Shirley Lin

Chemical amplification with encapsulated reagents

Autocatalysis and chemical amplification are characteristic properties of living systems, and they give rise to behaviors such as increased sensitivity, responsiveness, and self-replication. Here we report a synthetic system in which a unique form of compartmentalization leads to nonlinear, autocatalytic behavior. The compartment is a reversibly formed capsule in which a reagent is sequestered. Reaction products displace the reagent from the capsule into solution and the reaction rate is accelerated. The resulting self-regulation is sensitive to the highly selective molecular recognition properties of the capsule.

Evaluation of the antimicrobial activity of cationic polyethylenimines on dry surfaces

The antimicrobial activity of cationic N‐dodecyl‐N‐methylpolyethylenimine (PEI+) against S. aureus, A. baumannii, and E. coli was evaluated when the polymer was applied as a coating to various surfaces using a paint‐like procedure. Antimicrobial activity of PEI+ as a function of time was determined using an assay for long‐term survival involving placement of single drops of various bacterial concentrations on dry surfaces. These data were compared with an assay method where bacteria were applied by spraying and surfaces were incubated overnight under agar. PEI+‐coated surfaces were found to be highly bactericidal after 30 min when bacteria were sprayed onto surfaces. However, when bacteria were applied as single drops, PEI+‐coated surfaces were less biocidal at short contact times particularly for A. baumannii and E. coli. The observations are explained in the context of the difference in drying time between drops deposited on uncoated surfaces and PEI+‐coated surfaces and the sensitivity of bacterial survival to dehydration. These results demonstrate that PEI+‐coated surfaces are not effectively biocidal for some types of bacteria under certain conditions and that the method of assaying bactericidal efficiency can greatly affect the results obtained.

2,4,6-Tris-(4-fluoro-phen-yl)-2-(1-pyrid-yl)-boroxine.

Crystals of the title compound, C23H17B3F3NO3, were obtained unintentionally by slow evaporation of a chloroform solution of the preformed boroxine–pyridine adduct. The molecule contains three fluoro-substituted benzene rings, each bonded to one of the three B atoms of a six-membered boroxine ring. A pyridyl ring is also bound to one of the B atoms through a Lewis acid–base interaction. The binding of the pyridyl substituent causes the otherwise planar boroxine ring to twist, resulting in a maximum torsion angle within the ring of 17.6 (2)°.

2,5-Dioxopyrrolidin-1-yl 2-methyl-prop-2-enoate.

In the title compound, C8H9NO4, the pyrrolidine ring (r.m.s. deviation 0.014 Å) is almost normal to the mean plane of the propenoate group (r.m.s deviation 0.028 Å), making a dihedral angle of 86.58 (4)°. In the crystal, molecules are linked via pairs of weak C—H⋯O hydrogen bonds, forming inversion dimers which stack along the c axis.