Biomedical subjects

Anton Hartmann

Publications and source records attributed to Anton Hartmann.

21 records · Page 2Linked to original sources

PubMed2003

A simple and robust set-up for on-column sample preconcentration--nano-liquid chromatography--electrospray ionization mass spectrometry for the analysis of N-acylhomoserine lactones.

A simple method for the simultaneous, rapid and sensitive determination of N-acylhomoserine lactone signaling molecules in bacterial isolates, without prior sample preconcentration and with minimal sample cleanup, is presented. The analysis relies on the combination of analyte preconcentration and separation on a single device: a relatively large sample volume (1-5 microL) is directly loaded onto a laboratory-made, miniaturized (75 microm i. d.) reverse phase nano-liquid chromatography column, connected on-line to a microelectrospray-ionization ion trap mass spectrometer. In a first step the analyte is adsorbed (and so concentrated) at the beginning of the column, and is eluted and selectively separated in a second step by the organic mobile phase. Sample preconcentration follows the mechanisms of solid phase extraction on a nano-scale, while separation takes place according to classical liquid chromatography separation principles. The columns can be manufactured easily, are simply connected, and used with minimal solvent amounts; this makes this method extremely robust and cost-effective. The analytical setup was found to be routinely quantitative down to a concentration of 10 ng/mL (corresponding to a total analyte amount of 10 pg or ca. 50 fmol). The limit of detection was reached at 1 ng/mL (1 pg, ca. 5 fmol). Compared to the classical AHL analysis of bacterial cultures with biosensors, where selectivity and sensitivity is often limited, this rapid analytical technique is a substantial qualitative and quantitative improvement. Two unsubstituted N-acylhomoserine lactones could be identified and quantified from a Burkholderia cepacia culture supernatant in a chloroform extract.

4-Butyrolactone↗

PubMed2003

Analysis of N-acyl-L-homoserine lactones produced by Burkholderia cepacia with partial filling micellar electrokinetic chromatography--electrospray ionization-ion trap mass spectrometry.

A method for the analysis of N-acyl-L-homoserine lactones (AHLs) with micellar electrokinetic chromatography coupled to electrospray ionization-ion trap mass spectrometry, combining the flexibility of capillary electrophoresis with the unmatched structural information provided by mass spectrometry is presented. Different surfactants were evaluated, with sodium dodecyl sulfate (SDS) yielding the best results considering sensitivity and flexibility. We examined the interaction of AHLs with the SDS micelles at different analysis conditions and applied the optimized method to the analysis of a real bacterial sample. Two AHLs from Burkholderia cepacia colonizing the rhizosphere of traditional Indian rice cultivars could be unambiguously determined in an ethyl acetate extract with high resolution flexibility.

4-Butyrolactone↗

PubMed2003

Detection methods for the expression of the dissimilatory copper-containing nitrite reductase gene (DnirK) in environmental samples.

In situ assays, based on monoclonal antibodies (mAbs), were developed to study the microbial expression of the bacterial dissimilatory copper-containing nitrite reductase gene (DnirK), one of the key enzymes involved in denitrification, in different ecosystems. With a combination of an anti-DnirK mAb and phylogenetic oligonucleotide probes, it is possible to bring structural and functional aspects of microbial communities together. To perform a double labelling, yielding a high signal strength for both the oligonucleotide and the antibody, cells have to be labelled with the oligonucleotide first followed by immunostaining. When the labelling sequence was changed, the accessibility for the oligonucleotide was reduced if high amounts of DnirK were expressed. Using flow cytometry, it was possible to sort bacterial cells, which were stained by the antibody, from nonlabelled cells. This technique provides means for a detailed analysis of populations, which express DnirK genes in the environment, including structural aspects of a community and detailed promoter studies. Using the immunostaining approach, it was possible to identify bacteria, which have the DnirK system expressed, in samples from a wastewater sewage treatment plant as well as in samples from the rhizosphere of wheat roots. Furthermore, expression studies using an Ochrobactrum anthropi strain were carried out to investigate the correlation between N(2)O production rates and DnirK expression in batch cultures, which had been shifted from aerobic to anaerobic conditions. As expected, expression of DnirK was the highest during periods with the greatest synthesis rates for N(2)O. However, the amount of expressed enzyme was not reduced in the cells, although the N(2)O production rates dropped in the cultures 12 h after the shift from aerobic to anaerobic conditions.

Antibodies, Monoclonal↗