A simple method to prepare a biopterin sensor chip applicable to crude samples

Abstract

Biopterin (BP), which is structurally similar to flavin, is potentially associated with a UV-B photoreceptor yet to be identified. The stagnation of research on the BP-associated photoreceptor is because of the lack of a simple method to detect the protein that interacts with BP. We successfully immobilized BP by conducting a coupling reaction between one of the activated hydroxyl groups of BP and pre-introduced primary amino groups on the CM5 surface at a pH higher than usual. This enabled us to detect the protein that interacts with BP using Biacore measurements. The validity of the BP sensor chip was tested by applying the chip to fractions obtained by subjecting a crude extract of the paraflagellar body (PFB), which is the photosensory organelle of Euglena, to an anion exchange column; this test was performed because PFB was spectroscopically shown to contain a pterin binding protein. The BP sensor chip was useful to detect an unknown BP-binding protein in a crude sample.