Venturoli arrived at Bologna as a physics student and joined Melandri’s laboratory for his final experimental thesis, graduating in 1977 with work on electric phenomena in the energy-transducing membranes of photosynthetic bacteria. The thesis was so innovative and clear-cut that it was published immediately as a research paper, the first of a long series. He stayed on, improving the laboratory’s fast-spectrophotometry apparatus and patiently establishing conditions for accurate measurements of light-induced ATP synthesis in bacterial chromatophores during brief flashes of light. Colleagues quickly recognized a rare combination: marked experimental skill paired with an excellent ability to analyze data rigorously.

A central thread of his early research was the ubiquinone-10 (UQ10) molecule, the lipid-soluble electron carrier that shutters electrons between the photosynthetic reaction center and the cytochrome bc1 complex in bacterial chromatophores. Venturoli’s group investigated how extracting or enriching the endogenous UQ10 pool affected electron transport, and studied the kinetics of charge recombination from reduced primary and secondary quinone acceptors back to the oxidized bacteriochlorophyll special pair. The team also quantified the intrinsic buffering capacity of chromatophores, a crucial parameter for any quantitative account of how proton gradients drive ATP synthesis, and demonstrated a collisional interaction between ubiquinol and the ubiquinol-cytochrome c2 oxidoreductase complex.

Perhaps the most ambitious early project was the full reconstitution of the cyclic electron transport chain in artificial vesicles. Working with the laboratory of Dieter Oesterhelt at the Max Planck Institute of Biochemistry in Martinsried, Venturoli helped incorporate purified reaction center and cytochrome bc1 complexes from Rhodobacter capsulatus into liposomes enriched in UQ10 and loaded internally with cytochrome c2. The crowning achievement came when purified ATP synthase was inserted into the liposome bilayer with the correct orientation: the reconstituted system was competent to synthesize ATP from light, a landmark demonstration that the minimal photosynthetic machinery could be rebuilt from purified parts.

Venturoli also brought powerful physical methods to bear on metal-binding sites in photosynthetic complexes. In collaboration with physicist Federico Boscherini in Bologna, and using the European Synchrotron Radiation Facility in Grenoble, his group applied X-ray absorption spectroscopy to locate and characterize metal sites with atomic precision. Comparative studies of zinc-inhibited cytochrome bc1 complexes from bacteria, birds and cattle suggested that in all of them Zn2+ binds to a histidine residue, competing with its role as a proton donor and acceptor, and that a similar mechanism underlies zinc inhibition at the QB site of the reaction center. Another study resolved the coordination shell of the native non-heme iron lying between the QA and QB quinones, and showed how dried trehalose matrices perturb its bond lengths, a finding that foreshadowed his later work on sugar glasses.

One of the most celebrated results of Venturoli’s career concerns the PufX protein of Rhodobacter sphaeroides. Early work confirmed that PufX was required for photosynthetic growth under anaerobic conditions and for efficient ubiquinone exchange, but its precise role remained obscure. The turning point came when the purified reaction center-LH1 core complex was fractionated into monomeric and dimeric forms, with PufX required for dimer formation. The definitive answer arrived with a low-resolution cryo-electron microscopy structure of the dimer: an S-shaped assembly of two core complexes, each containing one reaction center surrounded by twelve LH1 heterodimers, joined by a central PufX dimer. Each core complex has an opening that permits rapid ubiquinone traffic to and from the QB site. PufX, in essence, prevents complete closure of the LH1 ring and welds the dimer together, keeping the quinone highway open.

The dominant theme of Venturoli’s later career, generating some twenty-five papers, was the behavior of proteins embedded in trehalose glasses. The inspiration came from the resurrection plant Craterostigma plantagineum, which survives months or years of extreme dehydration and resumes its vegetative cycle after watering, a latent-life state called anhydrobiosis. Such organisms accumulate high concentrations of the disaccharide trehalose. Venturoli’s team used the charge recombination reaction between the oxidized bacteriochlorophyll dimer and reduced quinones in purified bacterial reaction centers as a sensitive probe of protein dynamics. As trehalose matrices were progressively dried to 97 percent trehalose by weight, charge recombination from QA accelerated markedly, while electron transfer from QA to QB was blocked entirely, indicating that this step is rate-controlled by protein motions coupled to QB displacement and protonation.

Collaborations with Lorenzo Cordone in Palermo, and with Klaus Möbius and Wolfgang Lubitz in Berlin and Mülheim, extended these findings through high-field electron paramagnetic resonance spectroscopy. EPR studies of the native radical pairs and of spin probes attached to the reaction center confirmed that the vitreous trehalose matrix does not distort the distance or orientation of internal radicals, but clearly alters the properties of labels at the protein-solvent interface. The proposed mechanism holds that trehalose slows and eventually blocks protein dynamics through a hydrogen-bond network involving interfacial water, a protection that sucrose cannot match because sucrose-water matrices undergo nanophase separation. The work was extended to oxygenic photosynthesis as well: in trehalose-dried photosystem I, fast recombination phases dominated while in hydrated samples the slow phases prevailed, and in photosystem II, dehydration delayed electron donation to P680 and blocked transfer between the two plastoquinones, consistent with the matrix hindering the protein motions on which these redox reactions depend.

The final chapter connects this biophysics to one of the most striking phenomena in biology: the ability of tardigrades to survive desiccation. Venturoli’s laboratory contributed to a large twelve-institution study of CAHS D, a protein from the tardigrade Hypsibius exemplaris that forms a protective gel inside cells as water disappears. Using the same bacterial reaction center assay, the Bologna team showed that adding CAHS D to desiccated samples reproduced the effects of trehalose glasses, accelerating charge recombination in the same way, evidence that gel formation creates a protective shell at the protein-matrix interface. The combined evidence, from mutagenesis and scattering experiments to in vivo studies, supported a model in which CAHS proteins self-assemble into cytoskeleton-like filaments upon drying, condensing into a gel that suppresses metabolism, with both effects reversed upon rehydration.

Taken together, Venturoli’s work supports a unifying model of anhydrobiosis: trehalose or protective proteins form an amorphous matrix that interacts with hydrophilic protein surfaces not by direct bonding, but through a persistent hydration shell, slowing molecular dynamics until, in extreme dryness, mobility is fully arrested and native structures are shielded from thermal degradation. Beyond the laboratory, the tribute paints a portrait of an unusually complete scholar. Venturoli’s academic path was slow and principled; he spent two years teaching fundamental physics in Cosenza before returning to Bologna, becoming associate professor of photobiology in 1991 and of applied physics in 1994, and he declined career advances he judged inconsistent with his biophysical background. He is also a pianist devoted to Bach, a practicing painter and etcher, and a lifelong fossil hunter in the hills above Bologna. In an era of narrowing specialization, Melandri concludes, such all-round scholarship is rarely met.

Subject of Research: The research career of biophysicist Giovanni Venturoli, covering bacterial photosynthetic electron transport, quinone function, metal-binding sites, protein dynamics in trehalose matrices, and tardigrade anhydrobiosis proteins

Article Title: Giovanni Venturoli: The career of a real scholar

Article References: Melandri, B. A. (2026). Giovanni Venturoli: The career of a real scholar. Frontiers in Photobiology, 4, Article 1867742. https://doi.org/10.3389/fphbi.2026.1867742

Image Credits: AI Generated

DOI: 10.3389/fphbi.2026.1867742

Keywords: Giovanni Venturoli, photosynthesis, bacterial reaction centers, ubiquinone, cytochrome bc1, PufX protein, trehalose glass, protein dynamics, anhydrobiosis, tardigrades, CAHS D protein, EPR spectroscopy