14 research outputs found
Results of IEA SHC Task 45: Large Scale Solar Heating and Cooling Systems. Subtask A: âCollectors and Collector Loopâ
AbstractThe IEA SHC Task 45 Large Scale Solar Heating and Cooling Systems, carried out between January 2011 and December 2014, had the main objective to assist in the development of a strong and sustainable market of large solar heating systems by focusing on high performance and reliability of systems. Within this project, subtask A had the more specific objectives of investigating ways to evaluate the influence that different operating conditions can have on the collector performance, assure proper and safe installation of large solar collector fields, and guarantee their performance and yearly energy output. The results of the different investigations are presented, with a particular focus on how different parameters such as tilt, flow rate and fluid type, can affect the collector efficiency. Other presented results include methods to guarantee and check the thermal performance of a solar collector field and guidelines to design collector fields in such a way that the flow distribution is improved and the risks related to stagnation are minimized
Mesodynamics in the SARS nucleocapsid measured by NMR field cycling
Protein motions on all timescales faster than molecular tumbling are encoded in the spectral density. The dissection of complex protein dynamics is typically performed using relaxation rates determined at high and ultra-high field. Here we expand this range of the spectral density to low fields through field cycling using the nucleocapsid protein of the SARS coronavirus as a model system. The field-cycling approach enables site-specific measurements of R1 at low fields with the sensitivity and resolution of a high-field magnet. These data, together with high-field relaxation and heteronuclear NOE, provide evidence for correlated rigid-body motions of the entire ÎČ-hairpin, and corresponding motions of adjacent loops with a time constant of 0.8Â ns (mesodynamics). MD simulations substantiate these findings and provide direct verification of the time scale and collective nature of these motions
Kissing G Domains of MnmE Monitored by X-Ray Crystallography and Pulse Electron Paramagnetic Resonance Spectroscopy
The authors of this research article demonstrate the nature of the conformational changes MnmE was previously suggested to undergo during its GTPase cycle, and show the nucleotide-dependent dynamic movements of the G domains around two swivel positions relative to the rest of the protein. These movements are of crucial importance for understanding the mechanistic principles of this GAD
Canadian and Danish investigations on corrections of collector efficiency depending on fluid type, flow rate and collector tilt
The regulatory domain of the RIG-I family ATPase LGP2 senses double-stranded RNA
RIG-I and MDA5 sense cytoplasmic viral RNA and set-off a signal transduction cascade, leading to antiviral innate immune response. The third RIG-I-like receptor, LGP2, differentially regulates RIG-I- and MDA5-dependent RNA sensing in an unknown manner. All three receptors possess a C-terminal regulatory domain (RD), which in the case of RIG-I senses the viral pattern 5âČ-triphosphate RNA and activates ATP-dependent signaling by RIG-I. Here we report the 2.6 Ă
crystal structure of LGP2 RD along with in vitro and in vivo functional analyses and a homology model of MDA5 RD. Although LGP2 RD is structurally related to RIG-I RD, we find it rather binds double-stranded RNA (dsRNA) and this binding is independent of 5âČ-triphosphates. We identify conserved and receptor-specific parts of the RNA binding site. Latter are required for specific dsRNA binding by LGP2 RD and could confer pattern selectivity between RIG-I-like receptors. Our data furthermore suggest that LGP2 RD modulates RIG-I-dependent signaling via competition for dsRNA, another pattern sensed by RIG-I, while a fully functional LGP2 is required to augment MDA5-dependent signaling
Interactions of PAN's C-termini with archaeal 20S proteasome and implications for the eukaryotic proteasomeâATPase interactions
Protein degradation in the 20S proteasome is regulated in eukaryotes by the 19S ATPase complex and in archaea by the homologous PAN ATPase ring complex. Subunits of these hexameric ATPases contain on their C-termini a conserved hydrophobic-tyrosine-X (HbYX) motif that docks into pockets in the 20S to stimulate the opening of a gated substrate entry channel. Here, we report the crystal structure of the archaeal 20S proteasome in complex with the C-terminus of the archaeal proteasome regulatory ATPase, PAN. This structure defines the detailed interactions between the critical C-terminal HbYX motif and the 20S α-subunits and indicates that the intersubunit pocket in the 20S undergoes an induced-fit conformational change on binding of the HbYX motif. This structure together with related mutagenesis data suggest how in eukaryotes certain proteasomal ATPases bind to specific pockets in an asymmetrical manner to regulate gate opening
Post-translational Tyrosine Nitration of Eosinophil Granule Toxins Mediated by Eosinophil Peroxidase*
Nitration of tyrosine residues has been observed during various acute and
chronic inflammatory diseases. However, the mechanism of tyrosine nitration
and the nature of the proteins that become tyrosine nitrated during
inflammation remain unclear. Here we show that eosinophils but not other cell
types including neutrophils contain nitrotyrosine-positive proteins in
specific granules. Furthermore, we demonstrate that the human eosinophil
toxins, eosinophil peroxidase (EPO), major basic protein, eosinophil-derived
neurotoxin (EDN) and eosinophil cationic protein (ECP), and the respective
murine toxins, are post-translationally modified by nitration at tyrosine
residues during cell maturation. High resolution affinity-mass spectrometry
identified specific single nitration sites at Tyr349 in EPO and
Tyr33 in both ECP and EDN. ECP and EDN crystal structures revealed
and EPO structure modeling suggested that the nitrated tyrosine residues in
the toxins are surface exposed. Studies in EPO-/-,
gp91phox-/-, and NOS-/-
mice revealed that tyrosine nitration of these toxins is mediated by EPO in
the presence of hydrogen peroxide and minute amounts of NOx. Tyrosine
nitration of eosinophil granule toxins occurs during maturation of
eosinophils, independent of inflammation. These results provide evidence that
post-translational tyrosine nitration is unique to eosinophils