701
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Kurc M, Farina M, Lins U, Kachar B. Structural basis for mechanical transduction in the frog vestibular sensory apparatus: III. The organization of the otoconial mass. Hear Res 1999; 131:11-21. [PMID: 10355600 DOI: 10.1016/s0378-5955(99)00007-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The saccule and the utricle of the vestibular system detect linear acceleration and gravity. Sensory transduction in these organs depends on myriads of calcium carbonate crystals of high specific gravity, called otoconia, embedded in a filament matrix that overlies the sensory epithelium. The coexistence of hard crystals and slender filaments in this complex extracellular matrix makes it difficult to analyze by conventional electron microscopy. We have now examined this structure in the bullfrog saccule using the quick-freeze, deep-etch replica technique. The otoconia in their typical aragonite polymorph shape exhibit smooth surfaces and are embedded in a loose matrix made of two types of filaments. The regular surface of the otoconia forms a natural smooth background against which we could observe with unprecedented detail the network organization and substructure of the filaments. One type of filament is 8 nm in diameter, while the other, which has a characteristic beaded appearance, is 15 nm in diameter. Both types of filaments either make lateral connections with or end directly on the surface of the otoconia. A consistent observation was the presence of short filaments that directly cross-link adjacent otoconia. Very few otoconia were fractured in an orientation that would allow the study of their internal architecture. These otoconia presented a typical conchoidal cleavage of aragonite. Although crystallites were not clearly apparent, thin lamellar microstructures appeared oriented both perpendicularly and longitudinally to the major otoconial axis. This structural study establishes a framework for the identification of the molecular components present in this unique extracellular matrix and may also help elucidate their role in mechanical transduction.
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Affiliation(s)
- M Kurc
- Laboratory of Cellular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
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702
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Laiz L, Groth I, Gonzalez I, Saiz-Jimenez C. Microbiological study of the dripping waters in Altamira cave (Santillana del Mar, Spain). J Microbiol Methods 1999; 36:129-38. [PMID: 10353807 DOI: 10.1016/s0167-7012(99)00018-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The culturable microbial populations in dripping waters from Altamira cave were studied and compared with those of the ceiling rock. Water communities have low proportions of gram-positive bacteria, and are mainly composed of gram-negative rods and cocci (Enterobacteriaceae and Vibrionaceae), while those of ceiling rocks are mainly Streptomyces spp. The community differences are probably related to environmental cave conditions: high humidity, relatively low and stable temperature, water pH close to neutrality and nature of the organic matter. All these factors seem to favor colonization and long-term growth of actinomycetes over other heterotrophic bacteria on ceiling rocks.
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Affiliation(s)
- L Laiz
- Instituto de Recursos Naturales y Agrobiologia, CSIC, Sevilla, Spain
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703
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Methods for fabricating and characterizing a new generation of biomimetic materials. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 1999. [DOI: 10.1016/s0928-4931(98)00072-1] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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704
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Aizenberg J, Black AJ, Whitesides GM. Oriented Growth of Calcite Controlled by Self-Assembled Monolayers of Functionalized Alkanethiols Supported on Gold and Silver. J Am Chem Soc 1999. [DOI: 10.1021/ja984254k] [Citation(s) in RCA: 421] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joanna Aizenberg
- Contribution from Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, and Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138
| | - Andrew J. Black
- Contribution from Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, and Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138
| | - George M. Whitesides
- Contribution from Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974, and Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138
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705
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706
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707
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Xu G, Yao N, Aksay IA, Groves JT. Biomimetic Synthesis of Macroscopic-Scale Calcium Carbonate Thin Films. Evidence for a Multistep Assembly Process. J Am Chem Soc 1998. [DOI: 10.1021/ja9819108] [Citation(s) in RCA: 230] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Guofeng Xu
- Contribution from the Departments of Chemistry and Chemical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544
| | - Nan Yao
- Contribution from the Departments of Chemistry and Chemical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544
| | - Ilhan A. Aksay
- Contribution from the Departments of Chemistry and Chemical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544
| | - John T. Groves
- Contribution from the Departments of Chemistry and Chemical Engineering and the Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544
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708
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Long JR, Dindot JL, Zebroski H, Kiihne S, Clark RH, Campbell AA, Stayton PS, Drobny GP. A peptide that inhibits hydroxyapatite growth is in an extended conformation on the crystal surface. Proc Natl Acad Sci U S A 1998; 95:12083-7. [PMID: 9770443 PMCID: PMC22788 DOI: 10.1073/pnas.95.21.12083] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proteins play an important role in the biological mechanisms controlling hard tissue development, but the details of molecular recognition at inorganic crystal interfaces remain poorly characterized. We have applied a recently developed homonuclear dipolar recoupling solid-state NMR technique, dipolar recoupling with a windowless sequence (DRAWS), to directly probe the conformation of an acidic peptide adsorbed to hydroxyapatite (HAP) crystals. The phosphorylated hexapeptide, DpSpSEEK (N6, where pS denotes phosphorylated serine), was derived from the N terminus of the salivary protein statherin. Constant-composition kinetic characterization demonstrated that, like the native statherin, this peptide inhibits the growth of HAP seed crystals when preadsorbed to the crystal surface. The DRAWS technique was used to measure the internuclear distance between two 13C labels at the carbonyl positions of the adjacent phosphoserine residues. Dipolar dephasing measured at short mixing times yielded a mean separation distance of 3.2 +/- 0.1 A. Data obtained by using longer mixing times suggest a broad distribution of conformations about this average distance. Using a more complex model with discrete alpha-helical and extended conformations did not yield a better fit to the data and was not consistent with chemical shift analysis. These results suggest that the peptide is predominantly in an extended conformation rather than an alpha-helical state on the HAP surface. Solid-state NMR approaches can thus be used to determine directly the conformation of biologically relevant peptides on HAP surfaces. A better understanding of peptide and protein conformation on biomineral surfaces may provide design principles useful for the modification of orthopedic and dental implants with coatings and biological growth factors that are designed to enhance biocompatibility with surrounding tissue.
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Affiliation(s)
- J R Long
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
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709
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Parkinson GM. Crystal±macromolecule interactions in urolithiasis: lessons from healthy biomineralization systems. Curr Opin Urol 1998; 8:301-8. [PMID: 17038973 DOI: 10.1097/00042307-199807000-00008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Recent advances in understanding the molecular level mechanisms that control biomineralization and organic-inorganic interactions in urolithiasis are reviewed, and the validity of drawing parallels between them are considered. The multifunctional nature of many biomineralization molecules, particularly proteins, and the different roles they play in and out of solution suggest avenues for resolving the apparent paradox that urinary macromolecules have been observed both to inhibit and to promote stone formation.
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Affiliation(s)
- G M Parkinson
- School of Applied Chemistry, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia
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710
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Wesson JA, Worcester EM, Wiessner JH, Mandel NS, Kleinman JG. Control of calcium oxalate crystal structure and cell adherence by urinary macromolecules. Kidney Int 1998; 53:952-7. [PMID: 9551403 DOI: 10.1111/j.1523-1755.1998.00839.x] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Crystal polymorphism is exhibited by calcium oxalates in nephrolithiasis, and we have proposed that a shift in the preferred crystalline form of calcium oxalate (CaOx) from monohydrate (COM) to dihydrate (COD) induced by urinary macromolecules reduces crystal attachment to epithelial cell surfaces, thus potentially inhibiting a critical step in the genesis of kidney stones. We have tested the validity of this hypothesis by studying both the binding of monohydrate and dihydrate crystals to renal tubule cells and the effect of macromolecular urinary solutes on crystal structure. Renal tubule cells grown in culture bound 50% more CaOx monohydrate than dihydrate crystals of comparable size. The effects of macromolecules on the spontaneous nucleation of CaOx were examined in HEPES-buffered saline solutions containing Ca2+ and C2O4(2-) at physiologic concentrations and supersaturation. Many naturally occurring macromolecules known to be inhibitors of crystallization, specifically osteopontin, nephrocalcin and urinary prothrombin fragment 1, were found to favor the formation of calcium oxalate dihydrate in this in vitro system, while other polymers did not affect CaOx crystal structure. Thus, the natural defense against nephrolithiasis may include impeding crystal attachment by an effect of macromolecular inhibitors on the preferred CaOx crystal structure that forms in urine.
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Affiliation(s)
- J A Wesson
- Nephrology Division, Medical College of Wisconsin, Milwaukee, USA
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711
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712
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de Leeuw NH, Parker SC. Surface Structure and Morphology of Calcium Carbonate Polymorphs Calcite, Aragonite, and Vaterite: An Atomistic Approach. J Phys Chem B 1998. [DOI: 10.1021/jp973210f] [Citation(s) in RCA: 404] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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713
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Carrino DA, Rodriguez JP, Caplan AI. Dermatan sulfate proteoglycans from the mineralized matrix of the avian eggshell. Connect Tissue Res 1998; 36:175-93. [PMID: 9512887 DOI: 10.3109/03008209709160219] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The eggshell of the chicken is a useful model to study matrix components which affect biomineralization. As an extension of our previous immunohistochemical work which suggested the presence of dermatan sulfate proteoglycans in the mineralized region of the eggshell, a study was undertaken to characterize these molecules biochemically. After demineralization with HCl and extraction with 4 M guanidinium chloride containing protease inhibitors, the extract was partitioned by anion exchange chromatography. Step elution with 0.25 M and 1.0 M sodium chloride resulted in the generation of two fractions, both of which contain chondroitinase-sensitive proteoglycans with molecular weights estimated at 200,000 by gel electrophoresis. The proteoglycans in each fraction have core proteins with molecular weights of approximately 120,000 and glycosaminoglycans with average molecular weights of 22,000. Based on differential sensitivity to chondroitinase ABC and AC II, these glycosaminoglycans contain a small proportion of dermatan sulfate. The disaccharide compositions of these glycosaminoglycans differ for the proteoglycans eluted with 0.25 M and 1.0 M sodium chloride. Those eluted with lower sodium chloride are enriched in unsulfated chondroitin and have much more 4-sulfated than 6-sulfated disaccharides; those eluted with 1.0 M sodium chloride contain primarily 4-sulfated disaccharides, a small amount of 6-sulfated disaccharides, and less unsulfated disaccharides than the proteoglycans eluted with 0.25 M sodium chloride. The large difference in the proportions of unsulfated chondroitin may be the reason for the elution at different sodium chloride concentrations. Both of the anion exchange column fractions contain other proteins in addition to the proteoglycans. These proteins are not separated from the proteoglycans by a second anion exchange column or by molecular sieve chromatography under dissociative conditions. Of particular interest is the observation that the eggshell proteoglycans and their core proteins are recognized by a monoclonal antibody which recognizes an epitope on the core protein of avian versican. This suggests that, in spite of the large differences in the sizes of the core proteins of versican and the eggshell proteoglycans, these core proteins share some homology. Because anionic molecules are thought to be important regulators of biomineralization, and because preparations like those analyzed in this study have been shown to influence in vitro calcium carbonate crystallization, the eggshell proteoglycans may play a role in eggshell mineralization.
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Affiliation(s)
- D A Carrino
- Department of Biology, Case Western Reserve University, Cleveland, OH 44106-7080, USA
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714
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The formation of highly organized biogenic polymer/ceramic composite materials: The high-performance microaluminate of molluscan nacre. Curr Opin Colloid Interface Sci 1998. [DOI: 10.1016/s1359-0294(98)80042-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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715
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Shen X, Belcher AM, Hansma PK, Stucky GD, Morse DE. Molecular cloning and characterization of lustrin A, a matrix protein from shell and pearl nacre of Haliotis rufescens. J Biol Chem 1997; 272:32472-81. [PMID: 9405458 DOI: 10.1074/jbc.272.51.32472] [Citation(s) in RCA: 222] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A specialized extracellular matrix of proteins and polysaccharides controls the morphology and packing of calcium carbonate crystals and becomes occluded within the mineralized composite during formation of the molluscan shell and pearl. We have cloned and characterized the cDNA coding for Lustrin A, a newly described matrix protein from the nacreous layer of the shell and pearl produced by the abalone, Haliotis rufescens, a marine gastropod mollusc. The full-length cDNA is 4,439 base pairs (bp) long and contains an open reading frame coding for 1,428 amino acids. The deduced amino acid sequence reveals a highly modular structure with a high proportion of Ser (16%), Pro (14%), Gly (13%), and Cys (9%). The protein contains ten highly conserved cysteine-rich domains interspersed by eight proline-rich domains; a glycine- and serine-rich domain lies between the two cysteine-rich domains nearest the C terminus, and these are followed by a basic domain and a C-terminal domain that is highly similar to known protease inhibitors. The glycine- and serine-rich domain and at least one of the proline-rich domains show sequence similarity to proteins of two extracellular matrix superfamilies (one of which also is involved in the mineralized matrixes of bone, dentin, and avian eggshell). The arrangement of alternating cysteine-rich domains and proline-rich domains is strikingly similar to that found in frustulins, the proteins that are integral to the silicified cell wall of diatoms. Its modular structure suggests that Lustrin A is a multifunctional protein, whereas the occurrence of related sequences suggest it is a member of a multiprotein family.
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Affiliation(s)
- X Shen
- Molecular, Cellular and Developmental Biology Department, University of California, Santa Barbara, California 93106, USA
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716
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DeOliveira DB, Laursen RA. Control of Calcite Crystal Morphology by a Peptide Designed To Bind to a Specific Surface. J Am Chem Soc 1997. [DOI: 10.1021/ja972270w] [Citation(s) in RCA: 204] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel B. DeOliveira
- Contribution from the Department of Chemistry, Boston University, Boston, Massachusetts 02215
| | - Richard A. Laursen
- Contribution from the Department of Chemistry, Boston University, Boston, Massachusetts 02215
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717
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Falini G, Fermani S, Gazzano M, Ripamonti A. Biomimetic Crystallization of Calcium Carbonate Polymorphs by Means of Collagenous Matrices. Chemistry 1997. [DOI: 10.1002/chem.19970031113] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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718
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Micro-raman spectral study of vaterite and aragonite otoliths of the coho salmon, Oncorhynchus kisutch. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0300-9629(97)00059-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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719
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Antonietti M, Gröhn F, Hartmann J, Bronstein L. Ungewöhnliche Formen von Edelmetallkolloiden durch Synthese in Mikrogel-Nanoreaktoren. Angew Chem Int Ed Engl 1997. [DOI: 10.1002/ange.19971091913] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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720
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The Organic Shell Matrix of the Freshwater Snail Biomphalaria glabrata. Comp Biochem Physiol B Biochem Mol Biol 1997. [DOI: 10.1016/s0305-0491(97)00010-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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721
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Reeves NJ, Evans JS. Polypeptide Interactions at Ice and Biomineral Interfaces Are Defined by Secondary Structure-Dependent Chain Orientations. J Phys Chem B 1997. [DOI: 10.1021/jp971394s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nicholas J. Reeves
- Laboratory for Chemical Physics, New York University, 345 E. 24th Street, New York, New York 10010
| | - John Spencer Evans
- Laboratory for Chemical Physics, New York University, 345 E. 24th Street, New York, New York 10010
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722
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Lahiri J, Xu G, Dabbs DM, Yao N, Aksay IA, Groves JT. Porphyrin Amphiphiles as Templates for the Nucleation of Calcium Carbonate. J Am Chem Soc 1997. [DOI: 10.1021/ja961486f] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Joydeep Lahiri
- Departments of Chemistry and Chemical Engineering and Princeton Materials Institute Princeton University, Princeton, New Jersey 08544
| | - Guofeng Xu
- Departments of Chemistry and Chemical Engineering and Princeton Materials Institute Princeton University, Princeton, New Jersey 08544
| | - Daniel M. Dabbs
- Departments of Chemistry and Chemical Engineering and Princeton Materials Institute Princeton University, Princeton, New Jersey 08544
| | - Nan Yao
- Departments of Chemistry and Chemical Engineering and Princeton Materials Institute Princeton University, Princeton, New Jersey 08544
| | - Ilhan A. Aksay
- Departments of Chemistry and Chemical Engineering and Princeton Materials Institute Princeton University, Princeton, New Jersey 08544
| | - John T. Groves
- Departments of Chemistry and Chemical Engineering and Princeton Materials Institute Princeton University, Princeton, New Jersey 08544
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723
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Antonietti M, Göltner C. Überstrukturen funktioneller Kolloide: eine Chemie im Nanometerbereich. Angew Chem Int Ed Engl 1997. [DOI: 10.1002/ange.19971090904] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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724
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Abstract
Enamel is the outermost covering of teeth and contains the largest hydroxyapatite crystallites formed in the vertebrate body. Enamel forms extracellularly through the ordered assembly of a protein scaffolding that regulates crystallite dimensions. The two most studied proteins of the enamel extracellular matrix (ECM) are amelogenin and tuftelin. The underlying mechanism for assembly of the proteins within the enamel extracellular matrix and the regulatory role of crystallite-protein interactions have proven elusive. We used the two-hybrid system to identify and define minimal protein domains responsible for supra molecular assembly of the enamel ECM. We show that amelogenin proteins self-assemble, and this self-assembly depends on the amino-terminal 42 residues interacting either directly or indirectly with a 17-residue domain in the carboxyl region. Amelogenin and tuftelin fail to interact with each other. Based upon this data, and advances in the field, a model for amelogenin assemblies that direct enamel biomineralization is presented.
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Affiliation(s)
- M L Paine
- University of Southern California, School of Dentistry, Center for Craniofacial Molecular Biology, Los Angeles, USA
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725
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Stucky GD, Huo Q, Firouzi A, Chmelka BF, Schacht S, Voigt-Martin I, Schüth F. Directed synthesis of organic/inorganic composite structures. STUDIES IN SURFACE SCIENCE AND CATALYSIS 1997. [DOI: 10.1016/s0167-2991(97)80534-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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726
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Sasaki T, Takagi M, Yanagisawa T. Structure and function of secretory ameloblasts in enamel formation. CIBA FOUNDATION SYMPOSIUM 1997; 205:32-46; discussion 46-50. [PMID: 9189616 DOI: 10.1002/9780470515303.ch4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Secretory ameloblasts have multiple functions including the synthesis and resorption of enamel matrix proteins and calcium transport during enamel formation. We have examined these functions by means of cytochemistry and immunocytochemistry. Enamel proteins, amelogenins and enamelins are localized in the biosynthetic pathways of ameloblasts and in the forming enamel. Sulfated glycoconjugates are present in secretory ameloblasts. The distal junctional complex of ameloblasts may act as a permeability barrier to enamel proteins, thereby confining the secreted proteins to the growing enamel front. Secretory ameloblasts contain lysosomal enzymes in the Golgi lysosome endoplasmic reticulum system and also exhibit absorptive capacity, which might be associated with an early decrease in extracellularly degraded enamel proteins. Active calcium transport through the ameloblasts towards the growing enamel is indicated by the demonstration of Ca-ATPase activity along the plasma membranes. A calcium-dependent modulator protein, calmodulin, is localized in ameloblasts, suggesting that early enamel mineralization is dependent upon calmodulin-regulated Ca-ATPase in ameloblasts. These results suggest that the secretory ameloblast is a highly specialized multifunctional cell in the production, resorption and degradation of enamel matrix and in the active calcium transport essential for matrix mineralization during enamel formation.
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Affiliation(s)
- T Sasaki
- Department of Oral Anatomy 2, School of Dentistry, Showa University, Tokyo, Japan
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727
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George A, Bannon L, Sabsay B, Dillon JW, Malone J, Veis A, Jenkins NA, Gilbert DJ, Copeland NG. The carboxyl-terminal domain of phosphophoryn contains unique extended triplet amino acid repeat sequences forming ordered carboxyl-phosphate interaction ridges that may be essential in the biomineralization process. J Biol Chem 1996; 271:32869-73. [PMID: 8955126 DOI: 10.1074/jbc.271.51.32869] [Citation(s) in RCA: 155] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Phosphophoryns (PPs), a family of Asp and Ser(P)-rich dentin proteins, are considered to be archetypal regulators of several aspects of extracellular matrix (ECM) biomineralization. We have cloned a rat incisor PP gene, Dmp2, from our odontoblast cDNA library and localized it to mouse chromosome 5q21 within 2 centimorgans of Dmp1, another tooth-specific ECM protein. The carboxyl-terminal region of Dmp2 protein (60 residue % Ser, 31 residue % Asp) is divided into two domains, one with unique repetitive blocks of [DSS]n,3</=14, the other with [SD]m = 2,3. Conformational analysis shows the phosphorylated form of the [DS*S*]n repeats to have a unique structure with well defined ridges of phosphates and carboxyls available for counter ion binding. The [S*D]m domains have different phosphate and carboxylate interaction edges and thus different calcium ion and apatite surface binding properties. These two domains and the colocalization of Dmp1 and Dmp2 genes at a position equivalent to the dentinogenesis imperfecta type II location on human 4q21 all suggest that the PPs are indeed involved in some aspect of ECM mineralization.
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Affiliation(s)
- A George
- Northwestern University, Chicago, Illinois 60611, USA.
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728
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729
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Aksay IA, Trau M, Manne S, Honma I, Yao N, Zhou L, Fenter P, Eisenberger PM, Gruner SM. Biomimetic Pathways for Assembling Inorganic Thin Films. Science 1996; 273:892-8. [PMID: 8688064 DOI: 10.1126/science.273.5277.892] [Citation(s) in RCA: 651] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Living organisms construct various forms of laminated nanocomposites through directed nucleation and growth of inorganics at self-assembled organic templates at temperatures below 100°C and in aqueous solutions. Recent research has focused on the use of functionalized organic surfaces to form continuous thin films of single-phase ceramics. Continuous thin films of mesostructured silicates have also been formed on hydrophobic and hydrophilic surfaces through a two-step mechanism. First, under acidic conditions, surfactant micellar structures are self-assembled at the solid/liquid interface, and second, inorganic precursors condense to form an inorganic-organic nanocomposite. Epitaxial coordination of adsorbed surfactant tubules is observed on mica and graphite substrates, whereas a random arrangement is observed on amorphous silica. The ability to process ceramic-organic nanocomposite films by these methods provides new technological opportunities.
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Affiliation(s)
- IA Aksay
- The authors are at Princeton University, Princeton, NJ 08544-5263, USA. I. A. Aksay, M. Trau, and I. Honma are in the Department of Chemical Engineering and the Princeton Materials Institute; S. Manne and N. Yao are in the Princeton Materials Institute; and L. Zhou, P. Fenter, P. M. Eisenberger, and S. M. Gruner are in the Department of Physics and the Princeton Materials Institute
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730
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Schacht S, Huo Q, Voigt-Martin IG, Stucky GD, Schuth F. Oil-Water Interface Templating of Mesoporous Macroscale Structures. Science 1996; 273:768-71. [PMID: 8670410 DOI: 10.1126/science.273.5276.768] [Citation(s) in RCA: 686] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ordered mesostructured porous silicas that are also macroscopically structured were created by control of the interface on two different length scales simultaneously. Micellar arrays controlled the nanometer-scale assembly, and at the static boundary between an aqueous phase and an organic phase, control was achieved on the micrometer to centimeter scale. Acid-prepared mesostructures of silica were made with the p6, Pm3n, and the P63/mmc structures in the form of porous fibers 50 to 1000 micrometers in length, hollow spheres with diameters of 1 to 100 micrometers, and thin sheets up to 10 centimeters in diameter and about 10 to 500 micrometers in thickness. These results might have implications for technical applications, such as slow drug-release systems or membranes, and in biomineralization, where many processes are also interface-controlled.
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Affiliation(s)
- S Schacht
- S. Schacht and F. Schuth, Institut fur Anorganische Chemie, Johann Wolfgang Goethe Universitat Frankfurt, Marie Curie Strasse 11, 60439 Frankfurt, Germany. Q. Huo and G. D. Stucky, Department of Chemistry, University of California, Santa Barbara, CA 93106, USA. I. G. Voigt-Martin, Institut fur Physikalische Chemie, Johannes Gutenberg-Universitat Mainz, Welderweg 11, 55099 Mainz, Germany
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Belcher AM, Wu XH, Christensen RJ, Hansma PK, Stucky GD, Morse DE. Control of crystal phase switching and orientation by soluble mollusc-shell proteins. Nature 1996. [DOI: 10.1038/381056a0] [Citation(s) in RCA: 949] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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