title: A molecular rotor as viscosity sensor in aqueous colloid solutions.
abstract: BACKGROUND
  Molecular rotors exhibit viscosity-dependent quantum yield, allowing non-mechanical determination of fluid viscosity. We analyzed fluorescence in the presence of viscosity-modulating macromolecules several orders of magnitude larger than the rotor molecule.
  
  
  METHODS
  Fluorescence of aqueous starch solutions with a molecular rotor in solution was related to viscosity obtained in a cone-and-plate viscometer.
  
  
  RESULTS
  In dextran solutions, emission intensity was found to follow a power-law relationship with viscosity. Fluorescence in hydroxyethylstarch solutions showed biexponential behavior with different exponents at viscosities above and below 1.5 mPa s. Quantum yield was generally higher in hydroxyethylstarch than in dextran solutions. The power-law relationship was used to backcalculate viscosity from intensity with an average precision of 2.2% (range of -5.5% to 5.1%).
  
  
  CONCLUSIONS
  This study indicates that hydrophilic molecular rotors are suitable as colloid solution viscosity probes after colloid-dependent calibration.
authors.affiliation: University of Missouri-Columbia, Department of Biological Engineering, Columbia, MO 65211, USA.
authors.forename: W
authors.initials: W
authors.lastname: Akers
authors.forename: M A
authors.initials: MA
authors.lastname: Haidekker
mesh_terms: D001809:Blood Viscosity; D003102:Colloids / Q000032:analysis / Q000737:chemistry*; D003911:Dextrans / Q000032:analysis / Q000737:chemistry; D005456:Fluorescent Dyes; D006895:Hydroxyethyl Starch Derivatives / Q000032:analysis / Q000737:chemistry; D020409:Molecular Motor Proteins / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry; D012996:Solutions; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014159:Transducers; D014783:Viscosity; D014867:Water / Q000032:analysis / Q000737:chemistry*
chemical_list: D003102:Colloids; D003911:Dextrans; D005456:Fluorescent Dyes; D006895:Hydroxyethyl Starch Derivatives; D020409:Molecular Motor Proteins; D015335:Molecular Probes; D012996:Solutions; D014867:Water