Normal Mode Analysis BCKDHA
- 1 WEBnm@
- 2 ElNemo
- 3 Anisotropic Network Model web server
- 4 oGNM – Gaussian network model
- 5 NOMAD-Ref
- 6 All-atom NMA using Gromacs on the NOMAD-Ref server
- 7 Advantages and Disadvantages from NMA and MD
- 8 References
WEBnm@ provides two different modes:
The Single Analysis calculates the lowest frequency normal modes of the given protein and offers different types of calculations to analyse the modes that were calculated. The force field used for the Normal Modes Calculations is the C-alpha force field It uses only the Calpha atoms of the protein which are assigned the masses of the whole residue they represent.
The different types of calculation are:
- deformation energies of each mode
- calculation of normalized squared atomic displacements (results are provided for each low frequency mode, either as raw data or as plots with displacement vs. residue number)
- interactive visualization of the modes using vector field representation or vibrations
Comparative Analysis (beta version):
The Comparative Analysis calculates and compares the normal modes of a set of aligned protein structures. This tool is still under development. It also provides three types of calculations:
- Deformation Energy profiles
- Atomic Fluctuation profiles
- Conformational Overlap Comparison
- Single Analysis: structure file in the pdb format
- Comparative Analysis: a file containing the sequence alignment of the proteins which should be compared and a protein structure file for each of the proteins. The alignment file needs to be written in the Fasta format, and the header line of each sequence should contain the name of the structure file as first field, and the chain in the last field.
Below are the values of the deformation energy for modes 7 to 20
|Mode Index||Deformation Energy|
WEBnm@ visualised the normalized squared atomic displacements for the first five modes (modes 7 to 11). Figures 1-5 display the first five normal modes of our protein. Figure 6-10 show the square of the displacement of each C-alpha atom, normalized so that the sum over all residues is equal to 100. The highest values correspond to the most displaced regions. Cluster of peaks identify significantly big regions. Isolated peaks reflect local flexibility and are not relevant.
|mode 7||mode 8||mode 9||mode 10||mode 11|
The calculated normal modes of Webnma differ in the amplitude of movement. While modes 7 and 9-11 show the highest peak and therefore the most movement for residues 0-25, mode 8 has the highest peak for the last 40 residues in the sequence.
The normal modes calculated by Webnma show that the most displaced regions of the branched-chain alpha-keto acid dehydrogenase complex are the beginning and the end of the protein sequence. The two ends of the protein sequence which are also the outermost parts of the protein structure show some kind of hinge-movement. The protein motion could be described as an opening and closing complex.
The input for ElNemo is a protein structure in PDB format. From this PDB file only the residues that are encoded by ATOM are used in the calculations. The other residues are not taken into account. If there are other residues which should be used in the calculations they have to be encoded by ATOM. Additionally there are a lot of options which can be chosen.
- properties of the first 100 lowest frequency modes (frequency, collectivity of atom movement, overlap of each mode with the observed conformational change (if two conformations are available) and its corresponding amplitude)
- 3D animations from three orthogonal viewpoints in large and small sizes
- Comparison of a normal mode perturbed structure and a second conformation in terms of RMSD and number of residues that are closer than 3Å can be done
- cross plot where the analysis of distance fluctuations between all CA atoms is shown. Red (decreasing) and blue dots (increasing) indicate the residues for which the distance changes significantly in movement. (The upper left corner indicates the first residue. Grey lines are drawn every 10 residues, yellow lines are drawn every 100 residues.)
- ElNémo Webserver<ref>http://www.igs.cnrs-mrs.fr/elnemo/start.html</ref>
- K. Suhre and Y.-H. Sanejouand, ElNémo: a normal mode web server for protein movement analysis and the generation of templates for molecular replacement<ref>Karsten Suhre and Yves-Henri Sanejouand, ElNémo: a normal mode web server for protein movement analysis and the generation of templates for molecular replacement, Nucl. Acids Res, 2004</ref>
CA distance fluctuations for the six modes
|mode 7||mode 8||mode 9||mode 10||mode 11|
Figures 11-14 show that the greatest distance fluctuations are between the 10-20 first amino acids and the rest of the protein (residues 50-400). While mode 7 calculated only distance decreases, mode 8 seemed to have calculated almost only increasing distances between the first ~20 residues and the rest of the protein. The cross plots for mode 9 and 10 (figures 13 and 14) show strong distance fluctuations (decreases for residues 1-10 and increases for residues 10-20) between the first 20 residues and the rest of the protein. Mode 11 as displayed in figure 15 calculated completely different distance fluctuations. Here the highest distance fluctuations are between the last 40 residues and the rest of the protein. There are both increasing and decreasing distances. The totally different cross plot leads to the assumption, that the calculated mode 11 differs quite a lot from the other normal modes. It is very likely, that here the last part of the protein shows the greatest movement.
ElNemo prepared different views from three orthologuous viewpoints with MolScript for each mode.
The mode displayed in figure 16 agrees with the distance fluctuation seen in figure 11. The very beginning of the peptide chain moves away from the rest of the protein. It looks like a hinge-movement.
The mode shown in figure 17 shows that the beginning of the peptide sequence moves towards the protein. This observation can be confirmed when looking at the cross plot given in figure 12, where the decreasing distance for the first residues is given by blue dots. This mode shows another hinge-movement.
As seen at the distance fluctations plot (figure 13), the distances for the first residues in the peptide chain vary, some are decreasing and some are increasing. This can be explained by a twisting peptide sequence, where some residues come closer to the protein core and other move apart.
Mode 10 behaves similarily to mode 9, only the beginning of the protein chain seems not to be twisting but to be pulled in and out. This observation agrees with the increasing and decreasing distances shown in figure 14.
Figure 20 shows a hinge-movement of the last part of the protein sequence. The helix-part shown in red moves to and apart from the protein core, which is also displayed in figure 15.
Anisotropic Network Model web server
As the first 5 modes could not be displayed via pymol, we will analyse modes 6-11 in the following section.
oGNM – Gaussian network model
results here: []
The NOMAD <ref>[]</ref> server provides a lot of information and options. The interface is quite user friendly as all available parameter choices are explained in detail and there is also the runtime listed for an example NMA, which can be used to estimate the runtime for our own jobs.
The following parameters can be set:
- Number of modes to calculate
- As specified in the task description we wanted to obtain 10 modes. NOMAD does six zero modes which are just translation and rotation. Therefore we set the number of modes to calculate to 16.
- Distance weight parameter
- This parameter is used to introduce a smoother cutoff value that in the original Tirion model. All distances are weightend by exp(-(d_ij/d)^2), where d is the distance weight parameter. As proposed by NOMAD a distance weight parameter of 3Å is well suited for CA-only models. As we are doing no all-atom calculation, the distance weight parameter was set to 3.0Å.
- Cutoff to use for mode calculation
- The cutoff describes which pairs of atomes are linked by a spring of universal length according to the Tirion model (Elastic Network Model). The cutoff was set to 15Å.
- Average Rmsd in output trajectories
- For the average RMSD the default value (3.0) was used.
- Method to use
- Full matrix solver
- Sparse matrix solver
- Here we used the default option, the automatic mode.
The output contains one PDB file and one plot per mode. The plot contains the rmsd per residue, which can be interpreted as the amplitude of movement and which is controlled by the average rmsd of trajectory (input parameter).
What information do the different servers provide? Which regions of your protein are most flexible, most stable? When you visualize the modes (provided by server or using for example PyMol or VMD), try to describe what movements you observe? Hinge-movement, “breathing”…
|mode 1||mode 2||mode 3||mode 4||mode 5|
All-atom NMA using Gromacs on the NOMAD-Ref server
In order to do the all-atom NMA we needed an appropriate small molecule that contained not more than 2000 atoms. This small protien was found by searching for "all atom nma". We found a paper <ref>Hetunandan Kamisetty, Eric P. Xing and Christopher J. Langmead: Free Energy Estimates of All-atom Protein Structures Using Generalized Belief Propagation[]</ref>. They used the structure of a hen egg-white lysozyme for an all atom NMA. So we did all the calculations for the corresponding PDB entry 2lyz.
First, we needed to prepare our PDB file. The PDB file for 2LYZ protein contains 1001 atoms in total, all lines not beginning with "ATOM" were removed from the PDB file.
The following movies show the all-atom NMA for 2LYZ at 600K
|mode 1||mode 2||mode 3|
The following movies show the all-atom NMA for 2LYZ at 2000K
|mode 1||mode 2||mode 3|
Comparison to an Elastic Network
Frage: je berechnung eines elastic networks für mode 7, 8 und 9 oder berechnugn eines el networks für "normale" pdb und dann überlagerung mit den modes?
Ich habe jetzt mal für jeden mode (7,8,9) das vorher berechnete network einfach überlagert.
|mode 1||mode 2||mode 3|
Advantages and Disadvantages from NMA and MD
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