The amino acid composition of major ampullate gland silk (dragline) of Nephila clavipes (Araneae, Tetragnathidae)

• Published in: The Journal of arachnology 1990-01, Vol.18 (3), p.297-306
• Main Authors: Lombardi, S.J. (US Army Natick Research, Development, and Engineering Center, Natick, MA), Kaplan, D.L
• Format: Article
• Language: English
• Subjects: ACIDE AMINE; AMINO ACIDS; AMINOACIDOS; ANIMAL GLANDS; ARANEAE; Chemical composition; GLANDE ANIMALE; GLANDULAS ANIMALES; Hydrolysis; Nephila clavipes; Property composition; SEDA; SILK; SILK GLANDS; Silkworms; SOIE; Solubilization; Spiders; Tetragnathidae
• ISSN: 0161-8202; 1937-2396

Amino acid composition of major ampullate gland silk (dragline) produced by the mature, female golden orb-weaving spider, Nephila clavipes was determined. Several solvents were applied in order to solubilize the spider silk. Although several strong acids and bases were able to solubilize silk, the protein was apparently degraded by this treatment, as demonstrated by protein gel electrophoresis. Only a mixture of hydrochloric/propionic acid (50:50, v:v, final concentration 3N HCL/25% propionic acid) solubilized the silk while retaining the molecular weight integrity of the crystalline polymer. The results show that the major ampullate gland secretion is characterized by a high degree of small side chain amino acids (Ala, Gly, and Ser) and polar residues (Gly and Arg), comprising almost 75% of the total amino acids present. Contrary to published findings (Work and Young 1987), the composition of major ampullate gland silk appears to be uniform within the species. The composition of the secretion is discussed in relation to the known and implied functions of the major ampullate gland as well as in relation to the mechanical properties of the silk produced by orb-web building spiders.