Functional derivatives of human dentin matrix protein 1 modulate morphology of calcium carbonate crystals.

Dentin matrix protein 1 (DMP1) is an acidic, extracellular matrix protein essential for biomineralization of calcium phosphate, in bone and dentin. It is proteolytically processed into two fragments, 44K and 56K. Recently, the presence of DMP1 was noticed in inner ear, specifically in otoconia, which are calcium carbonate biominerals involved in sensing of balance. In this study, the solution structure and biomineralization activity of otoconial 44K and 56K fragments toward calcium carbonate were investigated. The results of analytical ultracentrifugation, circular dichroism, and gel filtration indicated that DMP1 fragments are disordered in solution. Notably, 56K formed oligomers in the presence of calcium ions. It was also observed that both fragments influenced the crystal growth by in vitro biomineralization assay and scanning electron microscopy. In addition, they sequester the calcium ions during the calcite formation. Calcium carbonate crystals precipitated in vitro changed their size and shape in the presence of DMP1 fragments. Oligomerization propensity of 56K may significantly enhance this function. Our study indicates that intrinsically disordered DMP1 has a previously unknown regulatory function for biomineralization of otoconia.

[Biomineralization--precision of shape, structure and properties controlled by proteins]. / Biomineralizacja--kontrolowana przez bialka precyzja ksztaltu, struktury i wlasciwosci.

ABSTRACT Biomineralization is the process of the formation of crystal structures that is under biological control. Living organisms produce structures such as bone, teeth, otoliths, otoconia or shells. Although the chemical composition of these tissues is similar to corresponding inorganic minerals, their structure and mechanical properties differ significantly. This may be because of how they are adapted for the functions they perform. The precise control of the formation of biominerals starting with the early nucleation stage influences how the final tissues are formed. The key factors which determine the size, shape, internal structure and properties of biominerals are proteins which control the nucleation and growth of the crystals. Biomineralization is a multi-step process involving protein-protein interactions, as well as interactions between proteins and inorganic fraction. Due to their specific properties, intrinsically disordered proteins (IDPs) perform a particularly important role in the control of the biomineralization process. This article contains an overview of biominerals that are naturally occurring and describes the structures and mineralization mechanisms of the most important of them. The main part of this work was dedicated to the role of proteins which control crystal growth.

Infant mortality--gynaecological and unemployment aspects in Opole Province, Poland.

In the study the results of the relation between infant (neonatal + post-neonatal) mortality and the gynaecological and unemployment factors are presented. The findings are based on Bayesian modelling and indicate the possible influence of the unemployment situation on mortality, whereas no correlation was found as regards access to the availability of gynaecological health care. The main conclusion is that elevated unemployment which could be referred to a poor socioeconomic situation (amongst other factors) may force pregnant women to pay more attention to improving their life conditions, than to sufficient medical controlling.