ABSTRACT
In weak acid medium, aluminum(III) can react with chlorophosphonazo III [CPA(III), H(8)L] to form a 1:1 coordination anion [Al(OH)(H(4)L)](2-). At the same time, proteins such as bovine serum albumin (BSA), lysozyme (Lyso) and human serum albumin (HSA) existed as large cations with positive charges, which further combined with [Al(OH)(H(4)L)](2-) to form a 1:4 chelate. This resulted in significant enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). In this study, we investigated the interaction between [Al(OH)(H(4)L)](2-) and proteins, optimization of the reaction conditions and the spectral characteristics of RRS, SOS and FDS. The maximum RRS wavelengths of different protein systems were located at 357-370 nm. The maximum SOS and FDS wavelengths were located at 546 and 389 nm, respectively. The scattering intensities (ΔI) of the three methods were proportional to the concentration of the proteins, within certain ranges, and the detection limits of the most sensitive RRS method were 2.6-9.3 ng/mL. Moreover, the chelate reaction mechanism or the reasons for the enhancement of RRS were discussed through absorption spectra, fluorescence spectra and circular dichroism (CD) spectra.
Subject(s)
Aluminum Compounds/chemistry , Muramidase/chemistry , Organometallic Compounds/chemistry , Organophosphorus Compounds/chemistry , Serum Albumin/chemistry , Animals , Cattle , Circular Dichroism , Humans , Muramidase/metabolism , Spectrometry, Fluorescence , Spectrophotometry, UltravioletABSTRACT
In Britton-Robinson (BR) buffer medium (pH 3.3), carbazochrome sodium sulfonate (CSS) can react with some aromatic amino acids such as tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) to form a 1:1 complex by electrostatic attraction, aromatic stacking interaction and Van der Waals' force, resulting in fluorescence quenching of these amino acids. Maximum quenching wavelengths were located at 352 nm (CSS-Trp system), 303 nm (CSS-Tyr system) and 284 nm (CSS-Phe system), respectively. The fluorescence quenching value (ΔF) was proportional to the concentration of CSS in a certain range. The fluorescence quenching method for the determination of CSS showed high sensitivity, with detection limits of 31.3 ng/mL (CSS-Trp system), 44.6 ng/mL (CSS-Tyr system) and 315.0 ng/mL (CSS-Phe system), respectively. The optimum conditions of the reaction conditions and the effect of coexisting substances were investigated and results showed that the method had good selectivity. The method was successfully applied for the rapid determination of CSS in blood and urine samples. Based on the bimolecular quenching constant Kq , the effect of temperature and Stern-Volmer plots, this study showed that quenching of fluorescence of amino acids by CSS was a static quenching process.
