Multivalent Sialosides: A Tool to Explore the Role of Sialic Acids in Biological Processes.

Sialic acids (Sias) are fascinating nine-carbon monosaccharides that are primarily found on the terminus of the oligosaccharide chains of glycoproteins and glycolipids on cell surfaces. These Sias undergo a variety of structural modifications at their hydroxy and amine positions, thereby resulting in structural diversity and, hence, coordinating a variety of biological processes. However, deciphering the structural functions of such interactions is highly challenging, because the monovalent binding of Sias is extremely weak.

Unraveling hidden regulatory sites in structurally homologous metalloproteases.

Monitoring enzymatic activity in vivo of individual homologous enzymes such as the matrix metalloproteinases (MMPs) by antagonist molecules is highly desired for defining physiological and pathophysiological pathways. However, the rational design of antagonists targeting enzyme catalytic moieties specific to one of the homologous enzymes often appears to be an extremely difficult task. This is mainly due to the high structural homology at the enzyme active sites shared by members of the protein family.

Antibodies targeting the catalytic zinc complex of activated matrix metalloproteinases show therapeutic potential.

Endogenous tissue inhibitors of metalloproteinases (TIMPs) have key roles in regulating physiological and pathological cellular processes. Imitating the inhibitory molecular mechanisms of TIMPs while increasing selectivity has been a challenging but desired approach for antibody-based therapy. TIMPs use hybrid protein-protein interactions to form an energetic bond with the catalytic metal ion, as well as with enzyme surface residues.

Toward iron sensors: bioinspired tripods based on fluorescent phenol-oxazoline coordination sites.

In the quest for fast throughput metal biosensors, it would be of interest to prepare fluorophoric ligands with surface-adhesive moieties. Biomimetic analogues to microbial siderophores possessing such ligands offer attractive model compounds and new opportunities to meet this challenge. The design, synthesis, and physicochemical characterization of biomimetic analogues of microbial siderophores from Paracoccus denitrificans and from the Vibrio genus are described.

Branched coordination multilayers on gold.

A C3-symmetric tridentate hexahydroxamate ligand molecule was specially synthesized and used for coordination self-assembly of branched multilayers on Au surfaces precoated with a self-assembled monolayer (SAM) of ligand anchors. Layer-by-layer (LbL) growth of multilayers via metal-organic coordination using Zr4+ ions proceeds with high regularity, adding one molecular layer in each step, as shown by ellipsometry, wettability, UV-vis spectroscopy, and atomic force microscopy (AFM). The branched multilayer films display improved stiffness, as well as a unique defect self-repair capability, attributed to cross-linking in the layers and lateral expansion over defects during multilayer growth.

Synthesis and biological evaluation of lipophilic iron chelators as protective agents from oxidative stress.

Lipophilic Fe(III) chelators were synthesized and shown to protect oligodendrial cells from oxidative damage induced by Fe(III) and hydrogen peroxide.

Preparative manipulation of gold nanoparticles by reversible binding to a polymeric solid support.

A preparative scheme is presented for controlled modification of gold nanoparticles (NPs) by using reversible binding to a polymeric solid support through boronic acid chemistry. Octanethiol-capped Au NPs were bound to a boronic acid functionalized resin by custom-synthesized bifunctional linker molecules. The NPs were chemically released from the resin to the solution, with one (or a few) linker molecules embedded in their capping layer.

Ferrioxamine B analogues: targeting the FoxA uptake system in the pathogenic Yersinia enterocolitica.

A series of ferrioxamine B analogues that target the bacterium Yersinia enterocolitica were prepared. These iron carriers are composed of three hydroxamate-containing monomeric units. Two identical monomers consist of N-hydroxy-3-aminopropionic acid coupled with beta-alanine, and a third unit at the amino terminal is composed of N-hydroxy-3-aminopropionic acid and one of the following amino acids: beta-alanine (1a), phenylalanine (1b), cyclohexylalanine (1c), or glycine (1d).

Chemical input multiplicity facilitates arithmetical processing.

We describe the design and function of a molecular logic system, by which a combinatorial recognition of the input signals is utilized to efficiently process chemically encoded information. Each chemical input can target simultaneously multiple domains on the same molecular platform, resulting in a unique combination of chemical states, each with its characteristic fluorescence output. Simple alteration of the input reagents changes the emitted logic pattern and enables it to perform different algebraic operations between two bits, solely in the fluorescence mode.

Direct photo-induced DNA strand scission by a ruthenium bipyridyl complex.

Irradiation of plasmid DNA in the presence of Ru(II)-2, a modified tris(2,2'-bipyridyl)Ru(II) complex, in which two hydroxamic acid groups are attached to one of the three bipyridyl ligands, results in total fragmentation of the DNA. The photo-chemical reaction products were analyzed by gel electrophoresis, which revealed complete fragmentation. Further evidence for the complete degradation of the DNA was obtained by imaging the pre- and post-treated plasmid DNA using atomic force microscopy (AFM).

Stable room-temperature molecular negative differential resistance based on molecule-electrode interface chemistry.

We show reproducible, stable negative differential resistance (NDR) at room temperature in molecule-controlled, solvent-free devices, based on reversible changes in molecule-electrode interface properties. The active component is the cyclic disulfide end of a series of molecules adsorbed onto mercury. As this active component is reduced, the Hg-molecule contact is broken, and an insulating barrier at the molecule-electrode interface is formed.

Synthesis and evaluation of iron chelators with masked hydrophilic moieties.

Synthetic iron chelators based on the natural siderophore ferrichrome have previously been shown to bind Fe(III) with high affinity (pKf > 27) and have shown no toxicity to mammalian cell cultures in vitro. A new class of lipophilic ferrichrome analogues carrying acetoxymethyl ester moieties has been synthesized. We have shown that these molecules penetrate rapidly through cell membranes and turn highly hydrophilic while inside the cells, upon esterase mediated hydrolysis of the lipophilic termini.