Precise beam-tilt alignment and collimation are required to minimize the phase error associated with coma in high-resolution cryo-EM.

Electron microscopy at a resolution of 0.4nm or better requires more careful adjustment of the illumination than is the case at a resolution of 0.8nm.

Automation in single-particle electron microscopy connecting the pieces.

Throughout the history of single-particle electron microscopy (EM), automated technologies have seen varying degrees of emphasis and development, usually depending upon the contemporary demands of the field. We are currently faced with increasingly sophisticated devices for specimen preparation, vast increases in the size of collected data sets, comprehensive algorithms for image processing, sophisticated tools for quality assessment, and an influx of interested scientists from outside the field who might lack the skills of experienced microscopists. This situation places automated techniques in high demand.

Automated electron microscopy for evaluating two-dimensional crystallization of membrane proteins.

Membrane proteins fulfill many important roles in the cell and represent the target for a large number of therapeutic drugs. Although structure determination of membrane proteins has become a major priority, it has proven to be technically challenging. Electron microscopy of two-dimensional (2D) crystals has the advantage of visualizing membrane proteins in their natural lipidic environment, but has been underutilized in recent structural genomics efforts.

A toolbox for ab initio 3-D reconstructions in single-particle electron microscopy.

Structure determination of a novel macromolecular complex via single-particle electron microscopy depends upon overcoming the challenge of establishing a reliable 3-D reconstruction using only 2-D images. There are a variety of strategies that deal with this issue, but not all of them are readily accessible and straightforward to use. We have developed a "toolbox" of ab initio reconstruction techniques that provide several options for calculating 3-D volumes in an easily managed and tightly controlled work-flow that adheres to standard conventions and formats.

Fully automated, sequential tilt-series acquisition with Leginon.

Electron tomography has become a uniquely powerful tool for investigating the structures of individual cells, viruses, and macromolecules. Data collection is, however, time consuming and requires expensive instruments. To optimize productivity, we have incorporated one of the existing tilt-series acquisition programs, UCSF Tomo, into the well-developed automatic electron microscopy data collection package Leginon to enable fully automatic, sequential tilt-series acquisition.

Towards automated screening of two-dimensional crystals.

Screening trials to determine the presence of two-dimensional (2D) protein crystals suitable for three-dimensional structure determination using electron crystallography is a very labor-intensive process. Methods compatible with fully automated screening have been developed for the process of crystal production by dialysis and for producing negatively stained grids of the resulting trials. Further automation via robotic handling of the EM grids, and semi-automated transmission electron microscopic imaging and evaluation of the trial grids is also possible.

Automation of random conical tilt and orthogonal tilt data collection using feature-based correlation.

Visualization by electron microscopy has provided many insights into the composition, quaternary structure, and mechanism of macromolecular assemblies. By preserving samples in stain or vitreous ice it is possible to image them as discrete particles, and from these images generate three-dimensional structures. This 'single-particle' approach suffers from two major shortcomings; it requires an initial model to reconstitute 2D data into a 3D volume, and it often fails when faced with conformational variability.

Automated cryoEM data acquisition and analysis of 284742 particles of GroEL.

One of the goals in developing our automated electron microscopy data acquisition system, Leginon, was to improve both the ease of use and the throughput of the process of acquiring low dose images of macromolecular specimens embedded in vitreous ice. In this article, we demonstrate the potential of the Leginon system for high-throughput data acquisition by describing an experiment in which we acquired images of more than 280,000 particles of GroEL in a single 25 h session at the microscope. We also demonstrate the potential for an automated pipeline for molecular microscopy by showing that these particles can be subjected to completely automated procedures to reconstruct a three-dimensional (3D) density map to a resolution better than 8 A.

Does contamination buildup limit throughput for automated cryoEM?

The development of automated systems for data acquisition in cryo electron microscopy has enabled the possibility of acquiring very large number of images from a single specimen grid. We have demonstrated that over images of 250,000 single particles can be acquired in a 24 h period. This has raised questions as to whether contamination buildup on the specimen limits the quality of the data that can be acquired during these long duration experiments and also whether the data acquisition session could be extended to allow acquisition of more than 1,000,000 particles.

Automated molecular microscopy: the new Leginon system.

We report here on the current state of our efforts in automated molecular microscopy. Our primary automated data acquisition software system, Leginon, has been completely redesigned over the past two years. The new distributed system has been developed using the Python programming language and is compatible with both Linux and Windows operating systems.

Robotic grid loading system for a transmission electron microscope.

The design, construction, and testing of a robotic grid loading system for a transmission electron microscope is presented. The system, when integrated with automated data collection software, has the potential to carry out large scale multi-grid experiments, as required, for example, by 2D protein crystallization screening trials. We present a detailed description of the system that utilizes a 6 axis articulate robotic arm to load microscope grids into a specimen holder and then load the holder into the microscope.

Rapid routine structure determination of macromolecular assemblies using electron microscopy: current progress and further challenges.

Although the methodology of molecular microscopy has enormous potential, it is time consuming and labor intensive. The techniques required to produce a three-dimensional (3D) electron density map of a macromolecular structure normally require manual operation of an electron microscope by a skilled operator and manual supervision of the sometimes complex software needed for analysis and calculation of 3D maps. Systems to automate the process of data acquisition from an electron microscope are being developing and these systems are being integrated with specimen handling operations and post acquisition data processing.

Automated three-dimensional reconstruction of keyhole limpet hemocyanin type 1.

We have reconstructed a three-dimensional map of keyhole limpet hemocyanin isoform 1 (KLH1), using our automated data collection software, Leginon, integrated with particle selection algorithms, and the SPIDER reconstruction package. KLH1, a 7.9 MDa macromolecule, is an extracellular respiratory pigment composed of two asymmetric decamers, and presents an overall D(5) point-group symmetry.

A relational database for cryoEM: experience at one year and 50 000 images.

For the past year we have been using a relational database as part of an automated data collection system for cryoEM. The database is vital for keeping track of the very large number of images collected and analyzed by the automated system and essential for quantitatively evaluating the utility of methods and algorithms used in the data collection. The database can be accessed using a variety of tools including specially developed Web-based interfaces that enable a user to annotate and categorize images using a Web-based form.