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E Eichler

Publications and source records attributed to E Eichler.

15 recordsLinked to original sources
PubMed1999

Synthesis of a disialylated hexasaccharide of type VIII group B Streptococcus capsular polysaccharide.

As part of our program to design, develop and prepare protective vaccines against the bacterial pathogens Group B Streptococcus, we report the synthesis of a disialylated hexasaccharide. This hexasaccharide represents a portion of the serotype-specific capsular polysaccharide of Type VIII that has the tetrasaccharide repeat unit [beta-L-Rhap-(1-->4)-beta-D-Glcp-(1-->4)-[alpha-Neu5Ac-(2--> 3)]-beta-D- Galp-(1-->4)]n. A tetrasaccharide corresponding to this repeat unit has been synthesized by us [E. Eichler, H.J. Jennings, D.M. Whitfield, J. Carbohydr. Chem., 16 (1997) 385-411]. Since the protective epitopes are believed to involve several repeat units, methods to extend this tetrasaccharide were examined. This objective requires a glycosylation of the unreactive OH-4 of the beta-L-Rhap, which was accomplished by coupling a D-Galp glycosyl trichloroacetimidate donor with a beta-L-Rhap-(1-->4)-D-Glcp acceptor. Subsequent coupling of this trisaccharide as a donor to an alpha-Neu5Ac-(2-->3)-D-Galp disaccharide acceptor gave a pentasaccharide. The pentasaccharide was deprotected and enzymatically sialylated using an alpha-(2-->3)-sialyltransferase from Campylobacter jejuni to give the title hexasaccahride alpha-Neu5Ac-(2-->3)- beta-D-Galp-(1-->4)-beta-L-Rhap-(1-->4)-beta-D-Glcp-(1-->4)-[alpha -Neu5Ac- (2-->3)]-beta-D-Galp-(1-->O)-(CH2)3N3.

Bacterial Capsules↗
PubMed1998

Large multi-chromosomal duplications encompass many members of the olfactory receptor gene family in the human genome.

The human genome contains thousands of genes that encode a diverse repertoire of odorant receptors (ORs). We report here on the identification and chromosomal localization of 74 OR-containing genomic clones. Using fluorescence in situ hybridization (FISH), we demonstrate a striking homology among a set of approximately 20 OR locations, illustrating a history of duplications that have distributed OR sequences across the genome. Half of the OR-containing BACs cloned from total genomic DNA and 86% of cosmids derived from chromosome 3 cross-hybridize to a subset of these locations, many to 17 of them. These paralogous regions are distributed on 13 chromosomes, and eight lie in terminal bands. By analyzing clones from an approximately 250 kb clone-walk across one of these sites (3p13), we show that the homology among these sites is extensive (>150 kb) and encompasses both OR genes and intergenic genomic sequences. The FISH signals appear significantly larger at some sites than at the native location, indicating that portions of some duplicons have undergone local amplification/attrition. More restricted duplications involving pairs of other genomic locations are detected with 12% of the OR-BACs. Only a small subset of OR locations is sufficiently diverged from the others that clones derived from them behave as single-copy FISH probes. We estimate that duplications encompassing members of the OR gene family account for >0.1% of the human genome. A comparison of FISH signals at orthologous locations in other primates indicates that a portion of this OR 'subgenome' has been in flux during the divergence of primates, possibly as a mechanism for evolving the repertoire of olfactory receptors.

Animals↗
PubMed1997

Cloning, sequencing, gene organization, and localization of the human ribosomal protein RPL23A gene.

The intron-containing gene for human ribosomal protein RPL23A has been cloned, sequenced, and localized. The gene is approximately 4.0 kb in length and contains five exons and four introns. All splice sites exactly match the AG/GT consensus rule. The transcript is about 0.6 kb and is detected in all tissues examined. In adult tissues, the RPL23A transcript is dramatically more abundant in pancreas, skeletal muscle, and heart, while much less abundant in kidney, brain, placenta, lung, and liver. A full-length cDNA clone of 576 nt was identified, and the nucleotide sequence was found to match the exon sequence precisely. The open reading frame encodes a polypeptide of 156 amino acids, which is absolutely conserved with the rat RPL23A protein. In the 5' flanking region of the gene, a canonical TATA sequence and a defined CAAT box were found for the first time in a mammalian ribosomal protein gene. The intron-containing RPL23A gene was mapped to cytogenetic band 17q11 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1996

FMR1 in global populations.

Fragile X syndrome, a frequent form of inherited mental retardation, results from the unstable expansion of a cryptic CGG repeat within the 5' UTR region of the FMR1 gene. The CGG repeat is normally polymorphic in length, and the content is frequently interrupted by AGG triplets. These interruptions are believed to stabilize the repeat, and their absence, leading to long tracts of perfect CGG repeats, may give rise to predisposed alleles. In order to examine the stability of normal FMR1 alleles, the repeat length of 345 chromosomes from nine global populations was examined with the content also determined from 114 chromosomes as assessed by automated DNA sequencing. The FMR1 alleles, defined by the CGG repeat, as well as by the haplotypes of nearby polymorphic loci, were very heterogeneous, although the level of variation correlated with the age and/or genetic history of a particular population. Native American alleles, interrupted by three AGG repeats, exhibited marked stability over 7,000 years. However, in older African populations, parsimony analysis predicts the occasional loss of an AGG, leading to more perfect CGG repeats. These data therefore support the suggestion that AGG interruptions enhance the stability of the FMR1 repeat and indicate that the rare loss of these interruptions leads to alleles with longer perfect CGG-repeat tracts.

Alleles↗
PubMed1994

Molecular recognition of a Salmonella trisaccharide epitope by monoclonal antibody Se155-4.

The binding site of monoclonal antibody Se155-4, which has been the object of successful crystallographic and antibody-engineering studies, is shown by solid-phase immunoassays to be complementary to a branched trisaccharide, alpha-D-Galp(1-->2) [alpha-D-Abep(1-->3)]-alpha-D-Manp(1, rather than to the tetrasaccharide repeating unit alpha-D-Galp(1-->2) [alpha-D-Abep(1-->3)]-alpha-D-Manp(1-->4) alpha-L-Rhap(1- of the bacterial antigen. Specificity for the 3,6-dideoxy-D-xylo-hexose (3,6-dideoxy-D-galactose) epitope present in Salmonella paratyphi B O-antigens was ensured by screening hybridoma experiments with glycoconjugates derived from synthetic oligosaccharides. Detailed epitope mapping of the molecular recognition by modified and monodeoxy oligosaccharide derivatives showed that complementary surfaces and three antibody-saccharide hydrogen bonds are essential for full binding activity. Both hydroxyl groups of the 3,6-dideoxy-D-galactose residue were obligatory for binding and consistent with the directional nature of their involvement in carbohydrate-protein hydrogen bonds; related tetrasaccharides built from the isomeric 3,6-dideoxyhexoses, 3,6-dideoxy-D-glucose, paratose, and 3,6-dideoxy-D-mannose, tyvelose were not bound by the antibody. Titration microcalorimetry measurements were consistent with the hydrogen-bonding map inferred from the crystal structure and suggest that the displacement of water molecules from the binding site accounts for the favorable entropy that accompanies binding of the native trisaccharide determinant. The protein sequences determined for the antibody VL and VH domains reveal somatic mutation of the VL germ line gene, implying that this antibody-binding site results from a mature antibody response.

Amino Acid Sequence↗
PubMed1994

Modulation of antibody affinity by synthetic modifications of the most exposed pyranose residue of a trisaccharide epitope.

When the Salmonella trisaccharide epitope, methyl 3-O-(3,6-dideoxy-alpha-D-xylo-hexopyranosyl)-2-O-(alpha-D-galactopyra nos yl)- alpha-D-mannopyranoside 12 is bound by a monoclonal antibody Se155.4, the 3,6-dideoxy-alpha-D-hexose is completely buried, while the galactopyranosyl mannopyranosyl units lay across the protein surface. Crystallography of an antibody complexed with 12 also shows that the galactose residue is the most exposed saccharide. A simplified strategy to synthesize 12 and analogues modified at the galactose residue is described. Monosaccharide building blocks containing benzyl ether and ester protecting groups were used for efficient assembly of trisaccharides that can be deprotected by a single hydrogenolysis step, or occasionally preceded by a transesterification stage. Glycosylation of methyl 2-O-benzoyl-4,6-di-O-benzyl-alpha-D- mannopyranoside 4 by 2,4-di-O-benzyl-3,6-dideoxy-D-xylo-hexopyranosyl chloride 8 affords after transesterification the disaccharide acceptor 10. This disaccharide serves as a universal acceptor for glycosylation by glycosyl donors that lead, following facile deprotection, to the alpha- and beta-D-galacto, alpha- and beta-D-gluco, and 2-amino-2-deoxy-alpha-D-galacto trisaccharides 12, 14, 17, 18 and 21. Only a small change in binding energy delta (delta G) occurs when the alpha-D-galactopyranosyl residue of 12 is replaced by either an alpha-D-glucopyranosyl 17 or a 2-amino-2-deoxy alpha-D-galactopyranosyl unit 21. Whereas binding of the beta-D-glucopyranose congener 18 was tolerated by the antibody, the beta-D-galactopyranose analogue 14, showed a 250 fold loss of affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1991

The design and synthesis of antibody binding site probes: three pentasaccharide analogues of the Brucella A antigen prepared by activation in situ of thioglycosides with bromine.

Three pentasaccharide analogues of the Brucella A antigen [----2)-alpha-D-Rhap4NFo-(1----], each with one formamido group replaced by a hydroxyl group, have been prepared as their methyl glycosides. Mono- and di-saccharide thioglycosides of D-rhamnose and 4-azido-4,6-dideoxy-D-mannose were used as glycosyl donors for the preparation of protected pentasaccharide derivatives with trisaccharides as intermediates. Glycosylations were performed by activation in situ of the thioglycosides with bromine in the presence of a glycosyl acceptor and silver triflate as promoter. Reduction of the azido groups with hydrogen sulfide. N-formylation with ethyl formate, and hydrogenolysis then gave the target pentasaccharides.

Antigens, Bacterial↗
PubMed1991

Access to fluorescent probes via allyl glycosides: the synthesis of a Brucella trisaccharide epitope linked to a coumarin.

Oligosaccharide allyl glycosides are demonstrated to provide a route to fluorescent probes and simple inhibitors. Ethyl 2-O-acetyl-4-azido-3-O-benzoyl-4,6-dideoxy-1-thio-alpha-D-mannopyranosid e (6) was used as glycosyl donor in the preparation of the trisaccharide [alpha-D-Rha p4NFo-(1----2)-]2-alpha-D-Rha p4NFo-O-allyl (16). Thioglycoside 6 was activated with N-iodosuccinimide and triflic acid or by bromine in the glycosylations and the inhibitor 16 was obtained after deprotection by transesterification, reduction of the azido groups with hydrogen sulfide, and N-formylation with ethyl formate. Ozonolysis of the allyl glycoside in 16 and reductive amination with 7-amino-4-methylcoumarin then gave the target fluorescent trisaccharide conjugate.

Allyl Compounds↗
PubMed1983

Inhibitors of glycolic acid oxidase. 4-Substituted 3-hydroxy-1H-pyrrole-2,5-dione derivatives.

An extensive series of novel 4-substituted 3-hydroxy-1H-pyrrole-2,5-dione derivatives has been prepared and studied as inhibitors of glycolic acid oxidase (GAO). Compounds possessing large lipophilic 4-substituents are, in general, potent, competitive inhibitors of porcine liver GAO in vitro. Methylation of the nitrogen or the 3-hydroxy substituent reduced potency dramatically, indicating the requirement for the two acidic functions on the 1H-pyrrole-2,5-dione nucleus. In rat liver perfusion studies, with three representative compounds, concentration-dependent inhibition of the conversion of [1-14C]glycolate to [14C]oxalate was observed. Chronic oral administration to ethylene glycol fed rats of the 4-(4'-bromo[1,1'-biphenyl]-4-yl) derivative (83) was shown to effect a significant reduction in urinary oxalate levels over a 58-day period.

Alcohol Oxidoreductases↗
PubMed1983

Inhibitors of glycolic acid oxidase. 4-substituted 2,4-dioxobutanoic acid derivatives.

Fourteen new 4-substituted 2,4-dioxobutanoic acids have been synthesized. These compounds, all of which contain lipophilic 4-substituents, are potent inhibitors in vitro of porcine liver glycolic acid oxidase. The I50 value of the two most potent representatives, 4-(4'-bromo[1,1'-biphenyl]-4-yl)-2, 4-dioxobutanoic acid (8) and 4-[4'-[[(3,4-dihydro-3-hydroxy-2H-1, 5-benzodioxepin-3-yl)methyl]thio][1,1'-biphenyl]-4-yl]-2, 4-dioxobutanoic acid (13) is 6 X 10(-8)M.

Alcohol Oxidoreductases↗
PubMed1980

Ectoenzymes on the surface of cells from human lymphoblastoid lines: 5'-nucleotidase and phosphatase.

Activities of the ecto-enzymes 5'-nucleotidase (5'-N) and phosphatase were determined on the surface of intact cells from 15 different established lines of human B- and T-lymphoblasts. Whereas all the lines express phosphatase, 10 of the lines were negative for 5'-N. 5'-N-negative cell lines are found among B as well as T cells, and they do not carry cryptic enzyme activity. In a 5'-N-positive line activity of this enzyme is correlated with growth showing a peak during the logarithmic phase. On the other hand, inhibition of 5'-N does not change the growth curve of this line. Neuraminidase treatment of the cell surface brings about an increase in phosphatase but not in 5'-N activity. 5'-N of two B-cell lines of human peripheral blood lymphocytes shows complete crossreactivity with an antiserum obtained against human placental 5'-N. However, the enzyme of one lymphoma line with B-cell properties (EHR-A-Ramos) does not cross-react with this serum. The results are discussed with respect to suitability of these lymphoblast lines as model systems for the study of immunodeficiencies.

B-Lymphocytes↗
PubMed1979

Quantitative structure-activity relationships involving the inhibition of glycolic acid oxidase by derivatives of glycolic and glyoxylic acids.

The enzyme glycolic acid oxidase oxidizes glycolate to glyoxylate and glyoxylate to oxalate. Three series of compounds related to the natural substrates, substituted glycolic, oxyacetic, and glyoxylic acids, have been investigated as inhibitors of this enzyme using the techniques of regression analysis and quantitative structure-activity relationships. The best overall correlation with inhibitory potencies was found with the Hansch hydrophobic parameter pi. The classical electronic parameters sigmap, sigmam, F, and R performed poorly. For the substituted glyoxylic acids, a dummy parameter relating to the presence of a nucleophilic group in close proximity to the alpha-carbonyl of the glyoxylate group was found to be highly significant. The syntheses of six novel glycolic and glyoxylic acids are described.

Acetates↗