The water around proteins absorbs more terahertz radiation than pure water, which helps our proteins fold correctly.
If unfolded or misfolded proteins start to accumulate, the endoplasmic reticulum becomes stressed and activates a signaling pathway called the unfolded protein response.
The unfolded protein response is implicated in many diseases. For example, the response is often activated in rapidly growing cancer cells, which enables the cells to fold the large numbers of mutated proteins they produce. Also, viruses can trigger this response as part of their strategy to trick host cells into producing a number of difficult to fold viral proteins.
The correct folding of proteins is essential for cellular homeostasis and the prevention of disease. During times of stress or changes in demand for newly synthesized proteins, signaling pathways cooperate with networks of protein-folding and protein-degradation factors to maintain the pools of non-native proteins within a tolerable range. Such events are crucial for survival, as aberrant protein homeostasis can result in diseases that range from cancer and diabetes to neurodegeneration.
Understanding molecular vibrations in proteins are important because they regulate the function of proteins, e.g., in enzyme catalysis and protein interactions. In particular, low-frequency collective vibrational modes of proteins in the terahertz frequency region are expected to have a strong influence on protein function because terahertz radiation is absorbed by proteins.
Image: A simulation showing water molecules around an unfolded and folded protein. The water molecules closest to the protein are highlighted bright red for effect. Terahertz spectroscopy has shown that the water molecules closest to the protein behave differently than the surrounding ones and actually participate in the folding process.