title: Identifying the bond responsible for the fluorescence modulation in an amyloid fibril sensor.
abstract: An ultrafast intramolecular bond twisting process is known to be the responsible mechanism for the sensing activity of the extensively used amyloid fibril sensor thioflavin T (ThT). However, it is not yet known which one of the two possible single bonds in ThT is actually involved in the twisting process. To resolve this fundamental issue, two derivatives of ThT have been designed and synthesized and subsequently their photophysical properties have been studied in different solvents. It is understood from the present study that the rotation around the central C-C single bond, and not that around the C-N single bond, is primarily responsible for the sensor activity of ThT. Detailed viscosity-dependent fluorescence studies revealed that the ThT derivative with restricted C-N bond rotation acts as a better sensor than the derivative with free C-N bond rotation. The better sensory activity is directly correlated with a shorter excited-state lifetime. Results obtained from the photophysical studies of the ThT derivatives have also been supported by the results obtained from quantum chemical calculations.
authors.affiliation: Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400 085, India.
authors.forename: Anvita
authors.initials: A
authors.lastname: Srivastava
authors.forename: Prabhat K
authors.initials: PK
authors.lastname: Singh
authors.forename: Manoj
authors.initials: M
authors.lastname: Kumbhakar
authors.forename: Tulsi
authors.initials: T
authors.lastname: Mukherjee
authors.forename: Subrata
authors.initials: S
authors.lastname: Chattopadyay
authors.forename: Haridas
authors.initials: H
authors.lastname: Pal
authors.forename: Sukhendu
authors.initials: S
authors.lastname: Nath
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D052160:Benzothiazoles; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013844:Thiazoles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D013844:Thiazoles; C009462:thioflavin T