Preparation of Sample Support Films in Transmission Electron Microscopy using a Support Floatation Block
April 8th, 2021
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Sample preparation for cryo-electron microscopy (cryo-EM) is a significant bottleneck in the structure determination workflow of this method. Here, we provide detailed methods for using an easy-to-use, three-dimensionally printed block for the preparation of support films to stabilize samples for transmission EM studies.
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Overview
This article presents improved protocols for preparing cryo-electron microscopy (cryo-EM) samples using a novel flotation block to handle delicate support films such as amorphous carbon, graphene, and graphene oxide. The flotation block streamlines the transfer and application of support films, minimizing manual handling, reducing contamination, and protecting samples from the damaging air-water interface. Step-by-step procedures are provided for preparing and applying these supports, enhancing sample integrity and accessibility for EM studies.
Key Study Components
Area of Science
- Cryo-electron microscopy (cryo-EM)
- Structural biology
- Sample preparation techniques
Background
- Cryo-EM structure determination has expanded rapidly, but sample preparation remains a bottleneck.
- Macromolecular samples are ideally imaged in vitreous ice, but many are sensitive to the air-water interface, leading to denaturation.
- Support films (amorphous carbon, graphene, graphene oxide) can protect samples but are challenging to handle without damage or contamination.
- Existing methods often require extensive washing, cleaning, or expensive treatments to render supports hydrophilic.
Purpose of Study
- To develop and demonstrate protocols for preparing cryo-EM samples with support films using a user-friendly flotation block.
- To minimize manual handling and contamination during support film transfer.
- To provide accessible methods that do not require costly hydrophilic treatments.
Methods Used
- Preparation and cleaning of TEM grids using distilled water, ethyl acetate, and plasma cleaning.
- Application of support films (carbon, graphene, graphene oxide) to grids using the flotation block.
- Stepwise transfer of films via wetted flotation, minimizing exposure to air and contaminants.
- Negative staining and vitrification protocols for sample preservation and imaging.
Main Results
- The flotation block enables efficient, reproducible transfer of support films with minimal breakage.
- Amorphous carbon and graphene oxide films provide good coverage and protect samples from the air-water interface.
- Graphene oxide grids can be prepared rapidly from raw materials and do not require hydrophilic treatment.
- The flotation block supports buffer exchange and on-grid affinity purification, expanding its utility.
Conclusions
- The flotation block simplifies the preparation of cryo-EM grids with support films, reducing manual steps and contamination risk.
- Protocols are accessible and do not require specialized equipment for hydrophilic treatment.
- This approach enhances sample integrity and broadens the applicability of support films in cryo-EM studies.
Frequently Asked Questions
What is the main advantage of using the flotation block in cryo-EM sample preparation?
The flotation block minimizes manual handling and contamination, preserving the integrity of delicate support films and protecting samples from the air-water interface.
Which support films can be prepared using the described protocols?
The protocols cover amorphous carbon, graphene, and graphene oxide support films for cryo-EM grids.
Do these methods require hydrophilic treatment of graphene?
No, the protocols avoid expensive hydrophilic treatments, making graphene supports more accessible to the EM community.
How does the flotation block help reduce contamination?
By minimizing the number of manual handling steps and exposure time, the flotation block reduces the risk of airborne contamination and hydrophobic buildup on support films.
Can the flotation block be used for buffer exchange or affinity purification?
Yes, the flotation block includes needle ports for buffer exchange and supports on-grid affinity purification methods using small volumes and functionalized films.
What are the typical results when using these protocols?
The protocols yield grids with good film coverage and minimal breakage, suitable for negative staining and cryo-EM imaging.
Executive Industry Relevance
Efficient and reproducible sample preparation for cryo-EM is critical for structural biology pipelines, yet remains a bottleneck due to sample fragility and contamination risks. The support flotation block enables streamlined transfer of delicate support films, reducing manual handling and preserving sample integrity for high-resolution imaging. This innovation enhances predictive confidence in early discovery and supports robust portfolio progression by minimizing artifacts and sample loss.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables reliable interrogation of macromolecular structure by protecting samples from air-water interface denaturation.
- Supports functional target validation by maintaining native conformations during grid preparation.
- Reduces mechanistic ambiguity by minimizing sample damage and contamination.
Screening & Assay Development
- Facilitates preparation of validated EM grids for downstream structural screening workflows.
- Improves reproducibility and standardization of support film application across batches.
- Enables rapid, scalable preparation of grids with amorphous carbon, graphene, or graphene oxide supports.
Translational & Preclinical Research
- Preserves sample integrity for translational studies requiring high-fidelity structural data.
- Supports continuity from discovery through preclinical validation by enabling robust imaging of challenging samples.
- Mitigates risk of false negatives due to sample denaturation or contamination.
Pipeline & Workflow Integration
The flotation block method integrates at the sample preparation stage, bridging early discovery and lead identification with preclinical imaging workflows.
- Discovery Biology: Supports hypothesis testing by enabling high-quality structural data acquisition.
- Screening: Delivers reproducible, contamination-minimized grids for reliable compound evaluation.
- Analytics: Provides quantitative, high-integrity imaging outputs for comparative analysis.
- Translational Research: Maintains sample fidelity for downstream biomarker or mechanistic studies.
- Enterprise Reuse: Offers a standardized, reusable protocol adaptable to various support films and sample types.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces structural ambiguity in target validation.
- Operational Value: Streamlines workflows, reduces manual steps, and minimizes contamination risk.
- Strategic Value: Enables better go/no-go decisions by improving data quality and reproducibility.
- Portfolio Impact: Supports risk-adjusted advancement by reducing sample loss and preparation failures.
Implementation Considerations
- Requires expertise in EM grid handling and support film transfer.
- Needs access to flotation block, plasma cleaning, and standard EM preparation infrastructure.
- Demands cross-team standardization for reproducible results across projects.
- Adaptable to carbon, graphene, and graphene oxide supports as demonstrated.
- Potential limitations include occasional film breakage and need for careful contamination control.
Biopharma FAQs
Why does null hypothesis testing matter for support film protocols?
Null hypothesis testing ensures that observed structural differences are due to biological variables, not artifacts from sample denaturation or contamination during support film preparation, thus increasing confidence in target validation.
How does independent variable isolation fit in flotation block workflows?
The flotation block enables isolation of variables such as support film type and buffer conditions, allowing systematic evaluation of their impact on sample integrity and imaging outcomes within the discovery pipeline.
What do quantitative dependent variable measurements enable in EM grid preparation?
Quantitative assessment of film coverage, contamination, and sample preservation enables teams to compare preparation conditions and optimize protocols for reproducible, high-quality imaging outputs.
Why are replication requirements critical for cross-functional EM teams?
Replication ensures that support film protocols yield consistent results across operators and projects, facilitating reliable data sharing and cross-functional collaboration in structural biology workflows.
What statistical analysis capabilities are needed before implementing flotation block protocols?
Teams should establish statistical methods to evaluate grid quality, film integrity, and contamination rates, supporting data-driven decisions for protocol adoption and workflow integration.
Chapters in this video
0:04
Introduction
0:47
Preparation of Negatively Stained Samples with Amorphous Carbon Support
2:21
Preparation of Graphene Oxide-coated TEM Grids
3:27
Preparation of Samples on Monolayer-graphene Films Using the Flotation Block
4:44
Results: Examples of Sample Support Films Prepared Using the Floatation Block
5:34
Conclusion
