Cryogenic Transmission Electron Microscopy Study of Amelogenin Self-Assembly at Different pH

Fang, Ping; Margolis, Henry C.; Conway, James F.; Simmer, James P.; Dickinson, Gary H.; Beniash, Elia

doi:10.1159/000324250

Cited by 16 publications

(19 citation statements)

References 51 publications

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“…These oligomers function as intermediates in self-assembly of larger oligomers and oligomer clusters, as well as in disassembly into monomers. We speculate that, in analogy to the roughly circular clusters of these oligomeric intermediates that form on the surface, the nanospheres observed in bulk solution by DLS and Cryo-EM 40,41 may consist of spherical clusters of these oligomeric intermediates forming in bulk solution.…”

Section: Resultsmentioning

confidence: 92%

In situ AFM Study of Amelogenin Assembly and Disassembly Dynamics on Charged Surfaces Provides Insights on Matrix Protein Self-Assembly

et al. 2011

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Because self-assembly of matrix proteins is a key step in hard tissue mineralization, developing an understanding of the assembly pathways and underlying mechanisms is likely to be important for successful hard tissue engineering. While many studies of matrix protein assembly have been performed on bulk solutions, in vivo these proteins are likely to be in contact with charged biological surfaces composed of lipids, proteins, or minerals. Here we report the results of an in situ AFM study of self-assembly by amelogenin - the principal protein of the extracellular matrix in developing enamel - in contact with two different charged substrates: hydrophilic negatively charged bare mica and positively charged 3-aminopropyl triethoxysilane (APS) silanized mica. First we demonstrate an AFM-based protocol for determining the size of both amelogenin monomers and oligomers. Using this protocol, we find that, although amelogenin exists primarily as ∼26 nm in diameter nanospheres in bulk solution at pH8.0 studied by DLS, it behaves dramatically differently upon interacting with charged substrates at the same pH, and exhibits complex substrate-dependent assembly pathways and dynamics. On positively charged APS-treated mica surfaces, amelogenin forms a relatively uniform population of decameric oligomers which then transforms into two main populations: higher-order assemblies of oligomers and amelogenin monomers, while on negatively charged bare mica surfaces, it forms a film of monomers that exhibits tip-induced desorption and patterning. The present study represents a successful attempt to identify the size of amelogenin oligomers and to directly monitor assembly and disassembly dynamics on surfaces. The findings have implications for amelogenin-controlled calcium phosphate mineralization in vitro and may offer new insights into in vivo self-assembly of matrix proteins, as well as their control over hard tissue formation.

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Section: Resultsmentioning

confidence: 92%

In situ AFM Study of Amelogenin Assembly and Disassembly Dynamics on Charged Surfaces Provides Insights on Matrix Protein Self-Assembly

et al. 2011

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“…Changes in physicochemical and biological properties of tumor vasculature and strategies to normalize it using anti-angiogenic factors have been reviewed by Fukumura et al (Fukumura and Jain, 2007). Leaky vasculature and a negative charge on the vessel luminal face can also be exploited by controlling the molecular weight of drug carrier polymers and using cationic molecules (Campbell et al, 2002, Fang et al, 2011). A device with a depot of growth factors to promote angiogenesis locally may help make systemic delivery of chemotherapeutic agents more effective to hypoxic regions of solid tumors.…”

Section: Therapeutic Approaches To Exploit Hypoxic Tumor Microenvimentioning

confidence: 99%

Hypoxic tumor microenvironment: Opportunities to develop targeted therapies

Patel

Sant

2016

Biotechnology Advances

170

111

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Recent few years have seen great progress in understanding tumor biology and surrounding microenvironment. Solid tumors create regions with low oxygen levels, generally termed as hypoxic regions. These hypoxic areas offer a tremendous opportunity to develop targeted therapies. Hypoxia is not a random by-product of cellular milieu due to uncontrolled tumor growth; rather it is a constantly evolving participant in overall tumor growth and fate. This article reviews current trends and recent advances in drug therapies and delivery systems targeting hypoxia in the tumor microenvironment. In the first part, we give an account of important physicochemical changes and signaling pathways activated in the hypoxic microenvironment. This is then followed by various treatment strategies including hypoxia-sensitive signaling pathways and approaches to develop hypoxia-targeted drug delivery systems.

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“…Amelogenin protein assembles into oligomers, nanospheres, nanochains and other elongated assemblies under a variety of different in vitro conditions (70–76). Since the 1960’s it has been well known that amelogenin has a strong tendency towards self-aggregation into large particles (1 to 4 million Dalton) (56, 57).…”

Section: The Extracellular Protein Matrixmentioning

confidence: 99%

“…Formation of dodecamers was illustrated by single particle reconstruction of cryo-TEM images of recombinant mouse amelogenin (76). These oligomers were defined as the basic subunits of the typical nanospheres, which have hydrodynamic radii (R H ) of about 20 nm.…”

Section: The Extracellular Protein Matrixmentioning

confidence: 99%

Protein-mediated Enamel Mineralization

2012

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Enamel is a hard nanocomposite bioceramic with significant resilience that protects the mammalian tooth from external physical and chemical damages. The remarkable mechanical properties of enamel are associated with its hierarchical structural organization and its thorough connection with underlying dentin. This dynamic mineralizing system offers scientists a wealth of information that allows the study of basic principals of organic matrix-mediated biomineralization and can potentially be utilized in the fields of material science and engineering for development and design of biomimetic materials. This chapter will provide a brief overview of enamel hierarchical structure and properties as well as the process and stages of amelogenesis. Particular emphasis is given to current knowledge of extracellular matrix protein and proteinases, and the structural chemistry of the matrix components and their putative functions. The chapter will conclude by discussing the potential of enamel for regrowth.

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Cryogenic Transmission Electron Microscopy Study of Amelogenin Self-Assembly at Different pH

Cited by 16 publications

References 51 publications

In situ AFM Study of Amelogenin Assembly and Disassembly Dynamics on Charged Surfaces Provides Insights on Matrix Protein Self-Assembly

In situ AFM Study of Amelogenin Assembly and Disassembly Dynamics on Charged Surfaces Provides Insights on Matrix Protein Self-Assembly

Hypoxic tumor microenvironment: Opportunities to develop targeted therapies

Protein-mediated Enamel Mineralization

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