title: Identification of low molecular weight molecules as new components of the nacre organic matrix.
abstract: Nacre of Pinctada margaritifera displays a number of interesting biological activities on bone, mainly concentrated in a water-soluble organic matrix representing 0.24% of the nacre weight. Dialysis of that matrix through 8 kDa and 1 kDa cut-off membranes showed that 60% of it is made of small molecules of molecular masses below 1 kDa. Reversed-phase high-performance liquid chromatography of the small molecule fractions and subsequent electrospray ionization mass spectrometric analysis of 19 fractions thereof indicated the presence of at least 110 different molecules, in the range 100 Da-700 Da. Evidence for aggregate-forming properties of the small molecules was given. Amino acid analysis revealed that most of the small molecules were not peptides and tandem mass spectrometric gas-phase fragmentations clearly indicated a structural relationship between several molecules. Intriguingly, differences of a single Dalton between mono-charged ions peaks were observed. Further, approximately 40 analytes could be arranged in a ladder-like manner with mass spaces of 57 Da. Some of the water-soluble peptide sequences obtained after MS/MS fragmentation revealed that the 57 Da shift corresponds to the repetition of glycine residues. Furthermore, the exchange of glycine against alanine explains the 14 Da shift observed between some peptides. These data show for the first time that small molecules, especially peptides, are prevalent components of nacre. The molecular species described in this report might have a functional role in nacre.
authors.affiliation: Muséum National d'Histoire Naturelle, USM 0401, ERT Valorisation de Molécules Bioactives d'Origine Marine, 7 rue Cuvier, Paris, France. bedouet@mnhn.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Bédouet
authors.forename: Filippo
authors.initials: F
authors.lastname: Rusconi
authors.forename: Marthe
authors.initials: M
authors.lastname: Rousseau
authors.forename: Denis
authors.initials: D
authors.lastname: Duplat
authors.forename: Arul
authors.initials: A
authors.lastname: Marie
authors.forename: Lionel
authors.initials: L
authors.lastname: Dubost
authors.forename: Karine
authors.initials: K
authors.lastname: Le Ny
authors.forename: Sophie
authors.initials: S
authors.lastname: Berland
authors.forename: Jean
authors.initials: J
authors.lastname: Péduzzi
authors.forename: Evelyne
authors.initials: E
authors.lastname: Lopez
mesh_terms: D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003956:Dialysis; D005998:Glycine / Q000737:chemistry*; D010455:Peptides / Q000032:analysis*; D049911:Pinctada / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D010455:Peptides; D002119:Calcium Carbonate; D005998:Glycine