{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,4]],"date-time":"2026-10-04T04:12:02Z","timestamp":1791087122399,"version":"4.1.0"},"reference-count":37,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2010,12,23]],"date-time":"2010-12-23T00:00:00Z","timestamp":1293062400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Protein Science"],"published-print":{"date-parts":[[2011,1]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Electron paramagnetic resonance (EPR) spectroscopy coupled with site\u2010directed spin labeling (SDSL) is a valuable tool for characterizing the mobility and conformational changes of proteins but has seldom been applied to intrinsically disordered proteins (IDPs). Here, IA<jats:sub>3<\/jats:sub> is used as a model system demonstrating SDSL\u2010EPR characterization of conformational changes in small IDP systems. IA<jats:sub>3<\/jats:sub> has 68 amino acids, is unstructured in solution, and becomes \u03b1\u2010helical upon addition of the secondary structural stabilizer 2,2,2\u2010trifluoroethanol (TFE). Two single cysteine substitutions, one in the N\u2010terminus (S14C) and one in the C\u2010terminus (N58C), were generated and labeled with three different nitroxide spin labels. The resultant EPR line shapes of each of the labels were compared and each reported changes in mobility upon addition of TFE. Specifically, the spectral line shape parameters <jats:italic>h<\/jats:italic><jats:sub>(+1)<\/jats:sub>\/<jats:italic>h<\/jats:italic><jats:sub>(0)<\/jats:sub>, the local tumbling volume (<jats:italic>V<\/jats:italic><jats:sub>L<\/jats:sub>), and the percent change of the <jats:italic>h<\/jats:italic><jats:sub>(\u22121)<\/jats:sub> intensity were utilized to quantitatively monitor TFE\u2010induced conformational changes. The values of <jats:italic>h<\/jats:italic><jats:sub>(+1)\/<\/jats:sub><jats:italic>h<\/jats:italic><jats:sub>(0)<\/jats:sub> as a function of TFE titration varied in a sigmoidal manner and were fit to a two\u2010state Boltzmann model that provided values for the midpoint of the transition, thus, reporting on the global conformational change of IA<jats:sub>3<\/jats:sub>. The other parameters provide site\u2010specific information and show that S14C\u2010SL undergoes a conformational change resulting in more restricted motion than N58C\u2010SL, which is consistent with previously published results obtained by studies using NMR and circular dichroism spectroscopy indicating a higher degree of \u03b1\u2010helical propensity of the N\u2010terminal segment of IA<jats:sub>3<\/jats:sub>. Overall, the results provide a framework for data analyzes that can be used to study induced unstructured\u2010to\u2010helical conformations in IDPs by SDSL.<\/jats:p>","DOI":"10.1002\/pro.547","type":"journal-article","created":{"date-parts":[[2010,11,16]],"date-time":"2010-11-16T00:40:41Z","timestamp":1289868041000},"page":"150-159","source":"Crossref","is-referenced-by-count":41,"title":["Characterization of the disordered\u2010to\u2010\u03b1\u2010helical transition of IA<sub>3<\/sub> by SDSL\u2010EPR spectroscopy"],"prefix":"10.1002","volume":"20","author":[{"given":"Natasha L.","family":"Pirman","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eugene","family":"Milshteyn","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luis","family":"Galiano","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Justin C.","family":"Hewlett","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gail E.","family":"Fanucci","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2010,12,23]]},"reference":[{"key":"e_1_2_7_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/S1093-3263(00)00138-8"},{"key":"e_1_2_7_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0968-0004(02)02169-2"},{"key":"e_1_2_7_4_2","doi-asserted-by":"publisher","DOI":"10.1110\/ps.4210102"},{"key":"e_1_2_7_5_2","doi-asserted-by":"publisher","DOI":"10.1038\/nrm1589"},{"key":"e_1_2_7_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.sbi.2005.01.002"},{"key":"e_1_2_7_7_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp063708u"},{"key":"e_1_2_7_8_2","doi-asserted-by":"publisher","DOI":"10.1002\/prot.22125"},{"key":"e_1_2_7_9_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0959-440X(02)00289-0"},{"key":"e_1_2_7_10_2","doi-asserted-by":"publisher","DOI":"10.1529\/biophysj.106.094045"},{"key":"e_1_2_7_11_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jmb.2004.03.017"},{"key":"e_1_2_7_12_2","doi-asserted-by":"publisher","DOI":"10.1038\/nsmb746"},{"key":"e_1_2_7_13_2","doi-asserted-by":"publisher","DOI":"10.1038\/72378"},{"key":"e_1_2_7_14_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi034823n"},{"key":"e_1_2_7_15_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi061358w"},{"key":"e_1_2_7_16_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi0497906"},{"key":"e_1_2_7_17_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp8057788"},{"key":"e_1_2_7_18_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.sbi.2006.08.008"},{"key":"e_1_2_7_19_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi962155i"},{"key":"e_1_2_7_20_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0959-440X(98)80158-9"},{"key":"e_1_2_7_21_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0959-440X(94)90219-4"},{"key":"e_1_2_7_22_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.bbrc.2006.02.138"},{"key":"e_1_2_7_23_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi027120z"},{"key":"e_1_2_7_24_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0401664102"},{"key":"e_1_2_7_25_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi050931t"},{"key":"e_1_2_7_26_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0702172104"},{"key":"e_1_2_7_27_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.bpj.2009.11.036"},{"key":"e_1_2_7_28_2","doi-asserted-by":"publisher","DOI":"10.1007\/978-1-4615-6534-5"},{"key":"e_1_2_7_29_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp063708u"},{"key":"e_1_2_7_30_2","doi-asserted-by":"publisher","DOI":"10.1016\/0376-7388(96)00070-1"},{"key":"e_1_2_7_31_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja803221c"},{"key":"e_1_2_7_32_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi000604f"},{"key":"e_1_2_7_33_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi035749b"},{"key":"e_1_2_7_34_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi00236a026"},{"key":"e_1_2_7_35_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi00103a016"},{"key":"e_1_2_7_36_2","doi-asserted-by":"publisher","DOI":"10.1006\/jmra.1996.0113"},{"key":"e_1_2_7_37_2","doi-asserted-by":"publisher","DOI":"10.1016\/S1570-0232(02)00908-X"},{"key":"e_1_2_7_38_2","doi-asserted-by":"publisher","DOI":"10.1007\/978-1-4613-0743-3_5"}],"container-title":["Protein 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