Luminescent ATP Cell Viability Assay Kit II assesses cell viability by quantitatively detecting intracellular adenosine triphosphate (ATP) an indicator proportional to metabolically active viable cells The assay utilizes thermostable firefly luciferase-mediated luminescence added reagents lyse cells releasing ATP which then reacts with supplied substrate under luciferase catalysis generating a luminescent signal directly proportional to live cell number This lyophilized formulation offers improved stability at -20 C storage short assay duration ( 10 min) enhanced sensitivity and linear quantification between approximately 10 to 30 000 cells facilitating biomedical assay applications