The Antarctic marine ecosystem contains low concentrations of a range of hydrocarbons, overwhelmingly biogenic in origin. The low natural levels of hydrocarbons and the small amount of local human activity make the Antarctic marine ecosystem suitable as a yardstick against which future global pollution by hydrocarbons can be assessed. At present, contamination is very low and difficult to resolve against the background. Local pollution is restricted to a very few events. A systematic programme with a clear definition of the natural background is proposed to monitor both global and local pollution.

Transmission electron diffraction patterns from ultra-thin aromatic and aliphatic organic films at beam energies of 200 eV–1 keV have been recorded in a custom low energy electron transmission (LEET) chamber. A significant reduction of the molecular damage cross-section, measured by fading of diffraction spots, was found for thin films of the aromatic perylene when the beam energy was reduced from 400 to 200 eV. The corresponding measurements for the aliphatic tetracontane showed a smaller “threshold energy” and the differences are discussed. Electron beam damage from other aromatic materials has also been studied at low energy. Comparison of the carbon K shell ionization cross-section and the measured damage cross-sections show that carbon K-shell ionization is strongly correlated with the damage observed in aromatics at beam energies higher than 284 eV. Calculation of the minimum number of unit cells needed for imaging a single molecule, and comparison of calculated elastic with measured damage cross-sections both indicate new possibilities for imaging biomolecules with low energy electrons.

An RNA family that binds isoleucine with Kd = 200–500 μM was repetitively isolated from a ribonucleotide transcript pool containing 50 randomized positions. The RNA site is specific, discriminating against branched side chains of different size (valine—one methylene smaller than isoleucine) by at least 1.3 kcal/mol and against the shape (linear) of norleucine by 0.6 kcal/mol. The binding site was localized by sequence comparison, by synthesis of mutant and truncated active derivatives, and by chemical modification–interference. The binding site is small, no more than 10–12 nt, containing an asymmetric internal loop (6 over 2 nt) that includes the isoleucine codon AUU and a sequence of four G's, two of which are involved in G·U and G·C base pairs. Areas of U/G concentration like these may signal a hydrophobic RNA site.