Structures and interaction energies of non-covalently bound molecular clusters playing a role in bio disciplines are investigated. Specifically, we consider H-bonded and stacked structures of DNA base pairs and amino acid pairs. Structure of pairs is either optimized or taken from experiment. Benchmark stabilization energies of complexes are determined as the Complete Basis Set (CBS) limit of the CCSD(T) calculations. Resulting stabilization energies of H-bonded and stacked pairs are very large, much larger than considered before. Calculated stabilization energies together with solvation energies are used for prediction of stability of DNA oligomers and good agreement between theoretical and experimental values resulted. The success and failure of the wave function theory and density function theory for complexes investigated is discussed.