The
outlier flooding method (OFLOOD) has been proposed as an enhanced
conformational sampling method of proteins. In OFLOOD, rarely occurring
states of proteins are detected as sparse conformational distributions
(outliers) with a clustering algorithm. The detected
outliers are intensively resampled with short-time molecular dynamics
(MD) simulations. As a set of cycles, OFLOOD repeats selections of
outliers and their conformational resampling. Herein, as an essential
issue to be tackled to perform OFLOOD efficiently, a selection rule
for outliers should be carefully specified. Generally, many outliers
are detected from distributions on conformational subspaces with the
clustering. Judging from its computational costs, it is unreasonable
to select all the detected outliers upon the conformational resampling.
Therefore, it is important to consider which outliers should be selected
from the sparse distributions when restarting their short-time MD
simulations with limited computational costs. In this sense, we investigated
the conformational sampling efficiency of OFLOOD by changing the selection
rules for outliers. To address the conformational sampling efficiency
of OFLOOD depending on its selection rules, outliers to be resampled
were selected by focusing their probability occurrences (populations
of outliers). As a comparison, a random selection rule for outliers
was also considered. Through the present assessment, the random selection
of outliers showed the most efficient conformational sampling efficiency
compared to the other OFLOOD trials using the biased selection rules,
indicating that a variety of outliers should be selected and resampled
during the OFLOOD cycles. In conclusion, the random outlier selection
rule is the best strategy to perform OFLOOD efficiently.