New BODIPY derivatives as OFF-ON fluorescent chemosensor and fluorescent chemodosimeter for Cu2+: cooperative selectivity enhancement toward Cu2+

New 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives (1 and 2) were synthesized as an "off-on" fluorescent chemosensor and fluorescent chemodosimeter for Cu2+ and Pb2+. Compound 1 displayed selective and large chelation enhanced fluorescence effects with Pb2+ and Cu2+ among the metal ions examined. On the other hand, compound 2, a fluorescent chemodosimeter, effectively recognized Cu2+ via a selective hydrolysis of the acetyl group.     

Total domination in 2‐connected graphs and in graphs with no induced 6‐cycles

A set S of vertices in a graph G is a total dominating set of G if every vertex of G is adjacent to some vertex in S. The minimum cardinality of a total dominating set of G is the total domination number γ_t(G) of G. It is known [J Graph Theory 35 (2000), 21–45] that if G is a connected graph of order n > 10 with minimum degree at least 2, then γ_t(G) ≤ 4n/7 and the (infinite family of) graphs of large order that achieve equality in this bound are characterized. In this article, we improve this upper bound of 4n/7 for 2‐connected graphs, as well as for connected graphs with no induced 6‐cycle. We prove that if G is a 2‐connected graph of order n > 18, then γ_t(G) ≤ 6n/11. Our proof is an interplay between graph theory and transversals in hypergraphs. We also prove that if G is a connected graph of order n > 18 with minimum degree at least 2 and no induced 6‐cycle, then γ_t(G) ≤ 6n/11. Both bounds are shown to be sharp. © 2008 Wiley Periodicals, Inc. J Graph Theory 60: 55–79, 2009     

Iterative In Situ Click Chemistry Creates Antibody‐like Protein‐Capture Agents

Special agents for protein capture : Iterative in situ click chemistry (see scheme for the tertiary ligand screen) and the one‐bead–one‐compound method for the creation of a peptide library enable the fragment‐based assembly of selective high‐affinity protein‐capture agents. The resulting ligands are water‐soluble and stable chemically, biochemically, and thermally. They can be produced in gram quantities through copper(I)‐catalyzed cycloaddition.

     

Effects of poloxamer on the gelation of silk fibroin

The influence of the concentration of poloxamer 407, the pH and the temperature on the gelation of silk fibroin (SF) were studied. It was found that the gelation of SF occurred in the presence of poloxamer at pH value of 7.0 while gelation of SF itself did not occur. The gelation time of SF was shortened with increasing the poloxamer concentration and the temperature. The sol‐gel transition of SF became reversible with an addition of poloxamer. From infrared (IR) and circular‐dichroism (CD) spectroscopy measurements, it was found that a conformational change of the SF in the SF/poloxamer system from random coil to β‐structure was accelerated after forming a polymer complex with the poloxamer. The crystallinity of the poloxamer was reduced by SF from X‐ray diffraction measurements.