In situ surface‐enhanced Raman spectra of the headspace above cultures of six bacterial species showed strong characteristic bands from chemisorbed methyl sulfide. This marker compound is created by dissociation of dimethyl disulfide (DMDS), a fermentative metabolite of bacteria, on the surface of the enhancing Au or Ag nanoparticle films. Kinetic binding plots of media spiked with DMDS and of live cultures showed that the Au‐based substrates were more suitable for the rapid detection of bacteria than Ag‐based substrates. For E. coli DH5α, the sensitivity limit for headspace SERS detection was 1.5×107 CFU mL−1, which corresponded to detection 15 min after inoculation of the growth medium. Since the metabolites are only produced by viable bacteria, antibiotic (gentamicin) treatment stopped the normal signal growth of the marker peak. This work is a promising step towards rapid bedside detection of bacterial infections and rapid screening of antibiotics against bacteria.
Hydrogenolysis of bark from three different species of tree using heterogeneous platinum group metal catalysts produces two major product streams. Aromatic substituted guaiacols are produced from lignin and the lignin-like regions of suberin and a range of saturated fatty acids and alcohols, including α,ω-functionalised species, are produced from the polyester regions of suberin. Control experiments demonstrate clear advantages of catalytic hydrogenolysis over base hydrolysis, both in terms of conversion and product selectivity.
Ž. Background: Chronic heart failure CHF is characterised by increased vascular resistance. This increased after load on the left ventricle contributes to the vicious cycle that leads to progression of myocardial failure, multiple organ failure and death. There is evidence for increased oxidative stress in heart failure, which will influence the myocardium but also peripheral vasculature endothelium. Aims: The aim of the present study was to examine the production of isoprene, reputed to reflect oxidative stress, in patients with CHF compared to control subjects. Methods: Twelve patients with CHF and thirty-one healthy control subjects free from heart disease were studied. Breath was collected via a two-way non-re-breathing valve into a 60-l gas collection bag. A sample of ambient air was collected at the same time. A measured aliquot of patient breath and Ž . ambient air approx. 1.5 l was adsorbed onto a gas adsorption tube packed with poropak-Q. Isoprene was measured using GCrMS and the production rate calculated. All samples of breath were collected at 10.00 h after subjects had been sitting at rest for 15 min. Results: Breath isoprene production in subjects with CHF was significantly reduced compared to controls Ž . Ž . y1 y183 23 vs. 168 20 pmol min kg . Conclusion: Breath isoprene does not directly reflect oxidative stress in CHF.
In situ surface‐enhanced Raman spectra of the headspace above cultures of six bacterial species showed strong characteristic bands from chemisorbed methyl sulfide. This marker compound is created by dissociation of dimethyl disulfide (DMDS), a fermentative metabolite of bacteria, on the surface of the enhancing Au or Ag nanoparticle films. Kinetic binding plots of media spiked with DMDS and of live cultures showed that the Au‐based substrates were more suitable for the rapid detection of bacteria than Ag‐based substrates. For E. coli DH5α, the sensitivity limit for headspace SERS detection was 1.5×107 CFU mL−1, which corresponded to detection 15 min after inoculation of the growth medium. Since the metabolites are only produced by viable bacteria, antibiotic (gentamicin) treatment stopped the normal signal growth of the marker peak. This work is a promising step towards rapid bedside detection of bacterial infections and rapid screening of antibiotics against bacteria.
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