title: Matching 4.7-Å XRD spacing in amelogenin nanoribbons and enamel matrix.
abstract: The recent discovery of conditions that induce nanoribbon structures of amelogenin protein in vitro raises questions about their role in enamel formation. Nanoribbons of recombinant human full-length amelogenin (rH174) are about 17 nm wide and self-align into parallel bundles; thus, they could act as templates for crystallization of nanofibrous apatite comprising dental enamel. Here we analyzed the secondary structures of nanoribbon amelogenin by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and tested if the structural motif matches previous data on the organic matrix of enamel. XRD analysis showed that a peak corresponding to 4.7 Å is present in nanoribbons of amelogenin. In addition, FTIR analysis showed that amelogenin in the form of nanoribbons was comprised of β-sheets by up to 75%, while amelogenin nanospheres had predominantly random-coil structure. The observation of a 4.7-Å XRD spacing confirms the presence of β-sheets and illustrates structural parallels between the in vitro assemblies and structural motifs in developing enamel.
authors.affiliation: Lawrence Berkeley National Laboratory, Molecular Foundry, Berkeley, CA 94720, USA Keck Science Department, Claremont McKenna, Scripps and Pitzer Colleges, Claremont, CA 91711, USA.
authors.forename: B
authors.initials: B
authors.lastname: Sanii
authors.affiliation: University of California, Department of Preventive and Restorative Dental Sciences, San Francisco, CA 94143, USA.
authors.forename: O
authors.initials: O
authors.lastname: Martinez-Avila
authors.affiliation: University of California, Department of Preventive and Restorative Dental Sciences, San Francisco, CA 94143, USA.
authors.forename: C
authors.initials: C
authors.lastname: Simpliciano
authors.affiliation: Lawrence Berkeley National Laboratory, Molecular Foundry, Berkeley, CA 94720, USA.
authors.forename: R N
authors.initials: RN
authors.lastname: Zuckermann
authors.affiliation: University of California, Department of Preventive and Restorative Dental Sciences, San Francisco, CA 94143, USA stefan.habelitz@ucsf.edu.
authors.forename: S
authors.initials: S
authors.lastname: Habelitz
mesh_terms: D053523:Amelogenin / Q000737:chemistry*; D020816:Amino Acid Motifs; D002122:Calcium Chloride / Q000737:chemistry; D003743:Dental Enamel / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D053758:Nanoparticles / Q000737:chemistry*; D054118:Nanospheres / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D011189:Potassium Chloride / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D011994:Recombinant Proteins; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D053523:Amelogenin; D010710:Phosphates; D017680:Potassium Compounds; D011994:Recombinant Proteins; D011189:Potassium Chloride; C013216:potassium phosphate; D002122:Calcium Chloride
keywords: Fourier transform infrared spectroscopy; development; powder diffraction; secondary protein structure; self-assembly; structure