Abstract: Mutated photoproteins derived from isolated jellyfish photoproteins, characterised in that they exhibit a thermostability higher than that of the photoproteins from which they are derived, and are called thermostable mutated photoproteins, and/or a luminescence duration longer than that of the photoproteins from which they are derived, and are called persistent mutated photoproteins. The invention also concerns the use of said mutated photoproteins in methods for detecting in vitro molecules in a biological sample, methods for detecting compounds with enzymatic activity in a biological sample, or methods for detecting intracellular calcium variations.