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- Gambardella, P., et al.
(författare)
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Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface
- 2009
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Ingår i: Nature Materials. - 1476-4660 .- 1476-1122. ; 8:3, s. 189-193
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic atoms at surfaces may provide the ultimate paradigm of a solid-state magnetic memory exhibiting either classical , or quantum , behaviour. Individual atoms, however, are difficult to arrange in regular patterns1,2,3,4, . Moreover, their magnetic properties are dominated by interaction with the substrate, which, as in the case of Kondo systems, often leads to a decrease or quench of their local magnetic moment , . Here we show that the supramolecular assembly of Fe and 1,4-benzenedicarboxylic acid molecules on a Cu surface results in ordered arrays of high-spin mononuclear Fe centres on a 1.5 nm square grid. Lateral coordination with the molecular ligands yields unsaturated yet stable coordination bonds, which allow for the chemical modification of the electronic and magnetic properties of the Fe atoms independently from the substrate. The easy magnetization direction of the Fe centres can be switched by oxygen adsorption, thus opening a way to control the magnetic anisotropy in supramolecular layers akin to that employed in metallic thin films , , , .
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- Lai, I. H, et al.
(författare)
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A unique tetrameric structure of deer plasma haptoglobin – an evolutionary advantage in the Hp 2-2 phenotype with homogeneous structure
- 2008
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Ingår i: FEBS Journal. - 1742-4658 .- 1742-464X. ; 275, s. 981-993
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Tidskriftsartikel (refereegranskat)abstract
- Similar to blood types, human plasma haptoglobin (Hp) is classified intothree phenotypes: Hp 1-1, 2-1 and 2-2. They are genetically inheritedfrom two alleles Hp 1 and Hp 2 (represented in bold), but only theHp 1-1 phenotype is found in almost all animal species. The Hp 2-2protein consists of complicated large polymers cross-linked by a2-bsubunits or (a2-b)n (where n ‡ 3, up to 12 or more), and is associatedwith the risk of the development of diabetic, cardiovascular and inflammatorydiseases. In the present study, we found that deer plasma Hpmimics human Hp 2, containing a tandem repeat over the a-chain basedon our cloned cDNA sequence. Interestingly, the isolated deer Hp ishomogeneous and tetrameric, i.e. (a-b)4, although the locations of )SHgroups (responsible for the formation of polymers) are exactly identicalto that of human. Denaturation of deer Hp using 6 m urea under reducingconditions (143 mm b-mercaptoethanol), followed by renaturation,sustained the formation of (a-b)4, suggesting that the Hp tetramers arenot randomly assembled. Interestingly, an a-chain monoclonal antibody(W1), known to recognize both human and deer a-chains, only binds tointact human Hp polymers, but not to deer Hp tetramers. This impliesthat the epitope of the deer a-chain is no longer exposed on the surfacewhen Hp tetramers are formed. We propose that steric hindrance playsa major role in determining the polymeric formation in human and deerpolymers. Phylogenetic and immunochemical analyses revealed that theHp 2 allele of deer might have arisen at least 25 million years ago. Amechanism involved in forming Hp tetramers is proposed and discussed,and the possibility is raised that the evolved tetrameric structure of deerHp might confer a physiological advantage.
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