| 1. |
- Eastoe, Julian, et al.
(författare)
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Interrogation of a dynamic multi-catalyst ensemble in asymmetric catalysis
- 2010
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Ingår i: Faraday Discussions. - : Royal Society of Chemistry (RSC). - 1359-6640. ; 145, s. 27-47
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Tidskriftsartikel (refereegranskat)abstract
- The Trost Standard Ligand (2) is a chiral diphosphine ligand that distinguishes itself by the high selectivity it induces in the Pd-catalysed reactions of allylic substrates that generate slim cyclic or small linear intermediates. However, a range of unusual features, including memory effects, inverse dependence of selectivity and rate on catalyst concentration, high sensitivity to counter-ion, particularly chloride, and decreasing enantioselectivities at lower temperatures, are often encountered, thus requiring considerable optimisation of reaction conditions to attain optimum selectivity. These features can be accounted for by a model involving a dynamic multi-catalyst ensemble. To gain evidence for this model, the manner in which diphosphine 2 interacts with Pd–allyl cations, and in particular the higher-order systems it generates, has been investigated by use of NMR, isotopic labelling, polarimetry, UV, neutron scattering, X-ray crystallography and molecular modeling. Ligand 2 coordinates to Pd–allyl cations to generate a mononuclear P,P-chelate. This is found to readily form non-chelate oligomers, present in a range of forms, including rings, for which high homochiral selectivity in oligomerisation is demonstrated by the technique of pseudoenantiomers. All of these species are in relatively rapid equilibrium, with half-lives for interconversion in the range 2–6 s. Higher-order aggregation is also detected, and thus at even moderate concentrations (>50 mM) large rod-like aggregates are formed.
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| 2. |
- Morganella, Sandro, et al.
(författare)
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The topography of mutational processes in breast cancer genomes
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Somatic mutations in human cancers show unevenness in genomic distribution that correlate with aspects of genome structure and function. These mutations are, however, generated by multiple mutational processes operating through the cellular lineage between the fertilized egg and the cancer cell, each composed of specific DNA damage and repair components and leaving its own characteristic mutational signature on the genome. Using somatic mutation catalogues from 560 breast cancer whole-genome sequences, here we show that each of 12 base substitution, 2 insertion/deletion (indel) and 6 rearrangement mutational signatures present in breast tissue, exhibit distinct relationships with genomic features relating to transcription, DNA replication and chromatin organization. This signature-based approach permits visualization of the genomic distribution of mutational processes associated with APOBEC enzymes, mismatch repair deficiency and homologous recombinational repair deficiency, as well as mutational processes of unknown aetiology. Furthermore, it highlights mechanistic insights including a putative replication-dependent mechanism of APOBEC-related mutagenesis.
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| 3. |
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| 4. |
- Shen, Xi, et al.
(författare)
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REV3 and REV1 play major roles in recombination-independent repair of DNA interstrand cross-links mediated by monoubiquitinated proliferating cell nuclear antigen (PCNA).
- 2006
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Ingår i: The Journal of biological chemistry. - 0021-9258. ; 281:20, s. 13869-72
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Tidskriftsartikel (refereegranskat)abstract
- DNA interstrand cross-links (ICLs) are the most cytotoxic lesions to eukaryotic genome and are repaired by both homologous recombination-dependent and -independent mechanisms. To better understand the role of lesion bypass polymerases in ICL repair, we investigated recombination-independent repair of ICLs in REV3 and REV1 deletion mutants constructed in avian DT40 cells and mouse embryonic fibroblast cells. Our results showed that Rev3 plays a major role in recombination-independent ICL repair, which may account for the extreme sensitivity of REV3 mutants to cross-linking agents. This result raised the possibility that the NER gap synthesis, when encountering an adducted base present in the ICL repair intermediate, can lead to recruitment of Rev3, analogous to the recruitment of polymerase eta during replicative synthesis. Indeed, the monoubiquitination-defective Proliferating Cell Nuclear Antigen (PCNA) mutant exhibits impaired recombination-independent ICL repair as well as drastically reduced mutation rate, indicating that the PCNA switch is utilized to enable lesion bypass during DNA repair synthesis. Analyses of a REV1 deletion mutant also revealed a significant reduction in recombination-independent ICL repair, suggesting that Rev1 cooperates with Rev3 in recombination-independent ICL repair. Moreover, deletion of REV3 or REV1 significantly altered the spectrum of mutations resulting from ICL repair, further confirming their involvement in mutagenic repair of ICLs.
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