一种天然纳米纤维捕鸟蛛丝的物理化学结构表征

蜘蛛丝作为功能性结构材料, 其独特的纤维成型方法与优良的结构和性能引起许多人的关注. 从20世纪80年代开始有关蜘蛛丝的研究报道日益增加1]. 与高温高压下或由溶剂纺丝成型的合成纤维相比, 蜘蛛丝在空气中凝固成型, 丝纤维成型安全、无害, 从腹部若干不同吐丝器产生不同种类的丝具有不同的用途2]. 蜘蛛拖曳丝(dragline silk)的比强度大于钢丝, 且具有较大的断裂伸长率(9%～30%)3,4], 抗张强度1.1～1.4 GPa. 在相对湿度50%和应变速率100%/min的条件下, 模量值可达10～50 GPa. 在所有已知纤维品种中, 蜘蛛丝的断裂能是最高的. 此外, 蜘蛛丝在许多方面的综合性能优于最优良的人造纤维. 另外, 蜘蛛丝的细度为已知纤度最小的天然有机纤维, 这种高性能丝具有捕捉昆虫甚至鸟类的功能, 因此蜘蛛丝是具有特异功能的天然纤维材料. 目前, 蜘蛛丝结构和性能的研究主要包括其化学组成5]、结晶结构6,7]、结构模型8,9]以及其NMR表征10]等, 这些研究揭示了蜘蛛丝的氨基酸组成、分子量及其分布、结晶度、晶胞尺寸、链构象以及结构模型等. 这些研究主要集中在少数几种蜘蛛品种上, 如金色圆网织网蛛(Nephila clavipes)、十字圆蛛(A.diadematus)和大腹圆蛛(A.ventrocosus)等. 目前, 已知的蜘蛛种类大于30 000种11], 以蜘蛛丝为例的生物大分子材料研究是一个挑战性的课题. 国内蜘蛛丝的研究仅有大腹圆蛛拖曳丝蛋白一级结构的研究报道12,13]. 本文报道了广西捕鸟蛛丝的红外光谱、形貌结构和原子力显微镜的初步研究结果.

Physico-chemical Structure Characterizations of the Silk from Spider Selenocosmia as a Kind of Natural Nanometer Fiber

The physicochemical structures of silk from spider selenocosmia were characterized by means of IR, SEM and AFM. Based on the data of SEM and AFM, the diameters for the silk from spider selenocosmia were in the range of 100-500 nm, with the lower end of which this spider silk was considered as a kind of nanometer fibers. This silk from spider selenocosmia was much thinner than the silk from mulberry silkworm and the silk from spider nephila davipes, the diameters of which were 4 μm and 10～20 μm, respectively. Thus, the silk from spider selenocosmia could be considered as a natural nanometer fiber, which was rare in nature, especially in the form of a monofilament. It was shown from the results of IR spectra that the absorbance peaks of 1 644.73cm-1, called as the amide Ⅰ structure, were correlated with the "random coil" and alpha-helix conformations in the amorphous part. The absorbance peaks of 1 517.44cm-1, called as the amide Ⅱ structure, indicated B-sheet region plus a small amount of helical conformation existed. These molecular characterizations of silk from spider selenocosmia were similar to those of the silk from mulberry silkworm and the silk from spider Nephila davipes.