Several different QSAR techniques have been applied to sweetness data for 50 sulfamates, RNHSO3Na (21 sweet, 20 sweet-bitter, and 9 bitter). Stepwise discriminant analysis has been used to
separate the 50 molecules into 3 classes, sweet, sweet-bitter, and bitter. Cluster analysis using
two principal components can clearly distinguish between the sweet and sweet-bitter molecules
but not between all three classes. Regression analysis has been used to develop equations for
parameters fitting to log(RS) (RS, relative sweetness). The genetic algorithm method has been used
to select parameters, and high correlations between log(RS) and a range of parameters have been
achieved. Molecular field analysis followed by selection of relevant grid points by genetic algorithm
yielded a result in which six grid points gave a high correlation coefficient (r
2 = 0.958, XVr
2 =
0.902).
Keywords: Sweetness; QSAR; sulfamates; bitterness
A data set of 101 hetero-(both cyclic and open chain) sulfamate sodium salts, whose taste data are known, have been assembled and divided into sweet (S) (20 compounds) and non-sweet (N) (81 compounds) categories. The data set is made up of 56 compounds reported earlier, 32 synthesised in this work and another 13 reported since the earlier publications. Using the parameters x, y and z (measured for the RNH portion of RNHSO 3 Na using CPK models) and first order molecular connectivity, 1 χ ν it has been possible to achieve a correct classification rate of approximately 65% using linear discriminant analysis (LDA): a compound is N if Ϫ3.285 ϩ 0.439x ϩ 0.662y ϩ 0.236z Ϫ 1.27 1 χ ν > 0 otherwise it would be S. Using quadratic discriminant analysis (QDA) the classification rate increased to approximately 80%. Finally a Tree-based analysis gave an 86% classification rate but performed poorly in classifying correctly the S group of compounds.
Turloughs, which are classified as priority habitats under the European Habitats Directive, are seasonally flooded depressions found almost exclusively in Ireland. In 2001, three adjacent fields with different stocking densities were selected and plant=dipteran communities within the same vegetation zone of each field (site) were investigated using quadrats and sweep netting, respectively. There was a significant positive relationship between Diptera morphospecies richness=Diptera abundance and mean vegetation height (P < 0.001). However, no significant relationship between Diptera morphospecies richness and plant species richness was found. Median Diptera morphospecies richness per sweep was lower at the site with the highest stocking density (17) than at the other two sites (22 and 31, respectively). Total species richness of Sciomyzidae was greater at the least grazed site (7) than at the more heavily grazed sites (2 and 1, respectively). The results suggest that an evaluation of turlough management practices based on plant communities alone is not sufficient and that at least some areas within the turlough basin remain ungrazed on a rotational basis to ensure maximum diversity of Diptera.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.