Kitadai Norio, Yokoyama Tadashi, Nakashima Satoru
Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
J Colloid Interface Sci. 2009 Jan 1;329(1):31-7. doi: 10.1016/j.jcis.2008.09.072. Epub 2008 Oct 1.
Attenuated total reflectance infrared (ATR-IR) spectroscopy was employed to quantitatively evaluate the dissociation states (di-cationic, cationic, zwitterionic, and anionic) of lysine adsorbed on amorphous silica. To determine the relationship between the ATR-IR spectra and each dissociation state, we first measured pH-induced spectral changes of dissolved lysine and correlated these changes with the thermodynamically calculated dissociation states of lysine. This procedure yielded calibration curves with good linearity; we used these curves for the quantitative analysis of adsorbed lysine. Our analysis revealed that 81+/-5% of the lysine adsorbed on amorphous silica was present in a cationic state and 19+/-5% was in a zwitterionic state; these percentages remained mostly unchanged over the whole range of pH values tested (pH = 7.1-9.8). We interpret the values obtained to indicate that lysine adsorption is mainly driven by electrostatic interaction with the negatively charged silica surface (SiO(-)...Lys(+), SiO(-)...Lys(+/-)).
采用衰减全反射红外（ATR-IR）光谱法定量评估吸附在无定形二氧化硅上赖氨酸的解离状态（双阳离子、阳离子、两性离子和阴离子）。为了确定ATR-IR光谱与每种解离状态之间的关系，我们首先测量了溶解态赖氨酸的pH诱导光谱变化，并将这些变化与赖氨酸的热力学计算解离状态相关联。该过程产生了具有良好线性的校准曲线；我们使用这些曲线对吸附的赖氨酸进行定量分析。我们的分析表明，吸附在无定形二氧化硅上的赖氨酸中81±5%呈阳离子状态，19±5%呈两性离子状态；在测试的整个pH值范围内（pH = 7.1 - 9.8），这些百分比基本保持不变。我们对所得值的解释是，赖氨酸的吸附主要由与带负电荷的二氧化硅表面的静电相互作用驱动（SiO(-)...Lys(+)，SiO(-)...Lys(+/-)）。
