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Folding of chains with random and edited sequences Oxana Galzitskaya, 142292, Pushchino, Moscow Region, Russia Institute of Protein Research Russian Academy of Sciences We found that exist a range of "optimal" temperatures and solvent strengths where the native fold is achieved by the MC process much faster than by exaustive sorting of all the chain folds. The "optimal" (for folding kinetics) conditions are essentially equal for different random and "edited" sequences (for the latter, the native fold energy is separated by a considerable gap from the energies of other low-energy folds; for random sequences, this gap is negligible). The native folds of "edited" chains are thermodynamically stable at conditions optimal for fast folding, while the native fold of random chains is unstable at these conditions. All the chains are capable of fast achievement of their lowest-energy ("native") folds. However, when the native folds are thermodynamically stable, they are formed slowly by random sequences and rapidly only by the "edited" ones. This is observed in computer simulation for both "protein-like" and "rna-like" models. We have obtained a characteristic first passage time dependence on the chain length using Monte Carlo simulations for a simple model of formation of RNA secondary structure. Our results are compatible with the dependence t=AL^b where t is a number of MC steps typical for achievement of energy minimum, L is the chain length, and A, B are some constants. Such dependences have been obtained for random sequences (for them, b is obove 5) as well as for the sequences edited as to stabilize their native folds (for them, b is below 3). ## Back to the list of abstracts