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- Dujon, B, et al.
(författare)
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The nucleotide sequence of Saccharomyces cerevisiae chromosome XV
- 1997
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 387:6632, s. 98-102
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Tidskriftsartikel (refereegranskat)abstract
- Chromosome XV was one of the last two chromosomes of Saccharomyces cerevisiae to be discovered(1). It is the third-largest yeast chromosome after chromosomes XII and IV, and is very similar in size to chromosome VII. It alone represents 9% of the yeast genome (8% if ribosomal DNA is included). When systematic sequencing of chromosome XV was started, 93 genes or markers were identified, and most of them were mapped(2). However, very little else was known about chromosome XV which, in contrast to shorter chromosomes, had not been the object of comprehensive genetic or molecular analysis. It was therefore decided to start sequencing chromosome XV only in the third phase of the European Yeast Genome Sequencing Programme, after experience was gained on chromosomes III, XI and II (refs 3-5). The sequence of chromosome XV has been determined from a set of partly overlapping cosmid clones derived from a unique yeast strain, and physically mapped at 3.3-kilobase resolution before sequencing. As well as numerous new open reading frames (ORFs) and genes encoding tRNA or small RNA molecules, the sequence of 1,091,283 base pairs confirms the high proportion of orphan genes and reveals a number of ancestral and successive duplications with other yeast chromosomes.
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| 2. |
- Sugiura, K., et al.
(författare)
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The importance of magnetic coupling through atoms with large spin densities - Structure and magnetic properties of meso-tetrakis-(4'-tert-butylphenyl)porphinatomanganese(III) hexacyanobutadienide, Mn(III)TtBuPP (+) C-4(CN)(6) (.-)
- 1997
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Ingår i: Chemistry-a European Journal. ; 3:1, s. 138-142
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Tidskriftsartikel (refereegranskat)abstract
- [Mn(III)TtBuPP](+)[C-4(CN)(6)](.-) . [(MnTrBuPP)-Tr-III = meso-tetrakis(4'-tert-butylphenyl)porphinatomanganese(III)] has been prepared and structurally and magnetically characterized. The uniform, linear-chain (1-D) coordination polymer comprises alternating cations and anions. The bond lengths in planar ion [C-4(CN)(6)](.-) are 1.377(10) (CC-CC), 1.418(7) (C-CCC), 1.414 (C-CN), 1.457 (C-CNMn), 1.150 (C=N), and 1.134 Angstrom (C=NMn). The Mn-N-C angle is 172.3 (4)degrees, and the intrachain Mn ... Mn separation is 10.655 Angstrom. Each [C-4(CN)(6)](.-) unit is bonded to two Mn-III atoms through the interior nitrogen atoms in a times-mu(2)-N-sigma manner with N-Mn bond lengths of 2.353 Angstrom. The (CN) absorptions are at 2217 (w,br) and 2190 (m) cm(-1). Above 50 K the magnetic susceptibility of [Mn(III)TtBuPP](+)[C-4(CN)(6)](.-) can be fitted to the Curie-Weiss expression, chi proportional to 1/(T - theta), with an effective theta of -13 K. This is consistent with weak antiferromagnetic coupling, which is in contrast to the effective theta of + 67 K for the uniform chain [(MnOEP)-O-III](+)[C-4(CN)(6)](.-) [OEP = octaethylporphinato]. Here, the [C-4(CN)(6)](.-) units are bonded to the Mn-III centers through endo CN nitrogen atoms in a similar trans-mu(2) manner. Density functional theory MO calculations reveal that the spin density of the CN nitrogen atom bound to [Mn-III- TtBuPP](+) (0.019 mu(B) Angstrom(-3)) is significantly lower than that of the N atom bound to [(MnOEP)-O-III]+ (0.102 mu(B) Angstrom(-3)). This is consistent with the reduced spin coupling observed for [Mn(III)TtBuPP](+)[C-4(CN)(6)](.-) with respect to [(MnOEP)-O-III](+)[C-4(CN)(6)](.-), as evidenced by the lower theta value. The different orientations of the [C-4(CN)(6)](.-) units-almost perpendicular (84.72 degrees) for [Mn(III)TtBuPP](+)[C-4(CN)(6)](.-) and substantially tilted (32.1 degrees) for [(MnOEP)-O-III](+)[C-4(CN)(6)](.-)-may also contribute to the poorer overlap and weaker spin coupling. Hence, binding between sites with large spin densities is needed to stabilize strong ferromagnetic coupling.
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