104,152 research outputs found
Fungal community survey of Fraxinus excelior in New Zealand
Get PDFThe European Ash tree (Fraxinus excelsior) is widely grown throughout Europe. As a large deciduous tree species, it grows a tall, domed crown and has an attractive tree shape, so it is considered as a popular amenity tree species. European Ash is planted as an important forestry species in some European countries, and also often used for furniture making, due to its excellent wood quality. Ash species were introduced into New Zealand upon colonization in the 1800s.
Recently, ash trees throughout Europe have been observed to become damaged or die due to a severe disease known as ash dieback, caused by the fungus Chalara fraxinea. We are concerned about what will happen to the introduced ash tree in New Zealand. To our knowledge, there have been no studies on the fungi that inhabit ash trees in New Zealand. It is unknown which fungal species were present in ash at the time of the introduction to New Zealand, or which New Zealand fungi colonized ash tree after the introduction. Currently, ash dieback is not believed to be present in New Zealand.
The aim of this project was to determine the possible fungal communities on ash trees in New Zealand. We collected bark, bud and wood from three healthy ash trees, and used DNA-based methods to identify the fungi that inhabited these trees. We compared our study with a similar Swedish study to find differences and similarities in the fungi present on New Zealand and European ash trees. In total, we found 90 different fungal species. Of these species found, seven fungi could be species that came to New Zealand with the introduced ash tree. We also found one fungus that could possibly be said to have come from New Zealand. The pathogen causing ash dieback, Chalara fraxinea, was not detected
Ion-mediated RNA structural collapse: effect of spatial confinement
Get PDFRNAs are negatively charged molecules residing in macromolecular crowding
cellular environments. Macromolecular confinement can influence the ion effects
in RNA folding. In this work, using the recently developed tightly bound ion
model for ion fluctuation and correlation, we investigate the confinement
effect on the ion-mediated RNA structural collapse for a simple model system.
We found that, for both Na and Mg, ion efficiencies in mediating
structural collapse/folding are significantly enhanced by the structural
confinement. Such an enhancement in the ion efficiency is attributed to the
decreased electrostatic free energy difference between the compact conformation
ensemble and the (restricted) extended conformation ensemble due to the spatial
restriction.Comment: 22 pages, 5 figure
Helices 2 and 3 are the initiation sites in the PrPc -> PrPsc transition
Full text linkIt is established that prion protein is the sole causative agent in a number
of diseases in humans and animals. However, the nature of conformational
changes that the normal cellular form PrPC undergoes in the conversion process
to a self-replicating state is still not fully understood. The ordered
C-terminus of PrPC proteins has three helices (H1, H2, and H3). Here, we use
the Statistical Coupling Analysis (SCA) to infer co-variations at various
locations using a family of evolutionarily related sequences, and the response
of mouse and human PrPCs to mechanical force to decipher the initiation sites
for transition from PrPC to an aggregation prone PrP* state. The sequence-based
SCA predicts that the clustered residues in non-mammals are localized in the
stable core (near H1) of PrPC whereas in mammalian PrPC they are localized in
the frustrated helices H2 and H3 where most of the pathogenic mutations are
found. Force-extension curves and free energy profiles as a function of
extension of mouse and human PrPC in the absence of disulfide (SS) bond between
residues Cys179 and Cys214, generated by applying mechanical force to the ends
of the molecule, show a sequence of unfolding events starting first with
rupture of H2 and H3. This is followed by disruption of structure in two
strands. Helix H1, stabilized by three salt-bridges, resists substantial force
before unfolding. Force extension profiles and the dynamics of rupture of
tertiary contacts also show that even in the presence of SS bond the
instabilities in most of H3 and parts of H2 still determine the propensity to
form the PrP* state. In mouse PrPC with SS bond there are about ten residues
that retain their order even at high forces
- …
