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Biomedical subjects

L Kenne

Publications and source records attributed to L Kenne.

At least 73 records · Page 4Linked to original sources
PubMed1989

Isolation and characterization of a glycosylated form of human insulin-like growth factor I produced in Saccharomyces cerevisiae.

Expression and secretion of human insulin-like growth factor-I (IGF-I) in Saccharomyces cerevisiae was achieved by linking an actin (ACT) promoter to an MF alpha 1 prepro leader peptide/IGF-I gene fusion. Purified human IGF-I from yeast culture media was found to contain, in addition to the native form, also a glycosylated variant. Structural studies showed that both IGF-I forms were processed identically, resulting in 70-amino-acid long polypeptides, with intact N-terminal and C-terminal residues of glycine and alanine, respectively. The glycosylation site was determined to threonine-29 (Thr29), by 1H NMR spectroscopy and protein sequence analysis of an isolated tryptic peptide(22-36). No other glycosylation sites were found. Only mannose was detected in the sugar analysis, with an estimated content of 4.5% w/w corresponding to 2 mannose residues per molecule of IGF-I. The carbohydrate structure, determined by 1H and 13C NMR spectroscopy, was found to be alpha-D-Manp(1----2)alpha-D-Manp(1----3)Thr corresponding to an O-linked glycoprotein structure. No other post-translational modifications could be identified in the glycosylated IGF-I form. Furthermore, this form was highly active, comparable to native IGF-I, exhibiting a specific activity of 20,500 units/mg, as determined by a radio-receptor assay.

Actins↗
PubMed1989

Computer-assisted structural analysis of polysaccharides with an extended version of CASPER using 1H- and 13C-n.m.r. data.

The computer program CASPER, used in the structural analysis of polysaccharides composed of repeating units, has been extended. The extended version uses either unassigned 1H- or 13C-n.m.r. chemical shifts or the complete unassigned C,H-correlation spectrum, and can predict the structure of linear and branched oligo- and poly-saccharides. The number of possible structures, consistent with sugar and methylation analysis, can be decreased by the use of 1JC,H and 3JH,H values. The database, which contains 1H- or 13C-n.m.r. chemical shift data for monosaccharides and 1H- or 13C-glycosylation shifts for all types of glycosidic linkages obtained by combination of the monosaccharides, has been increased and now also contains correction values for sugar residues present in branch-point regions. The program has been tested on four polysaccharides of known structure but with different degrees of complexity. For three polysaccharides, the correct structure was suggested; for the fourth, two structures were consistent with the n.m.r. data, one of them being correct.

Carbohydrate Conformation↗
PubMed1989

Topography and conformational preferences of 6,7,8,9-tetrahydro-1-hydroxy-N,N-dipropyl-5H-benzocyclohepten-6- ylamin e. A rationale for the dopaminergic inactivity.

In an attempt to rationalize the inability of phenolic benzocycloheptenylamines to activate dopamine (DA) D2 receptors, we have studied the conformational preferences and topography of 6,7,8,9-tetrahydro-1-hydroxy-N,N-dipropyl-5H-benzocyclohepten-6-++ +ylamine (1). Preferred conformations of 1 have been defined by use of experimental (NMR spectroscopic studies) and theoretical (MMP2, AM1, and MNDO calculations) methods. Topographical characteristics were studied by use of molecular graphics. Results from the MMP2 calculations agree with those from the AM1 calculations and the NMR spectroscopic study--1 seems to preferentially adopt chair conformations with a pseudoequatorial C6 substituent. The MNDO calculations, however, produced results that deviate considerably from those of the other theoretical methods. Most likely, pharmacophore conformations of (S)-1 do not present volumes that are part of the DA D2 receptor essential volume. Therefore, it appears that the energy penalty paid by the pharmacophore conformations is responsible for the dopaminergic inactivity of (S)-1. The inactivity of (R)-1 may be due to high energies of pharmacophore conformations and/or to steric factors since these conformations produce large excess volumes that may be part of the DA D2 receptor essential volume. The model used in the present report--a flexible pharmacophore combined with a partial receptor-excluded volume--might be used in the design of new DA D2 receptor agonists.

Benzocycloheptenes↗
PubMed1989

(R)- and (S)-5,6,7,8-tetrahydro-1-hydroxy-N,N-dipropyl-9H-benzocyclohepten- 8-ylamine. Stereoselective interactions with 5-HT1A receptors in the brain.

The enantiomers of 5,6,7,8-tetrahydro-1-hydroxy-N,N-dipropyl-9H-benzocyclohepten-8-++ +ylamine (3) have been synthesized and evaluated for central 5-hydroxytryptamine (5-HT) and dopamine (DA) receptor activity by use of behavioral and biochemical tests in rats. In addition, the ability of the compounds to displace [3H]-8-OH-DPAT from 5-HT1A binding sites was evaluated. The absolute configuration of the enantiomers of 3 was determined indirectly by X-ray diffraction of (+)-(8R,alpha R)-5,6,7,8-tetrahydro-1-methoxy-N-(alpha-phenethyl)-9H- benzocyclohepten-8-ylamine hydrochloride (9.HCl), a resolved synthetic precursor. The stereoselectivity of the interaction of 3 with 5-HT1A receptors was more pronounced than that of 8-hydroxy-2-(dipropylamino)tetralin (1; 8-OH-DPAT); only (R)-3 displayed 5-HT activity. However, (R)-3 was of lower potency than any of the enantiomers of 1. The enantiomer (S)-3, which was found to be inactive as a 5-HT-receptor agonist, appeared to be a weakly potent DA-receptor agonist whereas (R)-3 seemed to be devoid of dopaminergic activity. The conformational preferences of 3 were studied by use of NMR spectroscopy and molecular mechanics calculations. Preferred conformations of (R)-3 are similar in shape to those of the stereoselective 5-HT1A-receptor agonist (2R,3S)-8-hydroxy-3-methyl-2-(dipropylamino)tetralin.

Animals↗
PubMed1988

A 13C-n.m.r. study of some Shigella flexneri O-polysaccharides.

13C-N.m.r. data for some Shigella flexneri O-polysaccharides are reported. It is concluded that the chemical shifts observed for the linear Shigella flexneri type Y O-polysaccharide are similar to those calculated by adding substituent shifts, obtained from disaccharides with similar stereochemistry around the glycosidic linkage, to the chemical shifts for the monomers. The influence of substitution with alpha-D-glucopyranosyl and/or O-acetyl groups in different positions of this polysaccharide on the chemical shifts has been investigated. Possible interactions between sugar residues involved in the branching have been investigated by energy minimisations (GESA) of disaccharide and of trisaccharide elements.

Carbohydrate Conformation↗
PubMed1988

Structural factors of importance for 5-hydroxytryptaminergic activity. Conformational preferences and electrostatic potentials of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and some related agents.

The conformational characteristics of two series of 5-hydroxytryptamine (5-HT) receptor agonists, monophenolic N,N-dialkylated 2-aminotetralins and trans-2-phenylcyclopropylamines, have been studied by a combination of experimental (NMR spectroscopy) and theoretical (molecular mechanics and MNDO calculations) methods. In addition, molecular electrostatic potentials have been calculated for selected conformations and the absolute configuration of the potent 5-HT-receptor agonist (+)-cis-8-hydroxy-1-methyl-2-(di-n-propylamino)tetralin has been determined, by X-ray crystallography of the synthetic precursor, to be 1S,2R. Results obtained are discussed in terms of conformational, steric, and electronic requirements for 5-HT-receptor activation. It is suggested that different conformations of the 5-HT-receptor agonists (1R,2S)-2-(2-hydroxyphenyl)-N,N-di-n-propylcyclopropylamine [(1R,2S)-4] and its 3-hydroxy isomer (1R,2S)-5 are able to activate 5-HT receptors. The strongly increased stereoselectivity of 2, 4, and 5 as compared to that of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 1) is rationalized on the basis of steric factors. Conformational factors appear to be responsible for the inability of the trans-C1-methyl-substituted derivative of 1 to activate 5-HT receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1988

Central dopaminergic and 5-hydroxytryptaminergic effects of C3-methylated derivatives of 8-hydroxy-2-(di-n-propylamino)tetralin.

A number of stereochemically well defined C3-methylated derivatives of the potent 5-hydroxytryptamine (5-HT) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) have been synthesized, and their stereochemical characteristics have been studies by use of NMR spectroscopy, X-ray crystallography, and molecular mechanics calculations. The compounds were tested for activity at central 5-HT and dopamine (DA) receptors, by use of biochemical and behavioral tests in rats. In addition, the ability of the cis- and trans-8-hydroxy-3-methyl-2-(di-n-propylamino)tetralins (15 and 11) to displace [3H]-8-OH-DPAT from 5-HT1A binding sites was evaluated. The stereoselectivity of the interaction of 11 and 15 with 5-HT receptors was much greater than that of 8-OH-DPAT. Observed rank order of potencies in the 5-HT1A binding assay corresponds to that in the in vivo biochemical assay.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1987

Isolation and characterization of three different carbohydrate chains from melanoma tissue plasminogen activator.

Electrophoretic analysis of endoglycosidase-treated tissue plasminogen activator obtained from human melanoma cells showed that the heterogeneity observed for the protein in these preparations is caused by an N-glycosidically linked N-acetyllactosamine type of carbohydrate chain which is present in about 50% of the molecules. An oligomannose type and an N-acetyllactosamine type of glycan is present in all molecules. Three glycopeptides were isolated and characterized by 1H-NMR, sugar determination, methylation analysis and amino acid determination. The exact attachment site for each of the three glycans could be deduced from the amino acid compositions of the glycopeptides. Asn-117 carries the oligomannose type of glycan, the structure of which was completely determined. Asn-184 is the site where the presence or absence of a biantennary N-acetyllactosamine type of glycan causes the size heterogeneity. The third N-glycosylation site, Asn-448, was found to carry a triantennary or tetraantennary N-acetyllactosamine type of carbohydrate chain.

Amino Acids↗
PubMed1987

Structural analysis of two 2-deoxy analogues of alpha- and beta-KDO and the methyl alpha- and beta-glycosides of KDO, and determination of their metal-ion-binding properties.

Ammonium 2,6-anhydro-3-deoxy-D-glycero-D-talo-octonate (1), a potent inhibitor of the enzyme CMP-KDO synthetase, its C-2 epimer 2, and the methyl beta- (3) and alpha-glycoside (4) of KDO were studied by 1H- and 13C-n.m.r. spectroscopy. Compound 1 was also analysed by X-ray crystallography. Each compound adopted a 5C2 chair conformation with the side chain equatorial. The preponderant side-chain conformation of 1 in solution was the same as that in the crystal and was stabilised by an intramolecular hydrogen bond from HO-8 to the carboxylate group. This hydrogen bond appeared to be present also in 3. However, the side-chain conformation of 2 and 4 was different from that in 1 and 3. The metal-ion-binding properties, determined on the basis of the line-broadening effects of Mn2+ on the 13C-n.m.r. signals, showed that the carboxylate group was involved in the binding with O-8 in 1 and 3 and with O-6 and O-8 in 2 and 4.

Carbohydrate Conformation↗
PubMed1987

A 2D-1H-n.m.r. study of some Shigella flexneri O-polysaccharides.

A 1H-n.m.r. study of the O-polysaccharides from different types of Shigella flexneri has been performed. With the aid of 2D-n.m.r. techniques, namely, J-resolved, spin-spin correlation, and NOESY experiments, most of the structural features of these polysaccharides could be deduced. Sequences could generally be obtained from the NOESY experiments. When using a prolonged mixing time in these experiments, cross-peaks due to spin diffusion from one anomeric proton to the anomeric proton of an adjacent residue could be obtained, thereby giving complementary sequence information.

Carbohydrate Conformation↗
PubMed1987

C3-methylated 5-hydroxy-2-(dipropylamino)tetralins: conformational and steric parameters of importance for central dopamine receptor activation.

C3-Methyl-substituted derivatives of the potent dopamine (DA) receptor agonist 5-hydroxy-2-(di-n-propylamino)tetralin (5-OH-DPAT) have been synthesized and their conformational preferences have been studied by use of NMR spectroscopy, X-ray crystallography, and molecular mechanics calculations (MMP2). The compounds were tested for activity at central DA receptors, by use of biochemical and behavioral tests in rats. (2R,3S)-5-Hydroxy-3-methyl-2-(di-n-propylamino)tetralin [(-)-8] was demonstrated to be a highly potent DA receptor agonist, while the other new compounds were of low potency or inactive. Results obtained confirmed the hypothesis that the tetralin inversion angle phi and the direction of the N-electron pair (N-H) tau N are conformational parameters of critical importance for DA D2 receptor activation in the 2-aminotetralin series. The high potency of (-)-8 allowed an extension of a previously defined "partial DA D2 receptor excluded volume".

Animals↗
PubMed1987

C1- and C3-methyl-substituted derivatives of 7-hydroxy-2-(di-n-propylamino)tetralin: activities at central dopamine receptors.

C1- and C3-methyl-substituted derivatives of the potent dopamine (DA) receptor agonist 7-hydroxy-2-(di-n-propylamino)tetralin (7-OH-DPAT) have been synthesized, and their conformational preferences have been studied by use of NMR spectroscopy, X-ray crystallography, and molecular mechanics (MMP2) calculations. The compounds were tested for activity at central DA receptors, by use of biochemical and behavioral tests in rats. (1S,2R)-7-Hydroxy-1-methyl-2-(di-n-propylamino)tetralin [(+)-10] was demonstrated to be sevenfold less potent than (2R)-7-OH-DPAT as a DA receptor agonist. The other new compounds were of lower potency or inactive.

Animals↗