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- Harlang, Tobias C. B., et al.
(författare)
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Iron sensitizer converts light to electrons with 92% yield
- 2015
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Ingår i: Nature Chemistry. - 1755-4330 .- 1755-4349. ; 7:11, s. 883-889
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Tidskriftsartikel (refereegranskat)abstract
- Solar energy conversion in photovoltaics or photocatalysis involves light harvesting, or sensitization, of a semiconductor or catalyst as a first step. Rare elements are frequently used for this purpose, but they are obviously not ideal for large-scale implementation. Great efforts have been made to replace the widely used ruthenium with more abundant analogues like iron, but without much success due to the very short-lived excited states of the resulting iron complexes. Here, we describe the development of an iron-nitrogen-heterocyclic-carbene sensitizer with an excited-state lifetime that is nearly a thousand-fold longer than that of traditional iron polypyridyl complexes. By the use of electron paramagnetic resonance, transient absorption spectroscopy, transient terahertz spectroscopy and quantum chemical calculations, we show that the iron complex generates photoelectrons in the conduction band of titanium dioxide with a quantum yield of 92% from the 3MLCT (metal-to-ligand charge transfer) state. These results open up possibilities to develop solar energy-converting materials based on abundant elements.
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- Arroyo, Vidal M., et al.
(författare)
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Soft tissue sarcoma clinical presentation, treatment, and survival in adolescents and young adults compared to older adults : A report from the Scandinavian Sarcoma Group
- 2018
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Ingår i: Cancer Research. - : American Association for Cancer Research. - 0008-5472 .- 1538-7445. ; 78:13
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: Five-year survival rates for those diagnosed with soft tissue sarcoma (STS) have improved significantly among children and older adults (OAs), but these same trends have not been observed for adolescents and young adults (AYAs). While these disparities could be due to differences in biology or treatment, few studies have evaluated STS occurrence and outcome in AYAs. Therefore, the purpose of this study was to evaluate differences between adolescents and young adults (AYAs) and older adults (OAs) diagnosed with STS by stratifying analysis by: (1) clinical presentation; (2) treatment; and (3) survival.Methods: Data were obtained from the Scandinavian Sarcoma Group (SSG) Central Register, which includes information on 5,747 patients from Sweden and Norway, diagnosed with a STS during 1986-2011. Variables included: age at diagnosis, metastasis at diagnosis, tumor size, histology, adjuvant treatment, date of death or last follow-up. AYAs were defined as those diagnosed ages 15-39 years. Categorical variables were analyzed using chi-square tests, and continuous variables were analyzed using t-tests. Overall survival (OS) and recurrence-free survival (RFS) were compared between AYAs and OAs using Kaplan-Meier estimates and log-rank tests. All analyses were conducted overall and by common STS subtypes.Results: Overall and by STS subtype, there were significant differences between AYAs and OAs on presentation, treatment, and survival. The distribution of STS subtypes was different between OAs and AYAs. For example, OAs were more likely to be diagnosed with leiomyosarcoma compared to AYAs (18% vs. 10%, p<0.001), whereas AYAs were more likely to be diagnosed with malignant peripheral nerve sheath tumor (MPNST, 9% vs. 4%, p<0.001). OAs were also more likely to have larger tumors (>5 cm, 67% vs. 52%, p<0.001) and higher malignancy grade (grade IV, 45% vs. 31%, p<0.001). Interestingly, AYAs were more likely to be treated with radiotherapy and chemotherapy compared to OAs (12% vs. 5%, p<0.001). There were also differences within STS subtypes. For example, OAs were more likely to have metastasis compared to AYAs if diagnosed with leiomyosarcoma (18% vs. 10%, p=0.04). In most scenarios AYAs had significantly better OS and RFS compared to OAs, other than for MPNST (OS: p=0.19, RFS: p=0.28).Conclusions: There were several differences between AYAs and OAs on STS presentation, treatment, and outcome. AYAs not only had differences in terms of STS subtypes but also tumor size and malignancy grade within subtypes. Additional work is needed to characterize the biology underlying these differences, which will inform future treatment strategies for both AYAs and OAs with STS.
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| 6. |
- Berg, K. E., et al.
(författare)
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Covalently linked ruthenium(II)-manganese(II) complexes : Distance dependence of quenching and electron transfer
- 2001
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Ingår i: European Journal of Inorganic Chemistry. - 1434-1948 .- 1099-1948. ; 2001:4, s. 1019-1029
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Tidskriftsartikel (refereegranskat)abstract
- Continuing our development of artificial models for photosystem II in green plants, a series of compounds have been prepared in which a RU(bpy)(3)(2+) photosensitizer is covalently Linked to a manganese(II) electron donor. In addition to a trispicolylamine Ligand, two other manganese Ligands, dipicolylamine and aminodiacetic acid, have been introduced in order to study Ligands that are appropriate for the construction of manganese dimers with open coordination sites for the binding of water. Coordination equilibria of the manganese ions were monitored by EPR. The interactions between the ruthenium and manganese moieties were probed by flash photolysis, cyclic voltammetry and steady-state and time-resolved emission measurements. The quenching of the Ru-II excited state by Mn-II was found to be rapid in complexes with short Ru-Mn distances. Nevertheless, each Run species could be photo-oxidized by bimolecular quenching with methylviologen, and the subsequent electron transfer from Mn-II to Ru-III could be monitored.
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| 7. |
- Chábera, Pavel, et al.
(författare)
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A low-spin Fe(iii) complex with 100-ps ligand-to-metal charge transfer photoluminescence
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 543:7647, s. 695-699
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Tidskriftsartikel (refereegranskat)abstract
- Transition-metal complexes are used as photosensitizers1, in light-emitting diodes, for biosensing and in photocatalysis2. A key feature in these applications is excitation from the ground state to a charge-transfer state3,4; the long charge-transfer-state lifetimes typical for complexes of ruthenium5 and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron6 and copper7 being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs6,8,9,10, it remains a formidable scientific challenge11 to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered12 photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers13,14,15. Here we present the iron complex [Fe(btz)3]3+ (where btz is 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene)), and show that the superior σ-donor and π-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(iii) d5 complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer (2LMCT) state that is rarely seen for transition-metal complexes4,16,17. The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers.
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| 8. |
- Daniel, Quentin, et al.
(författare)
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Rearranging from 6-to 7-coordination initiates the catalytic activity : An EPR study on a Ru-bda water oxidation catalyst
- 2017
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Ingår i: Coordination chemistry reviews. - : Elsevier. - 0010-8545 .- 1873-3840. ; 346, s. 206-215
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Tidskriftsartikel (refereegranskat)abstract
- The coordination of a substrate water molecule on a metal centered catalyst for water oxidation is a crucial step involving the reorganization of the ligand sphere. This process can occur by substituting a coordinated ligand with a water molecule or via a direct coordination of water onto an open site. In 2009, we reported an efficient ruthenium-based molecular catalyst, Ru-bda, for water oxidation. Despite the impressive improvement in catalytic activity of this type of catalyst over the past years, a lack of understanding of the water coordination still remains. Herein, we report our EPR and DFT studies on Ru-bda (triethylammonium 3-pyridine sulfonate)(2) (1) at its Ru-III oxidation state, which is the initial state in the catalytic cycle for the O-O bond formation. Our investigation suggests that at this III-state, there is already a rearrangement in the ligand sphere where the coordination of a water molecule at the 7th position (open site) takes place under acidic conditions (pH = 1.0) to form a rare 7-coordinated Ru-III species.
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- Danielsson, Ravi, et al.
(författare)
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Dimeric and monomeric organization of photosystem II - Distribution of five distinct complexes in the different domains of the thylakoid membrane
- 2006
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 281:20, s. 14241-14249
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Tidskriftsartikel (refereegranskat)abstract
- The supramolecular organization of photosystem II (PSII) was characterized in distinct domains of the thylakoid membrane, the grana core, the grana margins, the stroma lamellae, and the so-called Y100 fraction. PSII supercomplexes, PSII core dimers, PSII core monomers, PSII core monomers lacking the CP43 subunit, and PSII reaction centers were resolved and quantified by blue native PAGE, SDS-PAGE for the second dimension, and immunoanalysis of the D1 protein. Dimeric PSII (PSII supercomplexes and PSII core dimers) dominate in the core part of the thylakoid granum, whereas the monomeric PSII prevails in the stroma lamellae. Considerable amounts of PSII monomers lacking the CP43 protein and PSII reaction centers (D1-D2-cytochrome b(559) complex) were found in the stroma lamellae. Our quantitative picture of the supramolecular composition of PSII, which is totally different between different domains of the thylakoid membrane, is discussed with respect to the function of PSII in each fraction. Steady state electron transfer, flash-induced fluorescence decay, and EPR analysis revealed that nearly all of the dimeric forms represent oxygen-evolving PSII centers. PSII core monomers were heterogeneous, and a large fraction did not evolve oxygen. PSII monomers without the CP43 protein and PSII reaction centers showed no oxygen-evolving activity.
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- Hammarstrom, L, et al.
(författare)
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Artificial photosynthesis: towards functional mimics of photosystem II?
- 1998
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Ingår i: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS. - : ELSEVIER SCIENCE BV. - 0005-2728. ; 1365:1-2, s. 193-199
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the initial development of a project aiming at the construction of functional mimics of the oxygen-evolving complex of photosystem II, coupled to photoinduced charge separation. Biomimetic electron donors, manganese complexes and tyro
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| 12. |
- Hammarstrom, L, et al.
(författare)
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Mimicking photosystem II reactions in artificial photosynthesis
- 1999
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Ingår i: ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS. - : R OLDENBOURG VERLAG. - 0942-9352. ; 213, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- The paper describes a project aiming at the construction of functional mimics of the oxygen evolving complex of Photosystem II, coupled to photoinduced charge separation. Biomimetic electron donors - manganese complexes and tyrosine - have been linked to
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| 14. |
- Hoganson, C W, et al.
(författare)
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A hydrogen-atom abstraction model for the function of Y-Z in photosynthetic oxygen evolution
- 1995
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Ingår i: Photosynthesis Research. - 0166-8595. ; 46:1-2, s. 177-184
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Tidskriftsartikel (refereegranskat)abstract
- Recent magnetic-resonance work on Y-Z suggests that this species exhibits considerable motional flexibility in its functional site and that its phenol oxygen is not involved in a well-ordered hydrogen-bond interaction (Tang et al., submitted; Tommos et al., in press). Both of these observations are inconsistent with a simple electron-transfer function for this radical in photosynthetic water oxidation. By considering the roles of catalytically active amino acid radicals in other enzymes and recent data on the water-oxidation process in Photosystem II, we rationalize these observations by suggesting that Y-Z functions to abstract hydrogen atoms from aquo- and hydroxy-bound manganese ions in the (Mn)(4) cluster on each S-state transition. The hydrogen-atom abstraction process may occur either by sequential or concerted kinetic pathways. Within this model, the (Mn)(4)/Y-Z center forms a single catalytic center that comprises the Oxygen Evolving Complex in Photosystem II.
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| 17. |
- Papworth, Karin E., 1964-, et al.
(författare)
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Soft-tissue sarcoma in adolescents and young adults compared with older adults : a report among 5000 patients from the Scandinavian Sarcoma Group Central Register
- 2019
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Ingår i: Cancer. - : American Cancer Society. - 0008-543X .- 1097-0142. ; 125:20, s. 3595-3602
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Tidskriftsartikel (refereegranskat)abstract
- Background: In recent years, there has been growing awareness of the distinct characteristics of adolescents and young adults (AYA) diagnosed with cancer. Soft-tissue sarcoma (STS) accounts for approximately 1% of all cancers diagnosed in adults and 8% of cancers diagnosed in AYA. To the best of our knowledge, only a few sarcoma registers include data regarding histological subtype, age at diagnosis, and detailed clinical information. Therefore, little is known regarding clinical presentation and outcomes in AYA diagnosed with STS.Methods: Using the Scandinavian Sarcoma Group Central Register, data were obtained regarding 4977 patients who were diagnosed with STS for the period between 1986 and 2011. AYA (those aged 18-39 years) were compared with older adults (OA; those aged 40-80 years) with respect to clinical presentation, treatment, and outcome.Results: There were 868 AYA and 4109 OA. Overall and by STS subtype, there were significant differences noted between AYA and OA with regard to presentation, treatment, and survival. The distribution of STS subtypes was different between OA and AYA (eg, OA were more likely to be diagnosed with malignant fibrous histiocytoma compared with AYA [34% vs 16%; P < .001]). OA also were more likely to have tumors measuring >= 5 cm (68% vs 56%; P < .001) and a higher malignancy grade (75% vs 67%; P < .001). In the majority of STS subtypes AYA had significantly better overall survival and less disease recurrence compared with OA, but this finding was not true for those with malignant peripheral nerve sheath tumors.Conclusions: There are several differences between AYA and OA with STS with regard to presentation, treatment, and survival, and such differences must be taken into consideration when designing clinical trials. Additional work also is needed to characterize the potential biological mechanisms underlying these differences.
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- Sun, LC, et al.
(författare)
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Towards artificial photosynthesis: ruthenium-manganese chemistry for energy production
- 2001
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Ingår i: CHEMICAL SOCIETY REVIEWS. - : ROYAL SOC CHEMISTRY. ; 30:1, s. 36-49 Language: English
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Recension (övrigt vetenskapligt/konstnärligt)abstract
- The synthesis and characterisation of supramolecular model systems mimicking the light reactions on the donor side of Photosystem II (PSII) in green plants have been reviewed. In these systems, manganese complexes and tyrosine are electron donors, modelli
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