4 research outputs found
Molecular dynamics simulations of the affinity of chitin and chitosan for collagen: the effect of pH and the presence of sodium and calcium cations
Chitosan and chitin are promising biopolymers used in many areas including
biomedical applications, such as tissue engineering and viscosupplementation.
Chitosan shares similar properties with hyaluronan, a natural component of
synovial fluid, making it a good candidate for joint disease treatment. The
structural and energetic consequences of intermolecular interactions are
crucial for understanding the biolubrication phenomenon and other important
biomedical features. However, the properties of biopolymers, including their
complexation abilities, are influenced by the nature of the aqueous medium with
which they interact. In this study, we employed molecular dynamics simulations
to describe the effect of pH and the presence of sodium and calcium cations on
the stability of molecular complexes formed by collagen type II with chitin and
chitosan oligosaccharides. Based on Gibbs free energy of binding, all
considered complexes are thermodynamically stable over the entire pH range. The
affinity between chitosan oligosaccharide and collagen is highly influenced by
pH, while oligomeric chitin shows no pH-dependent effect on the stability of
molecular assemblies with collagen. On the other hand, the presence of sodium
and calcium cations has a negligible effect on the affinity of chitin and
chitosan for collagen
Acute aquatic toxicity of arsenic-based chemical warfare agents to Daphnia magna
Sea dumping of chemical warfare (CW) took place worldwide during the 20th century. Submerged CW included metal bombs and casings that have been exposed for 50-100 years of corrosion and are now known to be leaking. Therefore, the arsenic-based chemical warfare agents (CWAs), pose a potential threat to the marine ecosystems. The aim of this research was to support a need for real-data measurements for accurate risk assessments and categorization of threats originating from submerged CWAs. This has been achieved by providing a broad insight into arsenic-based CWAs acute toxicity in aquatic ecosystems. Standard tests were performed to provide a solid foundation for acute aquatic toxicity threshold estimations of CWA: Lewisite, Adamsite, Clark I, phenyldichloroarsine (PDCA), CWA-related compounds: TPA, arsenic trichloride and four arsenic-based CWA degradation products. Despite their low solubility, during the 48 h exposure, all CWA caused highly negative effects on Daphnia magna. PDCA was very toxic with 48 h D. magna LC50 at 0.36 mu g x L-1- and Lewisite with EC50 at 3.2 mu g x L-1 . Concentrations at which no immobilization effects were observed were slightly above the analytical Limits of Detection (LOD) and Quantification (LOQ). More water-soluble CWA degradation products showed no effects at concentrations up to 100 mg x L-1.Peer reviewe