BSA与羟磷灰石相互吸附的FTIR-ATR光谱

采用傅里叶变换红外衰减全反射(FTIR-ATR)光谱法对牛血清白蛋白(BSA)在羟磷灰石(HA)Ca₁₀(OH)₂(PO₄)₆]表面不同时间的相互吸附作用进行了表征。在BSA溶液作用下,羟磷灰石表面的Ca²⁺、PO₄^3-和OH^-离子初始的溶解和再沉淀使得BSA与HA相互作用层层叠加,在HA表面形成从表层到次表层分子都包含有吸附的BSA的覆盖层,从而加深两者之间的相互作用。经红外差谱法处理过的相关ATR数据表明, BSA与HA之间的相互作用是快速的,并随时间变化进一步加强;来自HA上PO₄^3-的P=O基团对蛋白质肽键的酰胺II带(―CNH)、多肽链的甲基(―PO₃)和亚甲基(―CH₂)上氢的吸附作用要比P―O快速而且强烈。Ca²⁺在该吸附过程中起了极其重要的作用,其快速与蛋白质肽键的羰基氧发生作用,并诱导该蛋白质二级结构由β-折叠向α-螺旋和β-转角构象转变;伴随着这一构象变化,蛋白质多肽链上大多数肽键的―C=O和H―N―活性基团从链间氢键交联中释放出来,带动众多的氢分别参与同HA表面的Ca²⁺、PO43-和OH^-离子的相互吸附作用,并牢牢地结合于HA表面;这对硬组织的再生起着重要作用,促进了HA的生物矿化过程。

FTIR-ATR Spectrometry of BSA Adsorption on Hydroxyapatite

The microcosmic process of bovine serum albumin (BSA) adsorbing onto hydroxyapatite (HA) for different time intervals was investigated by Fourier transform infrared attenuated total internal reflectance (FTIRATR) spectrometry. The initial dissolution and re-precipitation of PO₄^3-, Ca²⁺, and OH^- ions from the HA coating led to the occurrence of the coating including adsorbed BSA on the HA from surface-to subsurface-molecular layers and to in-depth interaction between BSA and HA. The subtraction results gained in the adsorption regions of HA and BSA reveal that the binding of P=O, from the phosphate (PO₄^3-), to the hydrogen of amide II, methyl and methene of the BSA appears to be considerably more rapid and stronger than that of the P―O group. In addition, it is very likely that Ca²⁺ plays an important role in the interaction of BSA with HA. It appears that the binding of Ca²⁺ to the carbonyl-oxygen of the peptide bond in BSAcaused a significant, molecular, conformational rearrangement of polypeptide backbones from β-pleated sheet to helical circles of α-helix and β-turn. This change appears to have been followed by much hydrogen of polypeptides being driven to bind PO₄^3- and OHeffectively and much ―C=O and H―N―groups of the peptide bond being freed from inter-chain hydrogenbonding to act on Ca²⁺ and combine strongly with the HA surface. This might reasonably be expected to promote hard tissue regeneration. BSA seems to be activated by the inductive effect of Ca²⁺ via the molecular rearrangement of polypeptide backbones from pleated sheet to helical circles and in turn reacts strongly on the HA, resulting in profound effects on the course of biomineralization.