This unit presents an overview of computer simulation techniques as applied to nucleic acid systems, ranging from simple in vacuo molecular modeling techniques to more complete all-atom molecular dynamics treatments that include an explicit representation of the environment. The third in a series of four units, this unit focuses on critical issues in solvation and the treatment of electrostatics. UNITS 7.5 & 7.8 introduced the modeling of nucleic acid structure at the molecular level. This included a discussion of how to generate an initial model, how to evaluate the utility or reliability of a given model, and ultimately how to manipulate this model to better understand the structure, dynamics, and interactions. Subject to an appropriate representation of the energy, such as a specifically parameterized empirical force field, the techniques of minimization and Monte Carlo simulation, as well as molecular dynamics (MD) methods, were introduced as means to sample conformational space for a better understanding of the relevance of a given model. From this discussion, the major limitations with modeling, in general, were highlighted. These are the difficult issues in sampling conformational space effectively-the multiple minima or conformational sampling problems-and accurately representing the underlying energy of interaction. In order to provide a realistic model of the underlying energetics for nucleic acids in their native environments, it is crucial to include some representation of solvation (by water) and also to properly treat the electrostatic interactions. These are discussed in detail in this unit.
SubjectNucleic Acid Chemistry; Nucleic Acid Structure and Folding; Structural Analysis of Biomolecules; Experimental Determination of Structure
ELECTROSTATICS AND SOLVATIONAccurately modeling the structure and dynamics of nucleic acids with standard ab initio or empirical potentials presents special difficulties due to the highly charged phosphate backbone and the observation that nucleic acids are essentially always hydrated. Even under extremely dehydrating conditions, DNA still has very tightly associated water. To apply an accurate model, some representation of this structural and solvating water is likely necessary. Water has a structural role as both a donor and acceptor of hydrogen bonds, and
Internet ResourcesAscona B-DNA Consortium website.