A suppression strategy for antibiotic discovery

High-throughput phenotype screening and target identification have been combined in an effort to isolate antimicrobial, small-molecule therapeutics. This approach, developed by Brown and colleagues and reported in this issue, is a major technological advance for antimicrobial drug discovery.     

Vinyl sulfones: inhibitors of SrtA, a transpeptidase required for cell wall protein anchoring and virulence in Staphylococcus aureus

Several small molecule vinyl sulfones were found to exhibit irreversible time-dependent inhibition of the Staphylococcus aureus sortase SrtA in vitro. A representative of these compounds was shown to impair the ability of S. aureus bacteria to bind fibronectin-coated surfaces through in vivo inhibition of SrtA-mediated linkage of fibronectin to the cell surface. These data highlight the potential use of small molecule vinyl sulfones as chemotherapeutics to prevent adhesion to and colonization of host tissues during S. aureus infection.     

Zur Trennung des Zinns von Arsen und Antimon

Ohne Zusammenfassung     

Excitation energy transport in fractal aggregates

A theory is developed to describe excitation energy transport in fractal aggregates. These fractal structures have densities which scale as a fractional power of the radius. Because of this, each donor is in a different environment with respect to donor and/or trap density. Consequently, ensemble averages cannot be performed using centro-symmetric coordinates. This problem has great similarities to the case of excitation energy transport in finite volumes. In this work the theory developed by Ediger and Fayer for the finite volume case is adapted to the fractal case. Förster limit (donor-trap transfer) and one-component (donor-donor transfer) systems are considered. Specific examples of Förster transfer are treated for the infinite size fractal, two-dimensional fractals and transfer from the aggregate to the excluded volume. A simple formalism for deriving expressions for the mean relaxation time of excitation is presented.     

Measurements of anisotropic elastic constants of type 308 stainless-steel electroslag welds

In austenitic-stainless-steel weld metal, mechanical anisotropy is caused by preferred local orientation of elongated subgrains and preferred crystallographic orientation. Ultrasonic and static tensile-test methods used to determine elastic stiffness and compliance matrices, respectively, demonstrated that orthotropic symmetry exists. Inversion of this compliance matrix gave a stiffness matrix which showed general agreement between the two methods. It is suggested that the data can be used directly in finite-element analyses of weldments containing Type 308 stainless steel.     

On the extensional vibrations of rotating bars

The extensional equations of motion for a cantilever bar rotating about an axis fixed in space are derived. It is shown that the form of the non-linear strain-displacement relation is important in determining the nature of the relationship between the frequency of extensional oscillations and the rotational speed. In particular, the frequency may or may not increase monotonically with rotational speed, depending on the degree of hardening in the effective extensional spring. The determination whether an instability occurs as the rotational speed increases is beyond the limits of engineering beam theory.     

Laser photolysis of 2-phenylheptamethyltrisilane

Two transient absorptions have been detected in the 266 nm laser photolysis of 2-phenylheptamethyltrisilane in cyclohexane solution at room temperature, and their time evolution was recorded in the presence and absence of air and added trapping agents. The shorter-lived 440 nm transient (t1/2 < 20μs) is tentatively assigned to the silylene :SiMePh and the more persistent 380 nm transient to the disilene MePhSiSiMePh. The reactivity of this silylene is much lower than had been expected.