# Annealed importance sampling of dileucine peptide

## TL;DR

This paper demonstrates annealed importance sampling on a dileucine peptide, showing it can efficiently estimate equilibrium distributions during simulated annealing, with potential benefits for various molecular simulations.

## Contribution

The paper introduces a simple implementation of annealed importance sampling for peptides, highlighting its efficiency and ease of use in molecular simulation contexts.

## Key findings

- Equilibrium distributions are attainable with manageable cooling schedules.
- The method is modestly more efficient than constant temperature simulation.
- Naive implementation can be improved for better performance.

## Abstract

Annealed importance sampling is a means to assign equilibrium weights to a nonequilibrium sample that was generated by a simulated annealing protocol. The weights may then be used to calculate equilibrium averages, and also serve as an ``adiabatic signature'' of the chosen cooling schedule. In this paper we demonstrate the method on the 50-atom dileucine peptide, showing that equilibrium distributions are attained for manageable cooling schedules. For this system, as naively implemented here, the method is modestly more efficient than constant temperature simulation. However, the method is worth considering whenever any simulated heating or cooling is performed (as is often done at the beginning of a simulation project, or during an NMR structure calculation), as it is simple to implement and requires minimal additional CPU expense. Furthermore, the naive implementation presented here can be improved.