Conformational changes underpin function and encode complex
biomolecular
mechanisms. Gaining atomic-level detail of how such changes occur
has the potential to reveal these mechanisms and is of critical importance
in identifying drug targets, facilitating rational drug design, and
enabling bioengineering applications. While the past two decades have
brought Markov state model techniques to the point where practitioners
can regularly use them to glimpse the long-time dynamics of slow conformations
in complex systems, many systems are still beyond their reach. In
this Perspective, we discuss how including memory (i.e., non-Markovian
effects) can reduce the computational cost to predict the long-time
dynamics in these complex systems by orders of magnitude and with
greater accuracy and resolution than state-of-the-art Markov state
models. We illustrate how memory lies at the heart of successful and
promising techniques, ranging from the Fokker–Planck and generalized
Langevin equations to deep-learning recurrent neural networks and
generalized master equations. We delineate how these techniques work,
identify insights that they can offer in biomolecular systems, and
discuss their advantages and disadvantages in practical settings.
We show how generalized master equations can enable the investigation
of, for example, the gate-opening process in RNA polymerase II and
demonstrate how our recent advances tame the deleterious influence
of statistical underconvergence of the molecular dynamics simulations
used to parameterize these techniques. This represents a significant
leap forward that will enable our memory-based techniques to interrogate
systems that are currently beyond the reach of even the best Markov
state models. We conclude by discussing some current challenges and
future prospects for how exploiting memory will open the door to many
exciting opportunities.