(a) Time series of the Cα root-mean-square deviation (RMSD) of (i) TEM-1 ApoEQ, (ii) TEM-1 IBEQ, (iii) KPC-2 ApoEQ, and (iv) KPC-2 IBEQ systems, measured over the course of the 250 ns of each replica. The black line represents the average of the 20 replicates. (b) RMSD calculated as a function of the fraction of the total Cα atoms considered for structural alignment in (i) TEM-1 and (ii) KPC-2. The plots indicate that 80% of conformations in TEM-1 can be aligned to below 0.064 nm (ApoEQ; black) and 0.074 nm (IBEQ; red). Similarly, in KPC-2, 80% of the conformations could be superimposed to below 0.060 nm (ApoEQ; black) and 0.066 nm (IBEQ; red). This constitutes the core of the enzyme. (c) Fractional Cα RMSD calculated after identification of the core in (i) TEM-1 ApoEQ, (ii) TEM-1 IBEQ, (iii) KPC-2 ApoEQ, and (iv) KPC-2 IBEQ. The bottom black line denotes the stable core and consists of 80% Cα atoms. The top black line is the average of the remainder 20% Cα atoms calculated from all 20 replicates. These constitute the non-core Cα atoms that display deviation in all simulations.