Search keywords: biomineral protein control growth Search Date 1/16/07

Some abstracts of interest:

• J Biol Chem. 2007 Jan 12;282(2):1193-204. Epub 2006 Oct 19. Matrix macromolecules in hard tissues control the nucleation and hierarchical assembly of hydroxyapatite.

Gajjeraman S, Narayanan K, Hao J, Qin C, George A.

Department of Oral Biology, University of Illinois, Chicago, Illinois 60612.

Biogenic minerals found in teeth and bones are synthesized by precise cell-mediated mechanisms. They have superior mechanical properties due to their complex architecture. Control over biomineral properties can be accomplished by regulation of particle size, shape, crystal orientation, and polymorphic structure. In many organisms, biogenic minerals are assembled using a transient amorphous mineral phase. Here we report that organic constituents of bones and teeth, namely type I collagen and dentin matrix protein 1 (DMP1), are effective crystal modulators. They control nucleation of calcium phosphate polymorphs and the assembly of hierarchically ordered crystalline composite material. Both full-length recombinant DMP1 and post-translationally modified native DMP1 were able to nucleate hydroxyapatite (HAP) in the presence of type I collagen. However, the N-terminal domain of DMP1 (amino acid residues 1-334) inhibited HAP formation and stabilized the amorphous phase that was formed. During the nucleation and growth process, the initially formed metastable amorphous calcium phosphate phase transformed into thermodynamically stable crystalline hydroxyapatite in a precisely controlled manner. The organic matrix-mediated controlled transformation of amorphous calcium phosphate into crystalline HAP was confirmed by x-ray diffraction, selected area electron diffraction pattern, Raman spectroscopy, and elemental analysis. The mechanical properties of the protein-mediated HAP crystals were also determined as they reflect the material structure. Such understanding of biomolecule controls on biomineralization promises new insights into the controlled synthesis of crystalline structures.

PMID: 17052984 [PubMed - in process]

*Review: Annu Rev Phys Chem. 2003;54:531-71. Epub 2002 Mar 21. Structural studies of biomaterials using double-quantum solid-state NMR spectroscopy.

Drobny GP, Long JR, Karlsson T, Shaw W, Popham J, Oyler N, Bower P, Stringer J, Gregory D, Mehta M, Stayton PS.

Department of Chemistry, University of Washington, Seattle, WA 98195, USA. drobny@chem.washington.edu

Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-state NMR (ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.

PMID: 12709513 [PubMed - indexed for MEDLINE]

• Biochemistry. 2001 Dec 25;40(51):15451-5. Structure and dynamics of hydrated statherin on hydroxyapatite as determined by solid-state NMR.

Long JR, Shaw WJ, Stayton PS, Drobny GP.

Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.

Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composite technologies. Here, we have used solid-state NMR techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Backbone secondary structure for the N-terminal dodecyl region was determined using a combination of homonuclear and heteronuclear dipolar recoupling techniques. Both sets of experiments indicate the N-terminus is alpha-helical in character with the residues directly binding to the HAP being stabilized in the alpha-helical conformation by the presence of water. Dynamic NMR studies demonstrate that the highly anionic N-terminus is strongly adsorbed and immobilized on the HAP surface, while the middle and C-terminal regions of this domain are mobile and thus weakly interacting with the mineral surface. The direct binding footprint of statherin is thus localized to the negatively charged N-terminal pentapeptide sequence. Study of a site-directed mutant demonstrated that alteration of the only anionic side chain outside of this domain did not affect the dynamics of statherin on the HAP surface, suggesting that it does not play an important role in HAP binding.

PMID: 11747419 [PubMed - indexed for MEDLINE]

-- DaniPershouse - 22 Jan 2007