Karl-Erik Bergquist

Production of siderophores by strains of the genusTrichoderma

SummaryThe production of siderophores by nine strains (six species) of the genusTrichoderma was investigated. Under conditions of iron deficiency, the culture filtrate of all strains contained coprogen, coprogen B, and ferricrocin. In addition,T. longibrachiatum andT. pseudokoningii produced siderophores of the fusigen type. The yields of siderophores varied according to the strains examined from 270 mg/l (strain HA 34-88) to 2080 mg/l (strain HA 113-84). In extracts of the mycelia ofT. longibrachiatum andT. pseudokoningii no siderophores could be detected. From the mycelia of the other strains three siderophores, namely coprogen, ferricrocin and a new coprogen derivative which carried a palmitoyl instead of an acetyl group, were obtained. Palmitoylcoprogen is the first fungal siderophore which is solely found in the cells and is not excreted into the culture broth.

Use of acid-labile protective groups for carbohydrate moieties in synthesis of glycopeptides related to type II collagen

β-D-Galactopyranosyl and α-D-glucopyranosyl-β-D-galactopyranosyl moieties carrying silyl, isopropylidene and 4-methoxybenzyl protective groups have been attached to the amino acid 5-hydroxy-L-norvaline. The resulting glycosylated building blocks were used in Fmoc solid-phase synthesis of glycopeptides related to a fragment from type II collagen which is immunodominant in a mouse model for rheumatoid arthritis. The protective groups used for the carbohydrate moieties were completely removed during acid catalyzed cleavage of the glycopeptides from the solid phase under conditions which left the O-glycosidic bonds intact.

Piperidine is preferred to morpholine for Fmoc cleavage in solid phase glycopeptide synthesis as exemplified by preparation of glycopeptides related to HIV gp120 and mucins

Abstract Protected derivatives of the Tn antigens [Fmoc-Ser/Thr(Ac3GalNAcα)-OH, compounds 5 and 8] have been prepared by glycosylation of Fmoc-Ser/Thr-OAllyl with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-galactopyranosyl chloride (2), followed by conversion of the azido group to an acetamide and deallylation. The derivatives 5 and 8 were used for solid phase synthesis of glycopeptides related to HIV gp120 and mucins. In these syntheses piperidine was found to give efficient Fmoc removal whereas deprotection with morpholine was slow and incomplete for some steps. In contrast to previous concerns β-elimination and epimerization of glycopeptide stereocenters was not encountered when piperidine was used for Fmoc deprotection. However, it was found that for glycopeptides which side-chain deprotection and cleavage from the solid phase.

Preparation of a glycopeptide analogue of type II collagen — Use of acid labile protective groups for carbohydrate moieties in solid phase synthesis of O-linked glycopeptides

Abstract A glycopeptide analogue of the immunodominant T cell epitope on type II collagen has been prepared by solid phase synthesis. Preparation of a glycosylated amino acid from two monosaccharide units that carried silyl and isopropylidene protective groups and Fmoc 5-hydroxynorvaline was essential for the synthesis. After assembly of the glycopeptide the carbohydrate protective groups were removed simultaneously with acid catalyzed cleavage from the solid phase.

Microspectroscopic evidence of cretaceous bone proteins.

Low concentrations of the structural protein collagen have recently been reported in dinosaur fossils based primarily on mass spectrometric analyses of whole bone extracts. However, direct spectroscopic characterization of isolated fibrous bone tissues, a crucial test of hypotheses of biomolecular preservation over deep time, has not been performed. Here, we demonstrate that endogenous proteinaceous molecules are retained in a humerus from a Late Cretaceous mosasaur (an extinct giant marine lizard). In situ immunofluorescence of demineralized bone extracts shows reactivity to antibodies raised against type I collagen, and amino acid analyses of soluble proteins extracted from the bone exhibit a composition indicative of structural proteins or their breakdown products. These data are corroborated by synchrotron radiation-based infrared microspectroscopic studies demonstrating that amino acid containing matter is located in bone matrix fibrils that express imprints of the characteristic 67 nm D-periodicity typical of collagen. Moreover, the fibrils differ significantly in spectral signature from those of potential modern bacterial contaminants, such as biofilms and collagen-like proteins. Thus, the preservation of primary soft tissues and biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.

Fluorinated linkers for monitoring solid-phase synthesis using gel-phase 19F NMR spectroscopy

Abstract Three fluorinated linkers which are analogues of linkers commonly used in solid-phase peptide synthesis have been prepared. Using 19F NMR spectroscopy, the fluorine atom of the linker allowed monitoring of several transformations in the solid-phase synthesis of a peptoid having a coumarin moiety. Especially, attachment of the linker to the solid phase, coupling of the first building block to the linker and cleavage of the product were efficiently monitored and optimised.

Synthesis and self-aggregation of enantiopure and racemic molecular tweezers based on the bicyclo[3.3.1]nonane framework.

A pair of molecular tweezers (syn-4) that consists of quinoline and pyrazine units fused to a bicyclic framework is presented. The tweezers were synthesised both as a racemic mixture (rac-4) and an enantiomerically pure form ((R,R,R,R)-4) starting from either racemic or enantiomerically pure bicyclo[3.3.1]nonane-2,6-dione (3). Homochiral dimers were observed in the solid state for rac-4. The self-association of both rac-4 and (R,R,R,R)-4 was studied in solution. A weak self-association constant in CDCl(3) was estimated by (1)H NMR spectroscopic dilution titration experiments in both cases, following several proton resonances. For this purpose, a general normalisation model for the accurate determination of association constants from multiple datasets was developed. In contrast to the solid state, no diastereomeric discrimination was observed for rac-4 in solution.

Cyclodione, an unsymmetrical dimeric diterpene from Cylicodiscus gabunensis

Abstract The structure of cyclodione ( 4 ) isolated from the stem bark of the tree Cylicodiscus gabunensis has been determined by spectroscopic methods. Cyclodione ( 4 ) is a nonacyclic dimeric cassane-type diterpenoid.

Binding of peptides in solution by the Escherichia coli chaperone PapD as revealed using an inhibition ELISA and NMR spectroscopy

PapD is the prototype member of a family of periplasmic chaperones which are required for assembly of virulence associated pili in pathogenic, gram-negative bacteria. In the present investigation, an ELISA has been developed for evaluation of compounds as inhibitors of PapD. Synthetic peptides, including an octamer, derived from the C-terminus of the pilus adhesin PapG were able to inhibit PapD in the ELISA. Evaluation of a panel of octapeptides in the ELISA, in combination with NMR studies, showed that the peptides were bound as extended beta-strands by PapD in aqueous solution. The PapD-peptide complex was stabilized by backbone to backbone hydrogen bonds and interactions involving three hydrophobic peptide side chains. This structural information, together with previous crystal structure data, provides a starting point in efforts to design and synthesize compounds which bind to chaperones and interfere with pilus assembly in pathogenic bacteria.

Composition- and Size-Controlled Cyclic Self-Assembly by Solvent- and C60-Responsive Self-Sorting.

Synthesis, solvent-, and guest-controlled self-assembly, and self-sorting of new hydrogen-bonded chiral cavity receptors are reported. The design of the cavity is based on the cyclic self-aggregation of monomers containing the 4H-bonding ureidopyrimidinone motif fused with the bicylo[3.3.1]nonane framework. Selective formation of kinetically inert cyclic tetramers is observed in chloroform, while in toluene an equilibrium between tetrameric and pentameric forms exists. The high affinity of the tetrameric aggregates toward C60 and C70 is observed in aromatic solvents. The host-guest interaction of unconventional π-acidic supramolecular receptors for fullerenes is turned off and on by changing the solvent, whereas the selection of size and the very composition of the cavity aggregate is controlled by either the change of solvent or the addition of fullerene guest, making our systems a new type of self-sorting device.