The Precision of Place Fields Governs Their Fate across Epochs of Experience.

Spatial memories are represented by hippocampal place cells during navigation. This spatial code is dynamic, undergoing changes across time, known as representational drift, and across changes in internal state, even while navigating the same spatial environment with consistent behavior. A dynamic code may provide the hippocampus a means to track distinct epochs of experience that occur at different times or during different internal states and update spatial memories.

Surface-rolling molecules.

Design, syntheses, and testing of new, fullerene-wheeled single molecular nanomachines, namely, nanocars and nanotrucks, are presented. These nanovehicles are composed of three basic components that include spherical fullerene wheels, freely rotating alkynyl axles, and a molecular chassis. The use of spherical wheels based on C60 and freely rotating axles based on alkynes permits directed nanoscale rolling of the molecular structure on gold surfaces.

Synthesis and biological activity of new 5-O-sugar modified ketolide and 2-fluoro-ketolide antibiotics.

A series of new triazole-containing ketolides and 2-fluoro-ketolides in which the 5-O-desosamine was replaced by unnatural sugars were synthesized and evaluated against relevant macrolide-sensitive and macrolide-resistant respiratory pathogens. Excellent in vitro antibacterial activities were demonstrated for ketolide analogues having the 6'-OBz-3'-dimethylamino-glucose and 6'-OBz-4'-deoxy-3'-dimethylamino-glucose substituents.

Ternary ligand-zinc-hydroxamate complexes.

Because of the importance of the hydroxamic acid functional group in zinc protease inhibitors, we have measured the stability constants of the ternary complex LMG, where L is series of tridentate and tetradentate ligands containing amino, carboxylate, pyridyl, and/or imidazolyl groups as enzyme models and G is the guest molecule, acetohydroxamate or N-methylacetohydroxamate. All measurements were determined by pH titration which gave reproducible and reasonable results. A general correlation between binding of LMG and that of LM showed ligands that strongly chelated zinc gave less LMG formation.

Stability and acidity constants for ternary ligand-zinc-hydroxo complexes of tetradentate tripodal ligands.

Four series of tetradentate tripodal ligands containing pyridyl, 2-imidazolyl, 4-imidazolyl, amino, and/or carboxylic groups were synthesized as hydrolytic zinc enzyme models in order to elucidate the effect of various coordination environments on zinc binding and the acidity of zinc-bound water. In aqueous solution, ligands with same charges showed a good correlation between zinc binding (log K(ZnL)) and zinc-bound water acidity (pK(a) of LZnOH(2)); the stronger the zinc binding, the higher the pK(a). The zinc-bound water acidity decreased as pyridyl groups were replaced by carboxylate groups.