Two innovative sensor-protein platforms are disclosed. These sensors are designed for highly sensitive fluorescence resonance energy transfer (FRET)-based molecular assays. Both sensors are suited for homogeneous assays, with one of the sensors designed for noncompetitive assays, and the other for competitive assays. A wide range of molecular recognition domains (e.g., peptide epitopes) can be incorporated into these nanosensor proteins using recombinant DNA technology to create a vast variety of unique sensors. These nanosensor proteins can be mass produced inexpensively in bacteria. The assays can be performed in solution (in lieu of solid-phase assays) with high sensitivity and throughput. The disclosed fluorescent sensor protein concepts should find a broad range of applications in disease diagnosis and drug screening, detection of bio-terrorism agents, as well as in basic research of protein-protein interactions.

• Disease diagnosis
  
• Drug screening
  
• Biosensors
  
• Detection of bio-terrorism agents
  
• Analysis of protein-protein interactions
  
  
  

• Simple, robust and sensitive
  
• Suited for homogeneous molecular assays
  
• Versatile – can be tailored to create a broad range of unique sensor proteins