Photoelectron quantum yields of the amino acids

Area of Science:

• Photochemistry
• Biophysics
• Materials Science

Background:

• Amino acids are fundamental building blocks of proteins.
• Understanding their electronic properties is crucial for various applications.
• Photoelectron spectroscopy is a powerful tool for probing electronic structures.

Purpose of the Study:

• To measure the photoelectron quantum yields of common amino acids and polyamino acids.
• To investigate the wavelength dependence of these yields in the 180-240 nm range.
• To compare amino acid yields with a known dye for potential applications.

Main Methods:

• Photoelectron quantum yields were measured for 21 amino acids and 15 polyamino acids.
• Measurements were conducted in the ultraviolet (UV) wavelength region (180-240 nm).
• Quantum yields were compared to those of phthalocyanine dye.

Main Results:

• Amino acid and polyamino acid quantum yields showed similar wavelength dependence.
• Yields were below 10⁻⁷ electrons/photon for wavelengths > 220 nm.
• Yields increased to 5 x 10⁻⁶ electrons/photon at 180 nm, with L-tryptophan and L-tyrosine exhibiting higher values.
• Phthalocyanine dye showed quantum yields two orders of magnitude greater than amino acids.

Conclusions:

• Photoelectron quantum yields of amino acids and polyamino acids are wavelength-dependent.
• Specific amino acids like tryptophan and tyrosine have enhanced yields.
• The significant difference in quantum yields suggests potential for photoelectron labeling of biological surfaces using dyes.