| 1. |
- Barg, Sebastian, et al.
(författare)
-
Priming of insulin granules for exocytosis by granular Cl(-) uptake and acidification
- 2001
-
Ingår i: Journal of Cell Science. - 0021-9533 .- 1477-9137. ; 114:Pt 11, s. 2145-54
-
Tidskriftsartikel (refereegranskat)abstract
- ATP-dependent priming of the secretory granules precedes Ca(2+)-regulated neuroendocrine secretion, but the exact nature of this reaction is not fully established in all secretory cell types. We have further investigated this reaction in the insulin-secreting pancreatic B-cell and demonstrate that granular acidification driven by a V-type H(+)-ATPase in the granular membrane is a decisive step in priming. This requires simultaneous Cl(-) uptake through granular ClC-3 Cl(-) channels. Accordingly, granule acidification and priming are inhibited by agents that prevent transgranular Cl(-) fluxes, such as 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and an antibody against the ClC-3 channels, but accelerated by increases in the intracellular ATP:ADP ratio or addition of hypoglycemic sulfonylureas. We suggest that this might represent an important mechanism for metabolic regulation of Ca(2+)-dependent exocytosis that is also likely to be operational in other secretory cell types.
|
|
| 2. |
- Johansson, A., et al.
(författare)
-
Synthesis and photophysics of one mononuclear Mn(III) and one dinuclear Mn(III,III) complex covalently linked to a ruthenium(II) tris(bipyridyl) complex
- 2003
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42, s. 7502-7511
-
Tidskriftsartikel (refereegranskat)abstract
- The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-1).
|
|
| 3. |
- Lomoth, R., et al.
(författare)
-
Synthesis and characterization of a dinuclear manganese(III,III) complex with three phenolate ligands
- 2002
-
Ingår i: European Journal of Inorganic Chemistry. - 1434-1948 .- 1099-1948. ; 2002:11, s. 2965-2974
-
Tidskriftsartikel (refereegranskat)abstract
- A dinuclear manganese complex ([Mn2L(mu-OAc)(2)]PF6) has been synthesized, where L is the trianion of 2,6-bis{[(2-hydroxy-3,5-di- tert-butylbenzyl) (2-pyridylmethyl) amino] methyl)-4-methylphenol, a ligand with three phenolate groups. The two pseudo-octahedrally coordinated Mn ions are bridged via the two bidentate acetate ligands and the 4-methylphenolate group of the ligand. We have characterized the complex with electrochemistry, spectroelectrochemistry and EPR spectroscopy. Electrochemically the Mn-2(III,III) complex undergoes two metal-centered quasi-reversible one-electron reduction steps (E-1/2 = 0.04 and -0.32 V vs. SCE). Reduction to the Mn-2(II,III) state results in transformation into a modified complex with slightly different redox properties. One-electron oxidation (E-1/2 = 0.96 V vs. SCE) affords the Mn-2(III,IV) state while further one-electron oxidation (E-1/2 = 1.13 V vs. SCE) presumably involves ligand oxidation. High valent Mn complexes involving Mn-IV or Mn-V centers are of particular interest as intermediates in catalytic water oxidation. The redox potentials of [Mn2L(mu-OAC)(2)](+) show the expected stabilization of higher manganese oxidation states compared with the related complex, [Mn-2(bpmp)(mu-OAc)(2)](+).
|
|
| 4. |
- Magnuson, Ann, et al.
(författare)
-
High-valent Ruthenium-Manganese Complexes for Solar Energy Production.
- 2001
-
Ingår i: PS2001 Proceedings.
-
Konferensbidrag (refereegranskat)abstract
- We present progress in the development of artificial photosynthesis, as a means to harvesting and storage of solar energy. The plan is to compose molecular systems that combine known photochemistry with emerging functional model compounds. A photochemical device for solar energy conversion contains a photosensitizer, an electron acceptor system and a donor system that prevents charge recombination. Our goal is to utilize water as sacrificial electron donor, which will allow a net production of reducing equivalents, and the ultimate production of fuel. The only light-driven molecular catalyst for water oxidation exists in Photosystem II (PSII), which has a tetranuclear Mn-cluster in the active site. Here we present several Mn-compounds, that we have developed for the purpose of creating water-oxidizing catalysts. Our idea is to link Ru-tris(bipyridine) derivatives, which mimicks the function of the primary donor in PS II, with manganese complexes, mimicking the tetra-Mn cluster on the PSII donor side. We have constructed a number of heteronuclear complexes, containing a Ru-photosensitizer and various Mn-complexes. The compounds have been characterized with regards to their photophysical and photochemical properties, redox potentials and structure. The most promising compounds are capable of undergoing several electron transfers from the Mn-complex to the photosensitizer, leaving 3 to 4 oxidizing equivalents on the Mn. In the latest development, we have constructed ligands that stabilize higher oxidation states in Mn, in order to promote formation of Mn(V) which many believes is an intermediate in the water oxidation mechanism.
|
|
| 5. |
- Paulsson, Kajsa M, et al.
(författare)
-
Association of tapasin and COPI provides a mechanism for the retrograde transport of major histocompatibility complex (MHC) class I molecules from the Golgi complex to the endoplasmic reticulum
- 2002
-
Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:21, s. 18266-18271
-
Tidskriftsartikel (refereegranskat)abstract
- Tapasin is a subunit of the transporter associated with antigen processing (TAP). It associates with the major histocompatibility complex (MHC) class I. We show that tapasin interacts with beta- and gamma-subunits of COPI coatomer. COPI retrieves membrane proteins from the Golgi network back to the endoplasmic reticulum (ER). The COPI subunit-associated tapasin also interacts with MHC class I molecules suggesting that tapasin acts as the cargo receptor for packing MHC class I molecules as cargo proteins into COPI-coated vesicles. In tapasin mutant cells, neither TAP nor MHC class I are detected in association with the COPI coatomer. Interestingly, tapasin-associated MHC class I molecules are antigenic peptide-receptive and detected in both the ER and the Golgi. Our data suggest that tapasin is required for the COPI vesicle-mediated retrograde transport of immature MHC class I molecules from the Golgi network to the ER.
|
|
| 6. |
- Sun, Licheng C., et al.
(författare)
-
Towards an artificial model for Photosystem II : a manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative
- 2000
-
Ingår i: Journal of Inorganic Biochemistry. - 0162-0134 .- 1873-3344. ; 78:1, s. 15-22
-
Tidskriftsartikel (refereegranskat)abstract
- In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P-680(+) in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted L-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile, Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant k(ET)>1.0X10(7) s(-1), generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.
|
|
| 7. |
- Visscher, Peter M., et al.
(författare)
-
Genetic survival analysis of age-at-onset of bipolar disorder : evidence for anticipation or cohort effect in families
- 2001
-
Ingår i: Psychiatric Genetics. - : Lippincott Williams & Wilkins. - 0955-8829 .- 1473-5873. ; 11:3, s. 129-137
-
Tidskriftsartikel (refereegranskat)abstract
- Age-at-onset (AAO) in a number of extended families ascertained for bipolar disorder was analysed using survival analysis techniques, fitting proportional hazards models to estimate the fixed effects of sex, year of birth, and generation, and a random polygenic genetic effect. Data comprised the AAO (for 171 affecteds) or age when last seen (ALS) for 327 unaffecteds, on 498 individuals in 27 families. ALS was treated as the censored time in the statistical analyses. The majority of individuals classified as affected were diagnosed with bipolar I and II (n = 103) or recurrent major depressive disorder (n = 68). In addition to the significant effects of sex and year of birth, a fitted ‘generation’ effect was highly significant, which could be interpreted as evidence for an anticipation effect. The risk of developing bipolar or unipolar disorder increased twofold with each generation descended from the oldest founder. However, although information from both affected and unaffected individuals was used to estimate the relative risk of subsequent generations, it is possible that the results are biased because of the ‘Penrose effect’. Females had a twofold increased risk in developing depressive disorder relative to males. The risk of developing bipolar or unipolar disorder increased by approximately 4% per year of birth. A polygenic component of variance was estimated, resulting in a ‘heritability’ of AAO of approximately 0.52. In a family showing strong evidence of linkage to chromosome 4p (family 22), the ‘affected haplotype’ increased the relative risk of being affected by a factor of 46. In this family, there was strong evidence of a time trend in the AAO. When either year of birth or generation was fitted in the model, these effects were highly significant, but neither was significant in the presence of the other. For this family, there was no increase in trinucleotide repeats measured by the repeat expansion detection method in affected individuals compared with control subjects. Proportional hazard models appear appropriate to analyse AAO data, and the methodology will be extended to map quantitative trait loci (QTL) for AAO.
|
|
