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Biomedical subjects

H Schott

Publications and source records attributed to H Schott.

At least 109 records · Page 6Linked to original sources
PubMed1981

Electrokinetic studies of magnesium hydroxide.

The electrophoretic mobility of magnesium hydroxide was studied as a function of the concentration of its potential-determining ions, namely, of the magnesium ions, and of the hydroxide ions or pH. The zero point of charge was located at approximately 10.8. The zeta-potential of magnesium hydroxide below this pH was positive. The addition of magnesium nitrate to magnesium hydroxide suspensions increased the positive zeta-potential and lowered the pH. The low solubility of magnesium hydroxide in water prevented the attainment of substantial concentrations of magnesium ions in solution. Increasing the hydroxide-ion concentration or the pH produced charge inversion. The largest negative zeta-potential was attained at pH 11.5. Further increases in pH produced no significant increase in the negative value of the zeta-potential.

Chemical Phenomena↗
PubMed1980

Separation and sequencing of the sequence isomers of pyrimidine deoxypentanucleoside tetraphosphates by high-performance liquid chromatography.

Chemical synthesis of DNA fragments with a defined sequence is extremely long and complex. A simpler alternative is isolation of fragments from partially hydrolysed DNA. Mixtures of sequence isomers of pyrimidine oligonucleotides were recently isolated on a preparative scale from hydrolysates of depurinated herring sperm DNA. These, however, could not be further separated by conventional techniques. Using high-performance liquid chromatography (HPLC), sequence isomers of pyrimidine di-, tri- and tetranucleotides were successfully separated and sequenced. In the present work, separation and sequencing of sequence isomers of pyrimidine pentanucleotides by HPLC was achieved, demonstrating the applicability of this particular approach in preparation of desired DNA fragments.

Animals↗
PubMed1980

[Preparative isolation of deoxyriboadenylic acids from hydrolysates of oxidized herring-sperm DNA using template-chromatography (author's transl)].

The alkaline hydrolysis of oxidized DNA from herring sperm yields a complex mixture of deoxyriboadenylic acids. After the removal of the fragments containing 1-3 monomer units by column chromatography, approximately 10% of the partial hydrolysate remains. This remaining fraction which contains the fragments of higher molecular weight is separated into two fractions by the base-pairing mechanism on a PV(pT)n-DEAE-Cellulose column with a two-step temperature gradient. The first fraction eluted at -4 degrees, contains the substances (approximately equal to 95% of the sample) that undergo no base-pairing with the immobilised oligothymidylic acid units. The remaining 5% of the sample that hybridizes with PV(pT)n-DEAE-Cellulose at -4 degrees, is eluted at 30 degrees (fraction 2). After enzymatic dephosphorylation, homologues of deoxyriboadenylic acid containing up to 8 monomer units are isolated on a preparative scale in chromatographically pure form from fraction 2 using column chromatography. Purity and structure of the isolated adenylic acids are determined by paper chromatography and by enzymatic hydrolysis.

Animals↗
PubMed1980

Studies on interactions between immobilized lysine residues and oligomers of thymidylic and deoxyadenylic acids.

Two groups of crosslinked polyacrylic gels with immobilized lysine and lysine peptides (Lys)5 and (Lys)5-Pro have been used as models for the chromatographic investigation of lysine-peptide-oligonucleotide interactions. One group carries carboxylic groups in addition to the peptide residues in the gel matrix; the other gel type contains no such carboxylic groups in the gel matrix. Nucleotides of the series (dT)2-5, p(dT)1-4, p(dT)1-4p, (dA)2-5, p(dA)1-5 and p(dA)1-4p were chromatographed on these gels under various conditions in an aqueous buffer. On the gels of the first group the nucleotides were retarded only slightly, the positive charges of the epsilon-amino groups being compensated partially or totally by the negatively charged carboxyl groups of the polymer matrix. On the gels of the second group, however, the oligonucleotides underwent specific interactions. These interactions were based primarily upon electrostatic forces between the positively charged epsilon-amino groups of the immobilized peptides and the negatively charged phosphate groups of the oligonucleotides. Our results indicate that, in addition to the electrostatic interaction, the conformation plays a crucial role. We explain the selectivity of the interaction with a conformation-fit mechanism. The origin of this mechanism, which creates specific interactions from unspecific forces, is discussed.

Adenine↗
PubMed1980

Preparative isolation of oligonucleotides from chemically degraded DNA.

A simple alternative to complicated chemical synthesis of oligonucleotides is presented. Readily available DNA is partially hydrolyzed to preparative amounts of oligonucleotides using various methods. Chromatographically, pure defined pyrimidine and purine nucleotides, and/or mixtures of sequence isomers, are isolated on preparative scale from the various mixtures of oligonucleotides.

Animals↗
PubMed1979

[Preparative isolation of tri-, tetra-, penta- and hexapyrimidine nucleotides from hydrolysates of depurinated herring sperm DNA (author's transl)].

The pyrimidine nucleotides p(dC)3p, p(dT)3p and p(dT)4p and mixtures of the sequence isomers p(dC3, dT), (dC3, dT)p; p(dC3, dT)p; p(dC2, dT2)p; p(dC, dT3)p; p(dC3, dT2)p; p(dC2, dT3); p(dC2, dT3)p; p(dC, dT4)p; p(dC4, dT2); p(dC3, dT3); p(dC3, dT3)p and p(dC2, dT4)p have been isolated on a preparative scale from hydrolysates of depurinated herring sperm DNA. The DNA hydrolysate is first separated into a high- and a low-molecular weight pyrimidine nucleotide mixture by column chromatography at pH 7.5 on DEAE-cellulose. The high-molecular-weight pyrimidine nucleotide mixture is further separated into four peaks on QAE-Sephadex at pH 7.5. The second peak is re-chromatographed on QAE-Sephadex at pH 3.5. Pyrimidine nucleotides containing predominantly cytidylic acid units may thus be separated from these with predominantly thymidylic acid units. Subsequent separation according to number of phosphate groups at pH 7.5 on QAE-Sephadex yields products of 70--93% purity. In a final separation step, the pyrimidine nucleotides and mixtures of sequence isomers are once again chromatographed on QAE-Sephadex with 7 M urea at pH 7.5. The products thus obtained are generally chromatographically pure. Impurities which are not fully removed by column chromatography are separated by paper chromatography. The structure of the isolated DNA fragments and the composition of the mixtures of sequence isomers are determined from the chromatographic data, absorption characteristics and by enzymatic degradation.

Animals↗
PubMed1979

Osmolality/osmolarity data and calculations.

In view of the increasing interest in the osmolarity of parenteral solutions, an extensive compilation of pertinent numerical data is described. This compilation tabulates values of density, molar concentration, freezing point lowering,real osmolality, and molar concentration of the isotonic sodium chloride solution for 99 compounds, two-thirds of which are of use in pharmacy. A wide range of concentrations is covered for each compound, the values being listed in increments of 0.50, 1.00, or 2.00 percent w/w. Simple equations to convert molar into molal concentrations and to correlate freezing point lowering, osmotic pressure, osmolality and molality are presented. The practical use and theoretical meaning of the osmotic coefficient are discussed. As an example of a solution with several solutes, the real osmolality and osmolarity of Ringer's Solution is computed from the tabulated values of the freezing point depressions of the component salts.

Chemistry, Pharmaceutical↗
PubMed1979

[Determination of the interaction of oligopeptides and oligonucleotides by a chromatographic technique (author's transl)].

Homologues of deoxyriboadenylic and deoxyribothymidylic acid show different degrees of retardation in a pentalysine gel. This chromatographic retardation is directly related to the strength of the interaction between the oligonucleotides and the immobilized pentalysine peptide residues. The strength of this interaction is determined by the total negative charge of the oligonucleotide, and by the nature of the constituent base of the oligonucleotide. The specificity of the interaction depends upon differences in conformation of the oligonucleotides.

Chromatography, Gel↗
PubMed1978

[Gas gangrene].

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Gas Gangrene↗
PubMed1978

[Preparative isolation of deoxyriboadenylic acids from hydrolysates of oxidized herring sperm DNA (author's transl)].

The preparative-scale chemical degradation of DNA from herring sperm to mixtures of purine oligonucleotides or deoxyriboadenylic acids is described. The deoxyriboadenylic acid mixture was separated into six fractions according to increasing ionic charge by column chromatography on QAE-Sephadex A-25. Of the first fraction, 75% was deoxyriboadenosine monophosphate; of the second, 99% consisted of a mixture of p(dA)2 and (dA)2p, while of the third 93% was pdAp. The remaining fractions contained more or less complex mixtures of longer-chain oligonucleotides which could be further separated by subsequent re-chromatography on QAE-Sephadex at pH 9.6. By application of paper chromatography to the fractions obtained from column chromatography, the pure nucleotide phosphates pdAp, p(dA)2p, p(dA)3p, p(dA)4p and the mixtures of sequence isomers p(dA)2, (dA)2p; p(dA)3, (dA)3p; and p(dA)6, (dA)6p could be isolated preparatively. The nucleotide phosphates were converted to (dA)2, (dA)3 or (dA)4 and the mixtures of sequence isomers to (dA)2, (dA)3 or (dA)6 by treatment with alkaline phosphatase. By this means dephosphorylated, paper chromatographically pure oligodeoxyriboadenylic acid may be obtained in a preparative scale from the hydrolysates. The structures of the nucleotides thus isolated were deduced from the absorbtion characteristics, the RF values and the results of enzymatic degradation.

Animals↗