Marianne Booij

A FLUORESCENT COMPOUND IN BOVINE DENTAL ENAMEL MATRIX COMPARED WITH SYNTHETIC DITYROSINE

Dityrosine is a substance frequently found in structural proteins. Emission and excitation fluorescence spectra, absorption spectra, thin layer and molecular weight chromatography showed that the fluorescing enamel material isolated strongly resembled dityrosine and had at least an o,o-diphenyl bonding.

Mixed sandwiches of group 3 elements: synthesis and UPS studies of pentamethylcyclopentadienylcyclooctatetraenescandium, -yttrium and -lanthanum

Abstract The mixed sandwich complexes CP * MCOT (Cp * = η 5 -C 5 Me 5 ; M = Sc, Y, La; COT = η 8 -C 8 H 8 ) have been prepared and characterized. IR spectra indicate that in the solid state the La compound is polymeric (Cp * LaCOT) n , with cyclotetraene ligands. The complexes are strong Lewis acids and form bridging adducts Cp * MCOT·THF. For M = La the adduct has been isolated. The UPS spectra of Cp * MCOT are nearly identical with only minor differences in the ionizations from the highest e 2 (COT) and e 1 (Cp * ) orbitals; this is interpreted as a strong indication that the bonding in the complexes is virtually completely ionic.

The adsorption in vitro of purified salivary proteins on bovine dental enamel

The adsorption of proteins isolated from human submandibular saliva was studied on intact enamel surfaces and on enamel powder. All proteins adsorbed in a monolayer, in a single-step adsorption mechanism, suggesting that some of the molecules have a flexible (random coil) structure. The proteins did not release measurable amounts of ions from the adherent liquid layer during adsorption, in contrast to previous findings on the adsorption of several homopolypeptides (Juriaanse et al., J. Colloid Interface Sci.76, 212–220; 1980). Salivary phosphoproteins are more firmly bound to enamel surfaces than are non-phosphorylated proteins, which is due to an exchange reaction in which protein phosphate groups replace surface phosphates in the enamel mineral. In the model used for pellicle maturation, the enamelpellicle interface was slowly saturated with phosphoproteins which displaced non-phosphorylated proteins from the surface.

Isolation and partial characterisation of three acidic proteins from human submandibular saliva.

Abstract Three acidic proteins were isolated from stimulated submandibular saliva. The proteins were present in both stimulated and unstimulated saliva of four human donors. The proteins were demonstrated to be pure by polyacrylamide- and sodium dodecyl sulphate gel electrophoresis and isoelectric focusing. No sugars were present. Two of the proteins were phosphoproteins, with phosphate contents related to their adsorption behaviour to hydroxy-apatite.

Albumin Uptake by Caries Lesions in Bovine Enamel – An in vitro Study

Bovine dental enamel was demineralized in Ca- and phosphate-containing acetate buffers at pH 4.5, with and without albumin and fluoride. Demineralization in albumin-free solutions was followed by albu

Isolation and characterisation of the main neutral protein from human submandibular saliva

Abstract A neutral protein with pI 6.9 was isolated from fresh human submandibular saliva. The protein was present in both stimulated and unstimulated saliva and could be detected in an in vitro pellicle. The protein did not contain measurable amounts of sugar or phosphate groups or lytic activity.

ALBUMIN INTERACTION WITH CARIES-LIKE LESIONS IN BOVINE ENAMEL

The exposure of bovine enamel to an albumin-containing demineralizing solution results in penetration of protein into the porous enamel. Washing of this albumin-containing enamel results in a complete (low pretreatment albumin concentrations) or partial removal of the albumin (pretreatment concentrations greater than or equal to 200 micrograms/ml-1). Subsequent exposure to increasing salt concentrations of fluoride, phosphate, calcium or chloride shows a partial removal of albumin at fluoride or phosphate concentrations of 75 mM while complete removal occurred at 150-200 mM fluoride or phosphate. Exposure to either calcium or chloride, even at 3 M concentrations, showed a negligible albumin release. It is proposed that protein removed at high fluoride or phosphate concentrations is bound by a strong interaction between protein-carboxyl groups and calcium on the surface of the enamel mineral. The partial removal of albumin released at low fluoride or phosphate concentrations indicates an enamel-albumin interaction by means of Ca-bridging between protein-carboxyl groups and mineral phosphates. Finally, it is suggested that salt-free washing removes albumin that has lost its native form upon binding to the partially dissolved crystallites of the enamel. It is concluded that enamel is mainly protected from demineralization by the inhibitory effects of protein penetrated into the pores, in addition to possible protection by the pellicle on the surface.

Protein loss of bovine dental enamel during in-vitro subsurface demineralization

A chemical system based on the dialysis principle was used to study protein loss of dental enamel during demineralization with an acetic-acid buffer solution containing calcium and phosphate, in which the fluoride-ion activity was kept constant. This resulted in a subsurface lesion, with a depth of about 130 microns. After demineralization, protein material was isolated from the demineralization solution. u.v. Spectra of the protein showed strong absorbance between 240 and 300 nm. Amino-acid composition showed high glycine, glutamic acid, proline, serine and aspartic acid contents. After 10 days demineralization, the total protein loss was 3 micrograms cm-2; the mineral loss was 16 mg cm-2. Compared with the total enamel-protein content (0.06-0.09 wt per cent) protein loss (0.018 per cent of total lost material) was not proportional to the mineral loss, when a subsurface lesion was formed.

Protein and mineral changes in bovine enamel during in-vitro demineralization

Mineral distributions with and without a softened surface layer were studied. The molar Ca:P ratio of released material was due to preferential Ca-loss significantly higher from surface-softened enamel than from lesions. The molecular weight (less than 1800) distributions of released proteinaceous matter were similar. The protein release during surface softening contained more large peptides, whereas its amino-acid composition was more acidic amino acids compared with lesion formation. The protein content of released material during demineralization, acetic acid-soluble protein (at pH 4.5) and total protein of sound enamel showed that (i) enamel proteins were partially soluble in an acetic acid-buffer under mild acidic conditions and (ii) enamel proteins soluble in acetic acid-solution were partially released during demineralization. It is postulated that during enamel demineralization the dissolution of acid-soluble proteinaceous matter and its partial adsorption on newly-created sites of partially-dissolved crystals may explain the partial release of acid-soluble proteins. In case of lesion formation on the other hand new adsorption sites on new crystal surfaces formed in the surface layer are formed as well, which may account for the differences in mol.wt distribution and amino-acid composition.

Plasma Fluoride Levels in 9 Children with Acute Lymphatic Leukaemia Using Daily Self-Applied Fluoride Gels

Many patients with acute lymphatic leukaemia apply 1% NaF gel daily. Plasma fluoride levels and urinary excretion of 9 children using this regimen were followed in this study. Patients with a high dai