Editorial [Hot Topic: Calorimetry Guest Editor: Mike O' Neil ]

Calorimetric experiments on complex biological systems have been conducted since the 18th century. Lavoisier and Laplace developed an ice calorimeter to study the metabolism of a guinea pig through weighing the ice melted over the observation period and knowledge of the latent enthalpy of fusion of water. This early experiment set the scene for a number of other researchers but limitations in instrument design restricted their studies to relatively rapid reaction systems. A more advanced instrument was developed by Calvet in the first half of the 20th Century and marked an increase in the application of calorimetry to a wide variety of biological systems. As more advanced instruments were developed quantitative kinetic and thermodynamic analysis became possible. The emphasis then began to shift from more complex biological systems to relatively simple chemical systems. With the advent of more sophisticated analysis techniques for calorimetric data and with modern pharmaceutical therapies becoming increasingly designed for specific bio-therapeutic targets, for example protein-substrate interactions, we are now witnessing a shift back to investigations of complex systems of biological origin. In recognition of this revolution manufacturers are beginning again to modify and improve their products in order to facilitate this renewed interest with high throughput instruments being developed specifically for systems of a biological nature. The articles in this issue reflect the resurgence of calorimetry as a useful tool in the study of biologically important systems. A wide range of topics and calorimetric methods are covered they include: stability assessment of biopharmaceuticals, investigation of biopharmaceuticals by solution calorimetry, characterisation of freeze dried systems, assessment of polymorphic content, studies of microbiological systems and advances in calorimetric data analysis. In a manner analogous to the renaissance of calorimetry in the biopharmaceutical arena, the authors for this special issue were selected because they are all at the start of their research careers and thus represent the next generation of calorimetrists entering this field.