UV/VIS spectral properties of novel natural products from Turkish lichens

UV/VIS spectral characteristics of three new biologically active natural products, isolated from Turkish lichens, have been investigated in solvents of various polarity and proton donating ability. The effect of the solvent on spectral characteristics has been estimated. Quantum chemical calculations with the optimization of molecular geometry were done with the full-valent semiempirical methods AM1 and PM3 for conformational analysis and in order to discuss the charge distributions and dipole moments in the ground and in the excited states

Spectral-luminescent and solvatochromic properties of 2-(3 '-coumarinyl)-5-(2 '-(R-amino)-phenyl)-1,3,4-oxadiazoles

WOS: 000300650200004Spectral-luminescent properties of the newly synthesized 2-(3'-coumarinyl)-5-(2'-(R-amino)-phenyl)1,3,4-oxadiazoles has been investigated in solvents of various polarity and hydrogen-bonding ability. It has been found that for all the studied compounds no excited state intramolecular proton transfer occurs despite the presence of coumarinyl fragment - electron acceptor effect of the coumarinyl fragment is not sufficient to increase the excited state acidity of the amino group. It has been found that the absorption spectra of the studied compounds shift to higher energy with increase in solvent polarity, whereas corresponding fluorescence spectra shift to lower energy with solvent polarity increase. It has been suggested that long-wavelength shifts of the fluorescence spectra of the studied compounds with increase in solvent polarity is caused by the solvent relaxation. The observed solvent relaxation effect allow us to propose some of the studied compounds as potential probes to monitor changes in solvent relaxation in low-polar media and as potential probes for rigidochromic effect. (C) 2011 Elsevier B.V. All rights reserved.Alexander von Humboldt Foundation of GermanyAlexander von Humboldt Foundation; Ege University Research Funds OfficeEge University; TUBITAK-Scientific and Technical Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)The authors express their gratitude to Alexander von Humboldt Foundation of Germany, Ege University Research Funds Office and TUBITAK-Scientific and Technical Research Council of Turkey for their support

A study of enterocyte membranes during activation of apoptotic processes in chronic carrageenan–induced gastroenterocolitis

Aim To investigate the lipid membranes of rat enterocytes in chronic carrageenan-induced gastroenterocolitis accompanied by the activation of apoptotic processes. Methods Steady-state fluorescence spectroscopy: a study by fluorescent probes – by ortho-hydroxy derivatives of 2,5-diaryl-1,3-oxazole. Activity of apoptosis signal-regulating kinase 1 and poly (ADP-ribose) polymerase in small intestinal homogenates, blood serum levels of matrix metalloproteinase-2 and caspase-3 and the level of DNA fragmentation in small intestinal homogenates were determined. Results Biochemical analysis revealed that an activation of apoptotic processes occurred in the intestinal epithelium of rats during chronic carrageenan-induced gastroenterocolitis. The fluorescence probes showed that activation of apoptotic processes in carrageenan-induced gastroenterocolitis was accompanied by changes in polar regions of rat enterocyte membranes, while no changes were revealed in more hydrophobic regions of the membranes. Conclusion The increase in hydration of membranes was attributed to the activation of the apoptosis of enterocytes. It has been shown that a fluorescent probe (2-(2′-hydroxyphenyl)-5-phenyl-1,3-oxazole) can be used for the detection of apoptosis of enterocytes

FCS Study of the Thermodynamics of Membrane Protein Insertion into the Lipid Bilayer Chaperoned by Fluorinated Surfactants

Experimental determination of the free energy (ΔG) stabilizing the structure of membrane proteins (MPs) in their native environment has been hampered by the aggregation and precipitation of MPs outside the lipid bilayer. We recently demonstrated that the latter process can be prevented by the use of fluorinated surfactants, FTACs, that act as chaperones for MP insertion without partitioning in the membrane themselves. Here we combine the advantages of the chaperone-like ability of FTACs with the sensitivity of fluorescence correlation spectroscopy measurements to determine ΔG of bilayer insertion of model MPs. First, we calibrate our approach by examining the effects of chaperoned insertion on ΔG of transmembrane insertion of Annexin B12. We find that a shorter-chained surfactant, FTAC-C6, for which the working concentration range of 0.05–0.2 mM falls below CMC = 0.33 mM, has a mild effect on an apparent ΔG. In contrast, additions of a longer-chained FTAC-C8 (CMC = 0.03 mM) result in a steep and nonlinear concentration dependence of ΔG. We then apply the same methodology to the pH-triggered insertion of diphtheria toxin T-domain, which is known to be affected by nonproductive aggregation in solution. We find that the correction of the ΔG value needed to compensate for unchaperoned insertion of the T-domain exceeds 3 kcal/mole. A relatively shallow and linear dependence of the ΔG for Annexin B12 and T-domain insertion on FTAC-C6 concentration is encouraging for future applications of this surfactant in thermodynamic studies of the stability of other MPs