Full Length Research Paper

Using two-photon excitation methods for determination of Ca²⁺ in contamination with protein

A. S. M. Noor¹*, A. Miyakawa², W. Inami³ and Y. Kawata²

¹Wireless and Photonics Network Centre of Excellent (WiPNet), Department of Computer and Communication System Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Malaysia.

²Department of Mechanical Engineering, Faculty of Engineering, Shizuoka University, Johoku 3-5-1, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan.

³Division of Global Research Leaders, Shizuoka University, Johoku 3-5-1, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan.

*Corresponding author. E-mail: ashukri@eng.upm.edu.my.

Accepted 8 September, 2011

Abstract

Three emission wavelengths from two-photon excitation techniques were use to determine free Ca²⁺ using a new analytical calculation. This was achieved by considering the interaction of protein with free Ca²⁺ and indo-1 in protein contaminated sample. The emissions obtained from the excitation with the dissociation constants were used in the calculation. Agreement values of the Ca²⁺ from the calculation with the known Ca²⁺ buffer solution used for the measurement was obtained for various Ca²⁺ and protein concentration. The analytical analysis shows that dissociation constants for each binding’s deviation errors are small to affect free Ca²⁺ determination. This would provide an accurate measurement of free Ca²⁺ in biological cells than the typical two emission wavelength processes. Furthermore, using two-photon excitation methods, deep inside cells observation of free Ca²⁺ are possible using the methods introduced.

Key words: Free Ca²⁺, indo-1, two-photon excitation methods.