Melbourne Dental School - Research Publications

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    Kappacin, a novel antibacterial peptide from bovine milk
    Malkoski, M ; Dashper, SG ; O'Brien-Simpson, NM ; Talbo, GH ; Macris, M ; Cross, KJ ; Reynolds, EC (AMER SOC MICROBIOLOGY, 2001-08)
    Caseinomacropeptide (CMP) is a heterogeneous C-terminal fragment (residues 106 to 169) of bovine milk kappa-casein composed of glycosylated and phosphorylated forms of different genetic variants. We have demonstrated that CMP has growth-inhibitory activity against the oral opportunistic pathogens Streptococcus mutans and Porphyromonas gingivalis and against Escherichia coli. CMP was fractionated using reversed-phase high-performance liquid chromatography (RP-HPLC), and each fraction was tested for activity against S. mutans in a 96-well-plate broth assay. Fractions were characterized by N-terminal sequence analysis and mass spectrometry. The active form of CMP was shown to be the nonglycosylated, phosphorylated kappa-casein (residues 106 to 169) [kappa-casein(106--169)], which we have designated kappacin. Endoproteinase Glu-C was used to hydrolyze CMP, and the generated peptides were separated using RP-HPLC and gel filtration-HPLC and then tested for activity against S. mutans. The peptide Ser(P)(149)kappa-casein-A(138--158) was the only peptide generated by endoproteinase Glu-C digestion that exhibited growth-inhibitory activity. Peptides corresponding to the sequences of the inhibitory peptide Ser(P)(149)kappa-casein-A(138--158) and its nonphosphorylated counterpart kappa-casein-A(138--158) were chemically synthesized and tested for antibacterial activity. The synthetic Ser(P)(149) kappa-casein-A(138--158) displayed growth-inhibitory activity against S. mutans (MIC, 59 microg/ml [26 microM]). The nonphosphorylated peptide, however, did not inhibit growth at the concentrations tested, indicating that phosphorylation is essential for activity.
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    The evaluation of four conditioners for glass ionomer cements using field-emission scanning electron microscopy
    Tanumiharja, M ; Burrow, MF ; Cimmino, A ; Tyas, MJ (ELSEVIER SCI LTD, 2001-02)
    OBJECTIVES: The purpose of this study was to evaluate the GIC-dentine interface morphology using FE-SEM after four different conditioners (Ketac Conditioner, Dentin Conditioner, Cavity Conditioner, and an experimental conditioner K-930), used with two RM-GICs and one self-cured GIC, and to observe the effect with an AFM of the four different conditioners on the surface of polished human dentine. MATERIALS AND METHODS: SAMPLE PREPARATION FOR FE-SEM: Twenty-four 1-mm thick dentine discs were obtained from superficial occlusal dentine of extracted human third molars, and finished with wet 600-grit SiC paper. The discs were treated for each of the GICs using the conditioners according to the manufacturers' instructions. The specimens were kept in tap water for 24 h at 37 degrees C, and then assigned for one of two observational techniques; a fractured technique and an acid-base technique. Specimens were mounted on aluminium stubs, gold sputter-coated and observed using a FE-SEM. SAMPLE PREPARATION FOR AFM: Four rectangular dentine blocks approximately 2mm(3) were prepared from two extracted human third molars, polished and finished with diamond paste down to 0.25 microm particle size. One half of each sample was treated with one of the conditioners according to the manufacturers' instructions, and the other half was not conditioned. The samples were stored in distilled water prior to AFM contact mode observation. RESULTS: FE-SEM: All specimens of all materials demonstrated good adaptation to the underlying dentine. However, the specimens conditioned with K-930 showed increased demineralization and a thicker acid-base resistant layer (2.8-3.4 microm) compared with the others (1-2 microm). AFM: The images of conditioned specimens showed demineralization of peritubular dentine. Funneling of dentinal tubule orifices of specimens conditioned with K-930 was observed, and was also seen for the FE-SEM specimens. SIGNIFICANCE: The use of surface conditioners resulted in similar adaptation to the non-conditioned specimens at the GIC-dentine interface. All of the GICs demonstrated intimate adaptation to the dentine surface whether it was conditioned or not.