{ "type": "Document", "metadata": { "doi": "10.7554/eLife.108319", "title": "iGABASnFR2 is an improved genetically encoded protein sensor of GABA", "authors": [ "Kolb et al. (GENIE Project Team + Turner lab)" ] }, "children": [ { "type": "ClaimGraph", "identifier": "kolb-2026-igabasnfr2-claims", "children": [ { "type": "Claim", "identifier": "alt-signal-from-cross-reactivity", "role": "hypothesis", "children": [ { "type": "Text", "value": "The fluorescence response attributed to iGABASnFR2 reflects binding of, or interference by, compounds structurally related to GABA rather than GABA itself, so the reported sensitivity is not a measure of GABA detection." } ], "stance": "rejects", "metadata": { "uuid": "0b8f6f71-6251-48b6-9cca-738ba83a4942", "concepts": [ "selectivity", "cross-reactivity", "alternative explanation" ] } }, { "type": "Claim", "identifier": "crystal-structure-pdb-9d57", "role": "methodological", "children": [ { "type": "Text", "value": "The crystal structure of iGABASnFR2 is deposited at the Protein Data Bank (accession 9D57), providing atomic-resolution structural information on the binding pocket and cpGFP domain arrangement." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-cpgfp-rigid-on-gaba-binding", "relationType": "cito:usesMethodIn" } ], "metadata": { "uuid": "f7d3b257-5ae5-4122-a122-0184b12b15f7", "concepts": [ "crystal structure", "PDB", "X-ray crystallography", "binding pocket", "cpGFP" ] } }, { "type": "Claim", "identifier": "hypothesis-improved-sensor-enables-new-biology", "role": "hypothesis", "children": [ { "type": "Text", "value": "A GABA sensor with sufficiently improved sensitivity, kinetics, and affinity will cross qualitative capability thresholds — not merely improve signal-to-noise on measurements iGABASnFR1 could already make, but enable measurements that iGABASnFR1 cannot make at all. Specifically: detection of GABA release from individual inhibitory boutons in slice, single-trial detection of direction-selective GABA release from starburst amacrine cells in retina, and detection of volume-transmitted GABA in vivo following sensory stimulation." } ], "panel": [ "hypothesis" ], "relations": [ { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "claimrel:entails" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "claimrel:entails" }, { "xref": "igabasnfr2-invivo-barrel-cortex", "relationType": "claimrel:entails" } ], "metadata": { "uuid": "96510607-0b3e-42ef-8144-79bc0940eefe", "concepts": [ "sensor capability threshold", "single-bouton imaging", "direction selectivity", "in vivo GABA imaging", "volume transmission" ], "displayClaim": "A sufficiently improved GABA sensor will cross qualitative capability thresholds — enabling single-bouton, single-trial direction-selective, and in vivo volume-transmitted GABA measurements that iGABASnFR1 could not make at all.", "shortClaim": "A better GABA sensor unlocks single-bouton, single-trial, and volume-transmission measurements." } }, { "type": "Claim", "identifier": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "role": "hypothesis", "children": [ { "type": "Text", "value": "Targeted near-saturation mutagenesis at sites in and around the Pf622 GABA-binding pocket and the cpGFP-linker interfaces can yield a successor to iGABASnFR1 with substantially improved sensitivity (ΔF/F), increased on-cell affinity within the physiologically relevant range, faster binding kinetics, and improved expression / membrane trafficking — without sacrificing GABA selectivity. The performance ceiling of iGABASnFR1 is set by suboptimal residues at a small number of structurally identifiable positions, not by an intrinsic limit of the cpGFP-coupled Venus-flytrap scaffold." } ], "panel": [ "hypothesis" ], "relations": [ { "xref": "prediction-screen-yields-multiple-improved-variants", "relationType": "claimrel:entails" }, { "xref": "prediction-improved-sensor-enables-new-measurements", "relationType": "claimrel:entails" } ], "metadata": { "uuid": "ac2b204d-13a2-4aec-91b9-4792961bc503", "concepts": [ "sensor engineering", "saturation mutagenesis", "Pf622 binding pocket", "cpGFP linker", "directed evolution" ], "displayClaim": "Targeted saturation mutagenesis of the Pf622 binding pocket and cpGFP linkers can yield a substantially improved successor to iGABASnFR1 — the v1 ceiling is set by suboptimal residues, not the scaffold.", "shortClaim": "Saturation mutagenesis of Pf622 and cpGFP linkers yields a substantially improved GABA sensor." } }, { "type": "Claim", "identifier": "igabasnfr2-13fold-expression-increase", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 shows a 13.1-fold increase in responsive pixels (expression-weighted response) compared to iGABASnFR1, indicating both improved sensitivity and membrane trafficking." } ], "epistemicStrength": "moderate", "relations": [ { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:disagreesWith" }, { "xref": "prediction-screen-yields-multiple-improved-variants", "relationType": "claimrel:tests" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:confirms" } ], "metadata": { "uuid": "a8787aa1-9028-4ed0-827a-cdb38e9f59cb", "concepts": [ "iGABASnFR2", "expression", "responsive pixels", "membrane trafficking" ] } }, { "type": "Claim", "identifier": "igabasnfr2-2p-compatible", "role": "methodological", "children": [ { "type": "Text", "value": "iGABASnFR2 has two-photon excitation spectra similar to its one-photon spectra and is compatible with two-photon imaging; both v2 sensors show reduced pH dependence compared to iGABASnFR1." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "cito:usesMethodIn" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "cito:usesMethodIn" }, { "xref": "igabasnfr2-invivo-barrel-cortex", "relationType": "cito:usesMethodIn" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:disagreesWith" }, { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "cito:supports" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "cito:supports" } ], "metadata": { "uuid": "8e7427f6-8291-4eac-9f8f-7949b519beff", "concepts": [ "iGABASnFR2", "two-photon imaging", "excitation spectrum", "pH dependence", "photophysics" ] } }, { "type": "Claim", "identifier": "igabasnfr2-cpgfp-rigid-on-gaba-binding", "role": "interpretation", "children": [ { "type": "Text", "value": "GABA binding to iGABASnFR2 closes the Venus flytrap lobes of the Pf622 domain but produces negligible conformational change in cpGFP and its flanking linkers (RMSD 0.25 Å), contrasting with the large cpGFP interface rearrangement seen in GCaMP upon calcium binding." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:disagreesWith" }, { "xref": "crystal-structure-pdb-9d57", "relationType": "claimrel:interprets" }, { "xref": "crystal-structure-pdb-9d57", "relationType": "cito:supports" }, { "xref": "crystal-structure-pdb-9d57", "relationType": "cito:extends" } ], "metadata": { "uuid": "81a3fe0f-a268-4abf-8ad5-b4abbdb4b2dc", "concepts": [ "iGABASnFR2", "crystal structure", "cpGFP", "conformational change", "Venus flytrap", "allosteric mechanism" ], "shortClaim": "GABA closes the Pf622 lobes of iGABASnFR2 while leaving cpGFP nearly rigid." } }, { "type": "Claim", "identifier": "igabasnfr2-fourfold-sensitivity-gain", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 exhibits a 4.1-fold improvement in ΔF/F sensitivity compared to iGABASnFR1 under equivalent stimulation conditions in cultured neurons, quantified by the high-throughput screening pipeline." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2n-negative-going-variant", "relationType": "cito:disagreesWith" }, { "xref": "prediction-screen-yields-multiple-improved-variants", "relationType": "claimrel:tests" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:confirms" } ], "metadata": { "uuid": "f1d695b7-88cd-49d5-9fdc-f66cad65e1c8", "concepts": [ "iGABASnFR2", "sensitivity", "ΔF/F", "mutagenesis", "high-throughput screening" ] } }, { "type": "Claim", "identifier": "igabasnfr2-gaba-selective-specificity", "role": "control", "children": [ { "type": "Text", "value": "iGABASnFR2 displays high selectivity for GABA over structurally related compounds, none of which interfere with GABA binding as competitive or non-competitive antagonists at 1 mM concentrations." } ], "epistemicStrength": "strong", "relations": [ { "xref": "alt-signal-from-cross-reactivity", "relationType": "claimrel:rulesOut" }, { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-invivo-barrel-cortex", "relationType": "cito:confirms" } ], "metadata": { "uuid": "669554c3-7a4d-453b-b9bd-893e935e630c", "concepts": [ "iGABASnFR2", "GABA selectivity", "neurotransmitter specificity", "off-target binding" ] } }, { "type": "Claim", "identifier": "igabasnfr2-invivo-barrel-cortex", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 detects volume-transmitted extracellular GABA signals in vivo in mouse barrel cortex (layers L2–L3, ~300 μm depth) evoked by rhythmic whisker stimulation, corresponding to a transient GABA concentration increase of approximately 2–2.5 μM at peak." } ], "epistemicStrength": "moderate", "relations": [ { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "cito:disagreesWith" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "cito:disagreesWith" }, { "xref": "prediction-improved-sensor-enables-new-measurements", "relationType": "claimrel:tests" }, { "xref": "hypothesis-improved-sensor-enables-new-biology", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:supports" }, { "xref": "igabasnfr2-2p-compatible", "relationType": "claimrel:requires" } ], "metadata": { "uuid": "f2fccd5f-8ee8-4138-9e97-055ebda75cd8", "concepts": [ "iGABASnFR2", "in vivo imaging", "barrel cortex", "whisker stimulation", "volume transmission", "GABA" ] } }, { "type": "Claim", "identifier": "igabasnfr2-kinetics-rise-decay", "role": "empirical", "children": [ { "type": "Text", "value": "At 10 action potentials (83 Hz), iGABASnFR2 has a rise time constant of 43 ± 9 ms (faster than iGABASnFR1's 61 ± 13 ms) and a decay time constant of 73 ± 26 ms (slower than iGABASnFR1's 62 ± 29 ms), while iGABASnFR2n has a substantially slower rise time of 72 ± 8 ms." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:disagreesWith" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:supports" } ], "metadata": { "uuid": "a56b114d-fbe5-422f-91cd-00a7de8b98ee", "concepts": [ "iGABASnFR2", "kinetics", "rise time", "decay time", "iGABASnFR2n" ] } }, { "type": "Claim", "identifier": "igabasnfr2-oncell-affinity-sevenfold", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 expressed on the surface of cultured neurons has an on-cell EC50 of 6.4 ± 0.21 μM for GABA, representing a sevenfold higher affinity than iGABASnFR1 (EC50 ~45 μM on-cell) while remaining above the tonic extracellular GABA concentration range of 0.2–2.5 μM in the mammalian brain." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:disagreesWith" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:supports" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:extends" } ], "metadata": { "uuid": "10eb034c-f5b4-422e-a43b-8375a917111d", "concepts": [ "iGABASnFR2", "GABA affinity", "EC50", "on-cell titration", "tonic GABA" ] } }, { "type": "Claim", "identifier": "igabasnfr2-retina-direction-selectivity", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 directly demonstrates direction-selective GABA release from starburst amacrine cells in the intact retina, with significantly higher SNR and response reliability than iGABASnFR1; iGABASnFR1 signals were insufficient to detect direction selectivity even after trial-averaging." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "cito:disagreesWith" }, { "xref": "prediction-improved-sensor-enables-new-measurements", "relationType": "claimrel:tests" }, { "xref": "hypothesis-improved-sensor-enables-new-biology", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:supports" }, { "xref": "igabasnfr2-2p-compatible", "relationType": "claimrel:requires" } ], "metadata": { "uuid": "808a0591-b637-4f1a-9ff9-e05e779644bf", "concepts": [ "iGABASnFR2", "retina", "direction selectivity", "starburst amacrine cell", "GABA release", "two-photon imaging" ] } }, { "type": "Claim", "identifier": "igabasnfr2-single-bouton-hippocampus", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 detects GABA release from individual hippocampal interneuron axonal boutons using Tornado scanning two-photon microscopy; iGABASnFR1 failed to produce any detectable spike-evoked fluorescence signal across 15 trials in five separate experiments." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "cito:disagreesWith" }, { "xref": "prediction-improved-sensor-enables-new-measurements", "relationType": "claimrel:tests" }, { "xref": "hypothesis-improved-sensor-enables-new-biology", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:supports" }, { "xref": "igabasnfr2-2p-compatible", "relationType": "claimrel:requires" } ], "metadata": { "uuid": "ff5506c7-eac9-42f7-8643-d38068feafd5", "concepts": [ "iGABASnFR2", "hippocampus", "single bouton", "Tornado scan", "two-photon microscopy", "interneuron" ] } }, { "type": "Claim", "identifier": "igabasnfr2-single-exponential-kinetics", "role": "empirical", "children": [ { "type": "Text", "value": "iGABASnFR2 and iGABASnFR2n display single-exponential stopped-flow kinetics, whereas iGABASnFR1 exhibits biphasic kinetics; the observed reaction rate constants (Kobs) are far greater for both v2 sensors than for iGABASnFR1." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-kinetics-rise-decay", "relationType": "cito:disagreesWith" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:confirms" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:supports" } ], "metadata": { "uuid": "837eae22-f6f6-4d29-9696-c998ee633b7f", "concepts": [ "iGABASnFR2", "stopped-flow kinetics", "kon", "binding kinetics", "iGABASnFR1 comparison" ] } }, { "type": "Claim", "identifier": "igabasnfr2n-negative-going-variant", "role": "empirical", "children": [ { "type": "Text", "value": "A negative-going variant (iGABASnFR2n) achieves -2.2-fold ΔF/F with 10.3-fold increased responsive pixels, providing an alternative sensor with inverted fluorescence change direction for applications requiring negative-going signals." } ], "epistemicStrength": "moderate", "relations": [ { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:disagreesWith" }, { "xref": "prediction-screen-yields-multiple-improved-variants", "relationType": "claimrel:tests" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:confirms" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:confirms" } ], "metadata": { "uuid": "305140b5-5720-45d7-8706-593e29243fb6", "concepts": [ "iGABASnFR2n", "negative-going", "ΔF/F", "sensor variant", "GABA sensor" ] } }, { "type": "Claim", "identifier": "mutagenesis-3947-variants-screened", "role": "methodological", "children": [ { "type": "Text", "value": "High-throughput mutagenesis screening generated 3,947 total variants from 39 targeted sites; 93 variants exceeded iGABASnFR1 controls in ΔF/F, and 22 showed improvements in both sensitivity and expression." } ], "epistemicStrength": "strong", "relations": [ { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "cito:usesMethodIn" }, { "xref": "igabasnfr2-13fold-expression-increase", "relationType": "cito:usesMethodIn" }, { "xref": "igabasnfr2n-negative-going-variant", "relationType": "cito:usesMethodIn" }, { "xref": "prediction-screen-yields-multiple-improved-variants", "relationType": "claimrel:tests" } ], "metadata": { "uuid": "c0396bdd-9084-4a13-8dd8-f616c5cdecd9", "concepts": [ "mutagenesis", "high-throughput screening", "targeted sites", "variant count" ] } }, { "type": "Claim", "identifier": "prediction-improved-sensor-enables-new-measurements", "role": "prediction", "children": [ { "type": "Text", "value": "If iGABASnFR2's improvements (4-fold ΔF/F, 7-fold on-cell affinity, faster rise kinetics, 2P-compatible spectra) cross qualitative capability thresholds, then side-by-side comparison with iGABASnFR1 in three demanding preparations should show: (i) iGABASnFR2 detects single-bouton hippocampal GABA release where iGABASnFR1 yields no signal; (ii) iGABASnFR2 resolves direction-selective starburst GABA release on single trials where iGABASnFR1 cannot resolve direction even after trial-averaging; (iii) iGABASnFR2 detects whisker-evoked volume-transmitted GABA in vivo at cortical layers reachable by 2P imaging." } ], "panel": [ "prediction" ], "relations": [ { "xref": "hypothesis-improved-sensor-enables-new-biology", "relationType": "cito:citesAsSourceDocument" }, { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:citesAsSourceDocument" } ], "metadata": { "uuid": "ba1d6ed5-d8ba-40d2-b255-87315d83c216", "concepts": [ "capability threshold", "single-bouton GABA", "direction selectivity", "in vivo barrel cortex", "side-by-side sensor comparison" ], "displayClaim": "iGABASnFR2 should enable single-bouton, single-trial DS, and in vivo whisker-evoked GABA detection — three qualitative threshold crossings vs iGABASnFR1." } }, { "type": "Claim", "identifier": "prediction-screen-yields-multiple-improved-variants", "role": "prediction", "children": [ { "type": "Text", "value": "If the v1 performance ceiling is set by suboptimal residues at identifiable structural sites, then near-saturation mutagenesis at those sites should yield (i) multiple variants exceeding iGABASnFR1 in ΔF/F sensitivity, (ii) at least one variant simultaneously improved on sensitivity and expression / responsive-pixel count, and (iii) potentially variants with qualitatively new behaviour (e.g. inverted response). The screen should not be dominated by single-site marginal improvements." } ], "panel": [ "prediction" ], "relations": [ { "xref": "hypothesis-saturation-mutagenesis-yields-improved-sensor", "relationType": "cito:citesAsSourceDocument" } ], "metadata": { "uuid": "bce0de60-5b50-44e1-aafd-5d94c2f06e9b", "concepts": [ "saturation mutagenesis", "high-throughput screening", "variant recovery", "inverted-response sensor" ], "displayClaim": "Saturation mutagenesis should yield multiple variants exceeding iGABASnFR1, at least one improved on both sensitivity and expression, and potentially qualitatively novel variants such as inverted-response sensors." } }, { "type": "Claim", "identifier": "scope-sensor-engineering-paper", "role": "scope", "children": [ { "type": "Text", "value": "All findings are scoped to a sensor-engineering paper: the screen is wet-lab only (cultured rat primary neurons in 96-well format, evoked synaptic release as the ΔF/F readout); biophysical characterisation uses purified protein expressed in E. coli (stopped-flow, titration, 2P spectra); on-cell measurements use cultured neurons under perfusion; biological demonstrations use ex vivo retina (ChAT-Cre mice + AAV), acute and organotypic hippocampal slice (biolistic and AAV delivery), and in vivo cranial window in mouse barrel cortex (AAV9-hSyn-iGABASnFR2). The paper does not test iGABASnFR2 in non-mammalian preparations, in awake behaving animals at fine temporal resolution, or in genetic backgrounds beyond standard laboratory mouse and rat." } ], "panel": [ "scope" ], "relations": [ { "xref": "mutagenesis-3947-variants-screened", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-13fold-expression-increase", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2n-negative-going-variant", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-kinetics-rise-decay", "relationType": "claimrel:scopes" }, { "xref": "crystal-structure-pdb-9d57", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-cpgfp-rigid-on-gaba-binding", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-oncell-affinity-sevenfold", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-single-exponential-kinetics", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-2p-compatible", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-gaba-selective-specificity", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-invivo-barrel-cortex", "relationType": "claimrel:scopes" } ], "metadata": { "uuid": "a0fb081f-c245-4323-b15a-60d9496f6359", "concepts": [ "sensor engineering scope", "in vitro screen", "ex vivo demonstration", "in vivo demonstration", "preparation envelope" ], "displayClaim": "Sensor-engineering scope: in vitro screen (rat primary neurons, 96-well), purified protein (E. coli) for biophysics, ex vivo retina + slice, and a single in vivo demonstration in mouse barrel cortex. No awake behaviour; no non-mammalian preparations." } }, { "type": "Claim", "identifier": "screening-scope-wet-lab-only", "role": "scope", "children": [ { "type": "Text", "value": "The primary claims of iGABASnFR2 performance (sensitivity, kinetics, SNR) are established through wet-lab measurements (fluorescence imaging in cultured neurons, stopped-flow kinetics, two-photon excitation spectroscopy) that cannot be reproduced from deposited code and data alone; computational analysis of deposited source data covers only figure generation, not the underlying measurements." } ], "epistemicStrength": "strong", "relations": [ { "xref": "mutagenesis-3947-variants-screened", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-fourfold-sensitivity-gain", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-13fold-expression-increase", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2n-negative-going-variant", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-kinetics-rise-decay", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-cpgfp-rigid-on-gaba-binding", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-oncell-affinity-sevenfold", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-single-exponential-kinetics", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-2p-compatible", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-gaba-selective-specificity", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-retina-direction-selectivity", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-single-bouton-hippocampus", "relationType": "claimrel:scopes" }, { "xref": "igabasnfr2-invivo-barrel-cortex", "relationType": "claimrel:scopes" } ], "metadata": { "uuid": "0cdf69ab-ffa6-4e8b-a87b-e681ec8c2526", "concepts": [ "wet lab", "stopped-flow kinetics", "two-photon spectroscopy", "reproduction barrier" ] } } ] } ], "title": [ { "type": "Text", "value": "iGABASnFR2 is an improved genetically encoded protein sensor of GABA" } ] }