title: Thymine-based molecular beacon for sensing adenosine based on the inhibition of S-adenosylhomocysteine hydrolase activity.
abstract: This study presents a thymine (T)-based molecular beacon (MB) used for probing S-adenosylhomocysteine hydrolase (SAHH)-catalyzed hydrolysis of S-adenosylhomocysteine (SAH) and for sensing adenosine based on the inhibition of SAHH activity. The designed MB (T8-MB-T8) contained a 15-mer loop and a stem that consisted of a pair of 8-mer T bases, a fluorophore unit at the 5'-end, and a quencher unit at the 3'-end. In the presence of Hg(2+), a change in the conformation of T8-MB-T8 placed the fluorophore unit and the quencher in proximity to each other and caused collisional quenching of fluorescence between them. The Hg(2+)-induced fluorescence quenching of T8-MB-T8 occurred because the Hg(2+) induced T-T mismatches to form stable T-Hg(2+)-T coordination in the MB stem. SAHH catalyzed the hydrolysis of SAH to produce homocysteine. The generated homocysteine enabled the Hg(2+) to be removed from a hairpin-shaped T8-MB-T8 through the formation of a strong Hg(2+)-S bond, leading to the restoration of its fluorescence. The T8-MB-T8 · Hg(2+) probe showed a limit of detection for SAHH of 4 units L(-1) (approximately 0.24 nM) and was reusable for detecting the SAHH/SAH system. Because adenosine was an effective SAHH activity inhibitor, the T8-MB-T8 · Hg(2+) probe combining the SAHH and SAH systems was used for sensitive and selective detection of adenosine in urine without the interference of other adenosine analogs.
authors.affiliation: Department of Chemistry, National Sun Yat-sen University, 70, Lien-hai Road, Kaohsiung, Taiwan.
authors.forename: Chih-Chun
authors.initials: CC
authors.lastname: Nieh
authors.affiliation: Department of Chemistry, National Sun Yat-sen University, 70, Lien-hai Road, Kaohsiung, Taiwan; School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Taiwan. Electronic address: tsengwl@mail.nsysu.edu.tw.
authors.forename: Wei-Lung
authors.initials: WL
authors.lastname: Tseng
mesh_terms: D000241:Adenosine / Q000097:blood* / Q000378:metabolism / Q000652:urine*; D043383:Adenosylhomocysteinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000328:Adult; D015374:Biosensing Techniques / Q000379:methods*; D006801:Humans; D006868:Hydrolysis; D008297:Male; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods; D013941:Thymine / Q000737:chemistry*; D055815:Young Adult
chemical_list: D012435:S-Adenosylhomocysteine; D043383:Adenosylhomocysteinase; D000241:Adenosine; D013941:Thymine
keywords: Adenosine; Mercury ions; Molecular beacon; S-adenosylhomocysteine; S-adenosylhomocysteine hydrolase