Multiphasic analyses of the interaction between cariogenic polysaccharide and tooth enamel

已知在人类唾液中发现的细菌远缘链球菌（Streptococcus sobrinus）将蔗糖转化为称为α-葡聚糖的粘性多糖。这种被称为α-葡聚糖的葡聚糖在主链序列中由（1→3）-α-连接的D-葡萄糖组成，（1→6）-α-连接的D-葡萄糖作为侧残基附着在主链序列上，并且它通过粘附在人牙齿的表面（由羟基磷灰石组成的牙釉质）上而参与牙菌斑的形成。在牙菌斑中，细菌将蔗糖转化为乳酸，乳酸溶解羟基磷灰石（釉质脱钙），因此导致龋齿。本研究通过以下几种物理化学方法分析龋病的病因.利用X射线衍射结合能量计算对α-葡聚糖的构象进行了分析，结果表明，（1→3）-α-D-葡聚糖的主链是一个延伸的双螺旋结构（Z字形结构）。提出了葡聚糖的一些能量优选构象.对α-葡聚糖和假六方晶型羟基磷灰石晶体（类似于牙釉质）之间相互作用的光谱（红外、荧光和圆二色性）研究没有发现任何强键（如氢键）的存在。研究了几种防龋剂对羟基磷灰石在乳酸中溶解的影响，结果表明两种甲壳素衍生物（羧甲基甲壳素和乙二醇甲壳素）降低了羟基磷灰石的溶解度。

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.