New insight into the action of tryptanthrins against Plasmodium falciparum: Pharmacophore identification via a novel submolecular QSAR descriptor.

A new submolecular quantitative structure activity relationship (QSAR) descriptor was applied toward elucidating the anti-malarial pharmacophore of tryptanthrins, a class of compounds known for their anti-parasitic activities. The new descriptor is based on experimental and computational measurements of the tunneling barriers of individual lobes of the molecular orbitals. Lobe-by-lobe QSAR correlation plots revealed a single lobe of the LUMO to be strongly associated with tryptanthrin's anti-malarial activity.

Analysis of self-assembled monolayers on gold surfaces using direct analysis in real time mass spectrometry.

Mass spectrometry was performed on self-assembled monolayers (SAMs) of dodecanethiol on gold using the new direct analysis in real time (DART) ionization technique. Observed peaks for the SAMs included monomers, dimers, and trimers of the SAM molecules, with the dimer and trimer relative peak heights enhanced as compared to the spectra for neat dodecanethiol. The possibility that the observed peaks were due to residual (noncovalently bonded) material on the surface was tested by attempting to observe residual dodecanol.

Scanning tunneling microscopy with chemically modified gold tips: in situ reestablishment of chemical contrast.

A method was developed for the reestablishment of chemical contrast in STM images obtained with chemically modified gold tips. Such tips display selective chemical contrast, which allows the selective imaging of specific species on the sample surface. Chemically modified STM tips can be fabricated by forming a self-assembled monolayer (SAM) on an electrochemically etched gold tip.