38 research outputs found
Biodegradable Polymers for Medical Applications
Biodegradable polymers have a long history which, however, is difficult to be traced as some of them are natural products. The concept of synthetic biodegradable polymers, the topic of this special issue, was introduced in the 1980s. Since then the field has experienced a steady and stable growth as its outcomes are potentially relevant to the majority of population. This interdisciplinary field encompasses elements of materials science, biology, chemistry, medicine, tissue engineering, and others
The Effect of Surface Substrate Treatments on the Bonding Strength of Aluminium Inserts with Glass-Reinforced Poly(phenylene) Sulphide
Materials composed of a polymer matrix reinforced with carbon/glass fibres providing lightweight and superior mechanical properties are widely used as structural components for automotive and aerospace applications. However, such parts need to be joined with various metal alloys to obtain better mechanical performance in many structural elements. Many studies have reported enhancements in polymer–metal bonding using adhesives, adhesive/rivet combined joints, and different surface treatments. This study investigated the influences of various surface treatments on the adhesion between glass-reinforced poly(phenylene) sulphide (PPS) and aluminium alloy during the injection over-moulding process. Adhesion strength was evaluated via the shear test. Correlations for the shear strength of the polymer–metal with different metal–substrate treatments were studied. Since the strongest bonding was attained in the treatment with the highest roughness, this value, as it determines the level of micromechanical interlocking of connected materials, seems to be a critical factor affecting the adhesion strength. Three-dimensional (3D) topographic images characterized with a 3D optical microscope indicated that there was a meaningful influence exerted by the interface topologies of the aluminium substrates used for the over-moulding process. The results further indicated that increases in a substrate’s surface energy in connection with atmospheric plasma treatments negatively influence the final level of the bonding mechanism
Disruption of the dimerization interface of the sensing domain in the dimeric heme-based oxygen sensor AfGcHK abolishes bacterial signal transduction
The heme-based oxygen sensor protein AfGcHK is a globin-
coupled histidine kinase in the soil bacterium Anaeromyxobac-
ter sp. Fw109-5. Its C-terminal functional domain exhibits
autophosphorylation activity induced by oxygen binding to the
heme-Fe(II) complex located in the oxygen-sensing N-terminal
globin domain. A detailed understanding of the signal transduc-
tion mechanisms in heme-containing sensor proteins remains
elusive. Here, we investigated the role of the globin domain’s
dimerization interface in signal transduction in AfGcHK. We
present a crystal structure of a monomeric imidazole-bound
AfGcHK globin domain at 1.8 Å resolution, revealing that the
helices of the WT globin dimer are under tension and suggesting
that Tyr-15 plays a role in both this tension and the globin
domain’s dimerization. Biophysical experiments revealed that
whereas the isolated WT globin domain is dimeric in solution,
the Y15A and Y15G variants in which Tyr-15 is replaced with
Ala or Gly, respectively, are monomeric. Additionally, we found
that although the dimerization of the full-length protein is pre-
served via the kinase domain dimerization interface in all vari-
ants, full-length AfGcHK variants bearing the Y15A or Y15G
substitutions lack enzymatic activity. The combined structural
and biophysical results presented here indicate that Tyr-15
plays a key role in the dimerization of the globin domain of
AfGcHK and that globin domain dimerization is essential for
internal signal transduction and autophosphorylation in this protein. These findings provide critical insights into the signal
transduction mechanism of the histidine kinase AfGcHK from
Anaeromyxobacter