Analysis of the dielectrophoretic properties of cells using the isomotive AC electric field.

Various microfluidic devices utilizing the principle of dielectrophoresis (DEP) have been developed to separate, concentrate, and characterize biological cells; however, their performance is still limited by a lack of quantitative characterization. We addressed this limitation by employing a method capable of accurately quantifying a cell's response to an imposed field gradient. In this study, a simple method using a newly designed Creek-gap electrode was proposed, and the electrokinetic behavior of cells was characterized by DEP velocimetry under the exposure of an approximately constant gradient of electric field square established along the gap of the electrodes. Together with the numerical prediction of the electric field based on three-dimensional electric field analysis, the magnitude of DEP forces and the real part of the Clausius-Mossotti factor of cells were deduced from their movement. Results demonstrated that the proposed method was applicable to the determination of the dielectrophoretic properties of cells.

Comparative studies on the contribution of NHS hydrogen bonds in tungsten and molybdenum benzenedithiolate complexes.

A series of monooxotungsten(iv) and dioxotungsten(vi) benzenedithiolates, (NEt4)2[WIVO(1,2-S2-3-RCONHC6H3)2] (1-W; R = CH3 (a), t-Bu (b), or CF3 (c)) and (NEt4)2[WVIO2(1,2-S2-3-RCONHC6H3)2] (2-W), were synthesized and compared with the corresponding molybdenum analogues. Single crystals of trans-1b-W were successfully obtained, and the crystal structure was determined by X-ray analysis although 1b-Mo could not be crystallized. The NHS hydrogen bonds shifted the potential of the W(iv/v) redox couple to more positive values, and the strength of the hydrogen bond and the positive shift value were strongly correlated. The hydrogen bonds in both 1-W and 2-W were weaker than those in the corresponding molybdenum analogues; however, the effect of the hydrogen bonds on the redox potential was greater in 1-W.

Correction: Significant differences of monooxotungsten(IV) and dioxotungsten(VI) benzenedithiolates containing two intramolecular NH···S hydrogen bonds from molybdenum analogues.

Correction for 'Significant differences of monooxotungsten(IV) and dioxotungsten(VI) benzenedithiolates containing two intramolecular NH···S hydrogen bonds from molybdenum analogues' by Taka-aki Okamura et al., Dalton Trans., 2015, 44, 18090-18100.

Significant differences of monooxotungsten(IV) and dioxotungsten(VI) benzenedithiolates containing two intramolecular NHS hydrogen bonds from molybdenum analogues.

A monooxotungsten(iv) benzenedithiolate complex containing two intramolecular NHS hydrogen bonds, (NEt4)2[W(IV)O(1,2-S2-3-t-BuNHCOC6H3)2] (1-W), was synthesized via a ligand-exchange reaction between a new starting complex, (NEt4)2[W(IV)O(SC6F5)4], and a partially deprotonated dithiol. When dithiol was used in solution, the oxo ligand was protonated and removed to afford (NEt4)2[W(IV)(1,2-S2-3-t-BuNHCOC6H3)3]. The trans isomer, trans-1-W, was crystallized, and the molecular structure was determined via X-ray analysis. Trans-1-W was gradually isomerized by heating it in solution and it eventually achieved an approximately 1 : 1 mixture of trans/cis isomers after 48 days. However, a slightly excess amount of trans isomer remained, so the isomerization rate was considerably slower than that of the molybdenum analogue. In the presence of NEt4BH4, deuteration of the NH protons was observed in acetonitrile-d3. The oxidation of both trans- and cis-1-W by Me3NO afforded the corresponding dioxotungsten(vi) complex, (NEt4)2[W(VI)O2(1,2-S2-3-t-BuNHCOC6H3)2] (2-W), as a single isomer. The contributions of the NHS hydrogen bonds to the bond distances, vibrational data, and electrochemical properties are described via comparisons with their molybdenum analogues. The results of this comparative study yielded insights into both tungsten and molybdenum enzymes.

Strong NH···S hydrogen bonds in molybdoenzyme models containing anilide moieties.

Monooxomolybdenum(IV) and dioxomolybdenum(VI) benzenedithiolate derivatives containing anilide moieties were synthesized and characterized by (1)H NMR, UV-visible, IR, and Raman spectroscopies. These complexes exhibit very strong intramolecular NH···S hydrogen bonds formed by the acidic anilide NH proton and the desired coplanar structure, resulting in significantly positive redox potential and remarkable acceleration in the reduction of Me3NO in DMF.

Systematic investigation of relationship between strength of NH···S hydrogen bond and reactivity of molybdoenzyme models.

A series of monooxomolybdenum(IV) and dioxomolybdenum(VI) complexes containing two intramolecular NH···S hydrogen bonds were synthesized and characterized by (1)H NMR, UV-visible, IR, and Raman spectroscopies, and electrochemical measurements. Elimination of the steric effects enabled the accurate and quantitative evaluation of NH···S hydrogen bonds. Strong correlations among the strength of the hydrogen bond, the strength of the Mo(VI)═O bond, and the redox potential were clearly shown. The hydrogen bonds stabilize the intermediate in the reaction between the monooxomolybdenum(IV) and Me(3)NO, resulting in acceleration of the reaction or retardation of trans-cis rearrangement. The proposed intermediate and the reaction mechanism, discussed on the basis of theoretical calculations, provided a unified explanation of the reaction.

Selective and effective stabilization of Mo(VI)═O bonds by NH···S hydrogen bonds via trans influence.

A monooxomolybdenum(IV) complex containing two intramolecular NH···S hydrogen bonds, (NEt(4))(2)[Mo(IV)O(1,2-S(2)-3-t-BuNHCOC(6)H(3))(2)], was synthesized. The trans isomer was crystallized as the major product, and the molecular structure was determined by X-ray analysis. The trans isomer was isomerized by heating in solution to give a 1:1 mixture of trans and cis isomers. Oxidation of these isomers by Me(3)NO afforded (NEt(4))(2)[Mo(VI)O(2)(1,2-S(2)-3-t-BuNHCOC(6)H(3))(2)]. (1)H NMR analysis revealed that the dioxomolybdenum(VI) complex existed as a single isomer where both oxo ligands were trans to each of the two hydrogen-bonded thiolate ligands. The Mo(VI)═O bond was effectively stabilized by the NH···S hydrogen bond via trans influence, which was determined using resonance Raman spectroscopy. These results were supported by preliminary density functional theory calculations.