A letter in the Sept 22, 2010 issue of Nature magazine begins:
Howard Hughes Medical Institute
University of California, Berkeley
It could not escape my notice that your cover of 9 September (Nature 467, issue 7312; 2010) is dominated by a DNA molecule with a pronounced left-handed helical twist. In the structure originally proposed by James Watson and Francis Crick in your pages, however, the chains of DNA follow paired right-handed helices.
BONUS (Thanks to Chris [Right Hand, Left Hand] McManus for bringing this to our attention): More such examples can be found in the article “That famous double helix takes a sinister turn“, by Colin [not Cole!] Porter, Nature, 406, 234 (20 July 2000). And for a more general look at the, er, phenomenon, see The Left-Handed DNA Hall of Fame.