Relating matrix metalloproteinase structure to function: why the "hemopexin" domain?

Matrix metalloproteinases are thought to be key players in the remodelling activity of cells associated with both physiological and pathological processes. They share a relatively conserved structure with a number of identifiable modules linked to their specific functions. The structure of the individual domains of a number of matrix metalloproteinases have now been elucidated. Here we review these data in the light of complementary studies on the behaviour of these enzymes in biological systems. In particular we focus on the C-terminal hemopexin-like domain which has intriguingly specific roles in individual matrix metalloproteinases.     

Trifluoromethanesulphonic acid catalysed transalkylation between tetrabromobisphenol-a and toluene for the production of 2,6-dibromophenol

The preparation of 2,6-dibromophenol is described. This compound, useful as raw material for brominated poly(phenyleneoxide) and pyrogallol or derived pharmaceuticals/pesticides, was prepared in 80% (isolated) yield by a transalkylation reaction between tetrabromobisphenol-A and toluene. The catalyst, trifluoromethanesulphonic acid, can be simply recovered and recycled. Perfluorinated resin sulphonic acid (NAFION-H®, DuPont) did not effectively catalyse this transalkylation.     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

Summary Novel oxycarbonyl isocyanate telechelic polyisobutylenes have been prepared by conversion of hydroxylterminated polyisobutylenes with N-chlorocarbonyl isocyanate. This reaction is free from side-reactions and provides highly reactive isocyanate-terminated polyisobutylene prepolymers. Conversion of these prepolymers with glycol, urea, pentaerythritol, and polyethylene glycol led to linear chain extension, crosslinking, and multiblock copolymer formation, respectively.     

The reduction/oxidation behaviour of MnAPO-5 as studied by ESR spectroscopy

It is shown by ESR spectroscopy that Mn²⁺ ions in MnAPO-5 are oxidized to Mn³⁺ during calcination atT475 K. Mn²⁺ occupies variously distorted tetrahedral positions within the framework and in extra-lattice sites. Octahedrally coordinated Mn²⁺ presumably located in the channels becomes detectable after adsorption of water. The ESR spectra of reduced MnAPO-5 show line-narrowing due to spin exchange interactions. The material behaves reversible in redox cycles at temperatures near 500 K.     

New aspects of transversal1H-NMR relaxation in natural rubber vulcanizates

Summary Structure and dynamics of unfilled and carbon black filled natural rubber vulcanizates were investigated by means of transversal¹H-NMR-relaxation. A simple theoretical model including different motions in polymer network was extended by the discussion of an anisotropy parameter of segmental motion not only for the intercrosslink chains but also for the dangling ends. It makes characterization of the filling state of the network possible to approximate. The effect of increasing correlation times _f of the fast anisotropic local motion with reduction of the molecular mass of intercrosslink chains which was observed, but not cleared up in previous investigation is evidently smaller by using this modified model in accordance with the expectation of a local motion. The determined values of M_c are in good agreement with the results of fits by using the unmodified relaxation function.¹³C-NMR-spectra and stress-strain-experiments are leading in most cases to similar results, especially for M_c.     

Structural sensitivity analysis of flexible multibody systems modeled with the floating frame of reference approach using the adjoint variable method

For the efficient analysis and optimization of flexible multibody systems, gradient information is often required. Next to simple and easy-to-implement finite difference approaches, analytical methods, such as the adjoint variable method, have been developed and are now well established for the sensitivity analysis in multibody dynamics. They allow the computation of exact gradients and require normally less computational effort for large-scale problems. In the current work, we apply the adjoint variable method to flexible multibody systems with kinematic loops, which are modeled using the floating frame of reference formulation. Thereby, in order to solve ordinary differential equations only, the equations of motion are brought into minimal form using coordinate partitioning, and the constraint equations at position and velocity level are incorporated in the adjoint dynamics. For testing and illustrative purposes, the procedure is applied to compute the structural gradient for a flexible piston rod of a slider–crank mechanism.     

Iterative analysis of Markov regenerative models

Conventional algorithms for the steady-state analysis of Markov regenerative models suffer from high computational costs which are caused by densely populated matrices. In this paper, a new algorithm is suggested which avoids computing these matrices explicitly. Instead, a two-stage iteration scheme is used. An extended version of uniformization is applied as a subalgorithm to compute the required transient quantities “on-the fly”. The algorithm is formulated in terms of stochastic Petri nets. A detailed example illustrates the proposed concepts.