title: Quantitative biological imaging by ptychographic x-ray diffraction microscopy.
abstract: Recent advances in coherent x-ray diffractive imaging have paved the way to reliable and quantitative imaging of noncompact specimens at the nanometer scale. Introduced a year ago, an advanced implementation of ptychographic coherent diffractive imaging has removed much of the previous limitations regarding sample preparation and illumination conditions. Here, we apply this recent approach toward structure determination at the nanoscale to biological microscopy. We show that the projected electron density of unstained and unsliced freeze-dried cells of the bacterium Deinococcus radiodurans can be derived from the reconstructed phase in a straightforward and reproducible way, with quantified and small errors. Thus, the approach may contribute in the future to the understanding of the highly disputed nucleoid structure of bacterial cells. In the present study, the estimated resolution for the cells was 85 nm (half-period length), whereas 50-nm resolution was demonstrated for lithographic test structures. With respect to the diameter of the pinhole used to illuminate the samples, a superresolution of about 15 was achieved for the cells and 30 for the test structures, respectively. These values should be assessed in view of the low dose applied on the order of approximately 1.3x10(5) Gy, and were shown to scale with photon fluence.
authors.affiliation: Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany. k.giewek@phys.uni-goettingen.de
authors.forename: Klaus
authors.initials: K
authors.lastname: Giewekemeyer
authors.forename: Pierre
authors.initials: P
authors.lastname: Thibault
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kalbfleisch
authors.forename: André
authors.initials: A
authors.lastname: Beerlink
authors.forename: Cameron M
authors.initials: CM
authors.lastname: Kewish
authors.forename: Martin
authors.initials: M
authors.lastname: Dierolf
authors.forename: Franz
authors.initials: F
authors.lastname: Pfeiffer
authors.forename: Tim
authors.initials: T
authors.lastname: Salditt
mesh_terms: D000465:Algorithms; D034301:Deinococcus / Q000648:ultrastructure*; D005612:Freeze Drying; D006696:Holography / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008853:Microscopy / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D014961:X-Ray Diffraction / Q000379:methods*