A sunbeam hits a leaf, and inside, a relay race begins. Energy hops from one molecule to the next until it reaches its goal. In photosystem II (a protein complex that kicks off photosynthesis), the runners are pigment molecules: chlorophylls and pheophytins.
The authors used precise data on the distances and orientations of these molecules in the cyanobacterium Thermosynechococcus vulcanus. Based on Förster theory, they calculated energy transfer rates and built a network from them. In this network, each molecule is a node, and the lines between them represent possible energy transfer pathways with specific speeds. Then they applied network analysis tools: centrality (which nodes are most important for flows) and clustering (how interconnected a node's neighbors are).
This approach is reminiscent of analyzing a city's transportation network: without knowing bus schedules, you can predict from a street map where traffic jams will occur and where flow will be smooth. Similarly, the network structure hints at which molecules are critical for fast energy delivery.
The sunbeam fades, but the relay it started continues inside the leaf, and now it's clearer why it never misses a beat. The pigment network is wired so that energy finds the shortest path to its goal with almost no loss.
The 1.9-angstrom resolution used in the study allows individual atoms within a protein molecule to be distinguished, like spotting a pea from a kilometer away.
In Andy Weir's novel 'The Martian,' the protagonist survives thanks to photosynthesis in potatoes — perhaps understanding energy transfer networks will help create even more efficient life-support systems.