A. Total RyR2 abundance measured by Western blot (control n=6, sarcomere-mutation HCM n=16, sarcomere-negative HCM n=7). B. Phosphorylated RyR2 abundance by Western blot for the CaMKII/protein kinase A phosphorylation site (pS2808-RyR2) and the CaMKII-specific phosphorylation site (pS2814-RyR2). C. Total ryanodine receptor binding following addition of [3H]ryanodine to cardiac tissue homogenates. Control n=6, sarcomere-mutation HCM n=11 (MYBPC3-mutation n=7, MYH7-mutation n=4), sarcomere-negative HCM n=9. D. Relative change in RyR2 binding specific counts with pre-incubation with either H2O2 (oxidation) or spermine NONOate (nitrosyl donor).