Tian Zhenhua, Wu Kun, Liu Wentao, Shen Lirui, Li Guoying
The Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University, Chengdu 610065, PR China.
National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Apr 5;140:356-63. doi: 10.1016/j.saa.2015.01.003. Epub 2015 Jan 13.
The thermal stability of collagen solution (5 mg/mL) crosslinked by glutaraldehyde (GTA) [GTA/collagen (w/w)=0.5] was measured by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR), and the thermally induced structural changes were analyzed using two-dimensional (2D) correlation spectra. The denaturation temperature (Td) and enthalpy change (ΔH) of crosslinked collagen were respectively about 27°C and 88 J/g higher than those of native collagen, illuminating the thermal stability increased. With the increase of temperature, the red-shift of absorption bands and the decreased AIII/A1455 value obtained from FTIR spectra indicated that hydrogen bonds were weakened and the unwinding of triple helix occurred for both native and crosslinked collagens; whereas the less changes in red-shifting and AIII/A1455 values for crosslinked collagen also confirmed the increase in thermal stability. Additionally, the 2D correlation analysis provided information about the thermally induced structural changes. In the 2D synchronous spectra, the intensities of auto-peaks at 1655 and 1555 cm(-1), respectively assigned to amide I band (CO stretching vibration) and amide II band (combination of NH bending and CN stretching vibrations) in helical conformation were weaker for crosslinked collagen than those for native collagen, indicating that the helical structure of crosslinked collagen was less sensitive to temperature. Moreover, the sequence of the band intensity variations showed that the band at 1555 cm(-1) moved backwards owing to the addition of GTA, demonstrating that the response of helical structure of crosslinked collagen to the increased temperature lagged. It was speculated that the stabilization of collagen by GTA was due to the reinforcement of triple helical structure.
通过差示扫描量热法和傅里叶变换红外光谱（FTIR）测定了戊二醛（GTA）交联的胶原蛋白溶液（5mg/mL）[GTA/胶原蛋白（w/w）=0.5]的热稳定性，并使用二维（2D）相关光谱分析了热诱导的结构变化。交联胶原蛋白的变性温度（Td）和焓变（ΔH）分别比天然胶原蛋白高约27°C和88J/g，表明热稳定性提高。随着温度升高，FTIR光谱中吸收带的红移和AIII/A1455值的降低表明，天然和交联胶原蛋白的氢键均被削弱，三螺旋发生解旋；而交联胶原蛋白在红移和AIII/A1455值方面变化较小，这也证实了其热稳定性的提高。此外，二维相关分析提供了有关热诱导结构变化的信息。在二维同步光谱中，交联胶原蛋白在1655和1555cm-1处的自峰强度分别对应于螺旋构象中的酰胺I带（CO伸缩振动）和酰胺II带（NH弯曲和CN伸缩振动的组合），比天然胶原蛋白弱，表明交联胶原蛋白的螺旋结构对温度不太敏感。此外，带强度变化的顺序表明，由于添加了GTA，1555cm-1处的带向后移动，表明交联胶原蛋白的螺旋结构对温度升高的响应滞后。据推测，GTA对胶原蛋白的稳定作用是由于三螺旋结构的加强。
