Determination of association constants between 5 '-guanosine monophosphate gel and aromatic compounds by capillary electrophoresis

Hydro gel formed by 5'-guanosine monophosphate (GMP) in the presence of a potassium ion is expected to exhibit interesting selectivity in capillary electrophoretic separations. Here, we estimated the conditional association constants between the hydro gel (G-gel) and aromatic compounds by capillary electrophoresis in order to investigate the separation selectivity that is induced by the G-gel. Several aromatic compounds were separated in a solution containing GMP and potassium ion at different concentrations. The association constants were calculated by correlating the electrophoretic mobilities of the analytes obtained experimentally using a concentration of G-gel. During semi-quantitative estimation, naphthalene derivatives had larger association constants (K-ass = 10.3-16.8) compared with those of benzene derivatives (K-ass = 3.91-5.31), which means that the binding sites of G-gel match better to a naphthalene ring than to a benzene ring. A hydrophobic interaction was also found when the association constants for alkyl resorcinol were compared with those of different hydrocarbon chains. The association constants of nucleobases and tryptophan ranged from 6.05 to 12.6, which approximated the intermediate values between benzene and naphthalene derivatives. Consequently, the selective interaction between G-gel and aromatic compounds was classified as one of three types: (1) an intercalation into stacked planar GMP tetramers; (2) a hydrophobic interaction with a long alkyl chain; or, (3) a small contribution of steric hindrance and/or hydrogen bonding with functional groups such as amino and hydroxyl groups

Application of the Retention Index Concept in Micellar Electrokinetic Capillary Chromatography. [Erratum to document cited in CA120:123851]

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The effects of updating ability and knowledge of reading strategies on reading comprehesion

Updating ability and reading strategies are considered as important factors in the buildup of a mental model of a text. However, only few studies examined the relation of updating and knowledge of reading strategies with reading comprehension. The aim of the current study was to investigate the specific effects of updating ability and knowledge of reading strategies on reading comprehension, controlling for reading speed, vocabulary, and short-term memory. One-hundred-and-ninety-five Dutch fourth graders were administered two standard Dutch reading comprehension tests, and measures of updating ability, knowledge of reading strategies, reading speed, vocabulary, and verbal short term memory. The results showed that updating ability did not contribute to reading comprehension, when other predictors were controlled, whereas knowledge of reading strategies had an independent effect on reading comprehension. The relations of updating ability and knowledge of reading strategies, as well as those of other predictors, with reading comprehension were similar across the two reading comprehension tests. Keywords Reading comprehension; Updating; Reading strategie

Capillary zone electrophoresis of proteins with a dynamic surfactant coating: influence of a voltage gradient on the separation efficiency

In capillary zone electrophoresis of proteins, the adsorption of the proteins on the capillary wall is a considerable problem that seriously impairs the sepn. efficiency. The use of a dynamic surfactant coating is a possible way to diminish this adsorption. Highly efficient sepns. were achieved with a cationic fluorinated buffer additive as a dynamic surfactant coating in untreated fused-silica capillaries at neutral pH. The influence of a voltage gradient on the sepn. efficiency is discussed and a simple relationship is presented to calc. effective mobilities under voltage gradient condition

What does the CBM-maze test measure?

Contains fulltext : 168483.pdf (publisher's version ) (Open Access)In this study, we identified the code-related (decoding, fluency) and language comprehension (vocabulary, listening comprehension) demands of the CBM-Maze test, a formative assessment, and compared them to those of the Gates-MacGinitie test, a standardized summative assessment. The demands of these reading comprehension tests and their developmental patterns were examined with multigroup structural regression models in a sample of 274 children in Grades 4, 7, and 9. The results showed that the CBM-Maze test relied more on code-related than on language comprehension skills when compared to the Gates-MacGinitie test. These demands were relatively stable across grades.13 p

Application of the Retention Index Concept in Micellar Electrokinetic Capillary Chromatography

The application of the retention index concept in micellar electrokinetic capillary chromatog. (MECC) was evaluated for the identification of neutral species. Homologous series of alkylbenzenes and alkylaryl ketones were applied as retention index stds. and also for the calcn. of the micelle migration time by an iteration procedure. The relation between retention indexes, I, and octanol-H2O partition coeffs. is discussed, and DI values were calcd. from retention indexes, obtained with both anionic and cationic surfactant systems, to study the sepn. mechanism for solutes with different functionalities in MECC. The influence of the phase ratio is treated theor., and the capacity factor is linearly related to the surfactant concn., whereas the retention index is independent of the surfactant concn. The temp. dependence of the retention index was studied and the std. enthalpy, entropy, and Gibbs free energy for micellar solubilization of the sample compds. were detd., showing that the hydrophobic interaction plays a significant role in MECC ana