# Lyophilization protects [FeFe]-hydrogenases against O2-induced H-cluster degradation.
> 凍結乾燥による[FeFe]-ヒドロゲナーゼのO2誘発性Hクラスター分解からの保護


## Abstract

The [FeFe]-hydrogenase enzyme family exhibits high catalytic efficiency for H2 production but is typically inactivated by molecular oxygen in aqueous conditions. This study demonstrates that lyophilization (freeze-drying) renders these enzymes fully resistant to O2 exposure. When completely desiccated, both the protein scaffold and the inorganic active-site cofactor known as the H-cluster remained intact after prolonged exposure to 100% O2 over several days. Upon re-dissolution, full H2-forming activity was recovered. Notably, even trace moisture was sufficient to restore O2 sensitivity, underscoring the critical role of complete dryness. The lyophilized material also proved advantageous for advanced spectroscopic studies of H-cluster reaction mechanisms. This approach offers a practical route for long-term enzyme storage and has implications for biotechnological H2 production systems.

### Mechanism

Complete removal of water molecules prevents O2 from accessing and degrading the H-cluster active site. Rehydration immediately restores O2 sensitivity, indicating that water is an essential mediator of oxidative inactivation in [FeFe]-hydrogenases.

## Bibliographic

- **Authors**: Noth J, Kositzki R, Klein K, Winkler M, Haumann M, Happe T
- **Journal**: Sci Rep
- **Year**: 2015 (2015-09-14)
- **PMID**: [26364994](https://pubmed.ncbi.nlm.nih.gov/26364994/)
- **DOI**: [10.1038/srep13978](https://doi.org/10.1038/srep13978)
- **PMC**: [PMC4568494](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4568494/)
- **Study type**: in vitro study
- **Delivery route**: in vitro
- **Effect reported**: positive

## Delivery context

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 26364994. https://h2-papers.org/en/papers/26364994
> **Source**: PubMed PMID [26364994](https://pubmed.ncbi.nlm.nih.gov/26364994/)