26 research outputs found
Validating a screening agar for linezolidresistant enterococci
Background: Linezolid is an alternative treatment option for infections with multidrug-resistant Gram-positive bacteria
including vancomycin-resistant enterococci. Some countries report an increasing number of isolates with resistance to
linezolid. The recent publication of the Commission for Hospital Hygiene in Germany on enterococci/VRE recommends
screening for linezolid-resistant enterococci (LRE). However, a suitable selective medium or a genetic test is not
available. Our aim was to establish a selective screening agar for LRE detection and validate its application with a
comprehensive collection of clinical LRE and linezolid-susceptible enterococci.
Methods: We decided to combine the selective power of an enterococcal screening agar with a supplementation of
linezolid. Several rounds of analyses with reference, control and test strains and under varying linezolid concentrations
of a wider and a smaller range were investigated and assessed. The collection of linezolid-resistant enterococcal control
strains included isolates with different resistance mechanisms (23S rDNA mutations, cfr(B), optrA, poxtA). Finally, we
validated our LRE screening agar with 400 samples sent to our National Reference Centre in 2019.
Results: Several rounds of pre-tests and confirmatory analyses favored Enterococcosel® Agar supplemented with a
concentration of 2 mg/L linezolid. A 48 h incubation period was essential for accurate identification of LRE strains.
Performance of the LRE screening agar revealed a sensitivity of 96.6% and a specificity of 94.4%.
Conclusions: Here we describe preparation of a suitable screening agar and a procedure to identify LRE isolates with
high accuracyPeer Reviewe
Amine-Linked Single Molecule Circuits: Systematic Trends Across Molecular Families
A comprehensive review is presented of single molecule junction conductance
measurements across families of molecules measured while breaking a gold point
contact in a solution of molecules with amine end groups. A theoretical
framework unifies the picture for the amine-gold link bonding and the tunnel
coupling through the junction using Density Functional Theory based
calculations. The reproducible electrical characteristics and utility for many
molecules is shown to result from the selective binding between the gold
electrodes and amine link groups through a donor-acceptor bond to
undercoordinated gold atoms. While the bond energy is modest, the maximum force
sustained by the junction is comparable to, but less than, that required to
break gold point contacts. The calculated tunnel coupling provides conductance
trends for all 41 molecule measurements presented here, as well as insight into
the variability of conductance due to the conformational changes within
molecules with torsional degrees of freedom. The calculated trends agree to
within a factor of two of the measured values for conductance ranging from 10-7
G0 to 10-2 G0, where G0 is the quantum of conductance (2e2/h).Comment: Invited paper for forthcoming special issue of Journal of Physics:
Condensed Matte
Single-Molecule Circuits with Well-Defined Molecular Conductance
We measure the conductance of amine-terminated molecules by breaking Au point
contacts in a molecular solution at room temperature. We find that the
variability of the observed conductance for the diamine molecule-Au junctions
is much less than the variability for diisonitrile and dithiol-Au junctions.
This narrow distribution enables unambiguous conductance measurements of single
molecules. For an alkane diamine series with 2-8 carbon atoms in the
hydrocarbon chain, our results show a systematic trend in the conductance from
which we extract a tunneling decay constant of 0.91 +/- 0.03 per methylene
group. We hypothesize that the diamine link binds preferentially to
undercoordinated Au atoms in the junction. This is supported by density
functional theory-based calculations that show the amine binding to a gold
adatom with sufficient angular flexibility for easy junction formation but
well-defined electronic coupling of the N lone pair to the Au. Therefore, the
amine linkage leads to well-defined conductance measurements of a single
molecule junction in a statistical study
Is the future female? troubled thoughts on contemporary feminism
Book synopsis: The author challenges many feminist orthodoxies - on female sexuality, pornography, war and peace, psychanalysis and sociobiology. She argues against the exponents - such as Mary Daly, Andrea Dworkin and Dale Spender - of apocalyptic feminism, which says that men wield power over women through terror, greed and violence and that only women, because of their essentially greater humanity can save the world from social, ecological and nuclear disaster. Segal urges that to base the politics of feminism on innate and essential differences between men and women is mistaken, dangerous, and basically a counsel of despair, since its logical conclusion is that nothing can change. Things emphatically have changed for women, she asserts, and we must build on these changes, combining autonomy with alliances to alter power relations and forge a new future for both women and men
Recommended from our members
Mechanism of DNA compaction by yeast mitochondrial protein Abf2p.
We used high-resolution atomic force microscopy to image the compaction of linear and circular DNA by the yeast mitochondrial protein Abf2p, which plays a major role in packaging mitochondrial DNA. Atomic force microscopy images show that protein binding induces drastic bends in the DNA backbone for both linear and circular DNA. At a high concentration of Abf2p DNA collapses into a tight nucleoprotein complex. We quantified the compaction of linear DNA by measuring the end-to-end distance of the DNA molecule at increasing concentrations of Abf2p. We also derived a polymer statistical mechanics model that provides a quantitative description of compaction observed in our experiments. This model shows that sharp bends in the DNA backbone are often sufficient to cause DNA compaction. Comparison of our model with the experimental data showed excellent quantitative correlation and allowed us to determine binding characteristics for Abf2p. These studies indicate that Abf2p compacts DNA through a simple mechanism that involves bending of the DNA backbone. We discuss the implications of such a mechanism for mitochondrial DNA maintenance and organization
Mechanism of DNA Compaction by Yeast Mitochondrial Protein Abf2p
We used high-resolution atomic force microscopy to image the compaction of linear and circular DNA by the yeast mitochondrial protein Abf2p, which plays a major role in packaging mitochondrial DNA. Atomic force microscopy images show that protein binding induces drastic bends in the DNA backbone for both linear and circular DNA. At a high concentration of Abf2p DNA collapses into a tight nucleoprotein complex. We quantified the compaction of linear DNA by measuring the end-to-end distance of the DNA molecule at increasing concentrations of Abf2p. We also derived a polymer statistical mechanics model that provides a quantitative description of compaction observed in our experiments. This model shows that sharp bends in the DNA backbone are often sufficient to cause DNA compaction. Comparison of our model with the experimental data showed excellent quantitative correlation and allowed us to determine binding characteristics for Abf2p. These studies indicate that Abf2p compacts DNA through a simple mechanism that involves bending of the DNA backbone. We discuss the implications of such a mechanism for mitochondrial DNA maintenance and organization
Water-Assisted Growth of Uniform 100 mm Diameter SWCNT Arrays
We report a simple method for growing
high-quality single-walled
carbon nanotube (SWCNT) arrays on 100 mm wafers via the addition of
water vapor to highly purified gases during the CNT growth step. We
show that adding a small amount of water during growth helps to create
a uniform catalyst distribution and yields high-quality (Raman G/D
of 26 ± 3), high-density (up to 6 × 10<sup>11</sup> cm<sup>–2</sup>) and uniform SWCNT arrays on 100 mm large wafers.
We rationalize our finding by suggesting that the addition of water
decreases catalyst mobility, preventing its coarsening at higher temperatures.
We also report a new mechanism of catalyst inactivation in wafer-scale
growth using ultrapurified gas sources by the formation of large,
5 ± 3 μm iron particles. We found such formations to be
common for substrates with large temperature gradients, such as for
wafers processed in a typical cold-wall chemical vapor deposition
reactor