Low-cost and portable UV holographic microscope for high-contrast protein crystal imaging
Daloglu, Mustafa Ugur (University of California)
Ray, Aniruddha (University of California)
Collazo, Michael J. (University of California)
Brown, Calvin (University of California)
Tseng, Derek (University of California)
Chocarro Ruiz, Blanca (Institut Català de Nanociència i Nanotecnologia)
Lechuga, Laura M (Institut Català de Nanociència i Nanotecnologia)
Cascio, Duilio (University of California)
Ozcan, Aydogan (University of California)

Date:	2019
Abstract:	Imaging protein crystals and distinguishing them from salt crystals is an important task for protein crystallographers. The conventional tool used for this purpose is a dual-mode microscope composed of bright-field and ultraviolet (UV) induced fluorescence modes. The distinction between a protein and a salt crystal is made based upon the fluorescence response to the UV excitation, where most protein crystals absorb the UV excitation and emit fluorescence, unlike salt crystals. These dual-mode optical microscopes are sensitive; however, they are relatively bulky and expensive as they require UV-grade optics. As an alternative, here we demonstrate that on-chip UV holographic imaging offers a low-cost, portable, and robust technique to image and distinguish protein crystals from salt crystals, without the need for any expensive and bulky optical components. Only composed of a UV light-emitting-diode at 280 nm and a consumer-grade complementary metal-oxide-semiconductor image sensor de-capped and interfaced to a Raspberry Pi single-board computer, the necessary information from the crystal samples (placed very close to the sensor active area) is captured in the form of in-line holograms and extracted through digital back-propagation. In these holographic amplitude reconstructions, protein crystals appear significantly darker compared to the background due to the strong UV absorption, unlike salt crystals which do not show any contrast, enabling us to clearly distinguish between them. We believe that the on-chip UV holographic microscope could serve as a low-cost, sensitive, and robust alternative to conventional lens-based UV-microscopes used in protein crystallography.
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Amplitude reconstruction ; Complementary metal oxide semiconductor image sensor ; Holographic imaging ; In-line holograms ; Optical components ; Optical microscopes ; Protein crystallography ; Single board computers
Published in:	APL Photonics, Vol. 4, Issue 3 (March 2019) , art. 30804, ISSN 2378-0967

DOI: 10.1063/1.5080158

9 p, 7.2 MB

The record appears in these collections:
Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Catalan Institute of Nanoscience and Nanotechnology (ICN2)
Articles > Research articles
Articles > Published articles