Multiphasic analyses of the interaction between cariogenic polysaccharide and tooth enamel

已经知道，在人类唾液中发现的一种细菌，远缘链球菌，可以将蔗糖转化为一种粘性多糖，称为α-葡聚糖。这种被称为α-葡聚糖的葡聚糖是由(1-→-3)-α连接的D-葡萄糖组成的骨架序列，(1-→-6)-α-连接的D-葡萄糖作为侧基连接在其上，它通过附着在牙齿表面(由羟基磷灰石组成的牙釉质)参与牙菌斑的形成。在牙菌斑中，细菌将蔗糖转化为乳酸，乳酸溶解羟基磷灰石(牙釉质的脱钙)，从而导致龋齿。我们研究了用不同的物理化学方法分析龋病的原因，具体如下。用X射线衍射和能量计算相结合的方法对α-葡聚糖的构象进行了分析，结果表明主链(1-→-3)-α-D-葡聚糖具有一个延伸的双螺旋(锯齿状结构)。提出了一些能量上较佳的葡聚糖构象。对α-葡聚糖与羟基磷灰石晶体相互作用的光谱(红外、荧光和圆二色)研究没有检测到氢键等强键的存在。一些防龋剂对羟基磷灰石溶解为乳酸的影响的研究表明，两种甲壳素衍生物(羧甲基和乙二醇几丁质)降低了溶解性。

It has been known that a bacteria, Streptococcus sobrinus, found in human saliva converts sucrose to a sticky polysaccharide called α-glucan. This glucan called α-glucan is composed of (1→3)-α-linked D-glucose in the backbone sequence on which (1→6)-α-linked D-glucose is attached as a side residue, and it is involved in dental plaque formation by sticking on the surface (tooth enamel composed of hydroxyapatite) of human teeth. In the plaque, the bacteria transforms sucrose to lactic acid which dissolves hydroxyapatite (decalcification of the enamel) and, consequently it causes of dental caries. We have studied to analyze the cause of dental caries by various physicochemical strategies as follows.1. The conformational analyses of α-glucan by using an X-ray diffraction coupled with an energy calculation indicated that the backbone (1→3)-α-D-glucan takes up an extended two-fold helix (a zigzag structure). Some energetically preferable conformations of the glucan were proposed.2. Spectroscopic (infrared, fluorescence and circular dichroism) studies on the interaction between α-glucan and a hydroxyapatite crystal of pseudohexagonal polymorph, which is likened to tooth enamel, did not detect the presence of any strong bond such as hydrogen bonding.3. Examinations of the effects of some caries preventers on the dissolution of hydroxyapatite to lactic acid indicated that two chitin derivatives (carboxymethyl and ethylene glycol chitins) decrease the soubility.