| 1. |
|
|
| 2. |
|
|
| 3. |
- Boyle, P, et al.
(författare)
-
Need for global action for cancer control
- 2008
-
Ingår i: Annals of oncology : official journal of the European Society for Medical Oncology. - : Elsevier BV. - 1569-8041. ; 19:9, s. 1519-1521
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 4. |
- Hoffmann, Markus, et al.
(författare)
-
Enhanced pi conjugation around a porphyrin[6] nanoring
- 2008
-
Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 47:27, s. 4993-4996
-
Tidskriftsartikel (refereegranskat)abstract
- (Figure Presented) Strong cycle: The cyclic hexamer-template complex 3 obtained through template-directed trimerization of a porphyrin dimer 2, using a hexapyridyl template 1, is extremely stable (K f =7×10 38 m -1 ), but the free macrocycle 4 can be liberated using amine ligands. Spectroscopic data and DFT calculations show that the cyclic hexamer is more conjugated than its linear analogue. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
|
|
| 5. |
- Kirstetter, Peggy, et al.
(författare)
-
Activation of the canonical Wnt pathway leads to loss of hematopoietic stem cell repopulation and multilineage differentiation block
- 2006
-
Ingår i: Nature Immunology. - : Springer Science and Business Media LLC. - 1529-2908 .- 1529-2916. ; 7:10, s. 1048-1056
-
Tidskriftsartikel (refereegranskat)abstract
- Wnt signaling increases hematopoietic stem cell self-renewal and is activated in both myeloid and lymphoid malignancies, indicating involvement in both normal and malignant hematopoiesis. We report here activated canonical Wnt signaling in the hematopoietic system through conditional expression of a stable form of beta-catenin. This enforced expression led to hematopoietic failure associated with loss of myeloid lineage commitment at the granulocyte-macrophage progenitor stage; blocked erythrocyte differentiation; disruption of lymphoid development; and loss of repopulating stem cell activity. Loss of hematopoietic stem cell function was associated with decreased expression of Cdkn1a ( encoding the cell cycle inhibitor p21(cdk)), Sfpi1, Hoxb4 and Bmi1 ( encoding the transcription factors PU.1, HoxB4 and Bmi-1, respectively) and altered integrin expression in Lin(-)Sca-1(+)c-Kit(+) cells, whereas PU.1 was upregulated in erythroid progenitors. Constitutive activation of canonical Wnt signaling therefore causes multilineage differentiation block and compromised hematopoietic stem cell maintenance.
|
|
| 6. |
- Kuimova, M. K., et al.
(författare)
-
Determination of the triplet state energies of a series of conjugated porphyrin oligomers
- 2007
-
Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 6:6, s. 675-682
-
Tidskriftsartikel (refereegranskat)abstract
- We report a systematic study of the photophysical parameters relevant to photodynamic therapy (PDT) by a new type of sensitizers, conjugated porphyrin oligomers. Due to the strong nonlinear properties of oligomers containing 2, 4 and 8 porphyrin units, these molecules are attractive candidates for PDT via multiphoton excitation. The triplet state energy levels for all molecules have been determined by the triplet quenching method, phosphorescence measurements and DFT calculations. We find that the triplet energies of all the oligomers are sufficient to generate singlet oxygen, > 94 kJ mol(-1). However, low singlet oxygen quantum yields are observed for the tetramer and the octamer, as compared to the conjugated dimer and monomeric porphyrin, reflecting the decrease in triplet yield. Thus the conjugated porphyrin dimer is the most promising core structure for PDT applications via multiphoton excitation.
|
|
| 7. |
- Winters, Mikael, 1976, et al.
(författare)
-
Control of electron transfer in a conjugated porphyrin dimer by selective excitation of planar and perpendicular conformers
- 2007
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 13:26, s. 7385-7394
-
Tidskriftsartikel (refereegranskat)abstract
- A donor-acceptor system is presented in which the electron-transfer rates can be sensitively controlled by means of excitation wavelength and temperature. The electron donor is a butadiyne-linked zinc porphyrin dimer that is connected to a C-60 electron acceptor. The broad distribution of conformations allowed by the butadiyne linker makes it possible to selectively excite perpendicular or planar donor conformers and thereby prepare separate initial states with driving forces for electron transfer that differ by almost 0.2 eV This, as well as significant differences in electronic coupling, leads to distinctly different rate constants for electron transfer, which in consequence can be controlled by changing excitation wavelength. By extending the system with a secondary donor (ferrocene), a second, long-range charge-separated state can be formed. This system has been used to test the influence of conformational heterogeneity on electron transfer mediated by the porphyrin dimer in the ground state. It was found that if the dimer is forced to a planar conformation by means of a bidentate ligand, the charge recombination rate increased by an order of magnitude relative to the unconstrained system. This illustrates how control of conformation of a molecular wire can affect its behaviour.
|
|
| 8. |
- Winters, Mikael, 1976, et al.
(författare)
-
Photophysics of a butadiyne-linked porphyrin dimer: Influence of conformational flexibility in the ground and first singlet excited state
- 2007
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:19, s. 7192-7199
-
Tidskriftsartikel (refereegranskat)abstract
- The photophysics of a butadiyne-linked porphyrin dimer has been investigated by spectroscopy and quantum mechanical calculations. Primarily, the influence of conformation on the ground and first singlet excited states was studied, and two spectroscopically distinct limiting cases were identified. Experiments show that the twisted and planar conformers are separate spectroscopic species that can be selectively excited and have unique absorption and emission spectra. Calculated ground-state spectra compare well with experimental spectra of the two species. A spectrum of the planar conformer was obtained by the addition of a dipyridyl pyrrole ligand, which forms a 1:1 complex with the dimer and thus forces it to stay planar. The absorption spectrum of the twisted conformer could be deduced from the excitation spectrum of its emission. The interpretation of the ground-state spectrum of the free noncomplexed dimer is that it represents an average of a broad distribution of conformations. Calculations support this conclusion by indicating that the barrier for rotation is relatively small in the ground state (0.7 kcal/mol). Studies of the temperature dependence of the fluorescence spectrum of the dimer indicate a mother-daughter relationship between the twisted and planar conformations in the excited state, where the former has approximately 3.9 kcal/mol higher energy. Furthermore, time-correlated single-photon counting experiments also suggest that the twisted population adopts a planar configuration in the first singlet excited state with a rate constant of k(rot) = 8.8 x 10(9) s(-1) in 2-MTHF at room temperature. The temperature dependence of the fluorescence lifetimes indicated that an activation energy barrier of approximately 2 kcal/mol, in part related to solvent viscosity, is associated with this rate constant.
|
|
| 9. |
- Winters, Mikael, 1976, et al.
(författare)
-
Probing the efficiency of electron transfer through porphyrin-based molecular wires
- 2007
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 129:14, s. 4291-4297
-
Tidskriftsartikel (refereegranskat)abstract
- Electron transfer over long distances is important for many future applications in molecular electronics and solar energy harvesting. In these contexts, it is of great interest to find molecular systems that are able to efficiently mediate electrons in a controlled manner over nanometer distances, that is, structures that function as molecular wires. Here we investigate a series of butadiyne-linked porphyrin oligomers with ferrocene and fullerene (C-60) terminals separated by one, two, or four porphyrin units (P-n, n = 1, 2, or 4). When the porphyrin oligomer bridges are photoexcited, long-range charge separated states are formed through a series of electron-transfer steps and the rates of photoinduced charge separation and charge recombination in these systems were elucidated using time-resolved absorption and emission measurements. The rates of long-range charge recombination, through these conjugated porphyrin oligomers, are remarkably fast (k(CR2) = 15 - 1.3 x 10(8) s(-1)) and exhibit very weak distance dependence, particularly comparing the systems with n = 2 and n = 4. The observation that the porphyrin tetramer mediates fast long-range charge transfer, over 65 angstrom, is significant for the application of these structures as molecular wires.
|
|
