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String tension and stability of magic tip-suspended nanowires.

Multishell helical gold nanowires were recently imaged by electron microscopy. We show theoretically that the contact with the gold tips at either end of the wire plays a crucial role and that local minima in the string tension rather than the total wire free energy determine the nanowire stability. Density functional electronic structure calculations of the simplest and thinnest coaxial gold and silver wires of variable radius and chirality were carried out. We found a string tension minimum for a single-tube gold nanowire that is chiral and consists of seven strands, in striking agreement with observation. In contrast, no such minimum was found for silver, where the s-d competition leading to surface reconstruction is lacking.

Journal Article↗

Antisense oligonucleotides as therapeutic agents--is the bullet really magical?

Because of the specificity of Watson-Crick base pairing, attempts are now being made to use oligodeoxynucleotides (oligos) in the therapy of human disease. However, for a successful outcome, the oligo must meet at least six criteria: (i) the oligos can be synthesized easily and in bulk; (ii) the oligos must be stable in vivo; (iii) the oligos must be able to enter the target cell; (iv) the oligos must be retained by the target cell; (v) the oligos must be able to interact with their cellular targets; and (vi) the oligos should not interact in a non-sequence-specific manner with other macromolecules. Phosphorothioate oligos are examples of oligos that are being considered for clinical therapeutic trials and meet some, but not all, of these criteria. The potential use of phosphorothioate oligos as inhibitors of viral replication is highlighted.

Animals↗

Susceptibility testing of anaerobic bacteria: myth, magic, or method?

The demand for susceptibility testing of anaerobes has increased, yet consensus as to procedure and interpretation in this area has not been achieved. While routine testing of anaerobic isolates is not needed, certain isolates in specific clinical settings should be tested. Also, laboratories may monitor their local antibiograms by doing periodic surveillance batch testing. The National Committee for Clinical Laboratory Standards has published a protocol of methods approved for susceptibility testing of anaerobic bacteria. Both agar and broth microdilution are included; however, the broth disk elution method is no longer approved by the National Committee for Clinical Laboratory Standards because of method-related interpretive errors. A number of newer methods are undergoing evaluation and seem promising. Clinicians and microbiologists reviewing susceptibility reports should be aware of sources of variability in the test results. Variables in susceptibility testing of anaerobes include the media and methods used, organisms chosen for testing, breakpoints chosen for interpretation, antibiotic, and determination of endpoint. Clustering of MICs around the breakpoint may lead to significant variability in test results. Adherence of testing laboratories to approved methods and careful descriptions of the method and the breakpoints used for interpretation would facilitate interlaboratory comparisons and allow problems of emerging resistance to be noted. A variety of resistance mechanisms occurs in anaerobic bacteria, including the production of beta-lactamase and other drug-inactivating enzymes, alteration of target proteins, and inability of the drug to penetrate the bacterial wall. Antimicrobial resistance patterns in the United States and abroad are described.

Animals↗