  The pyriform silk of the attachment disc of a spider was studied using
infrared-visible vibrational sum frequency generation (SFG) spectroscopy. The
spider can attach dragline and radial lines to many kinds of substrates in
nature (concrete, alloy, metal, glass, plant branches, leaves, etc.) with the
attachment disc. The adhesion can bear the spider's own weight, and resist the
wind on its orb web. From our SFG spectroscopy study, the NH group of arginine
side chain and/or NH$_{2}$ group of arginine and glutamine side chain in the
amino acid sequence of the attachment silk proteins are suggested to be
oriented in the disc. It was inferred from the observed doublet SFG peaks at
around 3300 cm$^{-1}$ that the oriented peptide contains two kinds of
structures.
