| 1. |
- Takala, Heikki, et al.
(författare)
-
Connection between Absorption Properties and Conformational Changes in Deinococcus radiodurans Phytochrome
- 2014
-
Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 53:45, s. 7076-7085
-
Tidskriftsartikel (refereegranskat)abstract
- Phytochromes consist of several protein domains and a linear tetrapyrrole molecule, which interact as a red-light-sensing system. In this study, size-exclusion chromatography and light-scattering techniques are combined With UV-vis spectroscopy to investigate light-induced changes in dimeric Deinococcus radiodurans bacterial phytochrome (DrBphP and, its,subdornams. The potosensory unit (DrCBD-PHY), shows an unusually stable Pfr state with reversion, whereas the histidine, kinase (HK) domain facilitates dark reversion to the resting state. Size-exclusion chromatography reveals that all phytochrorne fragments remain as dimers in the illuminated state and dark state. Still, the elution profiles of all phytochronle fragments differ between the illuminated and dark states. The differences are observed reliably only when the whole UV-vis spectrum is characterized along the elution profile and show more Pfr-state characteristics at later elution volumes in DrBphP and DrCBD-PHY fragments. This implies that the Pliy:domain has an important role in amplifying and relaying light-induced conformational changes to the HK domain. In the illuminated state, the HK domain appears partially unfolded and prone to form oligomers. The oligoinerization of DrBphp can be diminished by converting the molecule back to the resting Pr state by using far-red light.
|
|
| 2. |
- Takala, Esa-Pekka, et al.
(författare)
-
Systematic evaluation of observational methods assessing biomechanical exposures at work
- 2010
-
Ingår i: Scandinavian Journal of Work, Environment and Health. - : Finnish Institute of Occupational Health; National Research Centre for the  . - 0355-3140 .- 1795-990X. ; 36:1
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: This systematic review aimed to identify published observational methods assessing biomechanical exposures in occupational settings and evaluate them with reference to the needs of different users.Methods: We searched scientific databases and the internet for material from 1965 to September 2008. Methods were included if they were primarily based on the systematic observation of work, the observation target was the human body, and the method was clearly described in the literature. A systematic evaluation procedure was developed to assess concurrent and predictive validity, repeatability, and aspects related to utility. At least two evaluators independently carried out this evaluation.Results: We identified 30 eligible observational methods. Of these, 19 had been compared with some other method(s), varying from expert evaluation to data obtained from video recordings or through the use of technical instruments. Generally, the observations showed moderate-to-good agreement with the corresponding assessments made from video recordings; agreement was the best for large-scale body postures and work actions. Postures of wrist and hand as well as trunk rotation seemed to be more difficult to observe correctly. Intra- and inter-observer repeatability were reported for 7 and 17 methods, respectively, and were judged mostly to be moderate or good.Conclusions: With training, observers can reach consistent results on clearly visible body postures and work activities. Many observational tools exist, but none evaluated in this study appeared to be generally superior. When selecting a method, users should define their needs and assess how results will influence decision-making
|
|
| 3. |
- Takala, Heikki, et al.
(författare)
-
Signal amplification and transduction in phytochrome photosensors
- 2014
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 509:7499, s. 245-248
-
Tidskriftsartikel (refereegranskat)abstract
- Sensory proteins must relay structural signals from the sensory site over large distances to regulatory output domains. Phytochromes are a major family of red-light-sensing kinases that control diverse cellular functions in plants, bacteria and fungi(1-9). Bacterial phytochromes consist of a photosensory core and a carboxy-terminal regulatory domain(10,11). Structures of photosensory cores are reported in the resting state(12-18) and conformational responses to light activation have been proposed in the vicinity of the chromophore(19-23). However, the structure of the signalling state and the mechanism of downstream signal relay through the photosensory core remain elusive. Here we report crystal and solution structures of the resting and activated states of the photosensory core of the bacteriophytochrome from Deinococcus radiodurans. The structures show an open and closed form of the dimeric protein for the activated and resting states, respectively. This nanometre-scale rearrangement is controlled by refolding of an evolutionarily conserved 'tongue', which is in contact with the chromophore. The findings reveal an unusual mechanism in which atomic-scale conformational changes around the chromophore are first amplified into ana angstrom-scale distance change in the tongue, and further grow into a nanometre-scale conformational signal. The structural mechanism is a blueprint for understanding how phytochromes connect to the cellular signalling network.
|
|
| 4. |
- Takala, M., et al.
(författare)
-
Dielectric Properties and Partial Discharge Endurance of Polypropylene- Silica Nanocomposite
- 2010
-
Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 17:4, s. 1259-1267
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of the dielectric properties and partial discharge endurance measurements conducted on polypropylene (PP)-silica nanocomposite. The material compounds were analyzed with micro-Raman spectroscopy, X-ray tomography and transmission electron microscopy (TEM). ac and dc breakdown strength of the materials was measured. Dielectric response, capacitance and loss factor of the film samples were measured as a function of temperature and frequency. Partial discharge (PD) endurance of the reference PP and PP Silica nanocomposite was studied as a function of ac voltage. Material surfaces were analyzed after PD stress with optical microscopy. All dielectric measurements were done for oriented thin films with a thickness of 11-23 μm. The results were analyzed statistically to determine the effects of the additive on the properties of PP. The paper discusses the potential of PP Silica nanocomposite with a view to high voltage applications, especially power capac itors. © 2010 IEEE.
|
|
| 5. |
- Takala, M., et al.
(författare)
-
Effect of low amount of nanosilica on dielectric properties of polypropylene
- 2010
-
Ingår i: Proceedings of the 2010 IEEE International Conference on Solid Dielectrics, ICSD 2010. - 9781424479443
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents the results of the dielectric properties measurements conducted on Silica-Polypropylene (PP) nanocomposites. According to prior investigations by the authors silica nanoparticles have improved the performance of the dielectric material considering capacitor applications. Especially breakdown strengths with ac and dc voltages and resistance against surface degradation have increased. The relative permittivity and dielectric losses have also been comparable to reference PP. In this paper the results of the dielectric measurements conducted on composites with 1-2 wt-% silica are compared with reference PP. Silica dispersion in PP was confirmed with transmission electron microscopy (TEM). Weibull analysis was applied to the breakdown strength measurement results with dc voltage. Capacitance and loss factor measurements were conducted as a function of temperature to study thermal behavior. The measurements were conducted at the high voltage laboratories of Tampere University of Technology and Chalmers University of Technology. Statistical analysis was applied to the results to determine the significance of the differences between the materials. ©2010 IEEE.
|
|
