Abinitio Pipeline - Experimental Data Empiar 10073

This notebook introduces a selection of components corresponding to loading real Relion picked particle cryo-EM data and running key ASPIRE-Python Abinitio model components as a pipeline.

This demonstrates using the Global BandedSNRImageQualityFunction approach starting with Relion polished picked particles.

Specifically this pipeline uses the EMPIAR 10073 picked particles data, available here:

https://www.ebi.ac.uk/empiar/EMPIAR-10073

https://www.ebi.ac.uk/emdb/EMD-8012

Imports

First import some of the usual suspects. In addition, import some classes from the ASPIRE package that will be used throughout this experiment.

import logging
from pathlib import Path

import numpy as np

from aspire.abinitio import CLSyncVoting
from aspire.basis import FFBBasis2D
from aspire.classification import (
    BandedSNRImageQualityFunction,
    BFRAverager2D,
    GlobalWithRepulsionClassSelector,
    RIRClass2D,
)
from aspire.denoising import ClassAvgSource
from aspire.reconstruction import MeanEstimator
from aspire.source import OrientedSource, RelionSource

logger = logging.getLogger(__name__)

Parameters

Example simulation configuration.

n_imgs = None  # Set to None for all images in starfile, can set smaller for tests.
img_size = 32  # Downsample the images/reconstruction to a desired resolution
n_classes = 2000  # How many class averages to compute.
n_nbor = 50  # How many neighbors to stack
starfile_in = "10073/data/shiny_correctpaths_cleanedcorruptstacks.star"
data_folder = "."  # This depends on the specific starfile entries.
volume_output_filename = f"10073_abinitio_c{n_classes}_m{n_nbor}_{img_size}.mrc"
pixel_size = 1.43

Source data and Preprocessing

RelionSource is used to access the experimental data via a starfile. Begin by downsampling to our chosen resolution, then preprocess to correct for CTF and noise.

# Create a source object for the experimental images
src = RelionSource(
    starfile_in, pixel_size=pixel_size, max_rows=n_imgs, data_folder=data_folder
)

# Downsample the images
logger.info(f"Set the resolution to {img_size} X {img_size}")
src = src.downsample(img_size)

src = src.cache()

Class Averaging

Now perform classification and averaging for each class.

logger.info("Begin Class Averaging")

# Now perform classification and averaging for each class.
# This also demonstrates customizing a ClassAvgSource, by using global
# contrast selection.  This computes the entire set of class averages,
# and sorts them by (highest) contrast.

# Build up the customized components.
basis = FFBBasis2D(src.L, dtype=src.dtype)
classifier = RIRClass2D(src, n_nbor=n_nbor, nn_implementation="sklearn")
averager = BFRAverager2D(basis, src, num_procs=16)
quality_function = BandedSNRImageQualityFunction()
class_selector = GlobalWithRepulsionClassSelector(averager, quality_function)

# Assemble the components into the Source.
avgs = ClassAvgSource(
    src, classifier=classifier, averager=averager, class_selector=class_selector
)

# Save out the resulting Nearest Neighbor networks arrays.
np.savez(
    "experimental_10073_class_averages_class_indices.npz",
    class_indices=avgs.class_indices,
    class_refl=avgs.class_refl,
    class_distances=avgs.class_distances,
)

# Save the class selection rankings.
np.save(
    "experimental_10073_class_averages_selection_indices.npy",
    avgs.selection_indices,
)

# We'll continue our pipeline with the first `n_classes` from `avgs`.
avgs = avgs[:n_classes]

# Save off the set of class average images.
avgs.save("experimental_10073_class_averages_global.star", overwrite=True)

Common Line Estimation

Next create a CL instance for estimating orientation of projections using the Common Line with Synchronization Voting method.

logger.info("Begin Orientation Estimation")

# Create a custom orientation estimation object for ``avgs``.
orient_est = CLSyncVoting(avgs, n_theta=72)

# Create an ``OrientedSource`` class instance that performs orientation
# estimation in a lazy fashion upon request of images or rotations.
oriented_src = OrientedSource(avgs, orient_est)

Volume Reconstruction

Using the oriented source, attempt to reconstruct a volume.

logger.info("Begin Volume reconstruction")

# Setup an estimator to perform the back projection.
estimator = MeanEstimator(oriented_src)

# Perform the estimation and save the volume.
estimated_volume = estimator.estimate()
estimated_volume.save(volume_output_filename, overwrite=True)
logger.info(f"Saved Volume to {str(Path(volume_output_filename).resolve())}")