Spectroscopic study on the binding of a cationic porphyrin to DNA G-quadruplex under different K+ concentrations.
ABSTRACT We have performed systematic spectroscopic titrations to characterize the binding reaction of cationic meso-tetrakis(4-(N-methylpyridiumyl))porphyrin (TMPyP4) with the G-quadruplex (G4) of human telomeric single-strand oligonucleotide d[TAGGG(TTAGGG)3T] (S24), for which special effort was made to examine the TMPyP4-G4 binding stoichiometry, the binding modes, and the conformational conversion of the G4 structure under different potassium ion (K+) concentration. It is found that, in the presence of 0, 10 mM, and 100 mM K+, TMPyP4 forms a complex with the anti-parallel G4 in a TMPyP4-to-G4 molar ratio of 5, 5 and 3, respectively, and the increase of K+ concentration would reduce the binding affinity of TMPyP4 to G4. For the TMPyP4-G4 complex, the end-stacking mode and groove binding mode were presumed mainly by the results of time-resolved fluorescence spectroscopy in the three cases. Most importantly, it is found that TMPyP4 can directly induce the formation of the anti-parallel G4 structure from the single-strand oligonucleotide S24 in the absence of K+, and that it can preferentially induce the conformational conversion of the G4 structure from the hybrid-type to the anti-parallel one in the presence of K+.
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ABSTRACT: Although it is very common to hear about the professional ethos and to use this concept in the educational world, nonetheless there is a forgotten and proper idea given by the necessity of fitting the concept into its proper measurement and context. The professional task in education has an ethical dimension which is higher than technical. This task is focused on the idea that educational performance cannot separate teaching from formation. Teaching is not only instruction but mainly formation of persons fostered by the practice of habits and virtues. Therefore educational ethos has to be focused toward the development of virtues: justice, fortitude, temperance and prudence, in the teacher and the student. These virtues are not exclusive of the educational world. They have been considered all together, compatible with personal values, as an act coming from the teacher and going to the student, helping her to integrate her personal world as well as her relations with the rest of the studentsProcedia - Social and Behavioral Sciences 01/2011; 15:1661-1666.
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ABSTRACT: The main purpose of this research is to examine the model of the relationship between leadership styles, decision making styles and organizational trust with teachers’ perceived organizational justice. The method of study is correlation. The statistical population consists of all high school teachers of Esfahan city, a central region in Iran. The data collection instruments were four questionnaires (Nihof&Moormans’ organizational Justice, Bass leadership Style, Ruders’ organizational trust, and a researcher's constructed questionnaire based on Tatum's category of decision making styles). The reliability of the questionnaires were estimated for organizational justice (=0/95), leadership styles (0/89), decision making styles (α=0/93), and organizational trust α=0/91). The results indicated that organizational justice can be predicted by transformational leadership style (Variances=0/593) which increased with interactional leadership style (Variances=0/336). Based on β coefficient, with an increase of one unit of comprehensive leadership style, organizational justice was increased to 0/626 while with one unit of increased in limited leadership style; organizational justice was decreased to-0/38.Procedia - Social and Behavioral Sciences 01/2011; 15:1696-1704.
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ABSTRACT: Equilibrium model of a ligand binding with DNA oligomer has been considered as a process of small molecule adsorption onto a lattice of multiple binding sites. An experimental example has been used to verify the assertion that during saturation of the macromolecule by a ligand should expect effect of cooperativity due to changes in DNA conformation or the mutual influence between bound ligands. Such phenomenon cannot be entirely described by the classical stepwise complex formation model. To evaluate a ligand binding affinity and cooperativity of ligand-oligomer complex formation the statistical approach has been proposed. This new computational approach used to re-examine previously studded ligand binding towards DNA quadruplexes targets with multiple binding sites. The intrinsic equilibrium constants K1-3 of the mesotetrakis-(N-methyl-4-pyridyl)-porphyrin (TMPyP4) binding with the [d(T4G4)]4 and with the [AG3(T2AG3)3] quadruplexes and the correction for the mutual influence between bound ligands (cooperativity parameters ω) was determined from the Job plots based upon the nonlinear least-squares fitting procedure. The re-examination of experimental curves reveals that the equilibrium is affected by the positive cooperative (ω>1) binding of the TMPyP4 ligand with tetramolecular [d(T4G4)]4. However for an intramolecular antiparallel-parallel hybrid structure [AG3(T2AG3)3] the weak anti-cooperativity of TMPyP4 accommodation (ω<1) onto two from three nonidentical sites was detected.Talanta 11/2013; 116:541-7. · 3.50 Impact Factor