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H Paulsen

Publications and source records attributed to H Paulsen.

At least 109 records · Page 6Linked to original sources
PubMed1984

Incorporation of 1,N6-ethenoadenosine into the 3' terminus of tRNA using T4 RNA ligase. 2. Preparation and ribosome interaction of fluorescent Escherichia coli tRNAMetf.

A fluorescent derivative of tRNAMetf from Escherichia coli has been prepared which contains 1,N6-etheno-adenosine (epsilon A) in the place of adenosine 73, the fourth residue from the 3' end. The labeled tRNA, tRNAMetf epsilon A73, is fully active with respect to aminoacylation, formylation and formylmethionyl transfer to puromycin. The preparation procedure entails the chemical removal of four nucleotides from the 3' end of tRNAMetf, ligation of the truncated molecule with epsilon A 3',5'-bisphosphate by use of T4 RNA ligase and repair of the C-C-A end with nucleotidyl transferase. The fluorescence of fMet-tRNAMetf epsilon A73 has been exploited for studying tRNA-ribosome complexes. Upon binding the tRNA into the ribosomal P site, the fluorophor experiences a change of its molecular environment as indicated by an increased fluorescence intensity. On the other hand, iodide quenching experiments indicate that, in the complex, the fluorophor is not shielded against solvent access. The results suggest that (a) adenosine 73 is not involved in direct contacts with the ribosome and (b) the stacking of the 3'-terminal A-C-C-A sequence is changed upon binding to the ribosome.

Adenosine↗
PubMed1984

Plasmodium falciparum: carbohydrates as receptor sites of invasion.

Monosaccharides, disaccharides, and trisaccharides were tested as inhibitors of the in vitro growth of Plasmodium falciparum (strain FCB). While certain monosaccharides (N-acetyl-D-glucosamine, D-mannose, and 3-O-methyl-D-glucose) proved to exhibit a toxic or reversibly retarding effect on the intraerythrocytic development of the parasite, the corresponding alpha- or beta-methylglycosides did not. Several methylglycosides, synthetic di- and tri-saccharides, and artificial blood group antigens were further tested for inhibitory effects on invasion of host red blood cells in vitro. The synthetic disaccharides beta DGlcNAc(1----4) alpha DManOMe and beta DGlcNAc(1----4) DGlcNAc (chitobiose) were good inhibitors of invasion at 10 mM concentration, whereas beta DGal(1----4)beta DGlcNAcOMe was negligibly inhibitory. The inhibition rate of N-acetyl-D-glucosamine, beta-glycosidically linked to bovine serum albumin (BSA) by an alipathic spacer, -(CH2)8CO-, was not enhanced, compared to the corresponding hapten, beta DGlcNAcO(CH2)8COOCH3. The inhibition rates of blood group A- and B-trisaccharide haptens, which were inhibitors of invasion, were also not significantly enhanced when coupled to BSA by way of the corresponding amide spacer, -(CH2)2NHCO(CH2)7CO-. A remarkable enhancement of the inhibition rate was, however, observed when beta DGal(1----3) alpha DGalNAcO(CH2)2NHCO(CH2)7COOCH3 (T-hapten) was coupled to BSA. A clear-cut decrease in the inhibition rates of different beta-glycosides of N-acetyl-D-glucosamine, beta DGlcNAcOR, was observed, depending on the nature of the aglycon R(p-nitrophenyl greater than -(CH2)8COOCH3 greater than -(CH2)2NHCO(CH2)2COOCH3 greater than -CH3). Also, p-nitrophenyl-alpha-D-glucopyranoside was a much better inhibitor of invasion than the corresponding methyl glycoside, alpha DGlcOMe, which was not inhibitory. The properties of the aglycon spacer, used for the covalent attachment of the carbohydrate to the carrier protein, may thus be crucial for the outcome of the inhibition rate.

Animals↗
PubMed1984

Control of glycoprotein synthesis. IX. A terminal Man alpha l-3Man beta 1- sequence in the substrate is the minimum requirement for UDP-N-acetyl-D-glucosamine: alpha-D-mannoside (GlcNAc to Man alpha 1-3) beta 2-N-acetylglucosaminyltransferase I.

Twenty low molecular weight compounds were tested as substrates for UDP-GlcNAc:alpha-D-mannoside (GlcNAc to Man alpha 1-3) beta 2-N-acetylglucosaminyltransferase I (GlcNAc-transferase I) purified from bovine colostrum. This enzyme is at a key control point in the biosynthetic path leading to complex Asn-linked oligosaccharides. The highest activity was obtained with the substrate Man alpha 1-3(R1 alpha 1-6)Man beta 1-R2 where R1 was Man alpha 1-3(Man alpha 1-6)Man- (Km = 0.20 mM) and R2 was -4GlcNAc beta 1-4GlcNAc-Asn. Somewhat less effective were substrates in which R1 was Man- (Km = 0.4-0.6 mM) and R2 was either-4GlcNAc or -4GlcNAc beta 1-4(Fuc alpha 1-6)GlcNAc-Asn. Removal of the Man alpha 1-6 arm (R1 = H-) or replacing R2 with an isopropyl group had no effect on Vmax but increased the Km about 10-fold, thereby leading to an 85% reduction in enzyme activity as measured under standard conditions. An 85% reduction in activity was also observed if R2 was replaced with N-acetylglucosaminitol. Enzyme activity was reduced 33% if R1 was Gal beta 1-4GlcNAc beta 1-2Man-. Any compounds lacking a Man alpha 1-3- terminus or in which the beta-linked Man had been replaced with an alpha-linked Man were totally inactive. It was concluded that a terminal Man alpha 1-3Man beta 1-sequence is a minimal structural requirement for a GlcNAc-transferase I substrate. The only effective substrate for partially purified UDP-GlcNAc:alpha-D-mannoside (GlcNAc to Man alpha 1-6) beta 2-N-acetylglucosaminyltransferase II (GlcNAc-transferase II) from bovine colostrum was R1-GlcNAc beta 1-2Man alpha 1-3(Man alpha 1-6)Man beta 1-R2 where R1 = H-. The absence of a terminal GlcNAc beta 1-2- residue or masking this residue by making R1 = Gal beta 1-4-, both prevented enzyme activity, indicating that GlcNAc-transferase I action must precede GlcNAc-transferase II action during biosynthesis of complex Asn-linked oligosaccharides.

Animals↗
PubMed1984

Controlled-release theophylline and proxyphylline in asthmatics: a comparative study.

In a short-term study, a new sustained-release preparation of proxyphylline (2400 mg/day) was compared to theophylline (800 mg/day) and placebo. A double-blind crossover design was used, and 10 adult asthmatics participated. No significant differences were found between the treatments with regard to relief of asthma symptoms, need for additional medication or incidence and intensity of side-effects. In the placebo period, morning peak-flow was significantly lower compared to active treatment periods.

Adult↗
PubMed1983

[Synthesis of beta-L-rhamnoside linked oligosaccharides of lipopolysaccharides from Shigella flexneri serotype 6].

The synthesis of the trisaccharide O-beta-L-rhamnopyranosyl-(1 leads to 4)-O-beta-L-rhamnopyranosyl-(1 leads to 2)-L-rhamnopyranose (14) and the tetrasaccharide O-2-acetamido-2-deoxy-beta-D-galactopyranosyl)-(1 leads to 2)-O-[beta-L-rhamnopyranosyl-(1 leads to 4)]-O-beta-L-rhamnopyranosyl-(1 leads to 2)-L-rhamnopyranose (21) is described. The latter structure has been proposed as the repeating unit of the O-specific side-chain of the lipopolysaccharide obtained from Shigella flexneri Serotype 6. The key-intermediate was 4-O-acetyl-2-O-allyl-3-O-benzyl-alpha-D-rhamnopyranosyl bromide, which was first linked to benzyl 3,4-di-O-benzyl-alpha-L-rhamnopyranoside, to give a blocked beta-linked disaccharide. This was O-deacetylated and coupled with 2,3,4-tri-O-benzyl-alpha-L-rhamnopyranosyl bromide at O-4' to afford benzyl O-(2,3,4-tri-O-benzyl-beta-L-rhamnopyranosyl)-(1 leads to 4)-O-(2-O-allyl-3-O-benzyl-beta-L-rhamnopyranosyl)-(1 leads to 2)-3,4-di-O-benzyl-alpha-L-rhamnopyranoside (11), which was deprotected to give 14. Deallylation of 11 and coupling with 6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-galactopyranosyl bromide led to a protected tetrasaccharide from which 21 was obtained. The method of catalysis by silver silicate was employed to obtain the beta-glycosidic linkage of all monosaccharide units.

Carbohydrate Conformation↗
PubMed1983

Topological arrangement of two transfer RNAs on the ribosome. Fluorescence energy transfer measurements between A and P site-bound tRNAphe.

The relative arrangement of two tRNAPhe molecules bound to the A and P sites of poly(U)-programmed Escherichia coli ribosomes was determined from the spatial separation of various parts of the two molecules. Intermolecular distances were calculated from the fluorescence energy transfer between fluorophores in the anticodon and D loops of yeast tRNAPhe. The energy donors were the natural fluorescent base wybutine in the anticodon loop or proflavine in both anticodon (position 37) and D loops (positions 16 and 17). The corresponding energy acceptors were proflavine or ethidium, respectively, at the same positions. Four distances were measured: anticodon loop-anticodon loop, 24(+/- 4) A; anticodon loop (A site)-D loop (P site), 46(+/- 12) A: anticodon loop (P site)-D loop (A site), 38(+/- 10) A: D loop-D loop, 35(+/- 9) A. Assuming that both tRNAs adopt the conformation present in the crystal and that the CCA ends are close to each other, the results are consistent with the two anticodons being bound to contiguous codons and suggest an asymmetric arrangement in which the planes of the two L-shaped molecules enclose an angle of 60 degrees +/- 30 degrees.

Anticodon↗
PubMed1983

Forssman antigenicity of chemically synthesized globopentaose.

The Forssman antigenicity of a chemically synthesized globopentaose was studied. Globopentaose at 40 ng showed strong inhibitory activity for the formation of a precipitin line between globopentaosylceramide (Forssman glycolipid) and anti-Forssman rabbit antiserum, while much more pentasaccharide (7 and 100 micrograms, respectively) was required to inhibit a 50% quantitative precipitin reaction and a hemolysis reaction. An immune complex of the 3H-labeled globopentaose with anti-Forssman antibody was hardly formed. Thus, the chemically synthesized globopentaose possesses the same antigenic specificity as globopentaosylceramide but it is difficult to achieve a stable complex with Forssman antibody.

Animals↗
PubMed1983

[Synthesis of the T-antigen trisaccharide O-beta-D-galactopyranosyl-(1 to 3)-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1 to 6)-D-galactopyranose and O-beta-D-galactopyranosyl-(1 to 3)-O-(2-acetamido-2-deoxy-alpha-D-galacopyranosyl)-(1 to 6)-D-glucopyranose and their binding to proteins].

The synthesis of the trisaccharides O-beta-D-galactopyranosyl-(1 to 3)-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1 to 6)-D-galactopyranose (15) and O-beta-D-galactopyranosyl-(1 to 3)-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1 to 6)-D-glucopyranose (27) is described and the synthesis of alpha-D-glycosides by reaction of 3,4,6-tri-O-acetyl-2-azido-2-deoxy-beta-D-galactopyranosyl chloride with highly reactive hydroxyl groups is discussed. The trisaccharide 27 was coupled with serum albumin by formation of an imine intermediate and reduced to an amine, to yield a synthetic T-antigen. A similar coupling of 15 was unsuccessful.

Antigens, Surface↗
PubMed1982

[Synthesis of the glycopeptide O-beta-D-galactopyranosyl-(1 to 3)-O-(2-acetamido-2-desoxy-alpha-D-galactopyranosyl)-(1 to 3)-L-serine and -L-threonine].

In the presence of silver carbonate-silver perchlorate and dichloromethane-toluene as solvent, 3,4,6-tri-O-acetyl-2-azido-2-deoxy-beta-D-galactopyranosyl chloride, and derivatives of L-serine and -L-serine and -L-threonine, gave, with high stereoselectivity, the benzyl esters of N-(benzyloxycarbonyl)-3-O-(3,4,6-tri-O-acetyl-2-azido-2-deoxy-alpha-D-galactopyranosyl)-L-serine (7) and -L-threonine (22), which were hydrogenolyzed and deblocked to give 3-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-L-serine and -L-threonine, respectively, corresponding to the hapten of the Tn-antigen. Reduction of the azido group of 7, followed by selective O-deacetylation and benzylidenation, gave a derivative that was glycosylated with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide to yield a disaccharide. A similar sequence of reactions, starting from 22, gave the L-threonine analog. Removal of the protecting groups from both compounds afforded O-beta-D-galactopyranosyl-(1 to 3)-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-L-serine and -L-serine and -L-threonine, respectively, the hapten of the T-antigen.

Antigens, T-Independent↗
PubMed1982

[Synthesis of oligosaccharide determinants with amide spacers of T-type antigens].

The hapten of the T-antigen was synthesized with a peptide-like amide-spacer as 2-(4-methoxycarbonylbutanecarboxamido)ethyl 2-acetamido-2-deoxy-3-O-beta-D-galactopyranosyl-alpha-D-galactopyranoside and coupled with serum albumin to give a synthetic antigen. Other O-beta-D-galactopyranosyl haptens, 2-(4-methoxycarbonylbutanecarboxamido)ethyl 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-alpha-D-galactopyranoside, O-beta-D-galactopyranosyl-(1 leads to 3)-O-[beta-D-galactopyranosyl-(1 leads to 4)]-2-acetamido-2-deoxy-alpha-D-galactopyranoside, and 2-acetamido-2-deoxy-3-O-beta-D-galactopyranosyl-alpha-D-glucopyranoside, the last compound being the determinant of the Lewis Lec antigen, were also synthesized.

Amides↗
PubMed1982

Effect of ribosome binding and translocation on the anticodon of tRNAPhe as studied by wybutine fluorescence.

The complexes of N-AcPhe-tRNAPhe (or non-aminoacylated tRNAPhe) from yeast with 70S ribosomes from E. coli have been studied fluorimetrically utilizing wybutine, the fluorophore naturally occurring next to the 3' side of the anticodon, as a probe for conformational changes of the anticodon loop. The fluorescence parameters are very similar for tRNA bound to both ribosomal sites, thus excluding an appreciable conformational change of the anticodon loop upon translocation. The spectral change observed upon binding of tRNAPhe to the P site even in the absence of poly(U) is similar to the one brought about by binding of poly(U) alone to the tRNA. This effect may be due to a hydrophobic binding site of the anticodon loop or to a conformational change of the loop induced by binding interactions of various tRNA sites including the anticodon.

Anticodon↗
PubMed1982

[Synthesis of the pentasaccharide chain of the Forsman antigen].

The pentasaccharide chain of the Forssman antigen, O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1 leads to 3)-O-(2-acetamido-2-deoxy-beta-D-galactopyranosyl)-(1 leads to 3)-O-alpha-D-galactopyranosyl-(1 leads to 4)-O-beta-D-galactopyranosyl-(1 leads to 4)-D-glucopyranose (46) was synthesized by a block synthesis in which an alpha-D-glycoside linkage between two D-galactose residues was formed. The trisaccharide O-(6-O-acetyl-2-azido-3,4-di-O-benzoyl-2-deoxy-alpha-D-galactopyranosyl)-(1 leads to 3)-O-(6-O-acetyl-4-O-bebenzyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl)-(1 leads to 3)-6-O-acetyl-2,4-di-O-benzyl-alpha-D-galactopyranosyl bromide (40) (this was obtained through acetolysis of O-(6-O-acetyl-2-azido-3,4-di-O-benzoyl-2-deoxy-alpha-D-galactopyranosyl)-(1 leads to 3)-O-(6-O-acetyl-4-O-benzyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl)-(1 leads to 3)-1,6-anhydro-2,4-di-O-benzyl-beta-D-galactopyranose to the acetyl derivative, followed by reaction with titanium tetrabromide under anhydrous conditions) was condensed with benzyl-4-O-)6-O-benzoyl-2,3-di-O-benzyl-beta-D-galactopyranosyl)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside were in the presence of silver carbonate and perchlorate. The resulting pentasaccharide was deprotected to give 46.

Carbohydrate Conformation↗
PubMed1976

[Isoenzymes of serum alkaline phosphatase in newborns and early infancy (authors transl)].

It was intendet to characterize the isoenzymes of serum alkaline phosphatase in healthy infants. Quantitative estimation of the activity of serum alkaline phosphatase resulted in relatively low values in the newborns and a distinct increase during the first three months of live. As a rule most of the newborns appeared to present one uniform isoenzyme fraction, which was comparable to the isoenzyme of bone origin of the adult. Some of the newborns already exhibited another less marked isoenzyme, the isoenzyme of liver origin. During babyhood this isoenzyme becomes more and more distinct. In most cases this development had become perfect at the end of the first year. Liver tissue of newborns apparently does not synthesize the same liver isoenzyme as liver tissue of adults.

Age Factors↗