A cyclophilin‐D affinity matrix was employed to isolate components of the mitochondrial permeability transition pore. A cDNA encoding cyclophilin‐D was cloned from a rat liver library and ligated into pGEX to allow expression of a glutathione S‐transferase/cyclophilin‐D fusion protein in Escherichia coli XL1 cells. The cyclophilin‐D in the fusion was functionally normal as judged by its peptidylprolyl cis‐trans‐isomerase activity and its inhibition by cyclosporin A. The fusion protein was bound to glutathione‐agarose to form the cyclophilin‐D affinity matrix. The matrix selectively bound 32‐kDa proteins of mitochondrial membrane extracts, but no H₂O‐soluble proteins were bound. The 32‐kDa band on SDS/PAGE resolved into a doublet and reacted with antibodies against the voltage‐dependent anion channel (porin) and the adenine nucleotide translocase. These two proteins were also selectively retained by the affinity matrix in the presence of cyclosporin A. The thus‐purified voltage‐dependent anion channel, adenine nucleotide translocase and the fusion protein were incorporated into phosphatidylcholine liposomes containing fluorescein sulphonate. The proteoliposomes were permeabilized by Ca²⁺ plus phosphate, and this was blocked completely by cyclosporin A. These properties are identical to those of the permeability transition pore in mitochondria. It is concluded that the basic permeability transition pore structure comprises the voltage‐dependent anion channel (outer membrane), adenine nucleotide translocase (inner membrane) and cyclophilin‐D, and forms at contact sites between the two membranes.

The damaging effect of ionising radiation on cellular structure is one of the prime limiting factors on the survival of life in potential astrobiological habitats. Here we model the propagation of solar energetic protons and galactic cosmic ray particles through the Martian atmosphere and three different surface scenarios: dry regolith, water ice, and regolith with layered permafrost. Particle energy spectra and absorbed radiation dose are determined for the surface and at regular depths underground, allowing the calculation of microbial survival times. Bacteria or spores held dormant by freezing conditions cannot metabolise and become inactivated by accumulating radiation damage. We find that at 2 m depth, the reach of the ExoMars drill, a population of radioresistant cells would need to have reanimated within the last 450,000 years to still be viable. Recovery of viable cells cryopreserved within the putative Cerberus pack‐ice requires a drill depth of at least 7.5 m.

In this review the current state‐of‐the‐art of S‐adenosylmethionine (SAM)‐dependent methyltransferases and SAM are evaluated. Their structural classification and diversity is introduced and key mechanistic aspects presented which are then detailed further. Then, catalytic SAM as a target for drugs, and approaches to utilise SAM as a cofactor in synthesis are introduced with different supply and regeneration approaches evaluated. The use of SAM analogues are also described. Finally O‐, N‐, C‐ and S‐MTs, their synthetic applications and potential for compound diversification is given.

Chemiosmotic coupling is universal: practically all cells harness electrochemical proton gradients across membranes to drive ATP synthesis, powering biochemistry. Autotrophic cells, including phototrophs and chemolithotrophs, also use proton gradients to power carbon fixation directly. The universality of chemiosmotic coupling suggests that it arose very early in evolution, but its origins are obscure. Alkaline hydrothermal systems sustain natural proton gradients across the thin inorganic barriers of interconnected micropores within deep-sea vents. In Hadean oceans, these inorganic barriers should have contained catalytic Fe(Ni)S minerals similar in structure to cofactors in modern metabolic enzymes, suggesting a possible abiotic origin of chemiosmotic coupling. The continuous supply of H₂ and CO₂ from vent fluids and early oceans, respectively, offers further parallels with the biochemistry of ancient autotrophic cells, notably the acetyl CoA pathway in archaea and bacteria. However, the precise mechanisms by which natural proton gradients, H₂, CO₂ and metal sulphides could have driven organic synthesis are uncertain, and theoretical ideas lack empirical support. We have built a simple electrochemical reactor to simulate conditions in alkaline hydrothermal vents, allowing investigation of the possibility that abiotic vent chemistry could prefigure the origins of biochemistry. We discuss the construction and testing of the reactor, describing the precipitation of thin-walled, inorganic structures containing nickel-doped mackinawite, a catalytic Fe(Ni)S mineral, under prebiotic ocean conditions. These simulated vent structures appear to generate low yields of simple organics. Synthetic microporous matrices can concentrate organics by thermophoresis over several orders of magnitude under continuous open-flow vent conditions.