Isotope Days 2024-NMR with Greg Holland, PhD, PhD

Feeding Spiders Isotope-Enriched Amino Acids to Label Their Silks for NMR Investigation
Dr. Greg Holland presents his lab's research on the structural biology of spider silk, focusing on how spiders produce silk. They use NMR spectroscopy to label the silks and fluids inside the spider's abdomen with isotopes, collecting silk from the spiders and feeding them solutions of different isotopes. The lab studies both the silk fibers and the silk-producing process as a whole, dissecting the spiders to remove and examine the fluid using solution NMR.
The lab's work is funded mainly by the Department of Defense, with interest in spider silk due to its mechanical properties. Spiders produce a range of different silks, each with varying properties. The dragline silk is stronger than steel by weight and tougher than Kevlar, while the prey-wrapped silk is more extensible and tougher than dragline silk.
The proteins that make up spider dragline silk are huge and highly repetitive, making them challenging to study. The lab uses solution NMR to understand the structure of the proteins before they're spun into fibers. They've been able to assign a 15-residue repeating unit and get all the relevant chemical shift information. This data is used with chemical shift Rosetta to produce structures of the proteins.
The lab also investigates liquid-liquid phase separation as an intermediate step in spider silk formation and uses solid-state NMR and dynamic nuclear polarization magic angle spinning to build a model of the spider silk fiber structure. They focus on understanding side chain interactions in the spun fibers, such as arginine-tyrosine and proline-tyrosine interactions.
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