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Model Sequences (model + sequence)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

The effects of Common Knowledge Construction Model sequence of lessons on science achievement and relational conceptual change

JOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 1 2010
Jazlin Ebenezer
Abstract The purpose of this study was to investigate the effects of the Common Knowledge Construction Model (CKCM) lesson sequence, an intervention based both in conceptual change theory and in Phenomenography, a subset of conceptual change theory. A mixed approach was used to investigate whether this model had a significant effect on 7th grade students' science achievement and conceptual change. The Excretion Unit Achievement Test (EUAT) indicated that students (N,=,33) in the experimental group achieved significantly higher scores (p,<,0.001) than students in the control group (N,=,35) taught by traditional teaching methods. Qualitative analysis of students' pre- and post-teaching conceptions of excretion revealed (1) the addition and deletion of ideas from pre- to post-teaching; (2) the change in the number of students within categories of ideas; (3) the replacement of everyday language with scientific labels; and (4) the difference in the complexity of students' responses from pre- to post-teaching. These findings contribute to the literature on teaching that incorporates students' conceptions and conceptual change. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47: 25,46, 2010 [source]

Chemical Approach for the Study of the ,Kissing Complex' of Moloney murine leukaemia Virus

HELVETICA CHIMICA ACTA, Issue 7 2008
Sébastien Porcher
Abstract The replication of Moloney murine leukaemia virus relies on the formation of a stable homodimeric ,kissing complex' of a GACG tetraloop interacting through only two C,G base pairs flanked of 5,-adjacent unpaired adenosines A9. Previous NMR investigations of a model stem loop 1 has not permitted to reveal the origin of this interaction. Therefore, with the aim of deeper comprehension of the phenomena, the model sequence 10 was prepared where position 9 has been substituted for a nucleoside offering a wider , -stacking. In this context, the wyosine phosphoramidite building block 2 was prepared and incorporated by adapting the conditions of the automated synthesis and developing original templated enzymatic ligation. However, no ,kissing interaction' has been observed for this model sequence 10 due to steric hindrance as confirmed by computational simulation. Consequently, several other model sequences, 18, 23,26, containing modified nucleosides were prepared. Finally, the importance of the cross-loop H-bond between G8 and G11 nucleobases was revealed by preparing a 18mer RNA hairpin 27, where the guanosine G8 has been substituted for inosine. The latter, which does not possess a C3 amino function compared to guanosine, is unable to form any ,kissing complex' demonstrating the importance of this secondary interaction in the formation of the complex. [source]

Mass spectrometric investigation of the sequence selectivity for adduction of heterocyclic aromatic amines on single-strand oligonucleotides

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2008
Emilien L. Jamin
Heterocyclic aromatic amines (HAAs) generated during the cooking of meats are known to be genotoxic substances able to form covalent bonds with DNA bases after metabolic activation. This work aimed at the investigation of the influence of the local environment of nucleobases along the nucleotidic sequence on its modification induced by two different HAAs, namely 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5- f]quinoline (IQ), in order to identify possible sequences more susceptible to modification. A systematic study of the neighbouring base effect on the adduction was emphasized. Thus, PhIP and IQ adducts have been synthesized with various T-rich model single-strand oligonucleotides displaying different flanking bases (A, G, C or T) at the 3, or the 5, side of the targeted guanine, which allowed a comparison of the flanking base effects on adduction. Modified oligonucleotides were then analyzed by high-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry. The localization of the modifications induced by PhIP or IQ along the oligonucleotide sequence was achieved by tandem mass spectrometry, and modification yields of the various model sequences were compared. Results indicate a favouring sequence context effect on the G-C8-IQ adduct formation with the sequence 5,GGG3,. Although higher than IQ, modification yields observed with PhIP showed a less obvious effect of the neighbouring base on the G-C8-PhIP adduct formation, with a preferential sequence 5,GGA/G/T3,. Copyright © 2008 John Wiley & Sons, Ltd. [source]