Mechanism of collagen folding propagation studied by Molecular Dynamics simulations

Collagen forms a characteristic triple helical structure and plays a central role for stabilizing the extra-cellular matrix. After a C-terminal nucleus formation folding proceeds to form long triple-helical fibers. The molecular details of triple helix folding process is of central importance for an understanding of several human diseases associated with misfolded or unstable collagen fibrils. However, the folding propagation is too rapid to be studied by experimental high resolution techniques. We employed multiple Molecular Dynamics simulations starting from unfolded peptides with an already formed nucleus to successfully follow the folding propagation in atomic detail. The triple helix folding was found to propagate involving first two chains forming a short transient template. Secondly, three residues of the third chain fold on this template with an overall mean propagation of ~75 ns per unit. The formation of loops with multiples of the repeating unit was found as a characteristic misfolding event especially when starting from an unstable nucleus. Central Gly→Ala or Gly→Thr substitutions resulted in reduced stability and folding rates due to structural deformations interfering with folding propagation.

Serendipita sacchari sp. nov. from a sugarcane rhizosphere in southern China

We isolated a new species, proposed here as Serendipita sacchari, from a sugarcane rhizosphere in Guangxi Province, China. This species is characterized by its unstable nucleus numbers (1–15) in its chlamydospores versus their regular distribution in hyphal cells. ITS rDNA and combined LSU+ TEF1-α sequence analyses also support the uniqueness of this new plant symbiont.

THEORETICAL PREDICTION OF EXTREMELY NEUTRON RICH Zr AND Pb

The properties of even–even Zr and Pb isotopes in the ground state are studied up to the neutron drip-lines on the basis of the Hartree–Fock method with Skyrme forces allowing for deformation (DHF). The DHF calculations with Ska forces predict the existence of stability peninsula (or island) around 152 Zr . On the example of Zr isotopes it is shown that adding neutrons to an already unstable nucleus with neutron excess can restore the stability. It is demonstrated that extremely neutron-rich Pb isotopes for 222≤A≤230 have abnormally large deformation parameters of proton and neutron density distributions. The existence of 266–288 Pb stable against one-neutron emission is also predicted.

DECAY OF 188Re AND TRS CALCULATIONS FOR ITS DAUGHTER NUCLIDE 188Os

The γ-ray spectra of 188 Re decay have been studied by using a Compton-suppressed spectrometer and a three parameters γ-γ- T list coincidence system. Experimental data analysis demonstrated that six γ-rays at 557, 810, 1463, 1867, 1936 and 2022 keV and three levels at 1443, 1936 and 2022 keV are confirmed again. Seven new γ-rays at 309.60±0.04, 826.90±0.02, 979.29±0.08, 1103.7±0.4, 1828.2±0.1, 1842.5±0.2 and 1982.5±0.2 keV have been identified, three new levels at 309.60, 1828.2 and 1982.5 keV are assigned. The β- decay branching ratio is deduced. In addition, in order to study this γ-unstable nucleus, shape calculations using the Hartree–Fock–Bogoliubov-like formalism were carried out for positive-parity states in 188 Os . The TRS plots reveal that, as the spin increases up the band, the triaxiality parameter γ changes.