| 1. |
- Hughes, Joseph L, et al.
(författare)
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The Native Reaction Centre of Photosystem II: A New Paradigm for P680
- 2004
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Ingår i: Australian Journal of Chemistry. - 0004-9425. ; 57:12, s. 1179-1183
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Tidskriftsartikel (refereegranskat)abstract
- Low-temperature spectra of fully active (oxygen-evolving) Photosystem II (PSII) cores prepared from spinach exhibit well developed structure. Spectra of isolated sub-fragments of PSII cores establish that the native reaction centre is better structured and red-shifted compared to the isolated reaction centre. Laser illumination of PSII cores leads to efficient and deep spectral hole-burning. Measurements of homogeneous hole-widths establish excited-state lifetimes in the 40–300 ps range. The high hole-burning efficiency is attributed to charge separation of P680 in native PSII that follows reaction-centre excitation via ‘slow transfer’ states in the inner light-harvesting assemblies CP43 and CP47. The ‘slow transfer’ state in CP47 and that in CP43 can be distinguished in the hole-burning action spectrum and high-resolution hole-burning spectra. An important observation is that 685–700 nm illumination gives rise to efficient P680 charge separation, as established by QA− formation. This leads to a new paradigm for P680. The charge-separating state has surprisingly weak absorption and extends to 700 nm.
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| 2. |
- Peterson Årsköld, Sindra, et al.
(författare)
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Optical Spectra of Synechocystis and Spinach Photosystem II Preparations at 1.7 K: Identification of the D1-Pheophytin Energies and Stark Shifts
- 2003
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 125:43, s. 13063-13074
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Tidskriftsartikel (refereegranskat)abstract
- We report and compare highly resolved, simultaneously recorded absorption and CD spectra of active Photosystem II (PSII) samples in the range 440-750 nm. From an appropriately scaled comparison of spinach membrane fragment (BBY) and PSII core spectra, we show that key features of the core spectrum are quantitatively represented in the BBY data. PSII from the cyanobacterium Synechocystis 6803 display spectral features in the Qy region of comparable width (50-70 cm-1 fwhm) to those seen in plant PSII but the energies of the resolved features are distinctly different. A comparison of spectra taken of PSII poised in the S1QA and S2QA- redox states reveals electrochromic shifts largely attributable to the influence of QA- on PheoD1. This allows accurate determinations of the PheoD1 Qy absorption positions to be at 685.0 nm for spinach cores, 685.8 nm for BBY particles, and 683.0 nm for Synechocystis. These are discussed in terms of earlier reports of the PheoD1 energies in PSII. The Qx transition of PheoD1 undergoes a blue shift upon QA reduction, and we place a lower limit of 80 cm-1 on this shift in plant material. By comparing the magnitude of the Stark shifts of the Qx and Qy bands of PheoD1, the directions of the transition-induced dipole moment changes, x and y, for this functionally important pigment could be determined, assuming normal magnitudes of the 's. Consequently, x and y are determined to be approximately orthogonal to the directions expected for these transitions. Low-fluence illumination experiments at 1.7 K resulted in very efficient formation of QA-. This was accompanied by cyt b559 oxidation in BBYs and carotenoid oxidation in cores. No chlorophyll oxidation was observed. Our data allow us to estimate the quantum efficiency of PSII at this temperature to be of the order 0.1-1. No Stark shift associated with the S1-to-S2 transition of the Mn cluster is evident in our samples. The similarity of Stark data in plants and Synechocystis points to minimal interactions of PheoD1 with nearby chloropyll pigments in active PSII preparations. This appears to be at variance with interpretations of experiments performed with inactive solubilized reaction-center preparations.
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| 3. |
- Prince, Barry J, et al.
(författare)
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Persistent spectral hole burning from oxygen-evolving Photosystem II cores from cyanobacteria and higher plants
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 108:1-4, s. 101-105
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Tidskriftsartikel (refereegranskat)abstract
- Persistent spectral hole burning was performed on active Photosystem II (PSII) cores from spinach and Synechocystis 6803, each containing about 32 chl a molecules per core. Hole-burning action spectra are presented. The data appear inconsistent with a mechanism involving non-photochemical hole burning, as has previously been observed in isolated PSII protein-pigment fragments. A photochemical hole-burning mechanism involving charge separation in P680 accounts for the features of the spectra presented.
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| 4. |
- Prince, J.A., et al.
(författare)
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Lack of replication of association findings in complex disease : An analysis of 15 polymorphisms in prior candidate genes for sporadic Alzheimer's disease
- 2001
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1018-4813 .- 1476-5438. ; 9:6, s. 437-444
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Tidskriftsartikel (refereegranskat)abstract
- There is considerable enthusiasm for the prospect of using common polymorphisms (primarily single nucleotide polymorphisms, SNPs) in candidate genes to unravel the genetics of complex disease. This approach has generated a number of findings of loci which are significantly associated with sporadic Alzheimer's disease (AD). In the present study, a total of 15 genes of interest were chosen from among the previously published reports of significant association in AD. Genotyping was performed on polymorphisms within those genes (14 SNPs and one deletion) using Dynamic Allele Specific Hybridization (DASH) in 204 Swedish patients with sporadic late-onset AD and 186 Swedish control subjects. The genes chosen for analysis were, low-density lipoprotein receptor-related protein (LRP1), angiotensin converting enzyme (DCP1), alpha-2-macroglobulin (A2M), bleomycin hydrolase (BLMH), dihydrolipoyl S-succinyltransferase (DLST), tumour necrosis factor receptor superfamily member 6 (TNFRSF6), nitric oxide synthase (NOS3), presenilin 1 (PSEN1), presenilin 2 (PSEN2), butyrylcholinesterase (BCHE), Fe65 (APBB1), oestrogen receptor alpha (ESR1), cathepsin D (CTSD), methylenetetrahydrofolate reductase (MTHFR), and interleukin 1A (IL1A). We found no strong evidence of association for any of these loci with AD in this population. While the possibility exists that the genes analysed are involved in AD (ie they have weak effects and/or are population specific), results reinforce the need for extensive replication studies if we are to be successful in defining true risk factors in complex diseases.
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| 5. |
- Blennow, Kaj, 1958, et al.
(författare)
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No association between the alpha2-macroglobulin (A2M) deletion and Alzheimer's disease, and no change in A2M mRNA, protein, or protein expression.
- 2000
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Ingår i: Journal of neural transmission (Vienna, Austria : 1996). - : Springer Science and Business Media LLC. - 0300-9564 .- 1435-1463. ; 107:8-9, s. 1065-79
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Tidskriftsartikel (refereegranskat)abstract
- A polymorphism consisting of a deletion near the 5' splice site of exon 18 on the alpha2-macroglobulin (A2M) gene (A2M-2) has been suggested to be associated with Alzheimer's disease (AD) in family-based studies. We studied the A2M-2 allele together with the ApoE alleles in a large series on patients with AD (n = 449) and age-matched controls (n = 349). Neuropathologically confirmed diagnoses were available in 199 cases (94 AD and 107 control cases). We found no increase in A2M-2 genotype or allele frequencies in AD (27.5% and 14.6%) versus controls (26.4% and 14.9%). In contrast, a marked increase (p < 0.0001) in ApoE epsilon4 genotype or allele frequencies was found in AD (66.6% and 41.2%) as compared with controls (29.8% and 16.5%), suggesting sufficient statistical power in our sample. No relation was found between the A2M-2 and the ApoE epsilon4 allele. No change in A2M exon 17-18 mRNA size or sequence or A2M protein size was found in cases carrying the A2M-2 deletion, suggesting that there is no biological consequences of the A2M intronic deletion. No change in A2M protein level in cerebrospinal fluid was found in AD, suggesting that the A2M-2 allele does not effect the A2M protein expression in the brain. The lack of an association between the A2M-2 allele and AD in the present study, and the lack of abnormalities in the A2M mRNA or protein suggest that the A2M-2 allele is not associated with AD.
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| 6. |
- Hughes, Joseph L, et al.
(författare)
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Photoconversion of chlorophylls in higher-plant CP43 characterized by persistent spectral hole burning at 1.7 K.
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 108:1-4, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- The chorophyll-protein complex CP43 is a proximal-antenna subunit important for excitation energy transfers from peripheral light-harvesting antenna to the Photosystem II (PSII) reaction centre. We report persistent spectral hole burning at 1.7 K in the Qy(0,0) origin and Qy(1,0) vibrational satellite bands of chorophyll a (chl a) in CP43 isolated from higher plants. The isolated CP43 is known to possess two quasi-degenerate 'red' trap states. We find persistent hole burning in the primary trap exhibits a photoconversion property, with a photoproduct located well outside its inhomogeneous distribution. This photoconversion of trap chl a molecules also occurs with non-selective white light illumination. The contribution of the 'red' states to CP43 absorption is discussed.
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| 7. |
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| 8. |
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| 9. |
- Peterson Årsköld, Sindra, et al.
(författare)
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Low-temperature spectroscopy of fully active cores. Comparison with CP43, CP47
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 108:1-4, s. 97-100
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Tidskriftsartikel (refereegranskat)abstract
- Comparisons of absorption spectra of photosystem II (PSII) core complexes with those of isolated CP43, CP47 and D1/D2/cyt b559 complexes show broadenings and shifts upon disassembly of the PSII core material. Spectra of PSII cores isolated from plants and cyanobacteria reveal marked changes in energies and intensities of the sharp features associated with P680. Low-temperature, illumination-induced electrochromic shifts in PSII cores allow identification of an excitation localized on pheopytin-a (pheo a) in D1. A weak interaction between an exciton component of P680 and the D1 pheo a, both located near 684 nm, is suggested. MCD spectra of 5- and 6-chlorophyll a D1/D2/cytochrome b559 preparations provide links to photoactive pigments in intact PSII cores.
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| 10. |
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