Solid-state NMR studies of proteins immobilized on inorganic surfaces

Abstract

Solid state NMR is the primary tool for studying the quantitative, site-specific structure, orientation, and dynamics of biomineralization proteins under biologically relevant conditions. Two calcium phosphate proteins, statherin (43 amino acids) and leucine rich amelogenin protein (LRAP; 59 amino acids), have been studied in depth and have different dynamic properties and 2D- and 3D-structural features. These differences make it difficult to extract design principles used in nature for building materials with properties such as high strength, unusual morphologies, or uncommon phases. Consequently, design principles needed for developing synthetic materials controlled by proteins are not clear. Many biomineralization proteins are much larger than statherin and LRAP, necessitating the study of larger biomineralization proteins. More recent studies of the significantly larger full-length amelogenin (180 residues) represent a significant step forward to ultimately investigate the full diversity of biomineralization proteins. Interactions of amino acids, a silaffin derived peptide, and the model LK peptide with silica are also being studied, along with qualitative studies of the organic matrices interacting with calcium carbonate. Dipolar recoupling techniques have formed the core of the quantitative studies, yet the need for isolated spin pairs makes this approach costly and time intensive. The use of multidimensional techniques to study biomineralization proteins is becoming more common, methodology which, despite its challenges with these difficult-to-study proteins, will continue to drive future advancements in this area.

Molecular insights into hypomineralized enamel

“…Nuclear magnetic resonance (NMR) has been utilized for structural investigations on bones and teeth, including studies of proteins (29)(30)(31)(32)(33)(34)(35)(36). Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) has proven to be a useful method for the chemical analyses of HAP in enamel and bone tissue, as well as for analyses of organic molecules, such as protein fragments (33,(37)(38)(39)(40)(41)(42)(43)(44)(45).…”

Dynamic interactions of amelogenin with hydroxyapatite surfaces are dependent on protein phosphorylation and solution pH

“…[17,18] Methods of solid-state NMR have opened the door to challenging but high resolution structural biology studies[19] of amelogenin in a mineral-bound state. Shaw and colleagues have recently demonstrated that mouse amelogenin undergoes a random coil to beta-sheet transition upon mineral binding,[20] that surface-induced structural changes occur for both phosphorylated and non-phosphorylated forms of LRAP,[21] and that molecular level interactions may change with phosphorylation state leading to macroscopic differences in adsorption or mineralization.…”

Secondary structure and dynamics study of the intrinsically disordered silica‐mineralizing peptide P5S3 during silicic acid condensation and silica decondensation

“…At globally undersaturated (that is, 1 mM) silicic acid concentrations, P 5 S 3 slowed down the dissolution of silica . Here, we report on the conformation of the peptide in the presence or absence of silica as derived from NMR and CD 19, spectroscopy. We show that the P 5 S 3 polypeptide backbone is disordered in solution but shifts to a higher α‐helical content upon binding silica.…”

“…In a solid state NMR approach, significant perturbations in the chemical shifts of both the peptide backbone and side‐chain C and N atoms were reported. These were attributed to differences in the chemical environments due to interaction with silica (that is, peptide‐silica interaction, peptide‐chain assembly), and no information about peptide folding was inferred . In another report, R5 was studied by solution state NMR in the presence of 50 μM (undersaturated) silicic acid.…”