The development of sensors that mimic the natural smell sensing mechanism and selectively recognizes the odorants remains highly challenging. Electrochemical based sensing approaches aiming at monitoring molecular recognition events between surface receptors and analytes in solution or in the gas phase, are one possible transduction platforms among others for the construction of an artificial nose. The principle of electrochemical detection lies on the shift of the potential/current during the recognition event, which is proportional to the concentration of the analyte, in our case the odorant. A tremendous amount of efforts has been put into making electrochemical sensors sensitive and selective to the analyte of interest through the use of nanomaterials, development of different detection schemes and application of innovative receptor ligands for selective detection of the analyte. There have been significant advances in electrochemical based odorant sensing by using odorant binding proteins (OBP) as surface receptors, small soluble proteins present in nasal mucus at millimolar concentrations where the hydrophobic binding pocket gives the ability to reversibly bind odorant molecules. As OBPs are robust and easy to produce receptors, they are good candidates for the design of biosensors. In this chapter, we focus on the progress made on the detection of odorant molecules using OBPs as a bioreceptor and electrochemistry as a transduction method.Pheromone binding proteins (PBPs) are small soluble proteins (about 15kDa) that play striking roles in the detection of sex pheromones in insects. Many studies including structural analysis, binding simulation, and in vitro assays have been performed to clarify the modes of action of PBPs. Although these studies have provided valuable contributions toward the understanding of which key amino acid components contribute to the correct folding of PBPs and their binding affinities to sex pheromones, the functional characteristics of PBPs in the natural environment is still obscure. Recent developments in genome editing have begun to enable the functional examination of PBPs in in vivo. Among insect PBPs, BmPBP1 is one of the most well-characterized, there being rich understanding of its structure, biochemical analysis, binding affinity, localization, and the relationship between the type of olfactory receptors and its expression. A recent study has shown that BmPBP1 contributes sensitivity, but not selectivity of sex pheromone detection in the silkmoth Bombyx mori. In this chapter, based on a current report of the functional characterization of BmPBP1 using genome editing, we provide one example of a useful analytical method to clarify the functional role of PBP in vivo.Modifying the affinity of odorant-binding proteins (OBPs) to small ligands by replacement of specific residues in the binding pocket may lead to several technological applications. Thanks to their compact and stable structures, OBPs are currently regarded as the best candidates to be used in biosensing elements for odorants and volatiles detection. The wide and rich information on the structure of these proteins both in their apo-forms and in complexes with specific ligands provides guidelines to design reliable mutants to monitor specific targets. The same engineered proteins may also find applications in the slow release of pheromones and other chemicals in the environment, as well as in the fine purification of drugs, including the resolution of racemates. Apart from such useful applications, site-directed mutagenesis represents an interesting approach to dissect the specific interactions between small chemicals and amino acid residues in the binding pocket. These studies can lead to design of better ligands, such as pheromone analogues with desired physico-chemical characteristics. In this chapter we examine the different uses of mutagenesis applied to OBPs and report a couple of protocols that have been successful in our hands.The technique of two-electrode voltage-clamp (TEVC) recording from the heterologous expression system of olfactory receptors (ORs) in Xenopus laevis oocytes has been widely used to deorphanize insect ORs, that is to identify specific ligands for each of them. However, there is a controversial issue on whether ORs are activated by the odorant/OBP complex or the odorant alone. The mechanism of interaction among odorants, odorant-binding proteins (OBPs) and ORs remains largely unknown, due to the limitations in the use of scientific and innovative methods. In this chapter, the modified Xenopus oocytes expression system combined with TEVC technique is used to approach this issue. We describe the experimental strategies and provide detailed protocols for recording the signals generated by ORs in response to odorant/OBP complex at different concentrations. Results obtained by this approach have revealed that the presence of OBPs in the system affects the selectivity and sensitivity responses of ORs. Such studies help understanding the molecular mechanism of odorant detection in peripheral nervous system.Fine structure immunocytochemistry enables the in situ localization of odorant-binding proteins with the high resolution of the electron microscope. SB203580 in vitro Protocols for successfully labeling these proteins in insect chemosensory sensilla are given and some pitfalls pinpointed as well as ways to avoid them. The major achievements accomplished by these methods are briefly reviewed.Assessing the ligand-binding properties of OBPs and CSPs is essential for understanding their physiological function. It also provides basic information when these proteins are used as biosensing elements for instrumental measurement of odors. Although different approaches have been applied in the past to evaluate the affinity of receptors and soluble binding proteins to their ligands, using a fluorescent reporter represents the method of choice for OBPs and CSPs. It offers the advantages of working at the equilibrium, being simple, fast and inexpensive, without requiring the use of radioactive tracers. However, as an indirect method, the fluorescence competitive binding approach presents drawbacks and sometimes requires an elaborate analysis to explain unexpected results. Here, after a brief survey of the different approaches to evaluate affinity constants, we focus on the fluorescence binding assay as applied to OBPs and CSPs, discussing situations that may require closer inspection of the results.