MILAN ŘEZÁČ Crop Research Institute, Prague SPIDER SILK and the glands that produce it Spider silk is a biological ‘supermaterial’ Characterizing silk: Nano Bionix tensile tester Silks are viscoelastic polymers Strength(force/area) extensibility ultimate strength extensibility toughness stiffnessStrength(force/area) extensibility Silks are viscoelastic polymers Silk proteins contain repetitive motifs Silk proteins contain repetitive motifs crystalline ß-sheet (GA)n / An ß-spiral GPGXX Morphology of the silk gland A – ampulla/zone A B – zone B D – duct S – spigot V - valv Spiders spin liquid crystals Knight & Vollrath 2002 Gland ampulla Vollrath & Knight 2001 Funnel between ampulla and duct Vollrath & Knight 2001 Functions of the duct Alignment of protein molecules Reabsorbtion of water Reabsorbtion of Na+ Acidification – pumping H+ Flask cells, internal draw down, water pump Vollrath & Knight 2001 Vollrath & Knight 2001 Vollrath & Knight 2001 Valve Vollrath & Knight 2001 Spigot, spinnerets SilkHuman hair Vollrath & Knight 2001 Final silk thread Cheliceral Epigastric Vas deferens Spinneret glands Spider silk gland types Silks vary in amino acid composition 0 25 50 75 100% prey wrap eggcase capture temp spiral dragline Gly Ala Ser Pro % of total protein Hayashi and others dragline prey wrapping temp. spiral egg case Strength(MPa) Extensibility (%) 20 40 60 80 2000 1200 800 1600 400 capture spiral 100 200 300 400 Silks have diverse properties Major ampullate glands Minor ampullate glands Pyriform glands Aciniform glands Tubuliform glands Cribellate capture thread – cribellate, paracribellate, and pseudoflafelliform glands Flagelliform glands Aggregate glands Aggregate glands Scytodidae – Cheliceral glands Variability of spider silk Up to nine silk gland types in one spider Each gland contains up to four secretory zones Each secretory zone produces more than one product (composite granules/more granule types) Properties of the final silk thread are given by the spinning conditions (duct morphology, diet, speed, temperature, etc.)