Many topological indices lack an interpretation in terms of simple physicochemical quantities. We have reexamined the structural interpretation of well-known topological indices: the connectivity index (1)chi, the Wiener index W, and the Hosoya topological index Z. We relate the success of various indices in structure-property studies to the degree to which they differentiate contributions from more exposed terminal bonds and more buried interior bonds. When considering bond additive properties of alkanes we find better regressions when greater weights are assigned to terminal CC bonds and lesser weights to internal CC. We suggest here that topological indices be discussed in terms of their partitioning into bond contributions, which for different indices and different bonds will assume different values. With this insight we modified the Wiener index W into a new index W, in which bond contributions are determined using the reciprocal of the product of the number of atoms on each side of a bond. Similarly we modified the Hosoya index Z into Z in which the frequency of occurrence of individual CC bonds in the patterns of disjoint bonds are considered. Novel indices are compared with other indices and they show to yield better regressions for boiling points of octane isomers. This suggests a useful classification of topological indices based on the relative magnitudes of the contributions of terminal and interior bonds. To extend such considerations to other indices one needs to consider partitioning of global molecular indices into bond additive terms. A general scheme for partitioning of molecular descriptors into bond contributions is outlined for indices derived from a selection of matrices associated with molecular graphs.

Journal Article↗

PubMedDate not supplied

On 3-D graphical representation of proteomics maps and their numerical characterization.

We consider numerical characterization of proteomics maps by representing a map as a three-dimensional graphical object based on x, y coordinates of the spots and using their relative abundance as the z coordinate. In our representation the protein spots are first ordered based on their relative abundance and labeled accordingly. In the next step a 3-D path is constructed connecting spots having adjacent labels. Finally a matrix is constructed by assigning to each pairs of labels (i, j) matrix element, the numerical value of which is based on the quotients of the Euclidean distance and the distance along the 3-D zigzag between the two points. The approach has been illustrated on a fragment of a proteomics map and compared with 2-D graphical representation of proteomics maps.

Computer Graphics↗

PubMedDate not supplied

Application of counterpropagation artificial neural network for modelling properties of fish antibiotics.

The present study focuses on fish antibiotics which are an important group of pharmaceuticals used in fish farming to treat infections and, until recently, most of them have been exposed to the environment with very little attention. Information about the environmental behaviour and the description of the environmental fate of medical substances are difficult or expensive to obtain. The experimental information in terms of properties is reported when available, in other cases, it is estimated by standard tools as those provided by the United States Environmental Protection Agency EPISuite software and by custom quantitative structure-activity relationship (QSAR) applications. In this study, a QSAR screening of 15 fish antibiotics and 132 xenobiotic molecules was performed with two aims: (i) to develop a model for the estimation of octanol--water partition coefficient (logP) and (ii) to estimate the relative binding affinity to oestrogen receptor (log RBA) using a model constructed on the activities of 132 xenobiotic compounds. The custom models are based on constitutional, topological, electrostatic and quantum chemical descriptors computed by the CODESSA software. Kohonen neural networks (self organising maps) were used to study similarity between the considered chemicals while counter-propagation artificial neural networks were used to estimate the properties.

Animals↗

PubMedDate not supplied

[Breech presentation delivery in Slovenia].

A computer-supported analysis of 722 breech presentations was performed, and the results were compared to those of 18,533 vertex presentations. This covered all labors performed in 10 Slovene obstetric hospitals in 1986. It was found that the greatest risk existed in the group of preterm breech deliveries. This group had the highest percentage of perinatal mortality (256%), unfavourable infant postpartum condition (1 min Apgar 1-3 24.8%; 5 min Apgar 1-3 11.4%), malformations (14.8%), intracranial bleeding (4.7%), respiratory distress (11.4%), and infections (2.7%). In term breech deliveries the number of malformations was also higher than in term vertex deliveries (3.9%: 1.1%). The cesarean section was used in 30% of breech presentations (8% in vertex presentation). The postpartum condition of preterm infants was slightly better when they had been delivered with a cesarean section (1 min Apgar 1-3 42.2%; 5 min Apgar 1-3 0%) than if delivered vaginally (1 min Apgar 1-3 25.0%; 5 min Apgar 1-3 14.6%), but this was not the case with infants born at term. Here the postpartum condition is better in vaginal deliveries. Surprisingly, the fetal monitoring was the least satisfactory in the group at the greatest risk.

Apgar Score↗