Definitive evidence is presented for the favourable electrochemical properties of carbon nanotube modified electrodes arising from the ends of SWNTs due to oxygenated carbon species in general, and carboxylic acid moieties in particular, produced during acid purification.

The HIV capsid is semipermeable and covered in electropositive pores that are essential for viral DNA synthesis and infection. Here, we show that these pores bind the abundant cellular polyanion IP₆, transforming viral stability from minutes to hours and allowing newly synthesised DNA to accumulate inside the capsid. An arginine ring within the pore coordinates IP₆, which strengthens capsid hexamers by almost 10°C. Single molecule measurements demonstrate that this renders native HIV capsids highly stable and protected from spontaneous collapse. Moreover, encapsidated reverse transcription assays reveal that, once stabilised by IP₆, the accumulation of new viral DNA inside the capsid increases >100 fold. Remarkably, isotopic labelling of inositol in virus-producing cells reveals that HIV selectively packages over 300 IP₆ molecules per infectious virion. We propose that HIV recruits IP₆ to regulate capsid stability and uncoating, analogous to picornavirus pocket factors. HIV-1/IP₆/capsid/co-factor/reverse transcription.

The ease of fabricating high quality photonic crystals from porous silicon and its biocompatibility have inspired the conception of various biosensing schemes using this material. However, the instability of porous silicon has significantly slowed progress in this area. Here we discuss the potential of different porous silicon photonic crystals for biosensing in the context of its surface chemistry and nanostructure, both of which need to be optimized to obtain sensitive and stable devices. Of particular promise are recent approaches that use porous silicon as sensors for enzymatic activity, for cell capture and concentration devices.