MPF-BML: A standalone GUI-based cross-platform package for maximum entropy model inference

Table of Contents

• Overview
• Details
• Requirements
• Installation
• Running the application
  • Input data
  • Setting the parameters
  • Running the MPF-BML method
  • Model verification
  • Saved output data
• Troubleshooting
• References
• Citation

Overview

MPF-BML-GUI is a standalone cross-platform package which features an easy-to-use GUI. The package only requires the input data (protein sequence data or data of multiple configura-tions of a complex system with large number of variables) and returns the maximum entropy model parameters inferred using the MPF-BML method.

Details

Title of paper

MPF-BML: A standalone GUI-based package for maximum entropy model inference

Authors

Ahmed A. Quadeer, Matthew R. McKay, John P. Barton, and Raymond H. Y. Louie.

Requirements

A PC with either macOS, Microsoft Windows, or Linux.

Installation

macOS

1. Download the installer from the "macOS" directory in this repository and install the application by following the guidelines in the setup window.

2. This will install MPF-BML-GUI as well as MATLAB runtime libraries (required to run the app). This procedure may take 10 – 15 minutes on a standard computer.

3. Open /Applications/MPF-BML-GUI/application/ directory and double click the installed application "MPF_BML". This will open the GUI of the MPF-BML-GUI software.

Windows

1. Download the installer from the "Windows" directory in this repository and install the application by following the guidelines in the setup window.

2. This will install MPF-BML-GUI as well as MATLAB runtime libraries (required to run the app). This procedure may take 10 – 15 minutes on a standard computer.

3. Open \Program Files\MPF-BML-GUI\application\ directory and double click the installed application "MPF_BML". Or the the can double click the shortcut to the application, in case the user opted for it during the installation. This will open the GUI of the MPF-BML-GUI software.

   Note that antivirus programs, if installed, may block running the software. If this problem arises (noticed for example in the case of Avast and F-secure antivirus), add the program in trusted applications and then run it.

Linux

1. Install the MPF-BML-GUI application as follows:

   • Download the installer from the "Linux OS" directory in this repository and install the application by following the guidelines in the setup window.

   Note: In case the installer doesn't start, open terminal and go to the "Documents" folder and type the following command:

   chmod +x MPF_BML.install
   

   • The installer will try to install the software in the /usr/ directory. If this directory in inaccessible, the user can choose any other directory to install the software. In this tutorial, we assume that you made a folder “MPF-BML-GUI” in your “Documents" folder. Install MATLAB Runtime in the same parent directory.
   • This will install MPF-BML-GUI as well as MATLAB runtime libraries (required to run the app). This procedure may take 10 – 15 minutes on a standard computer.

2. To run the application, open terminal and go to the directory /Documents/MPF-BML-GUI/application/ and type the following command:

   ./run_MPF_BML.sh /home/UserName/Documents/MPF-BML-GUI/v96/
   

   where “UserName” is the name of the directory in which the Documents folder is located. This will open the GUI of the MPF-BML-GUI software.

Running the application

Important note: The GUI panels may not appear properly if the resoulution of the user PC is low. Try maximizing the software window for proper display of panels or increase the resolution (if possible).

Input data

To infer maximum entropy model parameters using MPF-BML, you need to simply provide input data in FASTA/xlsx/csv format comprising either multiple sequence alignment of the protein or a categorical data (with rows and columns representing samples and variables, respectively).

Besides the mandatory input, optional inputs are:

• the maximum fraction of gaps above which the variable is removed (default value set to 0.5);

• an optional sub-sample number to train MPF (used if MPF is running slow);

• an optional input file in csv/xls format comprising of sample weights to reduce sampling bias (each sample is weighted according to a maximum fraction threshold of similar sequences as default); and

• an optional file comprising model parameters to initialize the method.

  For the third optional input above, reweighting is performed based on the provided threshold 0 < x < 1 as follows (Morcos 2011): Two sequences with Hamming distance less than xN (where N is the length of protein) are considered to carry almost the same information, and vice versa. Thus, for each sequence m, a weight w_m = 1/z_m is calculated, where z_m are all the sequences in the MSA having a hamming distance less than xN with the sequence m. A threshold value of 0.1 is used as default if the user does not provide any weight file.

  For the last optional input, the user can provide an optional input maximum entropy model to initialize the MPF-BML method. This model may be obtained from some other inference method or from a previous run of the MPF method (the model obtained after running MPF is automatically saved once the MPF method converges) for which the user is interested in running either BML method alone or both MPF (again) and BML methods with a different set of parameters. For the latter, the user needs to check the provided “Run only BML step on user-provided parameters” option in the “Input information” panel.

Different datasets are provided in the "Datasets" folder in this repository for testing the MPF-BML GUI framework. For demonstration purposes, we will focus here on the data of HIV p7 nucleocapsid protein "p7-alignment.fasta" present in this folder. Click the "Load data" button and select this dataset and leave the remaining optional inputs blank as shown below.

Setting the parameters

In the "Parameters" panel of MPF-BML GUI, the user can set values of the different parameters involved in the three steps of the MPF-BML method (see (Louie et al., 2018) and Supplementary Text S2 for details of these parameters). A brief description of all parameters is also provided as tooltip to assist the user. The default values of these parameters, which were found to return a reasonable model for the majority of the test data, are already set.

For the example dataset of HIV p7, we will only change the value of the BML parameter "Max eps" from 1.0 (default) to 1.5. This change enables the user to obtain a reasonable maximum entropy model in 10-20 minutes (on a standard computer with 1 processing core).

Running the MPF-BML method

After providing input data and setting the parameters, the user can run the method by clicking on the “Run MPF-BML” button in the MPF-BML GUI as shown below. A “Stop” button is also provided to the user to stop execution in case the algorithm is not converging.

Progress of the execution process is displayed in the “Processing information” panel of MPF-BML GUI as shown below.

For the example dataset of HIV p7, the MPF-BML model would take around 10-20 minutes (on a standard computer with 1 processing core).

Model verification

In the "Model verification" panel of MPF-BML GUI, the inferred models (MPF-only and MPF-BML) are validated by comparing the following statistical quantities of configurations in the data with those obtained from the inferred model:

• the individual frequencies (p_i),
• the pair-wise frequencies (p_ij),
• the connected correlations (p_ij - p_ip_j), and
• the probability P(k) of observing a configuration with k differences with the consensus configuration.

Note that additional information is displayed the when the user clicks any data point in these plots. For example, in the plot comparing individual frequencies of model and MSA, clicking any data point shows the information of the associated configuration as Xi, where X is the specific configuration at column i of the input data . Similarly, in the plot comparing pair-wise frequencies of model and MSA, the information of the involved pair associated with the data point is displayed as (Xi,Yj), where X and Y are the configurations at columns i and j of the input data.

Computing model-based energies

Once a model has been inferred, panel “Compute energies” appears for the user to calculate energies corresponding to new samples using the inferred model parameters.

Saved output data

The output files of the software are placed in a new subfolder within the folder where data is located. This new subfolder is named according to the data file, e.g., if data file is abc.fasta, the new subfolder is named as “abc_x_output”, where x is a random number to avoid overwriting the subfolder in case the user wants to run the software multiple times for the same data. The software saves the following files in the output folder:

• The inferred maximum entropy parameters using MPF and MPF-BML are saved in a matrix form in tab-delimited text format (shown below). The first row and column show the change of configuration at a position with A/1/B denoting a change from configuration A to configuration B at position 1. The diagonal entries of the matrix represent the inferred fields while the non-diagonal entries represent the inferred couplings.

  

• A tab-delimited text file is also provided as an output with pairs of positions arranged in descending order according to their computed Frobenius norm, a metric representative of the pairs in contact (shown below). This metric is calculated using the inferred couplings (Cocco et al., 2018) and the higher the value of this metric, the higher is the chance of this pair to be in contact, and vice versa.

  

• In case the user provides a data file to compute energies based on model parameters, the computed energies along with the corresponding samples are saved as a tab delimited output file.

  

• Vector graphics (eps format) of all model-verification results are also saved in the same directory for generating publication-quality figures.

Troubleshooting

For any questions or comments, please email at [email protected].

References

1. Morcos,F. et al. (2011) Direct-coupling analysis of residue coevolution captures native contacts across many protein families. Proceedings of the National Academy of Sciences, 108(49): E1293–E1301. doi: 10.1073/pnas.1111471108.

2. Louie, R. H. Y. et al. (2018) Fitness landscape of the human immunodeficiency virus envelope protein that is targeted by antibodies. Proceedings of the National Academy of Sciences, 115(4): E564–E573. doi: 10.1073/pnas.1717765115.

3. Cocco,S. et al. (2018) Inverse statistical physics of protein sequences: a key issues review. Reports Prog. Phys., 81, 032601. doi: 10.1088/1361-6633/aa9965.

Citation

Ahmed A Quadeer, Matthew R McKay, John P Barton, Raymond H Y Louie, MPF–BML: a standalone GUI-based package for maximum entropy model inference, btz925, https://doi.org/10.1093/bioinformatics/btz925