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Biomedical subjects

W Weinmann

Publications and source records attributed to W Weinmann.

26 records · Page 2Linked to original sources
PubMed1994

Isolation of hydrophobic lipoproteins in organic solvents by pressure-assisted capillary electrophoresis for subsequent mass spectrometric characterization.

Two capillary electrophoretic (CE) separation techniques with either simultaneous solvent flow induced by hydrostatic pressure or CE followed by low pressurization with helium were developed for the analysis of extremely hydrophobic proteins, such as the lung surfactant protein SP-C. For both related procedures, buffer solutions containing up to 70% of 2-propanol were used for the capillary electrophoretic separation. This high concentration of organic co-solvent, needed to solubilize the protein, dramatically reduces the electroosmotic flow (EOF) in aminopropyltrimethoxysilane-treated fused-silica capillaries. Because the EOF was insufficient to elute the separated analytes from the capillary, two "pressure-assisted" CE techniques were developed. An additional flow to elute the separated analytes was produced either by raising the inlet of the capillary or by helium pressure. Using the pressurization procedure a baseline separation of the SP-C protein and its dimeric complex was obtained in a 55-minute electrophoretic run, followed by pressure elution of the analyte to the detector. The present combination of pressurization and capillary electrophoresis does not require any detergents or involatile buffer additives, which are usually needed to solubilize extremely hydrophobic lipoproteins. It is therefore applicable to on-line coupling with electrospray mass spectrometry for the direct structural characterization of hydrophobic proteins.

Amino Acid Sequence↗
PubMed1994

Capillary electrophoresis combined with 252Cf plasma desorption and electrospray mass spectrometry for the structural characterization of hydrophobic polypeptides using organic solvents.

Capillary electrophoresis (CE) conditions have been developed for the separation of hydrophobic polypeptides, such as fatty acid-acylated peptides, and their subsequent structural identification by 252Cf plasma desorption (PDMS) and electrospray mass spectrometry (ESMS). Salt- and detergent-free aqueous acetic acid buffers containing up to 20% 2-propanol or 25% acetonitrile were employed for CE separations of hydrophobic peptides with (i) untreated, and (ii) 3-aminopropyltrimethoxysilane-derived fused silica capillaries. For both capillary types, electroosmotic flow rates suitable for sample isolation and transfer were determined, and CE separations of polypeptide mixtures were compared for aqueous buffers containing 2-propanol or acetonitrile. For the mass spectrometric identification of CE-separated peptides, a sheath flow sample isolation method was developed for subsequent transfer to PDMS. This procedure enabled the efficient isolation of peptide fractions for PDMS analysis, or alternative microanalytical techniques.

Amino Acid Sequence↗
PubMed1993

Structural characterization of polypeptides and proteins by combination of capillary electrophoresis and (252)Cf plasma desorption mass spectrometry.

An efficient and sensitive method for the isolation and transfer of peptides and proteins from capillary zone electrophoresis separation for subsequent analysis by 252Cf plasma desorption mass spectrometry was developed. Sample isolation on to nitrocellulose-coated targets for mass spectrometric analysis is performed by using a stainless-steel microtube pre-filled with aqueous buffer solution, to which the capillary end is connected, and the peptide is collected by applying a suitable transfer voltage according to the separation voltage. Low-and sub-picomolar sample amounts were isolated with high transfer efficiency and reproducibility, without the necessity for independent determination of electroosmotic flow-rates. Plasma desorption mass spectra of several peptides and proteins showed predominantly intact molecular ions; however, for several peptides partial oxidative modification was found which can be accounted for by the electrophoretic separation and/or transfer conditions. First applications to peptides and proteins show the feasibility of this off-line combination for primary structure characterization, such as by in situ chemical modification and enzymatic proteolysis reactions on the sample target prior to mass spectrometric analysis.

Amino Acid Sequence↗
PubMed1983

Safety and potency aspects in the preparation of an experimental HBsAg vaccine.

No experimental setting is available to exclude residual infectivity in HBsAg vaccines derived from human plasma. Thus, safety can be achieved only by means of their preparation. To reduce infectivity of the starting material, only plasma from healthy anti-HBe positive donors was used. In the FRG, 50% of all healthy HBsAg carriers with anti-HBe have a suitable serum level of 5 to 20 micrograms/ml. The purification procedure removed hepatitis B virus by a factor greater than 10(4). The purified product contained only the HBsAg proteins and no serum protein, as shown by SDS gel electrophoresis. The pure HBsAg was treated with formalin 1:500 at 37 degrees C for 4 days. A loss of 30 to 50% antigenicity was tolerated to achieve the highest possible destruction of known and unknown infectious agents. After inactivation, the HBsAg was bound to aluminium hydroxide gel. The gel was washed repeatedly to remove the formalin. Doses of 40 micrograms or 20 micrograms absorbed HBsAg protein were given to greater than 2500 persons without serious side effects. In greater than 97% anti-HBs was formed with a median titer of 1900 I.U./ml.

Follow-Up Studies↗
PubMedDate not supplied

Fast screening for drugs of abuse by solid-phase extraction combined with flow-injection ionspray-tandem mass spectrometry.

A fast analytical approach for the simultaneous quantitative screening for illicit drugs in serum and urine without tedious chromatographic separation steps was developed by combining solid-phase extraction (SPE) followed by flow-injection analysis (FIA) with ionspray-ionization and tandem mass spectrometry (MS-MS) detection using a PE Sciex API 300 triple-quadrupole MS. MS-MS analysis was performed by sequentially isolating the precursor ions of the analytes and their deuterated standards with subsequent fragmentation and monitoring of one fragment ion for each substance. A multiple-reaction monitoring experiment was set up for morphine (MO), codeine (COD), amphetamine (AMP), benzoylecgonine (BZE), and their deuterated analogues. For method evaluation, serum samples spiked with 2-1000 ng of each drug and deuterated standards were extracted by mixed-mode SPE, redissolved in CH3CN-NH4OAc-buffer, and directly injected by flow injection into the ionspray source. The specificity of this new method was demonstrated by testing compounds with similar chemical structure for interferences from the analytes of interest (e.g., dihydromorphone, morphine glucuronide, and 6-monoacetylmorphine with MO; dihydrocodeine and hydrocodone with COD; cocaine [COC] and ecgonine methylester with BZE; methamphetamine with AMP). The possibility of interferences of such compounds with the FIA-ionspray-MS-MS screening method is discussed. Spiked serum samples and serum and urine samples from drug addicts and victims of drug abuse were analyzed with FIA-MS-MS and, after derivatization, with gas chromatography-mass spectrometry (GC-MS). Comparable quantitative results were obtained with both methods; no interferences with metabolites or other compounds were found. The FIA-ionspray-MS-MS method is a fast, quantitative, sensitive, and highly specific alternative method to drug-screening by immunoassays, high-performance liquid chromatography, and GC-MS. It can be used for the simultaneous detection of different drugs and metabolites such as opiates, COC, AMP derivatives, and many other drugs.

Chromatography, Gas↗
PubMedDate not supplied

[Plastic bag as the method in suicide and homicide].

The report describes a suicide and a homicide by suffocation in a plastic bag. Both cases were copy-cat acts. The suicide copied the method--taking medicines and pulling a plastic bag over his head from a personal model. In the homicide the perpetrator followed the example of a film sequence from the US feature film "Charade".

Adult↗