Biological recognition of graphene nanoflakes.

The systematic study of nanoparticle-biological interactions requires particles to be reproducibly dispersed in relevant fluids along with further development in the identification of biologically relevant structural details at the materials-biology interface. Here, we develop a biocompatible long-term colloidally stable water dispersion of few-layered graphene nanoflakes in the biological exposure medium in which it will be studied. We also report the study of the orientation and functionality of key proteins of interest in the biolayer (corona) that are believed to mediate most of the early biological interactions. The evidence accumulated shows that graphene nanoflakes are rich in effective apolipoprotein A-I presentation, and we are able to map specific functional epitopes located in the C-terminal portion that are known to mediate the binding of high-density lipoprotein to binding sites in receptors that are abundant in the liver. This could suggest a way of connecting the materials' properties to the biological outcomes.

Metabolic responses to exhaustive exercise change markedly during the protracted non-trophic spawning migration of the lamprey Geotria australis.

Adults of the Southern hemisphere lamprey Geotria australis were subjected to an exercise/recovery regime at the commencement and end of their 12-15 month non-trophic, upstream spawning migration. In early (immature) migrants and pre-spawning females, muscle glycogen was markedly depleted during exercise, but became rapidly replenished. As muscle lactate rose during exercise and peaked 1-1.5 h into the recovery period, and therefore after muscle glycogen had become replenished, it cannot be the direct source for that replenishment. However, both plasma lactate and glycerol (but not muscle glycerol and glucose) rose sharply during exercise and then declined markedly during the first 0.5 h of recovery and thus exhibited the opposite trend to that of muscle glycogen, implying that these limited pools of glycogenic precursors contribute to glycogen replenishment. Although plasma glucose rose following exercise, and consequently could also be a precursor for muscle glycogen replenishment, it remained elevated even after muscle glycogen had become replenished. While resting pre-spawning females and mature males retained high muscle glycogen concentrations, this energy store became permanently depleted in females during spawning. In mature males, muscle glycogen remained high and lactate low during the exercise/recovery regime, whereas muscle glycerol declined precipitously during exercise and then rose rapidly. In summary, vigorous activity by G. australis is fuelled extensively by anaerobic metabolism of glycogen early in the spawning run and by pre-spawning females, but by aerobic metabolism of its energy reserves in mature males.

Muscle glycogen, lactate and glycerol-3-phosphate concentrations of larval and young adult lampreys in response to exercise.

When stimulated, the ammocoetes (larvae) of Geotria australis swim continuously at a moderate rate for only approximately 20 min, whereas the downstream migrants (young adults) of this species did not become exhausted following similar swimming activity over the same period. Mean concentrations of muscle glycogen in ammocoetes declined during exercise, but returned to resting levels within 30 min of recovery, whereas those in young adults changed little during the corresponding periods. Moreover, muscle lactate concentrations of ammocoetes rose markedly during exercise and the first 30 min of recovery, before declining significantly, while those of young adults remained similar during and immediately after exercise. Calculations, using the glycogen and lactate concentrations immediately after exercise, suggest that during exercise glycogen is, to some extent, utilised anaerobically (approx. 24%) by ammocoetes, but only aerobically by young adults. Furthermore, since young adults used only a small amount of glycogen, they presumably metabolised triacylglycerol aerobically to produce energy. Muscle glycerol-3-phosphate levels were far higher prior to and immediately after exercise in downstream migrants than in ammocoetes and then declined precipitously. The above trends in muscle glycogen and lactate of larval G. australis parallels, to some degree, those recorded by other workers for upstream migrant Petromyzon marinus that had been exercised to exhaustion.