Effect of ligand substitution on the SMM properties of three isostructural families of double-cubane Mn4Ln2 coordination clusters.

Three isostructural lanthanide series with a core of MnMnLn2 are reported. These three families have the formulae of [MnMnLn2(µ4-O)2(H2edte)2(piv)6(NO3)2] {no crystallization solvent, Ln = La, Ce, Pr, Nd, Eu (1-4, 6); solv = 3MeCN, Ln = Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y (5, 7-13)}, where H2edte = N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and piv = pivalate; [MnMnLn2(µ4-O)2(H2edte)2(benz)6(NO3)2], where benz = benzoate, or [MnMnLn2(µ4-O)2(edteH2)2(benz)6(NO3)2]·2MeCN {Ln = Gd, Tb, Dy (14-16); and [MnMnLn2(µ4-O)2(edteH2)2(piv)8].solv {solv = 4MeCN, Ln = La (17); solv = 2MeCN·tol·H2O, Ln = Pr, Nd, Sm, Tb (18-20, 22); solv = 2MeCN·H2O, Ln = Gd (21). These compounds crystallize in two different systems, namely, monoclinic in the space groups P21/n for 1-4, 6, and 14-16 and C2/c for 5, 7-13, 18-20, and 22 and triclinic in the space group P1[combining macron] for 17 and 21. The crystal structures of these compounds display a face-fused dicubane structure connected by different types of bridged oxygen atoms. Solid-state dc magnetic susceptibility characterization was carried out for 1-22, and fitting showed that MnIIIMnIII is antiferromagnetically (AF) coupled and MnIIMnIII, MnIILn and MnIIILn are weakly ferromagnetically coupled. In addition, ac measurements were carried out and showed that only 7, 15, and 22 for Tb, 8 and 16 for Dy, and 20 for Sm exhibited slow magnetization relaxation. In the case of 15, it was possible to determine the energy barrier of the slow-relaxation behavior by fitting peak temperatures to the Arrhenius law, which gave a value of Ueff = 21.2 K and a pre-exponential factor of τ0 = 4.0 × 10-9 s.

An automated benchmarking platform for MHC class II binding prediction methods.

Motivation: Computational methods for the prediction of peptide-MHC binding have become an integral and essential component for candidate selection in experimental T cell epitope discovery studies. The sheer amount of published prediction methods-and often discordant reports on their performance-poses a considerable quandary to the experimentalist who needs to choose the best tool for their research. Results: With the goal to provide an unbiased, transparent evaluation of the state-of-the-art in the field, we created an automated platform to benchmark peptide-MHC class II binding prediction tools. The platform evaluates the absolute and relative predictive performance of all participating tools on data newly entered into the Immune Epitope Database (IEDB) before they are made public, thereby providing a frequent, unbiased assessment of available prediction tools. The benchmark runs on a weekly basis, is fully automated, and displays up-to-date results on a publicly accessible website. The initial benchmark described here included six commonly used prediction servers, but other tools are encouraged to join with a simple sign-up procedure. Performance evaluation on 59 data sets composed of over 10 000 binding affinity measurements suggested that NetMHCIIpan is currently the most accurate tool, followed by NN-align and the IEDB consensus method. Availability and implementation: Weekly reports on the participating methods can be found online at: http://tools.iedb.org/auto_bench/mhcii/weekly/. Contact: mniel@bioinformatics.dtu.dk. Supplementary information: Supplementary data are available at Bioinformatics online.

Construction of magnet-type coordination polymers using high-spin {Ni4}-citrate cubane as secondary building units.

Three potassium(i)-nickel(ii)-citrate coordination polymers, [K4Ni6(cit)4(H2O)8]n (), [K14Ni17(cit)12(H2O)33]n·10nH2O () and [K8Ni12(cit)8(H2O)15]n·2nH2O (), have been self-assembled in a solvothermal synthesis. Interestingly, these three polymers share the common {Ni4(cit)4}(8-) cubane ({Ni4}-cit-cub) secondary building units. The diverse ways of linking the {Ni4}-cit-cubs and additional isolated octahedral Ni(ii) ions lead to disparate magnetic exchange-coupling interactions, namely ferromagnetic for and and antiferromagnetic for . More importantly, the weak ferromagnetic interactions do not lead to long-range magnetic ordering above 2 K in or , whereas the strong antiferromagnetic interaction in leads to uncompensated magnetic moment due to the non-collinear alignment of the spins. Further magnetic characterization confirms the coexistence of spin-canted antiferromagnetism and spin glass behaviour in .