By probing its molecular structure, biologists are uncovering how a tangle of unstructured proteins turns into a strong, flexible fiber.

Introduction

A spider, when knocked off a wall, doesn’t fall for long. Within milliseconds, it spins a soup of proteins into sturdy climbing gear. Using a thin, shimmering strand of silk, the spider hauls itself back up.

The strand is tougher than Kevlar, the synthetic fiber in bike tires and bulletproof vests, and stronger than steel. It’s flexible and biocompatible with human bodies. Scientists dream of making spider silk into high-performing materials for seat belts, helmets, naval materials, and even scaffolds to help repair brain cells.…