Protein determination using laser induced-thermal lens spectrometry

Laser induced-thermal lens spectrometry (LI-TLS), as well as other photothermal techniques, is based on generation of heat during the nonradiative relaxation of the absorbed optical radiation. The heat released inside the absorbing sample during the radiation-less de-excitation of excited species is proportional to the power of the excitation laser. This provides an inherently high sensitivity of the TLS technique, which was demonstrated capable of measuring absorbances as low as 10-7–10-8. Compared to conventional transmission techniques, TLS is much less subject to errors resulting from frequently present light scattering in environmental and food samples [1-2]. The interaction between methylene blue (MB) and bovine serum albumin (BSA) as a protein was investigated by Laser induced-thermal lens spectrometry (LI-TLS). The maximum excitation wavelength of MB is 664 nm therefore to obtain TLS signal, the diode laser (665 nm, 50 mW) was used as pump/probe source. It was proved that changes in TLS signal intensity at 664 nm is in proportion to the concentration of BSA. Changes in TLS signal of MB by BSA are mainly a result of the formation of MB–BSA complex and electrostatic interactions play an important role to stabilize the complex spectroscopy. Determination of protein content to be an important technique in life science applications. A new method for detecting protein by Laser induced-thermal lens spectrometry (LI-TLS) was developed. Some effective parameters on the complex formation and determination of TLS signal were selected and optimized.