Intermolecular proton transfer from flavonol to human serum albumin triggers a red-shifted ratiometric fluorescence response.

Intermolecular proton transfer from a flavonol-based probe to the arginine (Arg222) in drug site 1 of human serum albumin triggers an unusual red-shifted ratiometric fluorescence response, which can be applied in the point-to-care diagnosis of hypoalbuminemia.