Cationic Head Groups Research Articles

Monitoring Binding of Protamine with DNA Using Protein Charge Transfer Spectra.

In this work, novel intrinsic electronic absorption (250-400 nm) with a molar extinction coefficient of 752 M-1cm-1 at 250 nm, arising from photoinduced electron transfer involving charged amino acid side chains and the polypeptide backbone, along with luminescence (300-500 nm) with quantum yield of 0.011 from subsequent charge recombination, was observed in salmon sperm Protamine (PRM). The absorption of PRM was attributed to the previously identified Peptide Backbone-to-Side chain Charge Transfer (PBS-CT) from the polypeptide backbone to the abundant cationic headgroups of Arginine in PRM, while the luminescence was believed to originate from charge recombination within the charge-separated excited states of PRM. Remarkably, since Arg is the only charged residue in the PRM sequence, the PRM Protein Charge Transfer Spectra (ProCharTS) is both totally and uniquely Arg specific. Interestingly, the peak of PRM luminescence emission spectrum was independent of the excitation wavelength, unlike other proteins such as human serum albumin, displaying unconventional luminescence. Aggregation-induced effects on PRM absorbance and luminescence were ruled out, as both PRM absorbance and luminescence increase maintained linearity with increasing concentration in the 25-150 μM range. Nucleoprotamine complex formation, resulting from the binding of PRM with calf-thymus genomic DNA (gDNA), was monitored through increased scattering by the nucleoprotamine complex, a decrease in gDNA/PRM absorbance, a decrease in gDNA/PRM ellipticity, and shifts of nucleoprotamine complex band upon agarose gel electrophoresis. Upon binding with gDNA (700 μM base pair concentration), PRM ProCharTS absorbance at 260 nm decreased by 72%. This decrease was attributed to the formation and subsequent precipitation of nucleoprotamine complex upon PRM-gDNA binding. The application of ProCharTS absorbance to indirectly monitor DNA-protein binding in a label-free approach was thus demonstrated.

Multistep Array-Based Sensing of Bioanalytes Using Modified MoS2, Fluorescence Proteins, and Cucurbituril.

One pot sensor by multiplexing in the array is an attractive system for rapid discrimination of multiple analytes. Multiplexing can be achieved in two ways, i.e., using multiple signal transducers or adding sequential agents to the sensor media. Herein, we have used a combination of both multichannel and sequential ON-OFF strategies for the discrimination of different bioanalytes. The sensor array was constructed by implementing positively charged MoS2 as a receptor and different fluorescent proteins possessing distinguishable emission profiles as signal transducers. The sensing setup was constructed with the interaction between oppositely charged MoS2 and the host-guest combination between a cationic headgroup of MoS2 and Cucurbit [7] uril (CB7) to alter the fluorescence of signal transducers in situ noncovalently. Electrodynamic analysis and optical assays suggest that the electrostatic interaction played a major role in the modulation of the fluorescence outcomes in the array. Both cationic and anionic proteins were discriminated at a 50 nM concentration. The detection limit of the sensor array by using β-gal protein was found to be 1 nM. The sensor array was further implemented for the discrimination of normal and diseased cell lines and lysates, which indicates the versatile detection ability of this reported sensor array.

Thermodynamic characteristics and aggregation behavior of surface active ionic liquids in presence of vitamin B7 (biotin)

Abstract This study investigated the influence of vitamin B7 (biotin) at different concentrations (0.1, 0.3 and 0.5) mM on the micellisation behaviour of three different ionic liquids with different cationic headgroups, namely N-methylmorpholinium bromide [Mor1,12][Br], N-dodecyl-N-methylpyrrolidinium bromide [Pyrr1,12][Br], and 1-dodecyl-3-methylimidazolium bromide [C12mim][Br], at four different temperatures (298.15, 303.15, 308.15, and 313.15) K using electrical conductivity and surface tension measurements. The evaluated CMC values for the studied system were used to obtain information about the colloidal behavior of the ionic liquids in the presence of biotin. The different thermodynamic parameters were studied. Tensiometry was used to determine the interfacial properties. The parameters obtained were used to study the different types of interactions for micelle formation. The main objective of studying these interactions is to further utilize this type of mixture in pharmaceutical industry, medicinal chemistry, and bio industry.

Aromatic salt induced modulations in micellization behavior of amide functionalized surface-active ionic liquids: The role of cationic head group

The present study highlights the effect of aromatic salt i.e. sodium benzoate (NaBz) at fix concentration (1 mM), on the micellization behavior of four amide functionalized surface-active ionic liquids (SAILs) having different cationic head groups in aqueous medium. The adsorption behavior of the SAILs at the air-solution interface has been investigated by tensiometry, where improved surface activity was observed in all the investigated SAILs in the presence of added hydrotrope. The conductivity, steady-state fluorescence, dynamic light scattering (DLS), and zeta-potential measurements have been performed to probe the micellization of the SAILs in bulk solution. The position and orientation of aromatic anion, Bz-, at the micelle-water interface surface has been investigated by 1H NMR spectroscopy. The thermodynamic aspects of micellization have been examined by Isothermal titration calorimetry (ITC). It has been observed that the nature, geometry, and steric factor of the cationic head group of SAILs govern their interactions with Bz- and this influences the characteristic properties of micellization.

Cytotoxicity of acridinium-based ionic liquids: Structure-activity relationship and mechanistic studies

Ionic liquids (ILs) are a class of low melting point salts with physicochemical properties suitable for a range of industrial applications such as chemical processing and battery design. Major challenges to the wide-scale adoption of ILs in industry include their eco- and cytotoxic effects, however, this opens up the possibility of the use of ILs use as novel anticancer agents. Understanding the structural features that promote IL cytotoxicity is therefore important. Key structural features that can impact IL cytotoxicity include size and lipophilicity of the cationic head group. In this study, the cytotoxic effects of acridinium-based ILs containing relatively large tri- and tetracyclic cations were evaluated. It was found that 9-phenylacridinium-based ILs are potent cytotoxic agents that reduce the viability of human MDA-MB-231 breast cancer cells with IC50 concentrations in the nanomolar range. In mechanistic studies, it was found that unlike the pyridinium-based analogue, [C16Py][I], acridinium-based ILs did not inhibit oxidative phosphorylation or induce reactive oxygen species formation, and may instead target other mitochondrial processes or components such as mitochondrial DNA.

Towards high conductivity and stability diblock poly(norbornene)s-based anion exchange membranes crosslinked with alkyl quaternary ammonium cationic clusters

Anion exchange membranes (AEMs) with exceptional comprehensive performance, combining high conductivity, alkaline and dimensional stability, have been indispensable for the practical application in fuel cells. Herein, a robust addition poly(norbornene)s-based AEMs with an all-carbon-hydrogen bicyclic skeleton were fabricated by cross-linking of alkyl quaternary ammonium cationic clusters and further quaternization. The partially crosslinked AEMs adopt a synergistic strategy that combines diblock copolymer backbone, cationic cluster crosslinking structure, and long flexible spacer suspended with cationic head groups. Benefiting from these structural design advantages, the prepared AEMs possessed excellent hydroxide conductivity (133.9–146.9 mS cm−1) and low swelling ratio (SR ≦ 20%) at 80 °C. The robust crosslinked AEMs exhibited good mechanical properties and high thermostability, with onset of decomposition temperatures up to 240 °C. Furthermore, after 44 days treatment in 1 M NaOH solution at 80 °C, the hydroxide conductivity of AEMs maintained at 79.4–85.7% of the initial value depending on the crosslinking degree, demonstrating excellent alkaline stability. In addition, the H2/O2 single cell equipped with CL20-aPNB-TAT-QA-1.75 achieved a peak power density of 338.0 mW cm−2 at 80 °C. The study provided a meaningful insight to exploit the practical application of multi-cation clusters crosslinked addition poly(norbornene)s-based AEMs in fuel cells.

Insights into the role of ionic surfactants on the morphology of gold and gold@silver nanoparticles

Cyanidin-3, 5-di-O-glycoside (anthocyanin) was extracted from the red rose flower petals in an aqueous media. Anthocyanin was used as reductant to the preparation of gold nanoparticles with cationic and anionic surfactants. UV–visible absorption spectroscope, transmission electron microscope, scanning electron microscope, and energy dispersive X-ray spectroscope were employed to determine absorption bands of anthocyanin, surface Plasmon resonance (SPR) band, and morphology of the gold and gold@silver nanoparticles. Anthocyanin exhibited two absorption peaks at 284 and 518 nm, and one shoulder at 328 nm in the UV–visible spectrum. The intensity of these peaks decreases with time after the addition of HAuCl4. The color and the position of SPR band of gold nanoparticles depend on the concentration of gold salt with and without cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). The anionic and cationic head groups of SDS and CTAB micelles have significant impact of the morphology of gold nanoparticles. Seedless co-reduction method was used for the synthesis of gold@silver nanoparticles. TEM images clearly indicate the formation of bimetallic gold@silver core-shell nanoparticles. The antioxidant power of AuNPs and gold@silver nanoparticles were tested in terms of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity as a function of different concentrations of nanoparticles.

ROS-Responsive Bola-Lipid Nanoparticles as a Codelivery System for Gene/Photodynamic Combination Therapy.

The nonviral delivery systems that combine genes with photosensitizers for multimodal tumor gene/photodynamic therapy (PDT) have attracted much attention. In this study, a series of ROS-sensitive cationic bola-lipids were applied for the gene/photosensitizer codelivery. Zn-DPA was introduced as a cationic headgroup to enhance DNA binding, while the hydrophobic linking chains may facilitate the formation of lipid nanoparticles (LNP) and the encapsulation of photosensitizer Ce6. The length of the hydrophobic chain played an important role in the gene transfection process, and 14-TDZn containing the longest chains showed better DNA condensation, gene transfection, and cellular uptake. 14-TDZn LNPs could well load photosensitizer Ce6 to form 14-TDC without a loss of gene delivery efficiency. 14-TDC was used for codelivery of p53 and Ce6 to achieve enhanced therapeutic effects on the tumor cell proliferation inhibition and apoptosis. Results showed that the codelivery system was more effective in the inhibition of tumor cell proliferation than individual p53 or Ce6 monotherapy. Mechanism studies showed that the production of ROS after Ce6 irradiation could increase the accumulation of p53 protein in tumor cells, thereby promoting caspase-3 activation and inducing apoptosis, indicating some synergistic effect. These results demonstrated that 14-TDC may serve as a promising nanocarrier for gene/PDT combination therapy.

Synthesis of Amino Acid-Based Cationic Lipids and Study of the Role of the Cationic Head Group for Enhanced Drug and Nucleic Acid Delivery.

Leveraging liposomes for drug and nucleic acid delivery, though promising due to reduced toxicity and ease of preparation, faces challenges in stability and efficiency. To address this, we synthesized cationic amphiphiles from amino acids (arginine, lysine, and histidine). Histidine emerged as the superior candidate, leading to the development of three histidine-rich cationic amphiphiles for liposomes. Using the hydration method, we have prepared the liposomes and determined the optimal N/P ratios for lipoplex formation via gel electrophoresis. In vitro transfection assays compared the efficacy of our lipids to Fugene, while MTT assays gauged biocompatibility across cancer cell lines (MDA-MB 231 and MCF-7). The histidine-based lipid demonstrated marked potential in enhancing drug and nucleic acid delivery. This improvement stemmed from increased zeta potential, enhancing electrostatic interactions with nucleic acids and cellular uptake. Our findings underscore histidine's crucial role over lysine and arginine for effective delivery, revealing a significant correlation between histidine abundance and optimal performance. This study paves the way for histidine-enriched lipids as promising candidates for efficient drug and nucleic acid delivery, addressing key challenges in the field.

Cleavable Amphiphilic Biocides with Ester-Bearing Moieties: Aggregation Properties and Antibacterial Activity.

The rise of multidrug-resistant bacterial infections and the dwindling supply of newly approved antibiotics have emerged as a grave threat to public health. Toward the ever-growing necessity of the development of novel antimicrobial agents, herein, we synthesized a series of cationic amphiphilic biocides featuring two cationic headgroups separated by different hydrophobic spacers, accompanied by the inclusion of two lipophilic tails through cleavable ester functionality. The detailed aggregation properties offered by these biocides were investigated by small-angle neutron scattering (SANS) and conductivity. The critical micellar concentration of the biocides and the size and shape of the micellar aggregates differed with variation of pendant and spacer hydrophobicity. Furthermore, the aggregation number and size of the micelles were found to vary with changing concentration and temperature. These easily synthesized biocides exhibited potent antibacterial properties against various multidrug-resistant bacteria. The optimized biocides with minimum hematotoxicity and potent antibacterial activity against methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii exhibited rapid killing kinetics against planktonic bacteria. Also, these membrane-active agents were able to eradicate preformed biofilms. The enzymatic and acidic degradation profile further offered proof of gradual degradation. Collectively, these cleavable amphiphilic biocides demonstrated excellent potency for combating the multidrug-resistant bacterial infection.

Effects of cationic head group structure on cytotoxicity and mitochondrial actions of amphiphilic ionic liquids

Ionic liquids (ILs) are a class of low melting point salts with physicochemical properties that make them suitable for a range of industrial applications. Accumulating evidence suggests that certain ILs are cytotoxic and potential environmental pollutants, thus understanding the structural features that promote IL cytotoxicity is important. Amphiphilic ionic liquids (AmILs), a class of ILs with lipophilic N-alkyl chains, containing aromatic head groups are generally more cytotoxic than their aliphatic counterparts, however the impact of other head group properties are less clear. This study therefore sought to provide new structure activity relationship (SAR) insights regarding the role of the cationic head group on AmIL cytotoxicity. A series of AmILs bearing a range of structurally diverse aromatic cations varying in size, charge, and lipophilicity was synthesised and screened against human MDA-MB-231 breast cancer cells. It was found that larger and more lipophilic head groups increased cytotoxicity, although the magnitude of the changes were modest. The mitochondrial effects of representative ILs were assessed. The AmILs induced mitochondrial dysfunction in MDA-MB-231 cells at cytotoxic concentrations, suggesting that they target mitochondria. The new SAR information from this study may assist in the design of AmILs with controlled cytotoxicity.

Modulation of Gold Nanoparticle Ligand Structure-Dynamic Relationships Probed Using Solution NMR.

Ligand dynamics plays a critical role in the chemical and biological properties of gold nanoparticles (AuNPs). In this study, ligands featuring hydrophobic alkanethiol interiors and hydrophilic shells were used to systematically examine the effects of ligand headgroups on the ligand dynamics. Solution nuclear magnetic resonance (NMR) spectroscopy provided quantitative insight into the monolayer ligand dynamics. Notably, the introduction of hydrophobic moieties to the cationic headgroups significantly decreased ligand conformational mobility; however, variations in hydrophobicity among these moieties had a limited effect on this reduction. Further examination of ligand dynamics under various physiological conditions, including ionic strength and temperature, showed that ligands bound to the AuNP surface become less conformationally mobile with an increase in ionic strength or decreasing temperature. This exploration of ligand dynamics provides insight into designing nanoparticles tailored to specific biological applications.

Delineating effect of headgroup and preparation method on transfection versus toxicity of DNA-loaded lipid nanocarriers.

Aim: To perform a parallel comparison of key parameters affecting the safety and efficiency of lipid-based nanovectors (i.e., complexing headgroups, composition and preparation method). Materials & methods: Various cationic and ionizable headgroups were screened for formulating lipoplexes with GFP-plasmid DNA. Ethanol injection and microfluidics were used to prepare nanoparticles with GFP-plasmid DNA complexed on the surface or within the interior of lipid bilayers. Results: Lipoplexes composed of sphingomyelin 102 exhibited the highest transfection efficiency given their higher cellular uptake in BRAF inhibitor-resistant melanoma cells. Lipid nanoparticlesdemonstrated acceptable transfection efficiency and high spheroid penetration while protecting plasmid DNA under simulated physiological conditions. Conclusion: Selecting the right complexing lipid and preparation method is critical for developing lipid nanocarriers to treat intractable diseases.

Review: chitosan-based biopolymers for anion-exchange membrane fuel cell application.

Chitosan (CS)-based anion exchange membranes (AEMs) have gained significant attention in fuel cell applications owing to their numerous benefits, such as environmental friendliness, flexibility for structural alteration, and improved mechanical, thermal and chemical durability. This study aims to enhance the cell performance of CS-based AEMs by addressing key factors including mechanical stability, ionic conductivity, water absorption and expansion rate. While previous reviews have predominantly focused on CS as a proton-conducting membrane, the present mini-review highlights the advancements of CS-based AEMs. Furthermore, the study investigates the stability of cationic head groups grafted to CS through simulations. Understanding the chemical properties of CS, including the behaviour of grafted head groups, provides valuable insights into the membrane's overall stability and performance. Additionally, the study mentions the potential of modern cellulose membranes for alkaline environments as promising biopolymers. While the primary focus is on CS-based AEMs, the inclusion of cellulose membranes underscores the broader exploration of biopolymer materials for fuel cell applications.

Charge and lipophilicity are required for effective block of the hair-cell mechano-electrical transducer channel by FM1-43 and its derivatives.

The styryl dye FM1-43 is widely used to study endocytosis but behaves as a permeant blocker of the mechano-electrical transducer (MET) channel in sensory hair cells, loading rapidly and specifically into the cytoplasm of hair cells in a MET channel-dependent manner. Patch clamp recordings of mouse outer hair cells (OHCs) were used to determine how a series of structural modifications of FM1-43 affect MET channel block. Fluorescence microscopy was used to assess how the modifications influence hair-cell loading in mouse cochlear cultures and zebrafish neuromasts. Cochlear cultures were also used to evaluate otoprotective potential of the modified FM1-43 derivatives. Structure-activity relationships reveal that the lipophilic tail and the cationic head group of FM1-43 are both required for MET channel block in mouse cochlear OHCs; neither moiety alone is sufficient. The extent of MET channel block is augmented by increasing the lipophilicity/bulkiness of the tail, by reducing the number of positive charges in the head group from two to one, or by increasing the distance between the two charged head groups. Loading assays with zebrafish neuromasts and mouse cochlear cultures are broadly in accordance with these observations but reveal a loss of hair-cell specific labelling with increasing lipophilicity. Although FM1-43 and many of its derivatives are generally cytotoxic when tested on cochlear cultures in the presence of an equimolar concentration of the ototoxic antibiotic gentamicin (5µM), at a 10-fold lower concentration (0.5µM), two of the derivatives protect OHCs from cell death caused by 48h-exposure to 5µM gentamicin.

Benchmarking Cationic Monolayer Protected Nanoparticles and Micelles for Phosphate-Mediated and Nucleotide-Selective Proton Transfer Catalysis.

Both micelles and self-assembled monolayer (SAM)-protected nanoparticles are capable of efficiently hosting water-immiscible substrates to carry out organic reactions in aqueous media. Herein, we have analyzed the different catalytic effect of SAM-protected cationic nanoparticles and cationic surfactants of varying chain length towards base-catalyzed proton transfer mediated ring-opening reaction of 5-nitrobenzisoxazole (NBI) (also known as Kemp Elimination (KE) reaction). We use inorganic phosphate ion or different nucleotide (phosphate-ligated different nucleoside) as base to promote the reaction on micellar or nanoparticle interface. We find almost 2-3 orders of magnitude higher concentration of surfactants of comparable hydrophobicity required to reach the similar activity which attained by low cationic head group concentration bound on nanoparticle. Additionally, at low concentration of nanoparticle-bound surfactant or with high surfactant in micellar form, nucleotide-selectivity has been observed in activating KE reaction unlike free surfactant at low concentration. Finally, we showed enzyme-mediated nucleotide hydrolysis to generate phosphate ion which in situ upregulate the KE activity much more in GNP-based system compared to CTAB. Notably, we show a reasonable superiority of SAM-protected nanoparticles in activating chemical reaction in micromolar concentration of headgroup which certainly boost up application of SAM-based nanoparticles not only for selective recognition but also as eco-friendly catalyst.

Pathway for Water Transport through Breathable Nanocomposite Membranes of PEBAX with Ionic Liquid [C12C1im]Cl.

Water transport through membranes is an attractive topic among the research dedicated to dehydration processes, microenvironment regulation, or more simply, recovery of freshwater. Herein, an atomistic computer simulation is proposed to provide new insights about a water vapor transport mechanism through PEBAX membranes filled with ionic liquid (IL) [C12C1im]Cl. Starting from experimental evidence that indicates an effective increase in water permeation as the IL is added to the polymer matrix (e.g., up to 85·10-3 (g·m)/(m2·day) at 318.15 K for PEBAX@2533 membranes loaded with 70% of IL), molecular dynamics simulations are proposed to explore the key role of IL in water transport inside membranes. The polar region composed of anions and cationic head groups of the IL is demonstrated to serve as the pathway for water transport through the membrane. Water molecules always stay near the pathway, which becomes wider and thus has a larger water-accessible area with increasing IL concentration. Hence, the diffusion coefficients of water molecules and ions increase as the IL concentration increases. The simulation provides useful indications about a microscopic mechanism that regulates the transport of water vapor through a kind of PEBAX/IL membrane, resulting in full agreement with the experimental evidence.

Impact of the Cationic Moiety of Ionic Liquids on Chemoselective Artificial Olfaction.

Ionogels and derived materials are assemblies of polymers and ionic liquids characterized by high stability and ionic conductivity, making them interesting choices as gas sensors. In this work, we assessed the effect of the ionic liquid moiety to generate ionogels and hybrid gels as electrical and optical gas sensors. Six ionic liquids consisting of a constant anion (chloride) and distinct cationic head groups were used to generate ionogels and hybrid gels and further tested as gas sensors in customized electronic nose devices. In general, ionogel-based sensors yielded higher classification accuracies of standard volatile organic compounds when compared to hybrid material-based sensors. In addition, the high chemical diversity of ionic liquids is further translated to a high functional diversity in analyte molecular recognition and sensing.

Structure-Activity Relationships of Cationic Lipidoids against Escherichia coli.

Membrane-active molecules provide a promising strategy to target and kill pathogenic bacteria. Understanding how specific molecular features drive interactions with membrane components and subsequently cause disruption that leads to antimicrobial activity is a crucial step in designing next-generation treatments. Here, we test a library of lipid-like compounds (lipidoids) against Gram-negative bacteria Escherichia coli to garner in-depth structure-activity relationships using antimicrobial assays. Modular lipidoid molecules were synthesized in high-throughput, such that we could analyze 104 compounds with variable combinations of hydrophobic tails and cationic headgroups. Antibacterial activity was strongly correlated to specific structural features, including tail hydrophobicity and headgroup charge density, and also to the overall molecular shape and propensity for self-assembly into curved liquid crystalline phases. Dye permeabilization assays showed that E. coli membranes were permeabilized by lipidoids, confirming their membrane-active nature. The reduced permeabilization, as compared to Gram-positive Bacillus subtilis, alludes to the challenge of permeabilizing the additional outer membrane layer of E. coli. The effect of headgroup solubility in gemini-type lipidoids was also demonstrated, revealing that a headgroup with a more hydrophilic spacer between amine groups had enhanced activity against B. subtilis but not E. coli. This provides insight into features enabling outer membrane penetration and governing selectivity between bacterial species.

Inverse agonism of lysophospholipids with cationic head groups at Gi-coupled receptor GPR82

GPR82 is an orphan G protein-coupled receptor (GPCR) that has been implicated in lipid storage in mouse adipocytes. However, the intracellular signaling as well as the specific ligands of GPR82 remain unknown. GPR82 is closely related to GPR34, a GPCR for the bioactive lipid molecule lysophosphatidylserine. In this study, we screened a lipid library using GPR82-transfected cells to search for ligands that act on GPR82. By measuring cyclic adenosine monophosphate levels, we found that GPR82 is an apparently constitutively active GPCR that leads to Gi protein activation. In addition, edelfosine (1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine), an artificial lysophospholipid with a cationic head group that exerts antitumor activity, inhibited the Gi protein activation by GPR82. Two endogenous lysophospholipids with cationic head groups, lysophosphatidylcholine (1-oleoyl-sn-glycero-3-phosphocholine) and lysophosphatidylethanolamine (1-oleoyl-sn-glycero-3-phosphoethanolamine), also exhibited GPR82 inhibitory activity, albeit weaker than edelfosine. Förster resonance energy transfer imaging analysis consistently demonstrated that Gi protein-coupled GPR82 has an apparent constitutive activity that is edelfosine-sensitive. Consistent data were obtained from GPR82-mediated binding analysis of guanosine-5'-O-(3-thiotriphosphate) to cell membranes. Furthermore, in GPR82-transfected cells, edelfosine inhibited insulin-induced extracellular signal-regulated kinase activation, like compounds that function as inverse agonists at other GPCRs. Therefore, edelfosine is likely to act as an inverse agonist of GPR82. Finally, GPR82 expression inhibited adipocyte lipolysis, which was abrogated by edelfosine. Our findings suggested that the cationic lysophospholipids edelfosine, lysophosphatidylcholine and lysophosphatidylethanolamine are novel inverse agonists for Gi-coupled GPR82, which is apparently constitutively active, and has the potential to exert lipolytic effects through GPR82.