Palm trees are of immense economic, sociocultural, touristic and patrimonial significance all over the world, and date palm-related knowledge, traditions and practices are now included in UNESCO’s list of the Intangible Cultural Heritage of Humanity. Of all the pests that infest these trees, the red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) is its primary enemy. The RPW is a category-1 quarantine insect pest that causes enormous economic losses in the cultivation of palm trees worldwide. The RPW synchronizes mass gathering on the palm tree for feeding and mating, regulated by a male-produced pheromone composed of two methyl-branched compounds, (4RS,5RS)-4-methylnonan-5-ol (ferrugineol) and 4(RS)-methylnonan-5-one (ferrugineone). Despite the importance of odorant detection in long-range orientation towards palm trees, palm colonization and mating, nothing regarding the molecular mechanisms of pheromone detection in this species is known. In this study, we report the identification and characterization of the first RPW pheromone receptor, RferOR1. Using gene silencing and functional expression in Drosophila olfactory receptor neurons, we demonstrate that RferOR1 is tuned to both ferrugineol and ferrugineone and binds five other structurally related molecules. We reveal the lifetime expression of RferOR1, which correlates with adult mating success irrespective of age, a factor that could explain the wide distribution and spread of this pest. As palm weevils are challenging to control based on conventional methods, elucidation of the mechanisms of pheromone detection opens new routes for mating disruption and the early detection of this pest via the development of pheromone receptor-based biosensors.

Odorant binding proteins (OBPs) are small soluble proteins found in olfactory systems that are capable of binding several types of odorant molecules. Cantilevers based on polycrystalline diamond surfaces are very promising as chemical transducers. Here two methods were investigated for chemically grafting porcine OBPs on polycrystalline diamond surfaces for biosensor development. The first approach resulted in random orientation of the immobilized proteins over the surface. The second approach based on complexing a histidine-tag located on the protein with nickel allowed control of the proteins' orientation. Evidence confirming protein grafting was obtained using electrochemical impedance spectroscopy, fluorescence imaging and X-ray photoelectron spectroscopy. The chemical sensing performances of these OBP modified transducers were assessed. The second grafting method led to typically 20% more sensitive sensors, as a result of better access of ligands to the proteins active sites and also perhaps a better yield of protein immobilization. This new grafting method appears to be highly promising for further investigation of the ligand binding properties of OBPs in general and for the development of arrays of non-specific biosensors for artificial olfaction applications.

Palm trees are of immense economic, sociocultural, touristic and patrimonial significance all over the world, and date palm-related knowledge, traditions and practices are now included in UNESCO's list of the Intangible Cultural Heritage of Humanity. Of all the pests that infest these trees, the red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) is its primary enemy. The RPW is a category-1 quarantine insect pest that causes enormous economic losses in the

The binding pockets of odorant binding proteins from Anopheles gambiae (OBP1 and OBP47) were analysed using in silico modelling. The feasibility of creating mutant proteins to achieve a protein array capable of detecting drugs of abuse in solution or in vapour phase was investigated. OBP1 was found to be easily adapted and several mutant proteins were expressed and characterised. AgamOBP1_S82P was found to have high affinities to cannabinol, 3,4-methylenedioxy methamphetamine (MDMA/ Ecstasy) and cocaine hydrochloride. When these proteins were immobilised on a quartz crystal microbalance, saturated cocaine hydrochloride vapour could be detected. The sensors were stable over a period of at least 10 months in air. The approach taken allows flexible design of new biosensors based on inherently stable protein scaffolds taking advantage of the tertiary structure of odorant binding proteins.In vertebrates and insects, the process of chemoreception involves transmembrane receptors (olfactory receptors (ORs)) that are responsible for the transduction of a signal associated with the binding of a ligand to a receptor binding site 1,2 . However many volatile molecules of interest are generally hydrophobic and before reaching the dendrites of sensory neurons, they need to partition from air into an aqueous environment before they can reach the receptors 3 . The nasal mucus of non-aquatic vertebrates and the chemosensillar lymph of insect antennae contain large amounts of small soluble odorant-binding proteins (OBPs) that specifically and reversibly bind odour molecules and pheromones. In vertebrates these proteins form part of the lipocalin family -low molecular weight proteins characterised by a cage-like structure of beta-sheets that function as carriers of small ligands 4 . In insects there are two major families -OBPs and chemosensory proteins (CSPs), with a sub-group of OBPs, specifically tuned to pheromones, referred to as PBPs 5,6 . These proteins are also of low molecular weight but primarily consisting of alpha-helical structures in contrast to those of vertebrates.While it would be desirable to use olfactory receptors directly as biosensor recognition elements, there are practical difficulties because ORs are membrane bound G protein-coupled receptors (GPCRs) 1 or olfactory receptor-co-receptors (ORCO) 7,8 and it is much more difficult to stabilise these proteins outside the cellular environment. On the other hand, OBPs are attractive for use as bio-recognition elements for small ligands and have attracted the attention of a number of researchers who have successfully demonstrated that they can function as biosensors 9-11 . Mulla et al. demonstrated that the two enantiomers of carvone could be distinguished using a water gated field effect transistor 12 . Larisika et al. immobilised OBP14 from the honeybee on graphene and incorporated it into a field-effect transistor to produce biosensors able to discriminate ligands in a way that was similar to the specificity of the protein when measured in solution 13 . These de...

No abstract