Browsing by Subject "Cations"

Now showing 1 - 4 of 4

Open Access
Investigation of binding properties of dicationic styrylimidazo[1,2-a]pyridinium dyes to human serum albumin by spectroscopic techniques
(John Wiley and Sons Ltd, 2017) Özdemir, A.; Gökoğlu, E.; Yılmaz, Esra; Yalçın, E.; Gökoğlu, E.; Seferoğlu, Z.; Tekinay, T.
The binding interaction between two dicationic styrylimidazo[1,2-a]pyridinium dyes and human serum albumin (HSA) was investigated at physiological conditions using fluorescence, UV–vis absorption, and circular dichroism (CD) spectroscopies. Analysis of the fluorescence titration data at different temperatures suggested that the fluorescence quenching mechanism of HSA by these dyes was static. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that hydrogen bonding and van der Waals forces played a major role in the formation of the dye–HSA complex. Binding distances (r) between dyes and HSA were calculated according to Förster's non-radiative energy transfer theory. Studies of conformational changes of HSA using CD measurements indicate that the α-helical content of the protein decreased upon binding of the dyes.
Open Access
Ionic current inversion in pressure-driven polymer translocation through nanopores
(American Physical Society, 2015) Buyukdagli, S.; Blossey, R.; Ala-Nissila, T.
We predict streaming current inversion with multivalent counterions in hydrodynamically driven polymer translocation events from a correlation-corrected charge transport theory including charge fluctuations around mean-field electrostatics. In the presence of multivalent counterions, electrostatic many-body effects result in the reversal of the DNA charge. The attraction of anions to the charge-inverted DNA molecule reverses the sign of the ionic current through the pore. Our theory allows for a comprehensive understanding of the complex features of the resulting streaming currents. The underlying mechanism is an efficient way to detect DNA charge reversal in pressure-driven translocation experiments with multivalent cations. © 2015 American Physical Society.
Open Access
Local electric fields in aqueous electrolytes
(American Chemical Society, 2021-07-27) Drexler, C. I.; Cracchiolo, O. M.; Myers, R. L.; Okur, Halil İbrahim; Serrano, A. L.; Corcelli, S. A.; Cremer, P. S.
Vibrational Stark shifts were explored in aqueous solutions of organic molecules with carbonyl- and nitrile-containing constituents. In many cases, the vibrational resonances from these moieties shifted toward lower frequency as salt was introduced into solution. This is in contrast to the blue-shift that would be expected based upon Onsager’s reaction field theory. Salts containing well-hydrated cations like Mg2+ or Li+ led to the most pronounced Stark shift for the carbonyl group, while poorly hydrated cations like Cs+ had the greatest impact on nitriles. Moreover, salts containing I– gave rise to larger Stark shifts than those containing Cl–. Molecular dynamics simulations indicated that cations and anions both accumulate around the probe in an ion- and probe-dependent manner. An electric field was generated by the ion pair, which pointed from the cation to the anion through the vibrational chromophore. This resulted from solvent-shared binding of the ions to the probes, consistent with their positions in the Hofmeister series. The “anti-Onsager” Stark shifts occur in both vibrational spectroscopy and fluorescence measurements.
Open Access
Selective Hg(II) sensing with improved stokes shift by coupling the internal charge transfer process to excitation energy transfer
(American Chemical Society, 2010) Atilgan, S.; Ozdemir, T.; Akkaya, E. U.
Versatile chemistry of the Bodipy chromophore allows modular assembly of an excitation energy donor, acceptor, and a cation selective ligand in just a couple of steps. The new approach should be applicable in other designs which target molecular sensors with large Stokes shifts and red to near IR emission.