Structure and thermodynamics of H3O+(H2O)8 clusters: A combined molecular dynamics and quantum mechanics approach

We have studied the structure and stability of (H3O+)(H2O)8 clusters using a combination of molecular dynamics sampling and high-level ab initio calculations. 20 distinct oxygen frameworks are found within 2 kcal/mol of the electronic or standard Gibbs free energy minimum. The impact of quantum zero-point vibrational corrections on the relative stability of these isomers is quite significant. The box-like isomers are favored in terms of electronic energy, but with the inclusion of zero-point vibrational corrections and entropic effects tree-like isomers are favored at higher temperatures. Under conditions from 0 to 298.15 K, the global minimum is predicted to be a tree-like structure with one dangling singly coordinated water molecule. Above 298.15 K, higher entropy tree-like isomers with two or more singly coordinated water molecules are favored. These assignments are generally consistent with experimental IR spectra of (H3O+)(H2O)8 obtained at 150 K.

The continuum of intestinal CD4+ T cell adaptations in host-microbial mutualism

How a mutualistic relationship between the intestinal microbiota and intestinal T cell compartments is established is important, as a breakdown of intestinal T cell homeostasis may cause inflammatory bowel diseases. A number of studies have shown that different bacterial species modulate the intestinal CD4+ T cell compartment in different ways. We performed mechanistic in vivo studies that demonstrated the crucial requirement for regulatory T cells (Treg) and interleukin-10 (IL-10) in the induction of intestinal T cell homeostasis even following colonization with a completely benign microbiota. In the absence of a functional Treg response or IL-10 receptor signaling, the same bacteria that induced a Treg response in wild-type animals now induced T helper type 17 responses, without intestinal inflammation. Therefore, Treg, IL-10 and Th17 are crucial regulatory mechanisms in the intestine not only for controlling inflammation, but also to establish a continuum of CD4+ T cell homeostasis upon commensal colonization.

The function of secretory IgA in the context of the intestinal continuum of adaptive immune responses in host-microbial mutualism

The large production of immunoglobulin (Ig)A is energetically costly. The fact that evolution retained this apparent luxury of intestinal class switch recombination to IgA within the human population strongly indicates that there must be a critical specific function of IgA for survival of the species. The function of IgA has been investigated in a series of different models that will be discussed here. While IgA has clear protective functions against toxins or in the context of intestinal viral infections, the function of IgA specific for non-pathogenic commensal bacteria remains unclear. In the context of the current literature we present a hypothesis where secretory IgA integrates as an additional layer of immune function into the continuum of intestinal CD4 T cell responses, to achieve a mutualistic relationship between the intestinal commensal microbiota and the host.

Underneath the cerclage: an ex vivo study on the cerclage-bone interface mechanics

Cerclages regain interest due to a rising number of periprosthetic fractures. The contact distribution at the circumferential cerclage-bone interface is still unknown. Local interface pressure depends on the amount of contact area. Cortical damage at the interface would provoke cerclage loosening. Therefore, the contact area, the bone pressure along the interface and the cortical resistance underneath loaded cerclages were determined in an ex vivo model.