Single Molecule Imaging

The objective of this research is to develop methods of super resolution microscopy for imaging the chemical-spatial organization of biological materials and systems. Current projects are in collaboration with scientists at NREL, in Golden, Colorado (, and the Colorado School of Mines at the Photonics and Ultrafast Laser Science (PULSE) group there ( and the newly-formed center for Microintegrated Optics for Advanced Bioimaging and Control (MOABC, see The figure below illustrates one scheme for obtaining near molecular-level resolution imaging in living cells, known as Photo-Activated Localization Microscopy (PALM). Super-resolution is obtained by imaging sparse subsets of single fluorescent molecules after photoactivation, centroids are obtained with resolution limited only by shot noise, and composite images are obtained by repeating the process on ad infintum. We are applying the method to study the plant cell wall chemical structure, and microbial and enzymatic degradation processes important for production of cellulosic biofuels. The figure below shows (A) a schematic explanation of the Photo-Activated Localization Microscopy (PALM) method, (B) the architecture of a cellulase enzyme, (C) PALM images of carbohydrate Binding Modules (CBM) bound to a cellulose micro-fibril and (D) a micro-fibril bundle, and (E) the pair correlation function computed along the micro-fibril axis.

Figure 2: (A):Pictorial illustration of PALM method, (B): Schematic of cellulase enzyme system, PALM images of (C): cellulose micro-fibrils and (D): micro-fibril bundles, and (E): pair correlation function computed along the micro-fibril axis [1-3].

 Related Publications

[1] Dagel, D J; Liu, Y.-S.; Zhong, L; Luo, Y; Zeng, Y; Himmel, M; Ding, S.-Y.; Smith, S; "DOPI and PALM imaging of single carbohydrate binding modules bound to cellulose nanocrystals", in SPIE 7905, Single Molecule Spectroscopy and Imaging IV 79050P (2011).
[2]D. Dagel, L. Zhong, Y. Liu, S.-Y. Ding, S. Smith, "in situ imaging of single carbohydrate-binding modules on cellulose microfibrils," J Phys Chem B 115 (4) p. 635-41 (2011).
[3]Y. Liu, Y. Zeng, Y. Luo, Q. Xu, M.E. Himmel, S. Smith, and S-Y. Ding, "Does the cellulose-binding module move on the cellulose surface?" Cellulose, 16 pp. 587-597 (2009).

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