Terahertz Radiation Effects and Biological Applications

The spectral region from 0.1 to 10 THz represents an opportunity for research in physics, chemistry, biology, and medicine. This is especially because of the unique sensitivity of this spectral region to the global nuclear motions, which are important in biomolecular processes. More specifically, it is important to point out that THz radiation is generally non-invasive. THz waves have low photon energies (1 THz = 4.1meV), one million times weaker than x-rays, and do not cause harmful photoionization in biological tissues. THz radiation interrogates vibrational modes that extend across large portions of the biomolecular framework with length scales that extend over tens of angstroms. These extend motions are important for the functioning of proteins/RNA/DNA that undergo transformations in secondary and tertiary structures. THz frequencies provide access to timescales in the sub-picoseconds domain, which are difficult to attain using other methods. Ultimately, much larger systems than proteins and DNA strands will be accessible, particularly with the coupling of THz science with near-field probes. One envisions label-free measurement of protein-protein interactions as cellular activity is occurring in live cells. The opportunities for THz science in chemistry and biology are, therefore, wide ranging and some examples are given below.