Microsystems for UV-visible and x-ray analysis of protein crystals

Abstract

polydimethylsiloxane (PDMS) based microsystems have successfully been fabricated and characterized for studying protein crystals utilizing both UV-visible spectroscopy and X-ray crystallography. Transmittance tests have been conducted with PDMS and glass substrates; the measurements indicate that in PDMS, unlike glass, the emerging intensity is higher than 50% of the incident intensity as long as the total optical path is shorter than 100 mum. Indeed, both the UV-visible spectrum and X-ray diffraction of a protein crystal enclosed in a PDMS device are almost identical to those of the crystal alone. Hence, PDMS is suitable as substrate material in device fabrication to study protein crystals. In glass, however, the UV-visible spectrum is significantly distorted and the X-ray diffraction pattern is rather weak resulting in poor signal to noise ratio. Furthermore, microsystems integrated with micro- channels allowing continuous exchange of buffer solution around the protein crystals have been tested; this would greatly enhance the potential to induce, trap and characterize functional states in proteins.