This project focuses inside the mechanism by which dinitrogen is reduced by a catalytic enzyme called nitrogenase (NG). It is proposed to examine the changes in N| bond order via ||N kinetic isotope effect (KIE) studies, and to determine KIE for two of the three isotopic N| molecules (||N|, ||N-||N). To run this experiment it as necessary to prepare an enzymatic reaction mixture containing N| as a substrate, MgCl|, TES, ATP, creatine phosphate, creatine phosphokinase, dithionite, bis Tris, HEPPS, CHES; final pH was 7.4. After isolation the remaining nitrogen was taken for isotope ratio mass spectroscopy (IRMS) analysis. Utilizing the natural distribution of (||N|,||N-||N), I obtained that the KIE at 21∞C is 1.00278 (0.278%). The ongoing computer modeling of KIEs for different mechanisms of NG action will allow us to identify the most probably pathways of N| reduction.