20/11/2025
Research Updates ：COY Anaerobic Chamber : How to Solve the Problem of Anaerobic Protein Cryo-Electron Microscopy Preparation?
Anoxic proteins are a class of special proteins that can only maintain their structural stability and biological activity in anaerobic or extremely low oxygen concentration environments. They are widely present in microorganisms, plants, and animals, and are the "core molecular machines" that support key metabolic processes in life. Their core feature is the presence of oxygen-sensitive active centers (such as metal clusters, reduced thiol groups, special cofactors, etc.), which are easily oxidized upon exposure to molecular oxygen (O₂) — for example, the dissociation of metal clusters (such as [4Fe-4S], [8Fe-7S]), oxidation of active site amino acid residues, leading to protein inactivation, denaturation, or aggregation, and loss of physiological function.
From a physiological standpoint, anaerobic proteins cover three key areas: (more details in the photo)
• Biological nitrogen fixation: enzymes such as nitrogenase ( composed of iron protein and molybdenum-iron protein ) can reduce atmospheric N₂ to ammonia ( NH₃ ) that is available to organisms , and is the key driver of the global nitrogen cycle , providing nitrogen supply to agricultural ecosystems ;
•Energy metabolism: electron transport chain proteins (some complexes contain Fe-S clusters), hydrogenases (catalyze hydrogen oxidation/production), participate in cellular respiration and energy conversion;
•Molecular transformations: such as ribonucleotide reductase (containing an Fe-S cluster, catalyzing the reduction of ribonucleotides to deoxyribonucleotides for DNA synthesis) and CO dehydrogenase (catalyzing the oxidation of CO to CO₂), are key executors in microbial metabolism and biogeochemical cycles.
However, the structural analysis of anaerobic proteins has long been plagued by a "triple bottleneck":
• oxygen exposure risk : conventional protein purification and cryoEM sample preparation are usually carried out in an oxygenated environment , which leads to protein oxidation and inactivation ;
• poor equipment compatibility : existing anaerobic protocols require expensive cryo - electron microscopy equipment ( e.g . , Vitrobot ) to be placed inside the anaerobic chamber , which is not only costly but also suffers from difficulties in temperature and humidity control as well as complex equipment maintenance ;
• Oxidation monitoring is absent: It is impossible to track the oxidation state of samples in real time, and "hidden oxidation" may occur, where the appearance of proteins does not change明显 but their active centers are damaged. As a result, the structural analysis results cannot reflect their physiological functional states.
COY as the core " environmental housekeeper " directly penetrates the entire process of anaerobic protein cryo-electron microscopy research , making the high-resolution structure of oxygen - sensitive proteins no longer " unattainable " !
Pain point hit: The "life and death" of anaerobic protein structure research
Oxygen-sensitive proteins (e.g., nitrogenase, hemoglobin, hydrogenases) are the "stars" of life, but they are as fragile as glass regarding oxygen: they inactivate within milliseconds upon exposure to air, metal centers are oxidized, and proteins aggregate - traditional cryo-electron microscopy either "kills the sample with oxygen" or "is too expensive to operate in an anaerobic chamber," and the field was at an impasse.
COY anaerobic chamber: full chain protection from "purification" to "freezing"
Two top journal studies use different approaches to prove that the COY anaerobic chamber is no "simple glove box," but a "structural characterization bodyguard" tailored for anaerobic proteins!
✅1. Nature Communications (2025): "Extracapsular protection" strategy
The samples were pretreated in a COY乙烯膜 anaerobic chamber, and then the frozen samples of deoxygenated hemoglobin and reduced nitrogenase MoFeP were successfully prepared on an SPT Labtech chameleon in an aerobic environment with Al's oil protection layer + NaDT reducer.
Steps to prepare anaerobic proteins (More details in the photo)
👉 Highlight: The expensive equipment was not modified, and "quasi-anerobic" sample preparation was achieved, resulting in a near-atomic structure with a resolution of 2.08 Å!
✅ 2. Nature Protocols (2024): "In-box" whole protocol
The CalTech team integrated the Vitrobot plunge freezer directly into the COY Ethylene membrane anaerobic chamber to establish a gold standard purification to freezing workflow and innovatively used the mPlum fluorescent protein as an internal oxygen probe to monitor the absence of oxygen in real time.
The infrastructure used for the single-particle cryo-electron microscopy grid preparation of the anaerobic sample in this study. (More details in the photo)
→ Highlight: The whole process is under extreme oxygen control, and the structure of the nitrogen-fixing enzyme complex was determined at 2.12 Å, directly observing the metal cluster in its natural reduced state!
It's not just a chamber; it's a new key to structural biology.
Whether it's the flexible "beyond the box" protection or the ultimate "inside the box" full process, the COY anaerobic chamber provides a stable and reliable oxygen-free environment for studying these "elusive" life core proteins that were once considered "difficult to catch", and it is an indispensable tool for promoting the development of energy, agriculture, and enzyme catalysis and other fields!
References :
1. Narehood, Sarah M. , et al. "Structural basis for the conformational protection of nitrogenase from O2." Nature 637.8047(2025).
2. Warmack, Rebeccah A. , et al. "Anaerobic cryoEM protocols for air-sensitive nitrogenase proteins." Nature Protocols 19.7(2024).
