9 are ~4.5 μs at room temperature; solution Φ(PL) values are 0.31 and 0.22, respectively.     

Thiol redox status evaluation in red blood cells by capillary electrophoresis-laser induced fluorescence detection

Thiols and in particular glutathione (GSH) play a central role in human metabolism, including the detoxification of xenobiotics, cell homeostasis, radioprotection, and antioxidant defence. Here, a new method is provided for the measurement of reduced and total forms of thiols in red blood cells. In order to minimize oxidation of reduced thiols, a water erythrocyte lysis (15 min at 4 degrees C) was performed followed by a protein precipitation step with acetonitrile. The supernatant was rapidly derivatized with 5-iodoacetoamidefluorescein that trapped thiol groups, thus minimizing auto-oxidation. Derivatized samples were separated in a 57 cm x 75 microm ID capillary by using 5 mmol/L sodium phosphate, 4 mmol/L boric acid as electrolyte solution with 75 mmol/L N-methyl-D-glucamine at pH 11.0. Under these conditions, cysteinylglycine (CysGly), cysteine (Cys), glutathione, and gamma-glutamylcysteine (GluCys) were baseline-resolved in approximately 4 min. Precision tests showed a good repeatability of our method both for migration times (coefficient of variation CV < 0.8%) and areas (CV < 3.3%). Furthermore, a good reproducibility of intrassay and interassay tests was obtained (CV < 5% and CV < 8%, respectively). The method was employed to investigate the effect of acidic precipitation on intracellular thiol concentration. Our data suggest that sample acidification causes a modification of the measured redox thiol status due to the development of a pro-oxidant environment; moreover, the thiol redox status of red blood cells was evaluated in 22 healthy volunteers.     

Thermally induced alkylation of diamond

We present an approach for the thermally activated formation of alkene-derived self-assembled monolayers on oxygen-terminated single and polycrystalline diamond surfaces. Chemical modification of the oxygen and hydrogen plasma-treated samples was achieved by heating in 1-octadecene. The resulting layers were characterized using X-ray photoelectron spectroscopy, thermal desorption spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and water contact angle measurements. This investigation reveals that alkenes selectively attach to the oxygen-terminated sites via covalent C-O-C bonds. The hydrophilic oxygen-terminated diamond is rendered strongly hydrophobic following this reaction. The nature of the process limits the organic layer growth to a single monolayer, and FTIR measurements reveal that such monolayers are dense and well ordered. In contrast, hydrogen-terminated diamond sites remain unaffected by this process. This method is thus complementary to the UV-initiated reaction of alkenes with diamond, which exhibits the opposite reactivity contrast. Thermal alkylation increases the range of available diamond functionalization strategies and provides a means of straightforwardly forming single organic layers in order to engineer the surface properties of diamond.     

Morphology of small aggregates of red blood cells

Blood can be considered a two-phase liquid composed of plasma as well as cells and cell aggregates. The degree of cell aggregation is an important determinant of blood rheology: The size and shape of the aggregates affect blood viscosity. The microscopic mechanisms of red blood cell adhesion involve a complex interplay of electrostatic, van der Waals, and a range of specific biochemical inter-membrane interactions. Here we use an effective model of these interactions combined with the membrane elasticity theory to calculate the equilibrium shape of a red blood cell doublet and compare it with the experimentally observed red blood cell aggregates both in vitro and in vivo. Special attention is devoted to the shape of doublets formed by dissimilar cells. A possible effect of doublet shape on pathways of the formation of multicellular aggregates is discussed. Red blood cell rouleau formation is expected to take place at intermediate adhesion strengths where the outer doublet surfaces are either concave or flat, whereas in the strong-adhesion regime where the outer doublet surfaces are convex the cells should form rounded clump-like aggregates.     

High-voltage capillary zone electrophoresis of red blood cells

The high-voltage wide-bore capillary zone electrophoresis of red blood cells was investigated. The reproducibility of the retention time (electrophoretic mobility) is excellent and the differentiation among various species is good. The peaks in the electropherogram describe the distribution of the size and/or surface charge of the cells and are therefore broad. The relationship between the peak height and the number of cells injected is good, with linear correlation coefficients better than 0.98. Details of the preparation of cell suspensions and support electrolytes are given, which is essential for obtaining reproducible results. The inner surface of FEP capillary tubing is degraded by the application of high voltage and a pause is necessary between successive experiments if good and reproducible peak shapes are to be obtained. The length of the pause increases with the number of experiments made, and finally the tubing becomes useless. Inspection of the inner surface by X-ray photoelectron spectroscopy showed the breakdown of CHF bonds, but the actual mechanism is not known.     

PIXE determination of calcium in red blood cells

The determination of calcium in erythrocytes by the method PIXE requires the preliminary elimination of large amounts of potassium. The best results, with regard to potassium removal and calcium yield, were obtained by carrying out a coprecipitation of calcium and strontium in 80% nitric acid. The development of the method has shown the importance of the total elimination of leucocytes and platelets from the serum in order to avoid erroneously high values for erythrocyte calcium.     

High-throughput biophysical measurement of human red blood cells

This paper reports a microfluidic system for biophysical characterization of red blood cells (RBCs) at a speed of 100-150 cells s(-1). Electrical impedance measurement is made when single RBCs flow through a constriction channel that is marginally smaller than RBCs' diameters. The multiple parameters quantified as mechanical and electrical signatures of each RBC include transit time, impedance amplitude ratio, and impedance phase increase. Histograms, compiled from 84,073 adult RBCs (from 5 adult blood samples) and 82,253 neonatal RBCs (from 5 newborn blood samples), reveal different biophysical properties across samples and between the adult and neonatal RBC populations. In comparison with previously reported microfluidic devices for single RBC biophysical measurement, this system has a higher throughput, higher signal to noise ratio, and the capability of performing multi-parameter measurements.     

Electrokinetic transport of red blood cells in microcapillaries

Electrokinetic flow of a suspension of erythrocytes (red blood cells, RBCs) in 20 num cylindrical fused-silica capillaries is examined in the present work. Flow direction anomalies are observed experimentally and tentatively explained by the development of a pH gradient between the cathode well and the anode well due to electrolysis reactions at the electrodes. This pH gradient alters the local zeta potentials of both the capillary and the RBC and thus the local electroendosmotic liquid flow (EOF) velocities and RBC electrophoretic (EP) velocities. The two velocities are opposite in direction but with EOF dominating such that the RBC moves toward the cathode, opposite to the anode migration observed in bulk conditions. The opposing zeta potentials also lead to RBC aggregation at the anode end for low fields less than 25 V/cm. As the electroendosmotic velocity decreases at the anode end due to decreasing pH, pressure-driven back flow develops to oppose the original EOF at the remaining portions of the capillary ensuring constant fluid flux. When the anode EOF velocity is smaller in magnitude than the EP velocity, reversal of blood cell transport is observed after a short transient time in which a pH gradient forms. RBC velocities and pH dependencies on electric field and MgCl(2) concentration are presented along with data showing the accumulation of charge separation across the capillary. Also, a short-term solution to the pH gradient formation is presented that could help thwart development of pH gradients in micro-devices at lower voltages.     

Mitochondrial signaling in mammalian cells activated by red and near-IR radiation

Abstract Mitochondrial signaling is an information channel between the mitochondrial respiratory chain and the nucleus for the transduction signals regarding the functional state of the mitochondria. The present review examines the question whether radiation of visible and near-IR (IR-A) radiation can activate this retrograde-type cellular signaling pathway. Experimental data about modulation of elements of mitochondrial retrograde signaling by the irradiation (mitochondrial membrane potential DeltaPsi(m), reactive oxygen species ROS, Ca(2+), NO(*), pH(i), fission-fusion homeostasis of mitochondria) are reviewed. The terminal enzyme of the mitochondrial respiratory chain cytochrome c oxidase is considered as the photoacceptor. Functions of cytochrome c oxidase as a signal generator as well as a signal transducer in irradiated cells are outlined.     

Thermally induced paramagnetism of spiropyran salts

An increase in the effective magnetic moments and linewidths in ESR spectra caused by the presence of crystallization water molecules in crystals of tris(oxalato)chromium(III) complexes with spiropyran cations Sp⁺ was found. Dehydration (rehydration) of crystals causes a reversible decrease (increase) in thermally induced paramagnetism of Sp⁺. Thermally induced paramagnetism of crystals appears in the compounds synthesized in oxygen atmosphere but is not found in the compounds synthesized under argon atmosphere. The contributions of chromium oxalates and thermally excited spiropyran molecules to the magnetization were separated using ESR spectroscopy. The enthalpies of the biradical states of some types of spiropyran cations in crystals were determined.     

Structural and functional changes in the membrane and membrane skeleton of red blood cells induced by peroxynitrite

The changes in passive ion permeability of the red blood cell membrane after peroxynitrite action (3 microM-3 mM) have been studied by biophysical (using radioisotopes of rubidium, sodium and sulphur (sulphate)) and electrophysiological methods. The enhancement of passive membrane permeability to cations (potassium and sodium ions) and the inhibition of anion flux through the anion exchanger in peroxynitrite-treated red blood cells were revealed. In patch-clamp experiments the whole-cell conductance after peroxynitrite (80 muM) treatment of red blood cells increased 3-3.5-fold with a shift in the reversal potential from -7.0+/-1.5 mV to -4.3+/-0.9 mV (n=7, p=0.005). The addition of cobalt and nickel ions to red blood cell suspensions before peroxynitrite treatment had no effect on the peroxynitrite-induced cation flux but zinc ions in the same condition decreased cation flux about 2-fold. Using atomic force microscopy methods we revealed an increase in red blood cell membrane stiffness and the membrane skeleton complexity after peroxynitrite action. We conclude that the peroxynitrite-induced water and ion imbalance and reorganization in membrane structure lead to crenation of red blood cells.     

Agglutination of like-charged red blood cells induced by binding of beta2-glycoprotein I to outer cell surface

Plasma protein-mediated attractive interaction between membranes of red blood cells (RBCs) and phospholipid vesicles was studied. It is shown that beta(2)-glycoprotein I (beta(2)-GPI) may induce RBC discocyte-echinocyte-spherocyte shape transformation and subsequent agglutination of RBCs. Based on the observed beta(2)-GPI-induced RBC cell shape transformation it is proposed that the hydrophobic portion of beta(2)-GPI molecule protrudes into the outer lipid layer of the RBC membrane and increases the area of this layer. It is also suggested that the observed agglutination of RBCs is at least partially driven by an attractive force which is of electrostatic origin and depends on the specific molecular shape and internal charge distribution of membrane-bound beta(2)-GPI molecules. The suggested beta(2)-GPI-induced attractive electrostatic interaction between like-charged RBC membrane surfaces is qualitatively explained by using a simple mathematical model within the functional density theory of the electric double layer, where the electrostatic attraction between the positively charged part of the first domains of bound beta(2)-GPI molecules and negatively charged glycocalyx of the adjacent RBC membrane is taken into account.     

Mechanisms of red blood cells agglutination in antibody-treated paper

Recent reports on using bio-active paper and bio-active thread to determine human blood type have shown a tremendous potential of using these low-cost materials to build bio-sensors for blood diagnosis. In this work we focus on understanding the mechanisms of red blood cell agglutination in the antibody-loaded paper. We semi-quantitatively evaluate the percentage of antibody molecules that are adsorbed on cellulose fibres and can potentially immobilize red blood cells on the fibre surface, and the percentage of the molecules that can desorb from the cellulose fibre surface into the blood sample and cause haemagglutination reaction in the bulk of a blood sample. Our results show that 34 to 42% of antibody molecules in the papers treated with commercial blood grouping antibodies can desorb from the fibre surface. When specific antibody molecules are released into the blood sample via desorption, haemagglutination reaction occurs in the blood sample. The reaction bridges the red cells in the blood sample bulk to the layer of red cells immobilized on the fibre surface by the adsorbed antibody molecules. The desorbed antibody also causes agglutinated lumps of red blood cells to form. These lumps cannot pass through the pores of the filter paper. The immobilization and filtration of agglutinated red cells give reproducible identification of positive haemagglutination reaction. Results from this study provide information for designing new bio-active paper-based devices for human blood typing with improved sensitivity and specificity.     

Thermosensitivity of red blood cells from Down's syndrome individuals

Biochemical disturbances of the reactive oxygen species metabolism revealed in subjects with Down's syndrome (DS), and the findings indicating that heat-induced cell alterations have been, at least, partly mediated by reactive oxygen species, made the elucidation of the response of trisomic cells to elevated temperatures of special interest. Kinetic analysis of cell-survival curves, accompanied by the flow cytometry and the scanning electron microscopy (SEM) examinations, and their relationship with the cell membrane fluidity, were undertaken. At each temperature (48-54 degrees C), Dq parameters, representing the ability to accumulate sublethal damages, were similar for both cell groups. D0 parameters (inverse leakage rates; D0 = 1/k) were greater for DS cells at each temperature below 54 degrees C. The haemolysis sensitivity ratio (HSR) showed that DS erythrocytes were, in average, 1.60 times more resistant to heat injury than those from normal subjects. Activation energies of haemolysis, calculated according to the Arrhenius equation, were similar both for normal (290.8 +/- 6.5 [kJ/mol]) and DS erythrocytes (288.0 +/- 5.5 [kJ/mol]). Flow cytometry studies showed that the scattering properties of intact DS erythrocytes (reflecting size, volume, shape and cell membrane surface morphology) were different than those of normal cells. Scanning electron micrographs and scattering diagrams obtained for cells submitted to heat stress (51 degrees C) confirmed that DS erythrocytes were more resistant, to a certain extent, to heat-induced disruption than normal cells. The steady-state fluorescence anisotropy of TMA-DPH (1-(4-trimethyl-ammoniumphenyl)-6-phenyl-1,3,5-hexatriene) showed that untreated DS erythrocytes had substantially lower fluidity (r = 0.356 +/- 0.008) of the outer monolayer of cell membranes as compared to normal cells (r = 0.324 +/- 0.011). The increase of the cell membrane fluidity during exposure to heat was observed. The greatest elevation of cell membrane fluidity occurred during the preleakage period, immediately upon the heat treatment and was considered as a rate-limiting step of heat-induced haemolysis.     

Immunoelectrophoresis of red blood cells performed on microcapillary chips

Immunoanalysis of blood cells on a microcapillary electrophoresis (nuCE) chip has been studied using sheep erythrocytes (ShE) as an example. Two different buffer solutions, the phosphate-buffered saline (PBS) and the gelatin veronal buffer (GVB) were examined in regard to the electrokinetic transport behavior of ShE suspended in these solutions inside the rectangular channel engraved on a quartz chip. This clarified two advantages of the use of GVB for on-chip cell electrophoresis: gelatin coatings prevent (i) nonspecific sticking of ShE on the channel wall, and cause (ii) an appreciable reduction in the zeta potential of the wall suppressing the electroosmotic flow of the buffer solution. As a result ShE suspended in the GVB can smoothly migrate from the cathode to the anode, which is the opposite flow direction of immunoglobulin G (IgG) antibodies under the physiological pH condition of 7.4. Based on these results, on-chip capillary cell immunoelectrophoresis of ShE and rabbit anti ShE antibodies (IgG) have been proposed and successfully accomplished using the GVB. It is demonstrated that the variation of the cell migration velocity originating from the change in the surface charge after binding antibodies is applicable to the fast detection of immune reactions and also to single-cell typing.     

Molecular mechanism of naproxen photosensitization in red blood cells

Red blood cell lysis photosensitized by naproxen was investigated. The photohemolysis rate was enhanced by deuterium oxide and inhibited by butylated hydroxyanisole, reduced glutathione, sodium azide and superoxide dismutase. Photohemolysis was also observed under anaerobic conditions. In the absence of red cells the irradiation of deaerated solutions underwent a decarboxylation process via intermediate radicals, while under aerobic conditions photo-oxidation leading to the photoproduct 6-methoxy-2-acetonaphthone occurred. A molecular mechanism involving free radicals and singlet oxygen as important intermediates and consistent with the overall results is proposed.     

Influence of PAMAM dendrimers on human red blood cells

Polyamidoamine (PAMAM) dendrimers with different concentrations (1 nM-1 mM) (generations 2, 3, and 4) impact on human red blood cell morphology, and membrane integrity is studied. Erythrocyte shape changes from biconcave to echinocytic in dendrimers. Cell aggregation occurs. Polymers cause also concentration- and generation-dependent haemolysis.