Dataset Information

Deblurring of Class-Averaged Images in Single-Particle Electron Microscopy.

ABSTRACT: This paper proposes a method for deblurring of class-averaged images in single-particle electron microscopy (EM). Since EM images of biological samples are very noisy, the images which are nominally identical projection images are often grouped, aligned and averaged in order to cancel or reduce the background noise. However, the noise in the individual EM images generates errors in the alignment process, which creates an inherent limit on the accuracy of the resulting class averages. This inaccurate class average due to the alignment errors can be viewed as the result of a convolution of an underlying clear image with a blurring function. In this work, we develop a deconvolution method that gives an estimate for the underlying clear image from a blurred class-averaged image using precomputed statistics of misalignment. Since this convolution is over the group of rigid body motions of the plane, SE(2), we use the Fourier transform for SE(2) in order to convert the convolution into a matrix multiplication in the corresponding Fourier space. For practical implementation we use a Hermite-function-based image modeling technique, because Hermite expansions enable lossless Cartesian-polar coordinate conversion using the Laguerre-Fourier expansions, and Hermite expansion and Laguerre-Fourier expansion retain their structures under the Fourier transform. Based on these mathematical properties, we can obtain the deconvolution of the blurred class average using simple matrix multiplication. Tests of the proposed deconvolution method using synthetic and experimental EM images confirm the performance of our method.

SUBMITTER: Park W

PROVIDER: S-EPMC2835172 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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Publications

Deblurring of Class-Averaged Images in Single-Particle Electron Microscopy.

Park Wooram W Madden Dean R DR Rockmore Daniel N DN Chirikjian Gregory S GS

Inverse problems 20100301 3

This paper proposes a method for deblurring of class-averaged images in single-particle electron microscopy (EM). Since EM images of biological samples are very noisy, the images which are nominally identical projection images are often grouped, aligned and averaged in order to cancel or reduce the background noise. However, the noise in the individual EM images generates errors in the alignment process, which creates an inherent limit on the accuracy of the resulting class averages. This inaccu ...[more]

PMID: 20221416

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Project description:The protein is naturally dynamic and heterogeneous in solution. Protein dynamics involves both equilibrium fluctuations that regulate biological function and other non-equilibrium effects of biological motors, which convert chemical energy to mechanical energy. However, a single, unique structure of protein determined from X-ray crystal and conventional single-particle electron microscopy is insufficient to encompass the dynamic nature of proteins in solution. Structure determination of dynamic and heterogeneous protein is essentially required the determination of each individual particle of protein. Recently, Drs. Gang Ren and Lei Zhan published the first single molecule three-dimensional (3D) EM images of individual proteins ever obtained with enough clarity to determine their structure, an IgG antibody (14 Å resolution) and a 17nm HDL (36 Å resolution). These results depended upon four innovations: i) improved cryo-electron microscopy (cryoEM) sample preparation and Electron microscopy (EM) operation conditions resulted in the successful imaging of a 17 nm HDL particle (120-200kDa) by cryo-electron tomography (cryoET); ii) developed an optimized NS (OpNS) protocol that eliminates the rouleau artifact that has plagued EM research for three decades. This OpNS protocol provides high-contrast single lipoprotein images with similar size (<5%) and shape (<5%) to that seen by cryoEM; iii) developed a high-resolution and high contrast sample preparation protocol, cryo-positive-staining (cryoPS) that allows direct visualization of the secondary structure of a small protein, such as the β-strands in CETP and the helical double belt of apoA-I in spherical HDL; iv) developed a robust tomography reconstruction method, Individual Particle Electron Tomography (IPET) that is a high-resolution, high throughput reconstruction method that, to the best of our knowledge, is the only method for determining an individual protein structure. Remarkably, IPET went against the conventional wisdom that a single protein can NOT be reconstructed by EM and this opens a door for the study of protein dynamics via a particle-by-particle structural comparison.

Dataset Information

Deblurring of Class-Averaged Images in Single-Particle Electron Microscopy.

Publications

Deblurring of Class-Averaged Images in Single-Particle Electron Microscopy.

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