| AVS 62nd International Symposium & Exhibition | |
| Biomaterial Interfaces | Wednesday Sessions |
| Session BI-WeM |
| Session: | Biomolecules at Interfaces |
| Presenter: | Kathryn Wahl, US Naval Research Laboratory |
| Authors: | C. So, National Research Council postdoc cited at Naval Research Laboratory J. Liu, US Naval Research Laboratory K. Fears, US Naval Research Laboratory D. Leary, US Naval Research Laboratory J. Golden, US Naval Research Laboratory K. Wahl, US Naval Research Laboratory |
| Correspondent: | Click to Email |
Barnacles adhere by secreting a micron-thick proteinaceous layer between themselves and the marine environment that persists throughout their lifespan. These proteins play a dual role in adhering to both the native organism and a foreign substratum, which are often crystalline calcium carbonates from other marine invertebrates, cuticular exoskeleton or sedimentary minerals. Though the sequence and composition of several barnacle cement proteins have been reported, little is known about how these proteins become stably bound to surfaces. Here we use in situ atomic force microscopy (AFM) to examine a recombinantly expressed, acidic, calcite-binding 20kDa cement protein, MRCP20. We find that the protein immobilizes on the surface through recognition of distinct atomic steps on the [1014[ face of calcite, further assembling on these features into stable nanofibrils. The protein fibrils are continuous and organized at the nanoscale, exhibiting striations with a period of ca. 45 nm. The acidic fibrils are also found to manipulate calcite surfaces through the dissolution of underlying calcite features that display the same atomic arrangement. To quantify selectivity, we compare the velocity of atomic steps from calcite etch pits when exposed to water, bulk protein solution, and surface-associated nanofibrils. MRCP20 is found to favor interaction with distinct fast moving steps, where velocity is increased by four- and eight-fold upon exposure to bulk proteins and fibrils, respectively, over steps exposed to solution without protein present. Calcite mineralized in the presence of MRCP20 results in asymmetric crystals, suggesting a similar step-selective behavior by MRCP20 during crystal growth. Cooperative molecular processes with step edge atoms reveal a new regime of biotic interactions with calcite, where specific surface interactions are enhanced through templated long-range nanostructures.