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341.
Silvia Tomić Danijel Grgičin Tomislav Ivek Sanja Dolanski Babić Tomislav Vuletić Georg Pabst Rudi Podgornik 《Macromolecular Symposia》2011,305(1):43-54
Structural properties of Na-DNA and Na-HA aqueous solutions can be quantified using dielectric spectroscopy in the frequency range 100 Hz–100 MHz. Two relaxation modes are typically detected that can be attributed to diffusive motion of polyion counterions. The overall study as a function of polyion length, concentration and added salt concentration demonstrates that the motion of polyion counterions detected at MHz frequencies probes collective properties, whereas the motion at kHz range probes single-chain properties of polyelectrolytes. Fundamental length scales found to characterize the polyelectrolyte structure differ for the dilute and semidilute regime and also depend on the strength of electrostatic interactions and the flexibility. Characteristic length scales detected in the dielectric spectroscopy measurements compare well with the fundamental length scales predicted by theory and comply with those extracted from small-angle X-ray scattering. 相似文献
342.
Lea Kukoc-Modun Tomislav Kraljevi Dimitrios Tsikas Njegomir Radi Darko Modun 《Molecules (Basel, Switzerland)》2021,26(22)
A new flow injection spectrophotometric method for the determination of N-acetyl-l-cysteine ethyl ester (NACET) was developed and validated. The method is based on the reduction of Cu(II)-ligand complexes to chromophoric Cu(I)-ligand complexes with the analyte. The studied ligands were neocuproine (NCN), bicinchoninic acid (BCA) and bathocuproine disulfonic acid (BCS). The absorbance of the Cu(I)-ligand complex was measured at 458, 562 and 483 nm for the reactions of NACET with NCN, BCA and BCS, respectively. The method was validated in terms of linear dynamic range, limit of detection and quantitation, accuracy, selectivity, and precision. Experimental conditions were optimized by a univariate method, yielding linear calibration curves in a concentration range from 2.0 × 10−6 mol L−1 to 2.0 × 10−4 mol L−1 using NCN; 2.0 × 10−6 mol L−1 to 1.0 × 10−4 mol L−1 using BCA and 6.0 × 10−7 mol L−1 to 1.2 × 10−4 mol L−1 using BCS. The achieved analytical frequency was 90 h−1 for all three ligands. The method was successfully employed for NACET determination in pharmaceutical preparations, indicating that this FIA method fulfilled all the essential demands for the determination of NACET in quality control laboratories, as it combined low instrument and reagent costs with a high sampling rate. 相似文献
343.
Rafael A. Hernandez Irini Trakakis Jean-Louis Do Prof. Louis A. Cuccia Prof. Tomislav Friščić Prof. Pat Forgione 《European journal of organic chemistry》2023,26(29):e202300374
A mechanochemical desymmetrization of symmetrical bis- and tris-alkynes by a controlled 1,3-dipolar cycloaddition reaction using nitrile oxide dipoles (NOs). This operationally simple protocol allows access to 3,5-isoxazole-alkyne adducts from easily prepared or commercially available symmetrical bis- and tris-alkynes in moderate to excellent yields. In addition, we have highlighted the synthetic utility of 3,5-isoxazole-alkyne by developing a route to access, for the first time, β-ketoenamine-alkyne derivatives, and unsymmetrical bis-3,5-isoxazoles. 相似文献