Assessing the inhibitory potency of galectin ligands identified from combinatorial (glyco)peptide libraries using surface plasmon resonance spectroscopy.

Combinatorial (glyco)peptide libraries offer the possibility to define effective inhibitors of protein (lectin)-glycan interactions. If a (glyco)peptide surpasses the inhibitory potency of the free sugar, then the new peptide-lectin contacts underlying the affinity enhancement may guide further rational drug design. Focusing on the adhesion/growth regulatory human galectins 1 and 3, a screening of three combinatorial solid-phase (glyco)peptide libraries, containing Gal(beta1-O)Thr, Gal(beta1-S)Cys/Gal(beta1-N)Asn, and Lac(beta1-O)Thr, with the fluorescently labeled lectins had led to a series of lead compounds.

The application of neoglycopeptides in the development of sensitive surface plasmon resonance-based biosensors.

The development of a biosensor based on surface plasmon resonance is described for the detection of carbohydrate-binding proteins in solution on a Biacore 2000 instrument, using immobilized glycopeptides as ligands. Their selection was based on previous screenings of solid-phase glycopeptide libraries with Ricinus communis agglutinin (RCA(120)) and human adhesion/growth-regulatory galectin-1 (h-Gal-1). Glycopeptides were immobilized on Au sensor chips functionalized with mixed self-assembled monolayers of different ratios of 11-mercapto-1-undecanol and 11-mercaptoundecanoic acid, and of 3-mercapto-1-propanol and 11-mercaptoundecanoic acid.

Affinity determination of ricinus communis agglutinin ligands identified from combinatorial O- and S-,N-glycopeptide libraries.

Two combinatorial glycopeptide libraries were synthesized on solid support via the "split-and-mix" method combined with the ladder synthesis strategy. The O-glycopeptide library contained Gal(beta1-O)Thr, whereas the S-,N-glycopeptide library contained both Gal(beta1-S)Cys and Gal(beta1-N)Asn. In this model study, the two libraries were screened against the fluorescently labeled lectin Ricinus communis agglutinin (RCA120).

Discovery of galectin ligands in fully randomized combinatorial one-bead-one-compound (glyco)peptide libraries.

The involvement of human lectins (galectins) in disease progression accounts for the interest to design potent inhibitors. Three fully randomized hexa(glyco)peptide libraries were prepared using the portion mixing method combined with ladder synthesis. On-bead screening with fluorescently labelled galectin-1 and -3 yielded a series of lead structures, whose inhibitory activity on carbohydrate-dependent galectin binding was tested in solution by solid-phase and cell assays.

Critical elements of oligosaccharide acceptor substrates for the Pasteurella multocida hyaluronan synthase.

Three-dimensional structures are not available for polysaccharide synthases and only minimal information on the molecular basis for catalysis is known. The Pasteurella multocida hyaluronan synthase (PmHAS) catalyzes the polymerization of the alternating beta1,3-N-acetylglucosamine-beta1,4-glucuronic acid sugar chain by the sequential addition of single monosaccharides to the non-reducing terminus. Therefore, PmHAS possesses both GlcNAc-transferase and glucuronic acid (GlcUA)-transferase activities.

SPR studies of carbohydrate-protein interactions: signal enhancement of low-molecular-mass analytes by organoplatinum(II)-labeling.

The relatively insensitive surface plasmon resonance (SPR) signal detection of low-molecular-mass analytes that bind with weak affinity to a protein--for example, carbohydrate-lectin binding--is hampering the use of biosensors in interaction studies. In this investigation, low-molecular-mass carbohydrates have been labeled with an organoplatinum(II) complex of the type [PtCl(NCN-R)]. The attachment of this complex increased the SPR response tremendously and allowed the detection of binding events between monosaccharides and lectins at very low analyte concentrations.

Synthesis and conjugation of oligosaccharide analogues of fragments of the immunoreactive glycan part of the circulating anodic antigen of the parasite Schistosoma mansoni.

The gut-associated circulating anodic antigen (CAA) is one of the major excretory antigens produced by the parasite Schistosoma mansoni. The immunoreactive part of CAA is a threonine-linked polysaccharide composed of long stretches of the unique repeating disaccharide-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GalpNAc-(1-->. Previously, using surface plasmon resonance and ELISA techniques, it has been shown that some anti-CAA IgM monoclonal antibodies (MAbs) also recognize members of a series of bovine serum albumin (BSA)-coupled synthetic di- to penta-saccharide fragments of the CAA glycan.

Organoplatinum(II) complexes as a color biomarker in solid-phase peptide chemistry and screening.

[reaction: see text] A novel organoplatinum(II) biomarker is introduced to facilitate the solid-phase screening of combinatorial libraries for substrates and inhibitors of enzymes and receptors. The robust organoplatinum(II) biomarker can be incorporated, on amine functions, in peptides using standard peptide coupling techniques. The chemistry, stability, and (reversible) coloration process with KI(3) of the organoplatinum(II) biomarker was investigated.

Glycopeptides as oligosaccharide mimics: high affinity sialopeptide ligands for sialoadhesin from combinatorial libraries.

Two different sialic acid containing glycopeptide (sialopeptide) libraries were synthesized using the portion mixing method and ladder synthesis. The libraries were attached via an IMP spacer and a photolabile linker to PEGA(1900) resin in order to facilitate rapid and unambiguous structural analysis of hits by MALDI-TOFMS. One library contained a lactamized sialic acid moiety at the N terminus of a pentapeptide, while a second library displayed a sialic acid residue at the center of a heptapeptide.

A novel open-chain nononic acid linked by an ether bond to glucose as a polysaccharide constituent.

A novel sugar constituent was isolated from the heteropolysaccharide excreted by Streptococcus thermophilus 8 S when grown in skimmed milk. The structure and absolute configuration were determined by means of chemical analysis, mass spectrometry, NMR spectroscopy, along with molecular dynamics simulations, and was shown to be 6-O-(3',9'-dideoxy-D-threo-D-altro-nononic acid-2'-yl)-D-glucopyranose.

SPOCC-194, a new high functional group density PEG-based resin for solid-phase organic synthesis.

A novel polymer matrix for solid-phase synthesis, SPOCC(194) resin (1), was designed featuring a backbone of homogeneous tetraethylene glycol (TEG(194)) macromonomer linked by quaternary carbon junctions and terminating in primary alcohol functionality. Beaded SPOCC(194) resin was effectively prepared by suspension polymerization of oxetanylated TEG macromonomer 5 in stirred silicon oil. Mechanically stable and inert to a diverse range of reaction conditions, SPOCC(194) possessed a high hydroxyl group loading (0.

Palladium on carbon encapsulated in POEPOP(1500): a resin-supported catalyst for hydrogenation reactions.

[reaction: see text] A new a versatile catalyst for hydrogenation reactions wherein palladium on carbon is encapsulated in POEPOP(1500)-resin is described. This polymer-supported catalyst has been successfully used in solution phase hydrogenation of a double and a triple bond as well as hydrogenolysis of a benzyl-protecting group. While the activity of the new catalyst is marginally lower than standard 10% Pd/C, it has the advantage of being reused several times without significant loss of reactivity.