(Note: These tutorials are meant to provide illustrative examples of how to use the AMBER software suite to carry out simulations that can be run on a simple workstation in a reasonable period of time. They do not necessarily provide the optimal choice of parameters or methods for the particular application area.)
Copyright Ross Walker 2004

TUTORIAL 7

The Nudged Elastic Band Approach to Finding the Lowest Energy
Pathway Between two States

By Ross Walker

	Psi
Phi

Potential Energy Scan for Phi/Psi Rotation of Alanine Dipeptide.
Dots show path found by Nudged Elastic Band (NEB) method.
The surface was calculated by scanning the two angles and extracting the energy
represented by the amber force field.

This tutorial introduces the Nudged Elastic Band method for finding low energy pathways for transitions. This is a new feature in Amber v9 and as such you will require a copy of AMBER 9 to complete this tutorial. For details on how to obtain AMBER v9.0 please see the amber website.

This tutorial will show you how to use a simulated annealing version of Nudged Elastic Band (NEB) to locate a low energy transition pathway for the Phi-Psi isomerization of alanine dipeptide. The use of simulated annealing means that it is not necessary to provide an initial guess at the pathway, merely the end points will do. Secondly using simulated annealing means that the algorithm will not remain trapped in the local minimum.

This tutorial consists of seven sections:

1. section1.htm : Background

2. section2.htm : Constructing the Pathway End Points

3. section3.htm : Creating the NEB prmtop and inpcrd files

4. section4.htm : Heating the System

5. section5.htm : Simulated Annealing and Equilibration

6. section6.htm : Slow Cooling

7. section7.htm : Extracting the Final Pathway and Visualizing the Results