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H Seliger

Publications and source records attributed to H Seliger.

35 records · Page 2Linked to original sources
PubMed1989

Studies on the role of tetrazole in the activation of phosphoramidites.

The mechanism of the tetrazole-activated coupling step in the synthesis of oligonucleotides via phosphoramidites is studied with the help of model reactions: Treatment of diethoxydiisopropylaminophosphane with two equivalents of tetrazole resulted in a diethoxy-tetrazolophosphane, whose (31P)-NMR shift of 126 ppm is identical with the signal observed during internucleotide bond formation. A series of different related diethoxy-phosphorous-acid derivatives were also synthesized; their (31P)-NMR signals between 123.9 and 130.8 ppm are additional evidence for the intermediacy of a tetrazolide species. Further NMR investigations with more basic azoles showed that tetrazole is also active as a proton donor.

Amides↗
PubMed1989

Immunocytochemistry of 5-bromo-2'-deoxyuridine labelled oligonucleotide probes. A novel technique for in situ hybridization.

A synthetic oligonucleotide probe, complementary to oxytocin m-RNA was labelled enzymatically with 5-bromo-2'-deoxyuridine (5-BrdU) and with [gamma-32P]-ATP. The labelled probes were used for in situ hybridization of histological sections of the mouse hypothalamus. A monoclonal antibody to 5-BrdU and the streptavidine-peroxidase technique were used in order to visualize hybridization with the 5-BrdU labelled probe. In situ hybridization with [32P] labelling was detected autoradiographically. With both methods hybridized neurons were visible in the magnocellular hypothalamic nuclei. While immunostaining and radio-labelling provided similar localization of oxytocin m-RNA, only the immunocytochemical technique showed clear cellular resolution of the reaction product. In situ hybridization with 5-BrdU labelled probes followed by 5-brdU immunocytochemistry seems to be a powerful alternative to common autoradiographic techniques.

Adenosine Triphosphate↗
PubMed1988

In situ hybridization with complementary synthetic oligonucleotide and immunocytochemistry: a combination of methods to study transcription and secretion of oxytocin by hypothalamic neurons.

We have constructed an icosameric, anti-sense oligodeoxyribonucleotide probe derived from the published sequence of rat oxytocin gene precursor that was used for in situ hybridization, combined with immunostaining, to characterize the biosynthetic and secretory activity of hypothalamic oxytocin neurons. The population of hybridized neurons overlapped with the pattern of oxytocin immunoreactive cells, except for a fraction of these cells which remained unhybridized. A number of hybridized neurons remained unstained. The differential proportion of hybridized and immunostained neurons are interpreted as differences in secretory turnover of endocrine neurons.

Amino Acid Sequence↗
PubMed1988

Synthesis and structure-activity relationships in the cefpirome series. II. Analogues of cefpirome with different 7-heteroarylacetamido and 3'-ammonium substituents.

The synthesis and antibacterial activity in vitro of 7-(2-heteroarylacetamido)-3-[(2,3- cyclopentenopyridinium)methyl]cephalosporins and of some related compounds with different ammonium functions in 3'-position are described. The 7-[5-amino-1,2,4-thiadiazol-3-yl] and the 7-[4-aminopyrimidin-2-yl] analogues of cefpirome and compounds with 3-aliphatic ammoniummethyl functions have excellent antibacterial activity. Cephalosporins with different N-heterocycles other than pyridine in 3'-position are less active than their 3-pyridiniummethyl analogues. Attachment of a pyridinium group to a cephem at C-3 via a thiomethyl or an aminomethyl bridge causes reduction of antibacterial activity.

Cephalosporins↗
PubMed1987

Concurrent mutations in two different ras genes in acute myelocytic leukemias.

DNA transfection analyses (tumorigenicity assay) and hybridization to mutation specific oligonucleotide probes established point mutations in codon 61 of both, N-ras and Ki-ras genes in fresh leukemic cells of an AML patient. Concurrent activation of N-ras and Ki-ras sequences by point mutations in codons 12 were demonstrated for AML cell line Rc2a. Moreover, using a rapid and sensitive dot-blot screening procedure based on the combination of in vitro amplification of ras specific sequences and oligonucleotide hybridization we could show that ras gene activation was not present in primary leukemic cells of the patient this cell line had been derived from, but rather occurred during later passages of Rc2a.

Animals↗
PubMed1987

Polymer support synthesis. XII. Derivatization with the 4-decyloxytrityl group as an aid in the affinity chromatography of oligo- and polynucleotides.

In a continuation of previous studies on trityl groups substituted with long alkyl chains as affinity-protecting groups for oligonucleotides, the use of the (4-decyloxyphenyl)diphenylmethyl (DTr) group as an aid in the separation of solid-phase products has been investigated. This substituent, which can be introduced and removed from the 5'-position in a similar manner to the di-p-anisylphenylmethyl group, helps in the purification of deoxypolynucleotides with up to 140 bases. Their retention time was shown to depend not only on the length of the nucleotide chain and alkyl substituent, but also on the elution gradient rate. In oligoribonucleotide synthesis, the DTr group allows the purification of partially protected sequences, which are more stable to enzymatic degradation and, therefore, more suitable for handling and storage.

Chromatography, Affinity↗
PubMed1987

RAS gene mutations in acute and chronic myelocytic leukemias, chronic myeloproliferative disorders, and myelodysplastic syndromes.

We report on investigations aimed at detecting mutated RAS genes in a variety of preleukemic disorders and leukemias of myeloid origin. DNA transfection analyses (tumorigenicity assay) and hybridization to mutation-specific oligonucleotide probes established NRAS mutations in codon 12 or 61 of 4/9 acute myelocytic leukemias (AML) and three AML lines. Leukemic cells of another AML patient showed HRAS gene activation. By using a rapid and sensitive dot-blot screening procedure based on the combination of in vitro amplification of RAS-specific sequences and oligonucleotide hybridization we additionally screened 15 myelodysplastic syndromes, 26 Philadelphia chromosome-positive chronic myelocytic leukemias in chronic or acute phase, and 19 other chronic myeloproliferative disorders. A mutation within NRAS codon 12 could thus be demonstrated in a patient with idiopathic myelofibrosis and in another with chronic myelomonocytic leukemia. Moreover, mutated NRAS sequences were detected in lymphocytes, in granulocytes, as well as in monocytes/macrophages of the latter case.

DNA, Neoplasm↗
PubMed1981

Specifically primed synthesis in vitro of full-length DNA complementary to potato-spindle-tuber viroid.

Potato spindle tuber viroid (PSTV) RNA is transcribed in vitro by reverse transcriptase into complementary DNA in the presence of synthetic oligodeoxyribonucleotides as primers. In the case of priming with the pentadecadeoxyribonucleotide d(T-T-C-T-T-T-T-T-T-C-T-T-T-T-C) complementary to PSTV RNA from nucleotides 49 to 63, specificity of transcription initiation allows rapid sequencing of part of the viroid genome using chain-terminating dideoxyribonucleoside triphosphates. The DNA transcripts obtained represent distinct molecular species with the largest product being a full-length copy of the viroid RNA template. Molecular hybridization with 32P-labeled complementary DNA detects sequence homologies among different viroid species.

Base Composition↗
PubMed1981

Viroid structure.

Explore the source record for details and available documents.

Base Composition↗
PubMed1980

Preparation of immobilized phosphodiesterase from calf spleen and its use in oligonucleotide analysis.

The phosphodiesterase from calf spleen (EC 3.1.4.18) was immobilized on several supports. Some properties of the most suitable enzyme support system--calf spleen phosphodiesterase bound to agarose-Concanavalin A--were investigated, e.g., pH dependence, influence of ionic strength of the buffer medium, and Zn2+-ion inhibition. The immobilized spleen phosphodiesterase showed about 60% of the activity of the free enzyme; the activity toward several oligonucleotide test substrates was unchanged for two months.

Animals↗
PubMed1980

10-Hydroxy-3,4-dihydroacridine-1,9(2H,10H)-diones, a new group of malaricidal and coccidiostatic compounds.

2-Nitrobenzaldehydes and 1,3-cyclohexanediones condense in a mixture of hydrochloric acid and glacial acetic acid to 10-hydroxy-3,4-dihydroacridine-1,9(2H,10H)-diones. Many compounds of this group reveal a pronounced coccidiostatic and malaricidal effect in vivo even against drug-resistant malaria parasites. Synthesis and chemotherapeutic results as well as structure-activity relationships are described.

Acridines↗
PubMed1980

Non-stepwise methods in the preparation of building blocks for polynucleotide synthesis.

Oligonucleotide fragments of the general sequence ABn, BnC and ABnC as building units for polynucleotide synthesis can be obtained by three types of reactions, namely the sequence-specific co-condensation of nucleic acid constituents, the sequence-specific degradation of copolymers and the limited addition of nucleotides to primers. Examples for these reactions are described and the scope and application of the approach discussed.

Base Sequence↗
PubMedDate not supplied

Synthesis of oligodeoxynucleotides containing N4-mercaptoethylcytosine and their use in the preparation of oligonucleotide-peptide conjugates carrying c-myc tag-sequence.

The preparation and properties of oligodeoxynucleotides containing mercaptoethyl groups at position N-4 of cytosine are described. The resulting thiol-oligodeoxynucleotides were reacted with a maleimido-peptide carrying the c-myc tag-sequence. The peptide-oligonucleotide conjugate is specifically recognized by an anti c-myc monoclonal antibody, thus constituting a labeling system with sensitivity similar to other existing methods of nonradioactive labeling.

Antibodies, Monoclonal↗
PubMedDate not supplied

Synthesis and properties of 2'-deoxycytidine triphosphate carrying c-myc tag sequence.

The synthesis of 2'-deoxycytidine triphosphate carrying mercaptoethyl groups at position 4 of cytosine is described. This nucleoside triphosphate was reacted with a maleimido-peptide carrying the c-myc tag-sequence to yield a peptide-nucleoside triphosphate chimera. Primer extension studies showed that the nucleoside triphosphate modified with the peptide sequence is incorporated by DNA polymerases opposite guanine.

Amino Acid Sequence↗