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V Steiner

Publications and source records attributed to V Steiner.

25 records · Page 2Linked to original sources
PubMed1990

Isolation and purification of novel hirudins from the leech Hirudinaria manillensis by high-performance liquid chromatography.

The isolation and purification of novel hirudins from a crude extract of the leech Hirudinaria manillensis and their analytical characterization are reported. Initial purification by gel permeation chromatography on Sephadex G50 and anion-exchange chromatography on Q Sepharose fast-flow removed most contaminants and yielded a highly active extract. Two isohirudins (designated hirudin P6 and P18) were isolated and purified by successive reversed-phase high-performance liquid chromatography on silica-based stationary phases and anion-exchange chromatography on Mono Q. The final products were characterized by reversed-phase high-performance liquid chromatography, 252Cf plasma desorption time-of-flight mass spectrometry and capillary zone electrophoresis. The molecular masses determined by 252Cf plasma desorption mass spectrometry were 7416 dalton for hirudin P6 and 7199 dalton for hirudin P18.

Amino Acids↗
PubMed1987

Chemical modification of the carboxyl groups of protein substrates enhances their thrombin susceptibility.

Native or denatured protein substrates which are hardly digested by thrombin can become much more efficiently cleaved by the enzyme after chemical modification of their carboxyl groups. Five antibody kappa-chains were used to demonstrate this effect. The selective cleavage sites were determined by quantitative N-terminal analysis and N-terminal sequencing. All five kappa-chains share the same cleavage sites at Arg-Thr (residues 108-109), Arg-Glu (residues 142-143, Glu side chain modified with glycine amide), Lys-Ser (residues 207-208) and Arg-Gly (residues 211-212). One of the major cleavage sites (Arg-Thr) is located at the joint of the variable/constant region. The amino acids adjacent to these cleavage sites underline the proposed structural requirements for a potential thrombin substrate [(1985) Eur. J. Biochem. 151, 217-224]. This approach can facilitate the application of thrombin in generating large polypeptide fragments of proteins.

Amino Acid Sequence↗
PubMed1982

Population pharmacokinetic parameters in patients treated with oral mexiletine.

A new data analysis approach, NON-MEM, proposed by Sheiner and Beal, has been employed to estimate the population pharmacokinetic parameters of oral mexiletine in patients treated for arrhythmias. 452 serum concentration measurements in 58 patients were available for analysis. 27 patients had congestive heart failure and 8 had abnormal liver function tests at the time of the study. The population averages of the pharmacokinetic parameters and their interindividual variability were: oral total body clearance (Cl) 0.38 l/h/kg +/- 43% (C.V.), apparent volume of distribution (Vd) 5.3 l/kg +/- 40%, absorption rate constant 3.1 h-1 +/- 205%, absorption time-lag 0.3 h. Congestive heart failure and sex did not show a significant effect on Cl and Vd; the number of patients with severe liver function impairment was too small for a definite conclusion. Normalizing Cl and Vd for body weight significantly decreased their interindividual variability. Based on these results, a dosage regimen is recommended which is expected to produce a "therapeutic" serum concentration (0.8-2 mg/l) in over 60% of patients. Because of its unique features, which allow estimation of pharmacokinetic parameters and their variability from fragmentary patient data, the NONMEM system has great potential applicability to clinical pharmacokinetic studies.

Aged↗
PubMedDate not supplied

Analysis of synthetic peptides using matrix-assisted laser desorption ionization mass spectrometry.

Matrix-assisted laser desorption ionization mass spectroscopy (LDI MS), a novel method for analysis of large molecules, has been used for characterization of synthetic peptides and their by-products. The potential of LDI MS is demonstrated by analyzing crude synthetic peptides representing typical members of newly designed peptides and proteins. In the first case, a fragment condensation reaction yielding a highly hydrophobic six-helic bundle template-assembled synthetic protein (TASP) is monitored. Then, a crude 19-mer peptide designed to adopt an amphiphilic alpha-helical structure and its by-products from SPPS are identified. Finally, analysis of crude hirulog-1, a 20-mer peptide designed as a thrombin inhibitor, using C18 reversed phase high performance liquid chromatography (RP HPLC), capillary electrophoresis (CE) and LDI MS, manifests the potential of the latter method.

Amino Acid Sequence↗