Magnetic-field-induced stress in confined magnetoactive elastomers.

We present a theoretical approach for calculating the state of stress induced by a uniform magnetic field in confined magnetoactive elastomers of arbitrary shape. The theory explicitly includes the magnetic field generated by magnetizable spherical inclusions in the sample interior assuming a non-linear magnetization behavior. The initial spatial distribution of particles and its change in an external magnetic field are considered. This is achieved by the introduction of an effective demagnetizing factor where both the sample shape and the material microstructure are taken into account. Theoretical predictions are fitted to the stress data measured using a specifically designed experimental setup. It is shown that the theory enables the quantification of the effect of material microstructure upon introducing a specific microstructural factor and its derivative with respect to the extensional strain in the undeformed state. The experimentally observed differences between isotropic and anisotropic samples, compliant and stiff elastomer matrices are explained.

Residues responsible for distinct biological functions are characterized by different statistical features of sequential and spatial neighborhoods: a thermolysin example.

An investigation of the functional topography of thermolysin was carried out using frequency analysis of its primary and tertiary structures. The statistical validity of this approach was estimated for the enzyme active site, the substrate-binding pocket, the inter-domain interface and calcium-binding sites' predictions. We showed that frequency analysis of primary structure could be employed to predict the localization of contiguous parts of the inter-domain interface. The same approach appears to be unsuitable to a search for conformation-dependent enzyme active sites and substrate-binding pockets. In contrast, frequency analysis of the spatial neighborhood is not effective for predicting the inter-domain interface as distinct from the active site, substrate-binding pocket and calcium-binding sites. These differences should be taken into account when investigating and understanding protein structure-function relationships.

[Use of frequency analysis for localization of functionally important regions of thermolysin]. / Ispol'zovanie chastotnogo analiza dlia lokalizatsii funktsional'no znachimykh oblastei termolizina.

A theoretical investigation of the functional topography of thermolysin molecule was carried out using frequency analysis of its primary and tertiary structures. The statistical validity of predictions was estimated for the enzyme active site, substrate-binding pocket, interdomain interface, and calcium-binding sites. It was shown that frequency analysis of primary structure could be employed to predict the localization of contiguous parts of the interdomain interface. Primary structure analysis cannot be used to search for the conformation-dependent enzyme active site and substrate-binding pocket. On the contrary, frequency analysis of interresidues contacts is not so effective for prediction of the interdomain interface as compared with active site, substrate-binding pocket, and calcium-binding sites. The set of original algorithms proposed could be used in searching for functional sites in various proteins.