{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T22:32:58Z","timestamp":1784932378326,"version":"3.55.0"},"reference-count":45,"publisher":"American Society for Microbiology","issue":"23","license":[{"start":{"date-parts":[[2019,12,1]],"date-time":"2019-12-01T00:00:00Z","timestamp":1575158400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"name":"NSF BEACON Center for the Study of Evolution in Action","award":["DBI-0939454"],"award-info":[{"award-number":["DBI-0939454"]}]},{"DOI":"10.13039\/100000011","name":"Howard Hughes Medical Institute","doi-asserted-by":"publisher","award":["52008124"],"award-info":[{"award-number":["52008124"]}],"id":[{"id":"10.13039\/100000011","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000185","name":"DOD | Defense Advanced Research Projects Agency","doi-asserted-by":"publisher","award":["HR0011-15-C0095"],"award-info":[{"award-number":["HR0011-15-C0095"]}],"id":[{"id":"10.13039\/100000185","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100008982","name":"National Science Foundation","doi-asserted-by":"publisher","award":["CBET-1554179"],"award-info":[{"award-number":["CBET-1554179"]}],"id":[{"id":"10.13039\/501100008982","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Appl Environ Microbiol"],"published-print":{"date-parts":[[2019,12]]},"abstract":"<jats:p>\n            Caffeine (1,3,7-trimethylxanthine) is the dominant neurostimulant found in coffee, teas, sodas, and energy drinks. Measuring the amount of caffeine and other methylxanthines in these beverages is important for quality assurance and safety in food science. Methylxanthines are also used in medicine and as performance-enhancing drugs, two contexts in which accurately determining their concentrations in bodily fluids is important. Liquid chromatography is the standard method for measuring methylxanthine concentrations in a sample, but it requires specialized equipment and expertise. We improved a previous bioassay that links\n            <jats:named-content content-type=\"genus-species\">E. coli<\/jats:named-content>\n            growth to methylxanthine demethylation so that it can now be used to determine the amounts of individual methylxanthines in complex mixtures or beverages, such as coffee.\n          <\/jats:p>","DOI":"10.1128\/aem.01965-19","type":"journal-article","created":{"date-parts":[[2019,9,20]],"date-time":"2019-09-20T11:25:18Z","timestamp":1568978718000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":7,"title":["Bioassay for Determining the Concentrations of Caffeine and Individual Methylxanthines in Complex Samples"],"prefix":"10.1128","volume":"85","author":[{"given":"Alejandro E.","family":"Gutierrez","sequence":"first","affiliation":[{"name":"Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Prachi","family":"Shah","sequence":"additional","affiliation":[{"name":"The Freshman Research Initiative, College of Natural Sciences, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Abigail E.","family":"Rex","sequence":"additional","affiliation":[{"name":"The Freshman Research Initiative, College of Natural Sciences, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tien C.","family":"Nguyen","sequence":"additional","affiliation":[{"name":"The Freshman Research Initiative, College of Natural Sciences, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Saamiha P.","family":"Kenkare","sequence":"additional","affiliation":[{"name":"The Freshman Research Initiative, College of Natural Sciences, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0888-7358","authenticated-orcid":false,"given":"Jeffrey E.","family":"Barrick","sequence":"additional","affiliation":[{"name":"Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dennis M.","family":"Mishler","sequence":"additional","affiliation":[{"name":"The Freshman Research Initiative, College of Natural Sciences, The University of Texas at Austin, Austin, Texas, USA"},{"name":"Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_2_2_2","doi-asserted-by":"publisher","DOI":"10.2478\/v10102-009-0012-4"},{"key":"e_1_3_2_3_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.marpolbul.2012.04.015"},{"key":"e_1_3_2_4_2","doi-asserted-by":"publisher","DOI":"10.3923\/jbs.2013.570.576"},{"key":"e_1_3_2_5_2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJM197309202891202"},{"key":"e_1_3_2_6_2","doi-asserted-by":"publisher","DOI":"10.2147\/JAA.S113747"},{"key":"e_1_3_2_7_2","unstructured":"World Anti-Doping Agency. 2017. 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