A message from the virus was detected by a peptide nucleic acid probe that contains thiazole orange as a fluorescent base surrogate (see picture). The high specificity and biostability of the probes lead to significant improvements to the signal‐to‐background ratio in imaging the mRNA from the influenza H1N1 virus in living infected cells.

Liquid crystal ordering is reported in aqueous solutions of the oligomer 5'-ATTAp-3' and of the oligomer 5'-GCCGp-3'. In both systems, we quantitatively interpret ordering as stemming from the chaining of molecules via a "running-bond" type of pairing, a self-assembly process distinct from the duplex aggregation previously reported for longer oligonucleotides. While concentrated solutions of 5'-ATTAp-3' show only a columnar liquid crystal phase, solutions of 5'-GCCGp-3' display a rich phase diagram, featuring a chiral nematic phase analogous to those observed in solutions of longer oligonucleotides and two unconventional phases, a columnar crystal and, at high concentration, an isotropic amorphous gel. The appearance of these phases, which can be interpreted on the basis of features of 5'-GCCGp-3'molecular structure, suggests distinctive assembly motifs specific to ultrashort oligonucleotides.

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A change of the energy transfer mechanism (from contact quenching to FRET) increases the responsiveness of fluorescent hybridization probes. The communication between a responsive fluorescent base surrogate (see picture, green) and a near‐infrared dye (red) in peptide nucleic acid provides probes that are extremely dark in the single strand. Hybridization furnishes strong fluorescence increase with a 200 nm shift in emission maximum.

Key components of the translational apparatus, i.e. ribosomes, elongation factor EF-Tu and most aminoacyl-tRNA synthetases, are stereoselective and prevent incorporation of d-amino acids (d-aa) into polypeptides. The rare appearance of d-aa in natural polypeptides arises from post-translational modifications or non-ribosomal synthesis. We introduce an in vitro translation system that enables single incorporation of 17 out of 18 tested d-aa into a polypeptide; incorporation of two or three successive d-aa was also observed in several cases. The system consists of wild-type components and d-aa are introduced via artificially charged, unmodified tRNAGly that was selected according to the rules of ‘thermodynamic compensation’. The results reveal an unexpected plasticity of the ribosomal peptidyltransferase center and thus shed new light on the mechanism of chiral discrimination during translation. Furthermore, ribosomal incorporation of d-aa into polypeptides may greatly expand the armamentarium of in vitro translation towards the identification of peptides and proteins with new properties and functions.