We demonstrate the use of "holey" graphene as a mask against molecular adsorption. Prepared porous graphene is transferred onto a Au{111} substrate, annealed, and then exposed to dilute solutions of 1-adamantanethiol. In the pores of the graphene lattice, we find islands of organized, self-assembled molecules. The bare Au in the pores can be regenerated by postdeposition annealing, and new molecules can be self-assembled in the exposed Au region. Graphene can serve as a robust, patternable mask against the deposition of self-assembled monolayers.

The PX motif of DNA is a four-stranded structure in which two parallel juxtaposed double-helical domains are fused by crossovers at every point where the strands approach each other. Consequently, its twist and writhe are approximately half of those of conventional DNA. This property has been shown to relax supercoiled plasmid DNA under circumstances in which head-to-head homology exists within the plasmid; the homology can be either complete homology or every-other-half-turn homology, known as PX homology. It is clearly of interest to establish whether the cell contains proteins that interact with this unusual and possibly functional motif. We have examined Escherichia coli extracts to seek such a protein. We find by gel mobility studies that the PX motif is apparently bound by a cellular component. Fractionation of this binding activity reveals that the component is DNA polymerase I (Pol I). Although the PX motif binds to Pol I, we find that PX-DNA is not able to serve as a substrate for the extension of a shortened strand. We cannot say at this time whether the binding is a coincidence or whether it represents an activity of Pol I that is currently unknown. We have modeled the interaction of Pol I and PX-DNA using symmetry considerations and molecular dynamics.

Trimethoprim/sulfamethoxazole (TMP/SMZ) is considered the treatment of choice for infections caused by Stenotrophomonas maltophilia , but limited pharmacodynamic data are available to support current susceptibility breakpoints or guide optimal dosing. Time-kill studies using a TMP/SMZ concentration of 4/40 μg/mL were conducted to compare 4 S. maltophilia with 4 Escherichia coli having the same MICs (0.25/4.75-4/76 μg/mL) in cation adjusted Mueller Hinton Broth (CAMHB) and ISO-Sensitest™ broth (ISO). With the exception of the resistant isolates (4/76 μg/mL), which resulted in regrowth approaching control, TMP/SMZ displayed significantly greater killing for E. coli compared with S. maltophilia at each MIC. Against E. coli , mean changes at 24 hour were -4.49, -1.73, -1.59, and +1.83 log 10 colony forming units (CFU) for isolates with MICs of 0.25/4.75, 1/19, 2/39, and 4/74 μg/mL, respectively. The f AUC/MIC required for stasis, 1-log 10 , and 2-log 10 CFU reductions were 40.7, 59.5, and 86.3, respectively. In contrast, TMP/SMZ displayed no stasis or CFU reductions against any S. maltophilia regardless of MIC, and no pharmacodynamic thresholds were quantifiable. Observations were consistent in both CAMHB and ISO broth. These data add increasing evidence that current TMP/SMZ susceptibility breakpoints against S. maltophilia should be reassessed.