一、What is Cross-Linked Allophycocyanin?

Since naturally extracted allophycocyanin (APC) undergoes hydrolysis in dilute solutions (low concentrations) or when exposed to lyotropic salt environments, APC is usually subjected to cross-linking treatment to maintain its stability in biological reaction systems. When natural phycocyanin is treated by chemical methods, chemical cross-linking occurs between the α and β subunits, resulting in the formation of cross-linked allophycocyanin, namely CL-APC. Being much more stable than APC, CL-APC not only enhances the stability of the product but also retains the fluorescence and spectral integrity of the natural dye.

二、Testing Indicators

1.The cross-linking ratio is defined as the ratio of A650 to A620 measured in a 25 mM Tris-HCl buffer (pH 7.7) containing 1 M sodium perchlorate. For non-cross-linked allophycocyanin (APC), this ratio is approximately 0.3.

2.The ratio of A652 to A280 (A652/A280) indicates the purity of allophycocyanin (APC) relative to other contaminating proteins. The absorbance at 280 nm in the solution is mainly derived from aromatic amino acids, so it is proportional to the total protein concentration in the solution (including APC). In contrast, the absorbance at 652 nm only reflects the concentration of APC in the solution. Therefore, a higher value of this parameter indicates a higher content of APC.

3.Spirulina produces allophycocyanin (APC) and phycocyanin (CPC). CPC has a maximum absorption at 620 nm. A ratio of A652 to A280 (A652/A280) greater than 1.5 indicates that APC is not severely contaminated by CPC.

Cross-link Radio＞1.0

A650/A280＞5.0

A650/A620 >1.5

Crystal Biology can provide cross-linked allophycocyanin (CL-APC) precipitated with ammonium sulfate in packaging specifications of 1mg/5mg/10mg/100mg/500mg/1g.