Molecular dynamics simulation study on the interaction of KRN 7000 and three analogues with human CD1d

Many analogues of KRN 7000, a synthetic glycolipid (α-galactosylceramide) exhibiting immuno-stimulatory activity and antitumor properties, were previously synthesized and tested in order to understand the reasons for the resulting biological activity and Th1/Th2 cytokine profile. Principles have been established for the interaction of such glycolipids with the human CD1d molecule but the exact mechanism by which different ligands with the same polar head elicit distinct biological responses remains unclear. Based on these experiments and on the available crystal structures, protein-ligand interactions are explored using molecular dynamics simulations. Hydrogen bond interactions are examined with regard to the polar group orientation. The influence of modulations on the dynamic behavior of the CD1d-glycolipid complex is addressed. Overall, our data support the mechanism by which the shortening of the α-GalCer sphingosine chain causes a significant twist of the CD1d α1 helix structure from residue Phe84 that affects the position of CD1d residues involved in the TCR recognition.     

Miniature potassium-sensitive electrodes with neutral carriers in a poly(vinyl chloride) matrix

A miniature version of the potassium ion-selective electrode with valinomycin or dimethyldibenzo-30-crown-10 in a poly(vinyl chloride) matrix is described. Electrodes having an effective membrane area of <0.2 mm(2) exhibit Nernstian behaviour within a range of activities of the potassium ion of 10(-1)-10(-5)M, a rapid response and good long-term potential stability.     

Copper(I) and silver(I) complexes of 2-amino-1,3,4-thiadiazole and 2-ethylamino-1,3,4-thiadiazole

The following copper(I) and silver(I) complexes of 2-amino-1,3,4-thiadiazole (atz) and 2-ethylamino-1,3,4-thiadiazole (eatz) have been prepared and studied by conductometric, IR and Raman methods: CuXL(X = Cl, Br, I; L = atz, eatz), CuXL₃(X = ClO₄, NO₃; L = atz, eatz), AgClO₄·1.5atz·1/3 EtOH, AgNO₃·2.5atz, AgClO₄·3eatz, AgNO₃·eatz. The ligands are bonded through the amine nitrogen atoms with ν(MN) bands in the 520–410 cm^?1 region. The CuXL complexes have a trigonal (N, 2X_b) coordination with a probable weaker axial interaction. The CuXL₃ and AgCIO₄·3eatz complexes probably have a trigonal pyramidal (3N,O) coordination. In the atz complexes of silver perchlorate and nitrate some ligand molecules are bridging. The AgNO₃·2.5atz complex is likely to have a dimeric structure with tetrahedral coordination of the silver ion.     

Synthesis and excited state properties of a [60]fullerene derivative bearing a star-shaped multi-photon absorption chromophore

The synthesis and excited state properties of a compound assembling C60 with a new multi-photon absorption chromophore are reported.     

A bound on the treewidth of planar even-hole-free graphs

The class of planar graphs has unbounded treewidth, since the k×k grid, ∀k∈N, is planar and has treewidth k. So, it is of interest to determine subclasses of planar graphs which have bounded treewidth. In this paper, we show that if G is an even-hole-free planar graph, then it does not contain a 9×9 grid minor. As a result, we have that even-hole-free planar graphs have treewidth at most 49.     

Characterizing Extremal Digraphs for Identifying Codes and Extremal Cases of Bondy’s Theorem on Induced Subsets

An identifying code of a (di)graph G is a dominating subset C of the vertices of G such that all distinct vertices of G have distinct (in)neighbourhoods within C. In this paper, we classify all finite digraphs which only admit their whole vertex set as an identifying code. We also classify all such infinite oriented graphs. Furthermore, by relating this concept to a well-known theorem of Bondy on set systems, we classify the extremal cases for this theorem.