Several studies have identified reduced tension and Ca 2+ sensitivity as key regulators that precipitate dilated cardiomyopathy (DCM). We are developing a novel therapy to increase tension using adeno-associated viral (AAV) vectors that increase intracellular 2 deoxy-ATP (dATP) via overexpression of the enzyme ribonucleotide reductase (RNR). We have reported that dATP substitution for ATP increases the magnitude and rate of contraction and that RNR overexpression increases intracellular dATP and enhances cardiac function. Here we use a multiscale approach to test the effect of dATP in a genetic model of dilated cardiomyopathy (DCM) with a missense mutation (D230N) in alpha-tropomyosin (Tm). Using recombinant proteins in the in vitro motility assay, we found that filament velocity was lower with D230N compared to WT Tm (2.03±0.04 vs. 2.44±0.04 μm/s). This deficit was corrected when dATP was substituted for ATP (2.90±0.04 μm/s). Next, we used transgenic D230N mice that show progressive ventricular dilation and systolic dysfunction. Intact and demembranated trabeculae from these mice have decreased tension and calcium sensitivity of force, and loss of length-dependent activation (LDA) compared to WT mice. Substitution of dATP for ATP, increased Ca 2+ sensitivity in D230N Tm myocardium (pCa 50 =5.48±0.02 vs. 5.57±0.02) and restored LDA. Complete replacement of ATP with dATP resulted in an ~70% increase in force at submaximal [Ca 2+ ] and force at submaximal Ca 2+ was significantly increased by replacement of only 5% of the nucleotide pool with dATP. For isolated myofibrils from D230N Tm and WT mice, tension at submaximal Ca 2+ (pCa=5.6) was lower in D230N mice compared to WT mice (51±4 vs. 75±8 mN/mm 2 ) and this deficit was improved with dATP (68±5 mN/mm 2 ). Similarly, the rate of activation in D230N myofibrils was slower than in WT mice (2.1±0.2 vs.3.3±0.2 s -1 ) and partially corrected with dATP (2.7±0.2 s -1 ). These results demonstrate that enhanced cross bridge binding, via increasing dATP, can recover lost contractile function in a thin filament mutation model of DCM. In ongoing studies, we are testing the ability of elevated dATP, via AAV- RNR, to protect against reduced systolic function and progressive ventricular dilation in 2-3 week old D230N mice .