{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T13:02:29Z","timestamp":1790254949037,"version":"4.1.0"},"reference-count":99,"publisher":"American Chemical Society (ACS)","issue":"38","license":[{"start":{"date-parts":[[2026,8,31]],"date-time":"2026-08-31T00:00:00Z","timestamp":1788134400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,24]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Heat shock protein 90 kDa (Hsp90) is an ATP-dependent molecular chaperone whose function relies on conformational rearrangements and interactions with cochaperones and clients. Binding of nucleotides, cochaperones, and clients leads to functional structural rearrangements, often associated with heterogeneous structural ensembles that are challenging to characterize using high-resolution structure determination methods alone. Electron paramagnetic resonance (EPR) spectroscopy has emerged as a powerful approach for tracking the conformational landscape of proteins. However, despite its great potential, its application to Hsp90 homologs has so far remained limited, and the insights gained have not yet been comprehensively reviewed. In this mini-review, we summarize EPR studies on cytosolic, mitochondrial, and endoplasmic reticulum Hsp90 with the aim of highlighting how EPR has advanced our understanding of nucleotide- and partner-dependent conformations. Specifically, we summarize how continuous wave EPR (CW-EPR), double electron\u2013electron resonance (DEER), and electron nuclear double resonance (ENDOR) spectroscopies revealed conformational equilibria, symmetry breaking, dissociation constants, and the structural role of intrinsically disordered regions within Hsp90, while also discussing methodological advances and recent extensions to cellular contexts. Overall, these studies establish EPR spectroscopy as a valuable biophysical tool for resolving conformational ensembles and structural heterogeneity underlying Hsp90\u2019s function, with general relevance to the structural biology, spectroscopy, and chaperone fields, and pave the way for future in vitro and in-cell investigations of this exciting molecular chaperone.<\/jats:p>","DOI":"10.1021\/acs.jpcb.6c03220","type":"journal-article","created":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T03:39:36Z","timestamp":1788406776000},"page":"9750-9763","source":"Crossref","is-referenced-by-count":0,"title":["Electron Paramagnetic\nResonance (EPR) Spectroscopy\nReveals Nucleotide- and Partner-Dependent Conformational Ensembles\nin Hsp90"],"prefix":"10.1021","volume":"130","author":[{"given":"Christini","family":"Fiotaki","sequence":"first","affiliation":[{"name":"University of Crete , , ,","place":["Heraklion, Greece, 70013"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5714-7159","authenticated-orcid":true,"given":"Daniella","family":"Goldfarb","sequence":"additional","affiliation":[{"name":"Weizmann Institute of Science , , ,","place":["Rehovot, Israel, 7610001"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8017-5457","authenticated-orcid":true,"given":"Angeliki","family":"Giannouli","sequence":"additional","affiliation":[{"name":"University of Crete , , ,","place":["Heraklion, Greece, 70013"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,8,31]]},"reference":[{"issue":"7","key":"2026092408092793700_cit1","doi-asserted-by":"publisher","first-page":"515","DOI":"10.1038\/nrm2918","article-title":"HSP90 at the hub of protein homeostasis:\nemerging mechanistic insights","volume":"11","author":"Taipale","year":"2010","journal-title":"Nat. Rev. Mol.\nCell Biol."},{"key":"2026092408092793700_cit2","doi-asserted-by":"publisher","first-page":"719","DOI":"10.1146\/annurev-micro-032421-035644","article-title":"The Bacterial Hsp90 Chaperone: Cellular\nFunctions and Mechanism of Action","volume":"75","author":"Wickner","year":"2021","journal-title":"Annu. Rev.\nMicrobiol."},{"issue":"5","key":"2026092408092793700_cit3","doi-asserted-by":"publisher","first-page":"715","DOI":"10.1016\/j.cell.2004.12.024","article-title":"Navigating\nthe Chaperone Network: An Integrative Map of Physical and Genetic\nInteractions Mediated by the Hsp90 Chaperone","volume":"120","author":"Zhao","year":"2005","journal-title":"Cell"},{"issue":"5","key":"2026092408092793700_cit4","doi-asserted-by":"publisher","first-page":"101905","DOI":"10.1016\/j.jbc.2022.101905","article-title":"Folding\nor holding? Hsp70 and Hsp90\nchaperoning of misfolded proteins in neurodegenerative disease","volume":"298","author":"Rutledge","year":"2022","journal-title":"J. Biol. Chem."},{"issue":"18 Pt B","key":"2026092408092793700_cit5","doi-asserted-by":"publisher","first-page":"3029","DOI":"10.1016\/j.jmb.2018.05.026","article-title":"Dancing with the Diva:\nHsp90-Client Interactions","volume":"430","author":"Radli","year":"2018","journal-title":"J. Mol. Biol."},{"issue":"18","key":"2026092408092793700_cit6","doi-asserted-by":"publisher","first-page":"15968","DOI":"10.1021\/acs.jmedchem.4c00966","article-title":"Targeting\nHSP90 for Cancer Therapy: Current Progress and Emerging Prospects","volume":"67","author":"Liang","year":"2024","journal-title":"J. Med. Chem."},{"issue":"5","key":"2026092408092793700_cit7","doi-asserted-by":"publisher","first-page":"636","DOI":"10.1021\/acscentsci.2c00013","article-title":"Development of a First-in-Class Small-Molecule\nInhibitor of the C-Terminal Hsp90 Dimerization","volume":"8","author":"Bhatia","year":"2022","journal-title":"ACS Cent. Sci."},{"issue":"1","key":"2026092408092793700_cit8","doi-asserted-by":"publisher","first-page":"65","DOI":"10.1016\/S0092-8674(00)80314-1","article-title":"Identification and\nStructural Characterization of the\nATP\/ADP-Binding Site in the Hsp90 Molecular Chaperone","volume":"90","author":"Prodromou","year":"1997","journal-title":"Cell"},{"issue":"6","key":"2026092408092793700_cit9","doi-asserted-by":"publisher","first-page":"1307","DOI":"10.1016\/s1097-2765(02)00785-2","article-title":"Activation of the ATPase\nactivity of Hsp90 by the stress-regulated\ncochaperone aha1","volume":"10","author":"Panaretou","year":"2002","journal-title":"Mol. Cell"},{"issue":"3","key":"2026092408092793700_cit10","doi-asserted-by":"publisher","first-page":"211","DOI":"10.1002\/bip.21292","article-title":"Hsp90 and co-chaperones\ntwist the functions of diverse\nclient proteins","volume":"93","author":"Zuehlke","year":"2010","journal-title":"Biopolymers"},{"issue":"1","key":"2026092408092793700_cit11","doi-asserted-by":"publisher","first-page":"87","DOI":"10.1016\/S0092-8674(03)01027-4","article-title":"The Mechanism of\nHsp90 regulation by the protein kinase-specific cochaperone p50(cdc37)","volume":"116","author":"Roe","year":"2004","journal-title":"Cell"},{"issue":"9","key":"2026092408092793700_cit12","doi-asserted-by":"publisher","first-page":"a034017","DOI":"10.1101\/cshperspect.a034017","article-title":"Function, and Regulation of the Hsp90\nMachinery","volume":"11","author":"Biebl","year":"2019","journal-title":"Cold Spring Harbor Perspect. Biol."},{"issue":"7087","key":"2026092408092793700_cit13","doi-asserted-by":"publisher","first-page":"1013","DOI":"10.1038\/nature04716","article-title":"Crystal structure\nof an Hsp90-nucleotide-p23\/Sba1 closed chaperone complex","volume":"440","author":"Ali","year":"2006","journal-title":"Nature"},{"issue":"1","key":"2026092408092793700_cit14","doi-asserted-by":"publisher","first-page":"6710","DOI":"10.1038\/s41467-025-61962-0","article-title":"ATP plays a structural\nrole in Hsp90 function","volume":"16","author":"Reidy","year":"2025","journal-title":"Nat. Commu.n"},{"issue":"3","key":"2026092408092793700_cit15","doi-asserted-by":"publisher","first-page":"464","DOI":"10.1016\/j.molcel.2012.11.017","article-title":"Uncovering a region\nof heat shock protein 90 important for client binding in E. coli and chaperone function in yeast","volume":"49","author":"Genest","year":"2013","journal-title":"Mol. Cell"},{"issue":"6","key":"2026092408092793700_cit16","doi-asserted-by":"publisher","first-page":"345","DOI":"10.1038\/nrm.2017.20","article-title":"The HSP90 chaperone\nmachinery","volume":"18","author":"Schopf","year":"2017","journal-title":"Nat. Rev. Mol. Cell Biol."},{"issue":"2","key":"2026092408092793700_cit17","doi-asserted-by":"publisher","first-page":"172","DOI":"10.1016\/j.bpj.2023.12.005","article-title":"C-terminal\ndomain dimerization in yeast Hsp90 is moderately modulated by the\nother domains","volume":"123","author":"Oranges","year":"2024","journal-title":"Biophys. J."},{"issue":"2","key":"2026092408092793700_cit18","doi-asserted-by":"publisher","first-page":"580","DOI":"10.1073\/pnas.1011867108","article-title":"N-terminal\ndomain of human Hsp90 triggers binding to\nthe cochaperone p23","volume":"108","author":"Karago\u0308z","year":"2011","journal-title":"Proc. Natl. Acad. Sci.\nU. S. A."},{"issue":"1","key":"2026092408092793700_cit19","doi-asserted-by":"publisher","first-page":"4192","DOI":"10.1038\/ncomms5192","article-title":"Four-colour FRET reveals directionality\nin the Hsp90 multicomponent machinery","volume":"5","author":"Ratzke","year":"2014","journal-title":"Nat.\nCommun."},{"issue":"8","key":"2026092408092793700_cit20","doi-asserted-by":"publisher","first-page":"108063","DOI":"10.1016\/j.celrep.2020.108063","article-title":"Hsp90 Co-chaperones\nForm Plastic\nGenetic Networks Adapted to Client Maturation","volume":"32","author":"Biebl","year":"2020","journal-title":"Cell Rep."},{"issue":"15","key":"2026092408092793700_cit21","doi-asserted-by":"publisher","first-page":"16469","DOI":"10.1021\/jacs.6c04189","article-title":"Beyond a Passive Tether: Structural\nInsights into the Disordered Tail of Hsp90","volume":"148","author":"Edinach","year":"2026","journal-title":"J. Am. Chem. Soc."},{"issue":"34","key":"2026092408092793700_cit22","doi-asserted-by":"publisher","first-page":"22559","DOI":"10.1074\/jbc.M109.031658","article-title":"The charged linker\nregion is an important regulator of Hsp90 function","volume":"284","author":"Hainzl","year":"2009","journal-title":"J. Biol. Chem."},{"issue":"1","key":"2026092408092793700_cit23","doi-asserted-by":"publisher","first-page":"8","DOI":"10.1016\/j.molcel.2015.02.022","article-title":"Hsp90: Breaking\nthe Symmetry","volume":"58","author":"Mayer","year":"2015","journal-title":"Mol. Cell"},{"issue":"7","key":"2026092408092793700_cit24","doi-asserted-by":"publisher","first-page":"880","DOI":"10.3390\/biom12070880","article-title":"The Mitochondrial HSP90 Paralog TRAP1:\nStructural Dynamics, Interactome, Role in Metabolic Regulation, and\nInhibitors","volume":"12","author":"Joshi","year":"2022","journal-title":"Biomolecules"},{"issue":"12","key":"2026092408092793700_cit25","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2309326121","article-title":"Structural transitions modulate the\nchaperone activities of Grp94","volume":"121","author":"Amankwah","year":"2024","journal-title":"Proc. Natl. Acad.\nSci. U. S. A."},{"issue":"2","key":"2026092408092793700_cit26","doi-asserted-by":"publisher","first-page":"330","DOI":"10.1016\/j.molcel.2013.12.023","article-title":"Structural\nasymmetry in the closed state of mitochondrial\nHsp90 (TRAP1) supports a two-step ATP hydrolysis mechanism","volume":"53","author":"Lavery","year":"2014","journal-title":"Mol. Cell"},{"issue":"12","key":"2026092408092793700_cit27","doi-asserted-by":"publisher","first-page":"2800","DOI":"10.1016\/j.celrep.2017.08.079","article-title":"Structural\nand Functional Analysis of GRP94 in the Closed State Reveals an Essential\nRole for the Pre-N Domain and a Potential Client-Binding Site","volume":"20","author":"Huck","year":"2017","journal-title":"Cell Rep."},{"issue":"2","key":"2026092408092793700_cit28","doi-asserted-by":"publisher","first-page":"174","DOI":"10.1038\/nmeth.4081","article-title":"Multidomain structure and correlated\ndynamics determined by self-consistent\nFRET networks","volume":"14","author":"Hellenkamp","year":"2017","journal-title":"Nat. Methods"},{"issue":"2","key":"2026092408092793700_cit29","doi-asserted-by":"publisher","first-page":"329","DOI":"10.1016\/j.cell.2006.09.027","article-title":"Structural Analysis\nof E. coli hsp90 reveals dramatic nucleotide-dependent\nconformational rearrangements","volume":"127","author":"Shiau","year":"2006","journal-title":"Cell"},{"issue":"30","key":"2026092408092793700_cit30","doi-asserted-by":"publisher","first-page":"21170","DOI":"10.1074\/jbc.M800046200","article-title":"Intra- and Intermonomer Interactions\nAre Required to Synergistically Facilitate ATP Hydrolysis in Hsp90","volume":"283","author":"Cunningham","year":"2008","journal-title":"J. Biol. Chem."},{"issue":"3","key":"2026092408092793700_cit31","doi-asserted-by":"publisher","first-page":"309","DOI":"10.1016\/j.str.2022.12.014","article-title":"Unique\ninterface and dynamics of the complex of HSP90 with a specialized\ncochaperone AIPL1","volume":"31","author":"Srivastava","year":"2023","journal-title":"Structure"},{"issue":"5","key":"2026092408092793700_cit32","doi-asserted-by":"publisher","first-page":"631","DOI":"10.1016\/j.molcel.2008.10.024","article-title":"Species-dependent\nensembles of conserved conformational\nstates define the Hsp90 chaperone ATPase cycle","volume":"32","author":"Southworth","year":"2008","journal-title":"Mol. Cell"},{"issue":"5","key":"2026092408092793700_cit33","doi-asserted-by":"publisher","first-page":"755","DOI":"10.1016\/j.str.2008.01.021","article-title":"Multiple\nConformations of E. coli Hsp90 in Solution:\nInsights into the Conformational Dynamics of Hsp90","volume":"16","author":"Krukenberg","year":"2008","journal-title":"Structure"},{"issue":"1","key":"2026092408092793700_cit34","doi-asserted-by":"publisher","first-page":"161","DOI":"10.1073\/pnas.1107930108","article-title":"Heat shock protein\n90\u2019s mechanochemical\ncycle is dominated by thermal fluctuations","volume":"109","author":"Ratzke","year":"2012","journal-title":"Proc. Natl. Acad. Sci. U. S. A."},{"issue":"3","key":"2026092408092793700_cit35","doi-asserted-by":"publisher","first-page":"281","DOI":"10.1038\/nsmb.1557","article-title":"The large\nconformational changes of Hsp90 are only weakly coupled to ATP hydrolysis","volume":"16","author":"Mickler","year":"2009","journal-title":"Nat. Struct. Mol. Biol."},{"issue":"51","key":"2026092408092793700_cit36","doi-asserted-by":"publisher","DOI":"10.1126\/sciadv.abl7295","article-title":"Client binding shifts\nthe populations\nof dynamic Hsp90 conformations through an allosteric network","volume":"7","author":"Lopez","year":"2021","journal-title":"Sci. Adv."},{"issue":"1","key":"2026092408092793700_cit37","doi-asserted-by":"publisher","first-page":"395","DOI":"10.1073\/pnas.1916030116","article-title":"Two closed\nATP- and ADP-dependent conformations in yeast Hsp90 chaperone detected\nby Mn(II) EPR spectroscopic techniques","volume":"117","author":"Giannoulis","year":"2020","journal-title":"Proc.\nNatl. Acad. Sci. U. S. A."},{"issue":"48","key":"2026092408092793700_cit38","doi-asserted-by":"publisher","first-page":"45942","DOI":"10.1074\/jbc.M207754200","article-title":"The Influence\nof ATP and p23 on the\nConformation of hsp90 *","volume":"277","author":"Sullivan","year":"2002","journal-title":"J. Biol. Chem."},{"issue":"6","key":"2026092408092793700_cit39","doi-asserted-by":"publisher","first-page":"1087","DOI":"10.1016\/j.str.2004.03.020","article-title":"The Crystal Structure of the Carboxy-Terminal\nDimerization Domain of htpG, the Escherichia coli Hsp90, Reveals a Potential Substrate Binding Site","volume":"12","author":"Harris","year":"2004","journal-title":"Structure"},{"issue":"37","key":"2026092408092793700_cit40","doi-asserted-by":"publisher","first-page":"16101","DOI":"10.1073\/pnas.1000916107","article-title":"Dynamics of\nheat shock protein 90 C-terminal dimerization is an important part\nof its conformational cycle","volume":"107","author":"Ratzke","year":"2010","journal-title":"Proc. Natl. Acad.\nSci. U. S. A."},{"issue":"12","key":"2026092408092793700_cit41","doi-asserted-by":"publisher","first-page":"10328","DOI":"10.1074\/jbc.M213094200","article-title":"Sti1 is a non-competitive inhibitor\nof the Hsp90 ATPase.\nBinding prevents the N-terminal dimerization reaction during the atpase\ncycle","volume":"278","author":"Richter","year":"2003","journal-title":"J. Biol. Chem."},{"issue":"3","key":"2026092408092793700_cit42","doi-asserted-by":"publisher","first-page":"802","DOI":"10.1016\/j.jmb.2005.12.008","article-title":"Substrate transfer\nfrom the chaperone Hsp70 to Hsp90","volume":"356","author":"Wegele","year":"2006","journal-title":"J. Mol. Biol."},{"issue":"1","key":"2026092408092793700_cit43","doi-asserted-by":"publisher","first-page":"828","DOI":"10.1038\/s41467-021-21063-0","article-title":"Structural\nelements in the flexible tail of the co-chaperone p23 coordinate client\nbinding and progression of the Hsp90 chaperone cycle","volume":"12","author":"Biebl","year":"2021","journal-title":"Nat. Commun."},{"issue":"1","key":"2026092408092793700_cit44","doi-asserted-by":"publisher","first-page":"260","DOI":"10.1038\/s42003-024-05959-3","article-title":"Structural\ndynamics\nof RAF1-HSP90-CDC37 and HSP90 complexes reveal asymmetric client interactions\nand key structural elements","volume":"7","author":"Finci","year":"2024","journal-title":"Commun. Biol."},{"issue":"3","key":"2026092408092793700_cit45","doi-asserted-by":"publisher","first-page":"295","DOI":"10.1016\/j.str.2022.12.013","article-title":"Cryo-EM\nstructure of the cytosolic AhR complex","volume":"31","author":"Wen","year":"2023","journal-title":"Structure"},{"issue":"6293","key":"2026092408092793700_cit46","doi-asserted-by":"publisher","first-page":"1542","DOI":"10.1126\/science.aaf5023","article-title":"Atomic structure\nof Hsp90-Cdc37-Cdk4\nreveals that Hsp90 traps and stabilizes an unfolded kinase","volume":"352","author":"Verba","year":"2016","journal-title":"Science"},{"issue":"7","key":"2026092408092793700_cit47","doi-asserted-by":"publisher","first-page":"102101","DOI":"10.1016\/j.jbc.2022.102101","article-title":"Extended conformational\nstates dominate the Hsp90 chaperone\ndynamics","volume":"298","author":"Jussupow","year":"2022","journal-title":"J. Biol. Chem."},{"issue":"17","key":"2026092408092793700_cit48","doi-asserted-by":"publisher","first-page":"3496","DOI":"10.1016\/j.molcel.2021.07.023","article-title":"The structure\nof an Hsp90-immunophilin\ncomplex reveals cochaperone recognition of the client maturation state","volume":"81","author":"Lee","year":"2021","journal-title":"Mol. Cell"},{"issue":"1","key":"2026092408092793700_cit49","doi-asserted-by":"publisher","first-page":"8","DOI":"10.1073\/pnas.55.1.8","article-title":"A nitroxide-maleimide\nspin label","volume":"55","author":"Griffith","year":"1966","journal-title":"Proc. Natl. Acad. Sci. U. S. A."},{"issue":"51","key":"2026092408092793700_cit50","doi-asserted-by":"publisher","first-page":"21637","DOI":"10.1073\/pnas.0912009106","article-title":"Site-directed spin labeling of a\ngenetically encoded unnatural amino acid","volume":"106","author":"Fleissner","year":"2009","journal-title":"Proc.\nNatl. Acad. Sci. U. S. A."},{"issue":"8","key":"2026092408092793700_cit51","doi-asserted-by":"publisher","first-page":"1480","DOI":"10.1002\/cbic.202000785","article-title":"Cell-Free Synthesis\nof Selenoproteins in High Yield and Purity for Selective Protein Tagging","volume":"22","author":"Welegedara","year":"2021","journal-title":"ChemBioChem"},{"issue":"6","key":"2026092408092793700_cit52","doi-asserted-by":"publisher","first-page":"1110","DOI":"10.1021\/bc4000542","article-title":"Enlarging the Panoply\nof Site-Directed\nSpin Labeling Electron Paramagnetic Resonance (SDSL-EPR): Sensitive\nand Selective Spin-Labeling of Tyrosine Using an Isoindoline-Based\nNitroxide","volume":"24","author":"Mileo","year":"2013","journal-title":"Bioconjugate Chem."},{"issue":"3","key":"2026092408092793700_cit53","doi-asserted-by":"publisher","first-page":"347","DOI":"10.1007\/s00249-025-01806-3","article-title":"Nitroxide spin, non-canonical\namino acids and SDSL-EPR spectroscopy: a winning combination for protein\ndynamics studies","volume":"55","author":"Bizet","year":"2026","journal-title":"Eur. Biophys. J."},{"issue":"17","key":"2026092408092793700_cit54","doi-asserted-by":"publisher","first-page":"9873","DOI":"10.1021\/acs.chemrev.3c00951","article-title":"Impact of\nCellular Crowding on Protein Structural Dynamics Investigated by EPR\nSpectroscopy","volume":"124","author":"Pierro","year":"2024","journal-title":"Chem. Rev."},{"issue":"7","key":"2026092408092793700_cit55","doi-asserted-by":"publisher","first-page":"140653","DOI":"10.1016\/j.bbapap.2021.140653","article-title":"Nitroxide\nspin labels and EPR spectroscopy: A powerful association for protein\ndynamics studies","volume":"1869","author":"Torricella","year":"2021","journal-title":"Biochim. Biophys. Acta, Proteins\nProteomics"},{"issue":"20","key":"2026092408092793700_cit56","doi-asserted-by":"publisher","first-page":"10217","DOI":"10.1039\/C8CP07249C","article-title":"DEER distance measurements on trityl\/trityl and Gd(III)\/trityl\nlabelled proteins","volume":"21","author":"Giannoulis","year":"2019","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026092408092793700_cit57","doi-asserted-by":"publisher","first-page":"78","DOI":"10.3109\/10715762.2014.979409","article-title":"Sterically\nshielded spin labels for\nin-cell EPR spectroscopy: analysis of stability in reducing environment","volume":"49","author":"Jagtap","year":"2015","journal-title":"Free Radic Res."},{"key":"2026092408092793700_cit58","doi-asserted-by":"publisher","first-page":"235","DOI":"10.1016\/bs.mie.2021.01.040","article-title":"Characteristics of\nGd(III) spin labels\nfor the study of protein conformations","volume":"651","author":"Giannoulis","year":"2021","journal-title":"Methods\nEnzymol."},{"issue":"34","key":"2026092408092793700_cit59","doi-asserted-by":"publisher","first-page":"11681","DOI":"10.1002\/anie.201904848","article-title":"Sub-Micromolar\nPulse Dipolar EPR Spectroscopy Reveals\nIncreasing CuII-labelling of Double-Histidine Motifs with\nLower Temperature","volume":"58","author":"Wort","year":"2019","journal-title":"Angew. Chem., Int. Ed."},{"key":"2026092408092793700_cit60","doi-asserted-by":"publisher","first-page":"66","DOI":"10.1039\/9781788013888-00066","article-title":"Nitroxide spin labels: fabulous spy\nspins for biostructural EPR applications","volume-title":"Electron Paramagnetic Resonance","author":"Martinho","year":"2018"},{"key":"2026092408092793700_cit61","doi-asserted-by":"publisher","first-page":"473","DOI":"10.1007\/BF03166213","article-title":"DeerAnalysis2006\u2500a\ncomprehensive software package for analyzing pulsed ELDOR data","volume":"30","author":"Jeschke","year":"2006","journal-title":"Appl. Magn. Reson."},{"issue":"3","key":"2026092408092793700_cit62","doi-asserted-by":"publisher","first-page":"1348","DOI":"10.3390\/molecules28031348","article-title":"Guidelines for the Simulations of\nNitroxide X-Band cw EPR Spectra from Site-Directed Spin Labeling Experiments\nUsing SimLabel","volume":"28","author":"Etienne","year":"2023","journal-title":"Molecules"},{"issue":"8","key":"2026092408092793700_cit63","doi-asserted-by":"publisher","first-page":"1057","DOI":"10.1002\/open.201900119","article-title":"gem-Diethyl\nPyrroline Nitroxide Spin Labels: Synthesis,\nEPR Characterization, Rotamer Libraries and Biocompatibility","volume":"8","author":"Bleicken","year":"2019","journal-title":"ChemistryOpen"},{"issue":"5","key":"2026092408092793700_cit64","doi-asserted-by":"publisher","first-page":"1366","DOI":"10.1002\/anie.201710184","article-title":"A Bioresistant Nitroxide\nSpin Label for In-Cell EPR Spectroscopy Vitro and In Oocytes Protein\nStructural Dynamics Studies","volume":"57","author":"Karthikeyan","year":"2018","journal-title":"Angew. Chem. Int.\nEd."},{"key":"2026092408092793700_cit65","doi-asserted-by":"publisher","first-page":"35","DOI":"10.1039\/9781782629436-00035","article-title":"Trityl\nradicals as spin labels","volume-title":"Electron Paramagnetic\nResonance","author":"Krumkacheva","year":"2016"},{"issue":"12","key":"2026092408092793700_cit66","doi-asserted-by":"publisher","first-page":"2278","DOI":"10.1007\/s11172-021-3345-6","article-title":"Trityl\nradicals: synthesis, properties, and applications","volume":"70","author":"Tormyshev","year":"2021","journal-title":"Russ. Chem. Bull."},{"key":"2026092408092793700_cit67","doi-asserted-by":"publisher","first-page":"102398","DOI":"10.1016\/j.sbi.2022.102398","article-title":"Exploring\nprotein conformations in vitro and in cell with EPR distance measurements","volume":"75","author":"Goldfarb","year":"2022","journal-title":"Curr. Opin. Struct. Biol."},{"issue":"36","key":"2026092408092793700_cit68","doi-asserted-by":"publisher","first-page":"23535","DOI":"10.1039\/C8CP03532F","article-title":"Small neutral\nGd(III) tags for distance measurements\nin proteins by double electron\u2013electron resonance experiments","volume":"20","author":"Mahawaththa","year":"2018","journal-title":"Phys. Chem. Chem. Phys."},{"issue":"21","key":"2026092408092793700_cit69","doi-asserted-by":"publisher","first-page":"6330","DOI":"10.1002\/anie.201501968","article-title":"The double-histidine\nCu2+ -binding motif: a highly rigid, site-specific spin\nprobe for electron spin resonance distance measurements","volume":"54","author":"Cunningham","year":"2015","journal-title":"Angew. Chem., Int. Ed."},{"issue":"63","key":"2026092408092793700_cit70","doi-asserted-by":"publisher","first-page":"8790","DOI":"10.1039\/D2CC02360A","article-title":"Pulse dipolar\nEPR for determining\nnanomolar binding affinities","volume":"58","author":"Ackermann","year":"2022","journal-title":"Chem. Commun."},{"issue":"24","key":"2026092408092793700_cit71","doi-asserted-by":"publisher","first-page":"6736","DOI":"10.1021\/acs.jpclett.6c01384","article-title":"Binding Affinity\nDetermines the Success of Endogenous CuII-NTA Spin Labeling\nfor In-Cell Electron Paramagnetic Resonance Distance Measurements","volume":"17","author":"Limbach","year":"2026","journal-title":"J. Phys. Chem. Lett."},{"issue":"16","key":"2026092408092793700_cit72","doi-asserted-by":"publisher","first-page":"1895","DOI":"10.1039\/b614920k","article-title":"Distance measurements\non spin-labelled biomacromolecules\nby pulsed electron paramagnetic resonance","volume":"9","author":"Jeschke","year":"2007","journal-title":"Phys.\nChem. Chem. Phys."},{"issue":"31","key":"2026092408092793700_cit73","doi-asserted-by":"publisher","first-page":"6614","DOI":"10.1039\/b907277b","article-title":"General and efficient\nsimulation of pulse EPR spectra","volume":"11","author":"Stoll","year":"2009","journal-title":"Phys. Chem.\nChem. Phys."},{"issue":"1","key":"2026092408092793700_cit74","doi-asserted-by":"publisher","first-page":"42","DOI":"10.1016\/j.jmr.2005.08.013","article-title":"EasySpin, a comprehensive software package for spectral\nsimulation and analysis in EPR","volume":"178","author":"Stoll","year":"2006","journal-title":"J. Magn. Reson."},{"issue":"51","key":"2026092408092793700_cit75","doi-asserted-by":"publisher","first-page":"12235","DOI":"10.1021\/acs.jpclett.1c03641","article-title":"Monitoring\nthe Conformation of the Sba1\/Hsp90 Complex in the Presence of Nucleotides\nwith Mn(II)-Based Double Electron\u2013Electron Resonance","volume":"12","author":"Giannoulis","year":"2021","journal-title":"J. Phys. Chem. Lett."},{"issue":"2","key":"2026092408092793700_cit76","doi-asserted-by":"publisher","first-page":"209","DOI":"10.5194\/mr-1-209-2020","article-title":"DeerLab: a comprehensive\nsoftware package for analyzing dipolar electron paramagnetic resonance\nspectroscopy data","volume":"1","author":"Fa\u0301bregas Iba\u0301n\u0303ez","year":"2020","journal-title":"Magn. Reson."},{"key":"2026092408092793700_cit77","doi-asserted-by":"publisher","first-page":"107186","DOI":"10.1016\/j.jmr.2022.107186","article-title":"Neural networks\nin pulsed dipolar spectroscopy: A practical guide","volume":"338","author":"Keeley","year":"2022","journal-title":"J. Magn. Reson."},{"issue":"2","key":"2026092408092793700_cit78","doi-asserted-by":"publisher","first-page":"316","DOI":"10.1016\/j.jmr.2011.08.035","article-title":"Dead-time\nfree measurement of dipole-dipole interactions between electron spins","volume":"213","author":"Pannier","year":"2011","journal-title":"J. Magn. Reson."},{"issue":"1","key":"2026092408092793700_cit79","doi-asserted-by":"publisher","first-page":"48","DOI":"10.1016\/j.jmr.2009.08.008","article-title":"A pulsed EPR\nmethod to determine distances between paramagnetic centers with strong\nspectral anisotropy and radicals: The dead-time free RIDME sequence","volume":"201","author":"Milikisyants","year":"2009","journal-title":"J. Magn. Reson."},{"issue":"17","key":"2026092408092793700_cit80","doi-asserted-by":"publisher","first-page":"2318","DOI":"10.1002\/cphc.201700666","article-title":"Monitoring\nComplex Formation by Relaxation-Induced\nPulse Electron Paramagnetic Resonance Distance Measurements","volume":"18","author":"Giannoulis","year":"2017","journal-title":"ChemPhysChem"},{"issue":"4","key":"2026092408092793700_cit81","doi-asserted-by":"publisher","first-page":"43","DOI":"10.3390\/magnetochemistry8040043","article-title":"A Low-Spin CoII\/Nitroxide Complex for Distance\nMeasurements at Q-Band Frequencies","volume":"8","author":"Giannoulis","year":"2022","journal-title":"Magnetochemistry"},{"key":"2026092408092793700_cit82","doi-asserted-by":"publisher","first-page":"77","DOI":"10.1039\/BK9781837670154-00077","article-title":"Electron Paramagnetic\nResonance in Structural Biology","volume-title":"Integrated\nStructural Biology","author":"Bogdanov","year":"2023"},{"issue":"1","key":"2026092408092793700_cit83","doi-asserted-by":"publisher","first-page":"9","DOI":"10.1042\/ETLS20170143","article-title":"The contribution\nof modern EPR to structural biology","volume":"2","author":"Jeschke","year":"2018","journal-title":"Emerg Top\nLife Sci."},{"key":"2026092408092793700_cit84","doi-asserted-by":"publisher","first-page":"103046","DOI":"10.1016\/j.sbi.2025.103046","article-title":"Characterization\nof conformationally heterogeneous proteins by electron paramagnetic\nresonance spectroscopy","volume":"92","author":"Jeschke","year":"2025","journal-title":"Curr. Opin. Struct.\nBiol."},{"issue":"25","key":"2026092408092793700_cit85","doi-asserted-by":"publisher","first-page":"5257","DOI":"10.1039\/C4CC08656B","article-title":"Assessing\ndimerisation degree and cooperativity in a biomimetic small-molecule\nmodel by pulsed EPR","volume":"51","author":"Ackermann","year":"2015","journal-title":"Chem. Commun."},{"issue":"9","key":"2026092408092793700_cit86","doi-asserted-by":"publisher","first-page":"1968","DOI":"10.1016\/j.bpj.2017.09.005","article-title":"Sparse\nLabeling PELDOR Spectroscopy on Multimeric Mechanosensitive Membrane\nChannels","volume":"113","author":"Ackermann","year":"2017","journal-title":"Biophys. J."},{"issue":"1","key":"2026092408092793700_cit87","doi-asserted-by":"publisher","first-page":"11757","DOI":"10.1038\/srep11757","article-title":"Mechanism of influenza\nA M2 transmembrane domain assembly in lipid membranes","volume":"5","author":"Georgieva","year":"2015","journal-title":"Sci. Rep."},{"issue":"5","key":"2026092408092793700_cit88","doi-asserted-by":"publisher","first-page":"1219","DOI":"10.1103\/PhysRev.114.1219","article-title":"Electron Spin\nResonance Experiments on Donors in Silicon. I. Electronic Structure\nof Donors by the Electron Nuclear Double Resonance Technique","volume":"114","author":"Feher","year":"1959","journal-title":"Phys. Rev."},{"issue":"1","key":"2026092408092793700_cit89","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/0375-9601(74)90078-4","article-title":"A new pulse\nendor technique","volume":"47","author":"Davies","year":"1974","journal-title":"Phys. Lett. A"},{"issue":"3","key":"2026092408092793700_cit90","doi-asserted-by":"publisher","first-page":"377","DOI":"10.1007\/s00723-012-0314-0","article-title":"MtsslWizard:\nIn Silico Spin-Labeling and Generation of Distance Distributions in\nPyMOL","volume":"42","author":"Hagelueken","year":"2012","journal-title":"Appl. Magn. Reson."},{"issue":"48","key":"2026092408092793700_cit91","doi-asserted-by":"publisher","first-page":"35386","DOI":"10.1074\/jbc.M703844200","article-title":"Dimerization of\nHsp90 Is Required for in Vivo Function","volume":"282","author":"Wayne","year":"2007","journal-title":"J. Biol.\nChem."},{"issue":"36","key":"2026092408092793700_cit92","doi-asserted-by":"publisher","first-page":"33689","DOI":"10.1074\/jbc.M103832200","article-title":"Coordinated ATP Hydrolysis\nby the Hsp90 Dimer","volume":"276","author":"Richter","year":"2001","journal-title":"J. Biol. Chem."},{"key":"2026092408092793700_cit93","doi-asserted-by":"publisher","DOI":"10.7554\/eLife.25235","article-title":"Symmetry broken and rebroken during the ATP hydrolysis\ncycle of the mitochondrial Hsp90 TRAP1","volume":"6","author":"Elnatan","year":"2017","journal-title":"Elife"},{"issue":"26","key":"2026092408092793700_cit94","doi-asserted-by":"publisher","first-page":"17757","DOI":"10.1074\/jbc.M800540200","article-title":"Conserved Conformational Changes\nin the ATPase Cycle of Human Hsp90","volume":"283","author":"Richter","year":"2008","journal-title":"J. Biol.\nChem."},{"issue":"49","key":"2026092408092793700_cit95","doi-asserted-by":"publisher","first-page":"35612","DOI":"10.1074\/jbc.M704647200","article-title":"The ATPase Cycle of\nthe Endoplasmic Chaperone Grp94","volume":"282","author":"Frey","year":"2007","journal-title":"J. Biol. Chem."},{"issue":"5","key":"2026092408092793700_cit96","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2118793119","article-title":"The endoplasmic reticulum chaperone BiP is a closure-accelerating\ncochaperone of Grp94","volume":"119","author":"Huang","year":"2022","journal-title":"Proc. Natl. Acad. Sci.\nU. S. A."},{"issue":"6","key":"2026092408092793700_cit97","doi-asserted-by":"publisher","first-page":"1339","DOI":"10.1039\/D5OB01930C","article-title":"Assessment of solvent\nexposure of native cysteines in human Hsp90 using thiol-reactive functional\ntags","volume":"24","author":"Xie","year":"2026","journal-title":"Org. Biomol. Chem."},{"issue":"66","key":"2026092408092793700_cit98","doi-asserted-by":"publisher","DOI":"10.1002\/chem.202202249","article-title":"Probing\nthe Structural Dynamics of a Bacterial Chaperone\nin Its Native Environment by Nitroxide-Based EPR Spectroscopy","volume":"28","author":"Pierro","year":"2022","journal-title":"Chem.\u2013Eur. J."},{"issue":"34","key":"2026092408092793700_cit99","doi-asserted-by":"publisher","first-page":"20566","DOI":"10.1073\/pnas.2005779117","article-title":"In-cell destabilization of a homodimeric\nprotein complex detected by DEER spectroscopy","volume":"117","author":"Yang","year":"2020","journal-title":"Proc. Natl. Acad. Sci. U. S. A."}],"container-title":["The Journal of Physical\nChemistry B"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.jpcb.6c03220","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/jpcbfk\/article-pdf\/130\/38\/9750\/68002931\/acs.jpcb.6c03220.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/jpcbfk\/article-pdf\/130\/38\/9750\/68002931\/acs.jpcb.6c03220.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T12:11:12Z","timestamp":1790251872000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/jpcbfk\/article\/130\/38\/9750\/5385657\/Electron-Paramagnetic-Resonance-EPR-Spectroscopy"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,31]]},"references-count":99,"journal-issue":{"issue":"38","published-online":{"date-parts":[[2026,8,31]]},"published-print":{"date-parts":[[2026,9,24]]}},"URL":"https:\/\/doi.org\/10.1021\/acs.jpcb.6c03220","relation":{},"ISSN":["1520-6106","1520-5207"],"issn-type":[{"value":"1520-6106","type":"print"},{"value":"1520-5207","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,31]]}}}