PROBING THE METAL BINDING SITES OF α-LACTALBUMIN WITH LASER-EXCITED Eu(III) IONS

Abstract

α-lactalbumin, also known as the B-protein of the lactose synthetase enzymatic complex, is a soluble milk protein which is secreted throughout lactation and functions as an "on-off" switch in the synthesis of lactose. The protein has a molecular weight of 14,200 and contains 123 amino acid residues arranged in a sequence similar to that of egg-white lysozyme [1]. The protein in its native form contains one or two Ca(II) ions per mole but despite extensive investigation, mainly by Kronman and coworkers [2,3,4,8], the number and location of the sites for attachment of calcium remain ill-defined. We have initiated a study to determine further the number and nature of the protein metallic sites using Eu(III) as a luminescent binding probe

Lanthanide luminescence for functional materials and bio-sciences

“…Number of metal-ion sites, N. High resolution of the Eu( 5 D 0 -7 F 0 ) transition, which is unique for a given chemical environment associated with spectral decomposition with Lorentzian-Gaussian shape functions 42,43 gives a direct access to N. Experimentally, laser-excited excitation spectra of the 5 D 0 ' 7 F 0 transition yield more sensitive results.…”