Why Is near Infrared Radiation Effective in Light Therapy?

The absorption and scattering spectra of various human subjects show that the human body absorbs radiation in the 750-2000 nm range. The influence of NIR on various tissues has been reported in recent years. However, the molecular mechanisms of the interaction of radiation with tissues are not yet clear. Our earlier studies on bovine erythrocytes irradiated with NIR revealed structural changes in the erythrocyte membrane lipid area. Polarity decreased in the vicinity of the polar heads and the presence of oxidative factors outside the membrane was monitored during the first 10 minutes of exposure to radiation. In the continuation of our research, we reported on the influence of NIR radiation on erythrocyte shape, electric zeta potential and osmotic hemolysis rate. All the observed phenomena were discussed as a result of NIR dehydration effects after exposure to NIR. Dehydration may follow the excitation of the overtones of the stretching vibrations of-OH,-POH,-NH, and-CH group stretching vibrations. All these groups are involved in hydrogen bonds. Zundel et al. studied the easily polarizable hydrogen bonds between various proton donors and acceptors, which are responsible for the presence of continua in IR spectra. Studies on these phenomena demonstrated that many types of H bond that form between proteins or H-bonded systems between side chains and phosphates show large proton polarizability. So, the proton transfer process can be easily controlled with local electric fields generated by fixed charged groups, cations, polar molecules and even by coupling proton motion with hydrogen bond stretching vibration. When H bonds with large proton polarizability are present, which is common for biological systems like the membrane surface, a proton within one of those H-bond shifts, and the subsequent conformational changes are strongly interdependent.