Portable UV holographic microscope for high-contrast protein crystal imaging

IN ProCrystal Protein Crystallization Covers

Methods and materials that facilitate the distinction between salt and protein crystals are extremely valuable to crystallographers. The rapid identification of promising crystallization conditions helps to streamline a process that is otherwise largely unpredictable. A commonly used approached is based on the properties of protein crystals to emit fluorescence when excited with UV light. It offers the advantage of conserving protein crystals for subsequent microseeding experiments. Dual-mode optical microscopes are typically used. However, they are relatively bulky and expensive as they require optical-grade optics. An interesting new paper demonstrates how a portable, cost-effective, on-chip holographic imaging device could be utilized to derive information about the nature of the crystal being observed. ProCrystals protein crystallization covers, are routinely used for crystallization screening and are compatible both with traditional fluorescent microscopy as well with the innovative device described in this study. Learn more here: https://aip.scitation.org/doi/10.1063/1.5080158

Portable UV holographic microscope for high-contrast protein crystal imaging
Brightfield microscope images (a), holographic amplitude reconstructions (b) and X-ray diffraction data (c) of proteinase K, sodium chloride, and ammonium sulfate crystals. Proteinase K crystals appear significantly darker compared to the background level due to the strong UV absorption at 280 nm, unlike salt crystals. X-ray diffraction data further confirm the distinction between macromolecule crystals and salt crystals by the lower resolution reflections that occur as the result of larger spacing between symmetric elements of the crystals.