Ratner's research interests are largely devoted to mechanistic behavior of molecular systems. Specifically, this includes charge transfer process in all of their manifestations from charge-transfer complexes to molecular wires, optical and nonlinear optical processes in molecular systems, coupled mode quantum dynamics, system/bath interactions using density matrix methods, nanoassembly schemes using both complex fluid and generalized Monte-Carlo approaches, biomacromolecule energetics and conformations. Methods development focuses on dynamical approximations using modified mean-filed theories , on molecular junction transport using Green's function methods and on quantum relaxation modeling using semigroup concepts.