Ultrastructural Location and Interactions of the Immunoglobulin Receptor Binding Sequence within Fibrillar Type I Collagen.

Collagen type I is a major constituent of animal bodies. It is found in large quantities in tendon, bone, skin, cartilage, blood vessels, bronchi, and the lung interstitium. It is also produced and accumulates in large amounts in response to certain inflammations such as lung fibrosis. Our understanding of the molecular organization of fibrillar collagen and cellular interaction motifs, such as those involved with immune-associated molecules, continues to be refined. In this study, antibodies raised against type I collagen were used to label intact D-periodic type I collagen fibrils and observed with atomic force microscopy (AFM), and X-ray diffraction (XRD) and immunolabeling positions were observed with both methods. The antibodies bind close to the C-terminal telopeptide which verifies the location and accessibility of both the major histocompatibility complex (MHC) class I (MHCI) binding domain and C-terminal telopeptide on the outside of the collagen fibril. The close proximity of the C-telopeptide and the MHC1 domain of type I collagen to fibronectin, discoidin domain receptor (DDR), and collagenase cleavage domains likely facilitate the interaction of ligands and receptors related to cellular immunity and the collagen-based Extracellular Matrix.

Structural and biomechanical basis of mitochondrial movement in eukaryotic cells.

Mitochondria serve as energy-producing organelles in eukaryotic cells. In addition to providing the energy supply for cells, the mitochondria are also involved in other processes, such as proliferation, differentiation, information transfer, and apoptosis, and play an important role in regulation of cell growth and the cell cycle. In order to achieve these functions, the mitochondria need to move to the corresponding location. Therefore, mitochondrial movement has a crucial role in normal physiologic activity, and any mitochondrial movement disorder will cause irreparable damage to the organism. For example, recent studies have shown that abnormal movement of the mitochondria is likely to be the reason for Charcot-Marie-Tooth disease, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, Parkinson's disease, and schizophrenia. So, in the cell, especially in the particular polarized cell, the appropriate distribution of mitochondria is crucial to the function and survival of the cell. Mitochondrial movement is mainly associated with the cytoskeleton and related proteins. However, those components play different roles according to cell type. In this paper, we summarize the structural basis of mitochondrial movement, including microtubules, actin filaments, motor proteins, and adaptin, and review studies of the biomechanical mechanisms of mitochondrial movement in different types of cells.

Topographic mapping and compression elasticity analysis of skinned cardiac muscle fibers in vitro with atomic force microscopy and nanoindentation.

Surface topography and compression elasticity of bovine cardiac muscle fibers in rigor and relaxing state have been studied with atomic force microscopy. Characteristic sarcomere patterns running along the longitudinal axis of the fibers were clearly observed, and Z-lines, M-lines, I-bands, and A-bands can be distinguished through comparing with TEM images and force curves. AFM height images of fibers had shown a sarcomere length of 1.22+/-0.02 microm (n=5) in rigor with a significant 9% increase in sarcomere length in relaxing state (1.33+/-0.03 microm, n=5), indicating that overlap moves with the changing physiological conditions. Compression elasticity curves along with sarcomere locations have been taken by AFM compression processing. Coefficient of Z-line, I-band, Overlap, and M-line are 25+/-2, 8+/-1, 10+/-1, and 17+/-1.5 pN/nm respectively in rigor state, and 18+/-2.5, 4+/-0.5, 6+/-1, and 11+/-0.5 pN/nm respectively in relaxing state. Young's Modulus in Z-line, I-band, Overlap, and M-line are 115+/-12, 48+/-9, 52+/-8, and 90+/-12 kPa respectively in rigor, and 98+/-10, 23+/-4, 42+/-4, and 65+/-7 kPa respectively in relaxing state. The elasticity curves have shown a similar appearance to the section analysis profile of AFM height images of sarcomere and the distance between adjacent largest coefficient and Young's Modulus is equal to the sarcomere length measured from the AFM height images using section analysis, indicating that mechanic properties of fibers have a similar periodicity to the topography of fibers.

Gloss phenomena and image analysis of atomic force microscopy in molecular and cell biology.

Proper sample preparation, scan setup, data collection and image analysis are key factors in successful atomic force microscopy (AFM), which can avoid gloss phenomena effectively from unreasonable manipulations or instrumental defaults. Fresh cleaved mica and newly treated glass cover were checked first as the substrates for all of the sample preparation for AFM. Then, crystals contamination from buffer was studied separately or combined with several biologic samples, and the influence of scanner, scan mode and cantilever to data collection was also discussed intensively using molecular and cellular samples. At last, images treatment and analysis with off-line software had been focused on standard and biologic samples, and artificial glosses were highly considered for their high probability. SCANNING 31: 49-58, 2009. (c) 2009 Wiley Periodicals, Inc.