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Biomedical subjects

C H Lochmüller

Publications and source records attributed to C H Lochmüller.

8 recordsLinked to original sources
PubMed1999

Separation of nucleotide oligomers by unitary anion-exchange.

This paper is the first report on the retention behavior of synthetic oligonucleotides and nucleotide oligomers on a continuous-bedmatrix, strong-anion-exchange column. The separation mechanism is predominantly an anion-exchange process, but hydrophobic interaction plays a role as well. The separation is based on the chain length of the oligonucleotide. Both the addition of organic mobile phase modifiers and changes in column temperature affect the retention of oligomers significantly. A volatile buffer system (e.g., triethylamine acetate) could be employed to purify oligonucleotides, and no desalting procedure would be required after the column separation step. The recoveries from the separation are 70% or higher. The maximum loading capacity of an analytical column (35 x 7-mm i.d.) was found to be more than 366 micrograms.

Anion Exchange Resins↗
PubMed1978

Kinetics and mechanism of dissociation of zinc ion from carbonic anhydrase.

The kinetics of dissociation of Zn2+ from the metalloenzyme carbonic anhydrase was measured over a range of pH, temperature, and acetate concentration. The rate of dissociation is extremely slow at neutral pH (t1/2 approximately 3) years, 4 degrees C), but increases in almost direct proportion to the hydrogen ion concentration and is enhanced in the presence of 1,10-phenanthroline or acetate. The thermodynamic stability of the zinc-apoenzyme complex was determined over a range of pH from rate data on binding and dissociation (stability constants 10(9)-10(11) M-1, 25 degrees C). The great stability of the complex and slow exchange of the apoenzyme ligand is attributed, at least in part, to the rigidity of the multidentate protein ligand.

Apoenzymes↗
PubMed1977

A systematic approach to thermal conductivity detector design I. Use of computer-aided data acquisition for the evaluation of cell contributions to peak shape.

The design of thermal conductivity detectors for open tubular gas chromatography was systematically investigated with the aid of modern digital data acquisition techniques. Two important factors in such a design are sensitivity and peak broadening. The latter factor was the principle thrust of this work and contributions to peak shape from both cell design and volume were analyzed by the method of statistical moments. Peak variance (the mean square displacement along the x-axis of a chromatographic peak) was shown to correlate directly with cell volume in cells of the same design but both variance and asymmetry were found to be design dependent.

Chromatography, Gas↗
PubMed1975

Chromatographic resolution of enantiomers selective review.

Recent research has produced a notable increase in knowledge useful for chromatographic enantiomer resolution. Some major advances have emerged in the understanding of asymmetric solute-solvent interactions, and many successful separations by gas and by liquid chromatography have been reported. This review presents a selective discussion of the major advances, with primary emphasis on the use of chiral stationary phases. The latter offer advantages (over indirect techniques) such as generally easier sample preparation, decreased analysis time, and simultaneous chemical as well as optical purity analysis.

Amino Acids↗
PubMed1975

13-C nuclear magnetic resonance studies on the mechanism of action of carbonic anhydrase.

Binding of the substrate, bicarbonate, to bovine cobalt carbonic anhydrase (carbonate hydrolyase, EC 4.2.1.1) has been studied with 13-C nuclear magnetic resonance. Two binding sites for bicarbonate have been identified. One loosely binds bicarbonate, inhibits p-nitrophenyl acetate activity, and must be the bicarbonate substrate binding site; the other tightly binds bicarbonate, is noninhibitory, and plays another role. Spinlattice relaxation times for the carbon atom of bicarbonate indicate that the substrate bicarbonate is bound directly to the metal center of the enzyme, while the other bicarbonate is bound in the outer coordination sphere of the metal. It is proposed that dehydration proceeds via HCO-3 minus coordinated directly to the metal center, while the outer sphere bicarbonate facilitates catalytically important proton transfers.

Animals↗