Myoglobin as an example of protein complexity

Fifty years ago, some proteins such as myoglobin appeared to be simple. As they were studied more deeply with sophisticated tools and over extended ranges of time, temperature, pressure, and in different environments, the simplicity turned into complexity and even today no protein is fully understood. Protein assemblies, cells, and extended biological systems (the brain!) display even more complexity. Here I sketch some of the steps that led to the present, still incomplete, understanding of the physics of a “simple” protein, myoglobin. The number of papers concerning myoglobin is vast. The choice made here is therefore exceedingly biased but I hope that it gives some insight into the present picture.