The stability of a protein is a complex topic, but important in countless ways. It can be investigated from different angles and with different methods. Typically, researchers are either looking for means to stabilize a protein (to keep it from unfolding before it's used in its target application) or to examine the influence of additives or ligands on protein stability (to understand the protein better). Prometheus can analyze protein stability in the following ways:

• Thermal stability is one aspect of protein stability and has proven useful as an easy-to-assess indicator of overall stability. To understand a protein’s thermal stability, it is denatured by heating.
• The propensity of the protein to aggregate is also an important piece in the protein stability puzzle. Aggregation can have many unwanted consequences and usually needs to be avoided. On Prometheus Panta, aggregation can be measured via light scattering with the DLS optics and via turbidity with the backreflection optics.

Thermal stability

Thermal stability is an easy-to-assess indicator of overall stability, where a protein is denatured by heating. During this process, also called thermal unfolding, the change in the protein’s structure is monitored, often via fluorescence. Typically, a constant heating rate is applied to heat the sample steadily over a defined time period. The information collected on the protein’s unfolding, the protein’s unfolding profile, can be used to compare different samples. The profile can be compared directly or via various derived parameters, most importantly inflection points or melting temperatures (Tm). Generally, the higher the temperature needed to denature a protein, the more stable the protein. The thermal (and overall) stability of a protein can be greatly influenced by buffer or storage conditions, additives, protein concentration, even expression conditions, and many other factors.

Most proteins unfold irreversibly when heated, but some can refold. PR.Panta Control software offers the option to also follow a protein's refolding after it has been unfolded.

For most proteins, temperatures of 95 °C are enough to denature them. There are some thermostable proteins, however, like proteins from thermophilic organisms including the well-known Taq polymerase, which require higher temperatures to denature. For studying such proteins, the Prometheus Panta system allows heating to up to 110 °C.