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Abstract: Validation of reducing-difference procedure based on subtracting of non-polarized infrared (IR) spectra of n-component solid mixtures is presented. The accuracy and precision are established. The limits of detection are 3.0, 2.5, 1.5 and 1.0wt.% for 5-, 4-, 3-and 2-component mixtures, respectively. Smoothing procedures for IR spectral analysis, based on Savitzky–Golay or Fourier methods are applied as well. The mean values and relative standard deviations for peak position (ν i ) and integral absorbance (A i ) obtained by this data processing approach have been examined using Student''s t-test. [Copyright &y& Elsevier]

Abstract: A linear dichroic infrared (IR-LD) spectral analysis of solid 4-aminopyridine (4-AP) samples was carried out using two orientation techniques, i.e., as polycrystalline layers and in a nematic mesophase. The so-called reducing-difference procedure was used for the polarized IR-spectra interpretation. By achieving a more precise assignment of a part of the 4-AP characteristic frequencies, the obtained data proved a Fermi-resonance splitting of the symmetrical NH2-stretch and confirmed the predominant aromatic character of the pyridine ring. The possibilities of the difference IR-LD technique used for the study of the supramolecular solid-state structure are also illustrated. [Copyright &y& Elsevier]

During the last 2 decades it was proposed that atherogenesis was closely related to the homeostasis of homocysteine (hCys) and/or copper. We hypothesized that the physiological action of hCys may be connected with its ability to form complexes with Cu. Our results showed the presence of two different Cu–hCys complexes. At a molar ratio Cu:hCys 1:1, a blue complex most probably consistent with a tentative dimeric CuII2(hCys)2(H2O)2 formula was formed, with tetrahedral Cu coordination and anti-ferromagnetic properties. The redox processes between Cu(II) and hCys, in a molar ratio ≥1:3 led to formation of a second yellow CuIhCys complex. Both Cu–hCys complexes affected the metabolism of extracellular thiols more than hCys alone and inhibited glutathione peroxidase-1 activity and mRNA abundance. The biological action of hCys and Cu–hCys complexes involved remodeling and phosphorylation of focal adhesion complexes and paxillin. The adhesive interactions of monocytes with an endothelial monolayer led to the redistribution of both paxillin and F-actin after all treatments, but the diapedesis of monocytes through endothelial cell monolayer was both greater and faster in the presence of the tentative CuII2(hCys)2(H2O)2 complex. Together, these observations suggest that Cu–hCys complexes actively participate in the biochemical responses of endothelial cells that are involved in the aethiopathogenesis of atherosclerosis. [Copyright &y& Elsevier]