Iron-sulfur clusters are ancient protein cofactors that are essential for electron transport, enzyme catalysis, and photosynthesis. However, their sensitivity to oxygen and inherent instability have long hindered their practical application.

Researchers from the Institute of Biophysics and the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences have now designed a condensed organic iron-sulfur framework (OISF) containing discrete iron-sulfur clusters. This material combines the electron-transfer function of iron-sulfur clusters with the stability of condensed metal-organic framework (MOF)-like structures.

Their study was published in Small on October 30.

To produce OISF, the researchers used a hydrothermal synthesis strategy, introducing terephthalic acid as an organic linking ligand to disrupt the dense lattice of conventional iron sulfide minerals. This yielded a nanosheet-like framework containing discrete iron-sulfur clusters.

Using multiple characterization techniques, including X-ray diffraction structural analysis, synchrotron radiation, and Mössbauer spectroscopy, the researchers verified the structure of OISF and its [2Fe-2S] core.

Further investigation revealed that OISF possesses strong electron-transfer capability, enabling it to donate electrons to various electron acceptors. Its redox process is tunable through chemical conditions.

Structural analysis indicated that this electron-transfer process involves the dynamic formation of S-S bonds between distinct iron-sulfur clusters in adjacent layers. Compared with conventional iron sulfide minerals, OISF exhibits higher redox activity and good oxygen stability, creating favorable conditions for its integration with biological systems.

Building on these properties, the researchers combined OISF with isolated chloroplasts to construct an OISF-chloroplast complex (OCC). Experimental results showed that, compared with chloroplasts alone, this complex system possesses higher carbon fixation activity.

Starting from the electron-transfer function of natural iron-sulfur clusters, this study provides new ideas for the design of biomimetic materials that balance stability and redox activity. It also provides experimental and theoretical evidence for using nanozymes to increase the efficiency of the electron transport chain during the dark reactions of photosynthesis.

Construction of OISF and its enhancement of chloroplast dark reactions (Image by GAO Lizeng's group)