Caption: Molecular imaging of a toll-like receptor (TLR). Every lung cell is studded with tens of thousands of receptors that form what biosemioticians call "semiotic bridges" -- molecular assemblages that transduce signals from an exterior environment (top) across the cell membrane (the thick and mostly colorless middle) to a semi-fluid cytoplasmic interior (bottom) crowded with diverse complex molecules that get mobilized into "signalling pathways." (These are not pictured here but some show up in the next image in the photo essay.) One common end result of such complex signal transduction is inflammation, or the constriction of lung passageways that are a symptom of respiratory conditions such as asthma.
At this scale of analysis toxicity acts via molecular mechanism such as these. Painting with a broad brush: an inhaled molecule binds, beacause of its particular pattern or shape, to the upper portion of the receptor with a complementary patterned shape. The shape of the receptor thus changes, and this changed shape is sensed at the other end, inside the cell membrane, and triggers a complex cascade of cellular reactions that result in some kind of harm.
The Toll-like Receptor or TLR is one of my favorite "matters of concern." These particular "pattern recognition molecules" (PRMs) are a relatively recent biomedical discovery, becoming visualizable and knowable only since the 1980s, a basic part of what we now call the innate immune system. On an evolutionary time scale, this is a very old set of molecular structures that we humans share with numerous organisms: fruitflies and fugu, mice and many other mammals. TLRs have differentiated and multiplied over this evolutionary history; scientists are also interested in how they also differ slightly within species. Enormous investments of time, money, resources, energy, and affect are mobilized -- largely in the Euro-American and East Asian societies that can afford such investments -- to understand these receptors and their complex signalling pathways in the more detailed way they demand.
Some scholars find such "molecularization" of life, health, and toxicity to be reductive, inappropriately mechanistic, or otherwise deserving only critique or dismissal; I am looking to activate a different set of semiotic pathways in my viewers and readers. I would like this image to transduce the intricate beauty of molecular structures and how that can capture the attention and interests of scientists; the commitments (vocations, for you Weberians) that those scientists embody in working out how variations in the molecule here may be associated with variations in different people's responses to inhaled pollutants; the importance of public investment in such "basic science" that will take years or maybe decades to "pay off," if it ever does; the collective effort to understand toxicity in its most minute enactments, and to stockpile and share data in public repositories like the Protein Database from which this image is taken; and the drives of curiousity, wonder, and for old-fashioned enlightenment that infrastructures a microscopic entity like this Toll-like receptor.
Design statement: Hyperrealistic visualizations of nanomolecular structures like cell surface receptors are a sign of both collective technical accomplishment, and invitation to sublime wonders. Mobilizing data from multiple expert communities accrued over years in expansive public databases, scientists work (perhaps to obsessive and excessive degrees) to understand the implications of difference at the molecular scale. Viewers are also interpellated into a scientific imaging tradition dating back to Robert Hooke’s Micrographia of 1665: asked to wonder, in amazement and curiosity, at the world contained within the world, the vital beautiful fragile structures of flesh.