| 1. |
- Dhaka, Veer, et al.
(author)
-
Aluminum-Induced Photoluminescence Red Shifts in Core-Shell GaAs/AlxGa1-xAs Nanowires
- 2013
-
In: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 13:8, s. 3581-3588
-
Journal article (peer-reviewed)abstract
- We report a new phenomenon related to Al-induced carrier confinement at the interface in core-shell GaAs/AlxGa1-xAs nanowires grown using metal-organic vapor phase epitaxy with Au as catalyst. All AlxGa1-xAs shells strongly passivated the GaAs nanowires, but surprisingly the peak photoluminescence (PL) position and the intensity from the core were found to be a strong function of Al composition in the shell at low temperatures. Large and systematic red shifts of up to similar to 66 nm and broadening in the PL emission from the GaAs core were observed when the Al composition in the shell exceeded 3%. On the contrary, the phenomenon was observed to be considerably weaker at the room temperature. Cross-sectional transmission electron microscopy reveals Al segregation in the shell along six Al-rich radial bands displaying a 3-fold symmetry. Time-resolved PL measurements suggest the presence of indirect electron-hole transitions at the interface at higher Al composition. We discuss all possibilities including a simple shell-core-shell model using simulations where the density of interface traps increases with the Al content, thus creating a strong local electron confinement. The carrier confinement at the interface is most likely related to Al inhomogeneity and/or Al-induced traps. Our results suggest that a low Al composition in the shell is desirable in order to achieve ideal passivation in GaAs nanowires.
|
|
| 2. |
- Happonen, Lotta, et al.
(author)
-
The Structure of the NTPase That Powers DNA Packaging into Sulfolobus Turreted Icosahedral Virus 2
- 2013
-
In: Journal of Virology. - 1098-5514. ; 87:15, s. 8388-8398
-
Journal article (peer-reviewed)abstract
- Biochemical reactions powered by ATP hydrolysis are fundamental for the movement of molecules and cellular structures. One such reaction is the encapsidation of the double-stranded DNA (dsDNA) genome of an icosahedrally symmetric virus into a preformed procapsid with the help of a genome-translocating NTPase. Such NTPases have been characterized in detail from both RNA and tailed DNA viruses. We present four crystal structures and the biochemical activity of a thermophilic NTPase, B204, from the nontailed, membrane-containing, hyperthermoacidophilic archaeal dsDNA virus Sulfolobus turreted icosahedral virus 2. These are the first structures of a genome-packaging NTPase from a nontailed, dsDNA virus with an archaeal host. The four structures highlight the catalytic cycle of B204, pinpointing the molecular movement between substrate-bound (open) and empty (closed) active sites. The protein is shown to bind both single-stranded and double-stranded nucleic acids and to have an optimum activity at 80 C and pH 4.5. The overall fold of B204 places it in the FtsK-HerA superfamily of P-loop ATPases, whose cellular and viral members have been suggested to share a DNA-translocating mechanism.
|
|
| 3. |
- Oksanen, Esko, et al.
(author)
-
The neutron structure of urate oxidase resolves a long-standing mechanistic conundrum and reveals unexpected changes in protonation.
- 2014
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:1
-
Journal article (peer-reviewed)abstract
- Urate oxidase transforms uric acid to 5-hydroxyisourate without the help of cofactors, but the catalytic mechanism has remained enigmatic, as the protonation state of the substrate could not be reliably deduced. We have determined the neutron structure of urate oxidase, providing unique information on the proton positions. A neutron crystal structure inhibited by a chloride anion at 2.3 Å resolution shows that the substrate is in fact 8-hydroxyxanthine, the enol tautomer of urate. We have also determined the neutron structure of the complex with the inhibitor 8-azaxanthine at 1.9 Å resolution, showing the protonation states of the K10-T57-H256 catalytic triad. Together with X-ray data and quantum chemical calculations, these structures allow us to identify the site of the initial substrate protonation and elucidate why the enzyme is inhibited by a chloride anion.
|
|
| 4. |
- Vaahersalo, Jukka, et al.
(author)
-
Therapeutic hypothermia after out-of-hospital cardiac arrest in Finnish intensive care units : the FINNRESUSCI study
- 2013
-
In: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 39:5, s. 826-837
-
Journal article (peer-reviewed)abstract
- We aimed to evaluate post-resuscitation care, implementation of therapeutic hypothermia (TH) and outcomes of intensive care unit (ICU)-treated out-of-hospital cardiac arrest (OHCA) patients in Finland. We included all adult OHCA patients admitted to 21 ICUs in Finland from March 1, 2010 to February 28, 2011 in this prospective observational study. Patients were followed (mortality and neurological outcome evaluated by Cerebral Performance Categories, CPC) within 1 year after cardiac arrest. This study included 548 patients treated after OHCA. Of those, 311 patients (56.8 %) had a shockable initial rhythm (incidence of 7.4/100,000/year) and 237 patients (43.2 %) had a non-shockable rhythm (incidence of 5.6/100,000/year). At ICU admission, 504 (92 %) patients were unconscious. TH was given to 241/281 (85.8 %) unconscious patients resuscitated from shockable rhythms, with unfavourable 1-year neurological outcome (CPC 3-4-5) in 42.0 % with TH versus 77.5 % without TH (p < 0.001). TH was given to 70/223 (31.4 %) unconscious patients resuscitated from non-shockable rhythms, with 1-year CPC of 3-4-5 in 80.6 % (54/70) with TH versus 84.0 % (126/153) without TH (p = 0.56). This lack of difference remained after adjustment for propensity to receive TH in patients with non-shockable rhythms. One-year unfavourable neurological outcome of patients with shockable rhythms after TH was lower than in previous randomized controlled trials. However, our results do not support use of TH in patients with non-shockable rhythms.
|
|
