Chemistry-specific surface adsorption of the barnacle settlement-inducing protein complex

Abstract

Gregarious settlement in barnacle larvae (cyprids) is induced by a contact pheromone, the settlement-inducing protein complex (SIPC). The SIPC has been identified both in the cuticle of adult barnacles and in the temporary adhesive secretion (footprint) of cyprids. Besides acting as a settlement inducer, the presence of the SIPC in footprints points to its additional involvement in the adhesion process. SIPC adsorption behaviour was therefore investigated on a series of self-assembled monolayers (SAMs) by surface plasmon resonance at the pH of seawater (8.3). Fibrinogen and α 2 -macroglobulin (A2M) (blood complement protease inhibitors with which the SIPC shares 29% sequence homology) were used in the adsorption experiments as positive and negative standards, respectively. The mass uptake of the SIPC was comparable to that of fibrinogen, with adsorption observed even on the protein-resistant oligo(ethylene glycol) surface. Notably, on the positively charged SAM the SIPC showed a kinetic overshoot, indicating a metastable configuration causing the amount of adsorbed protein to temporarily exceed its equilibrium value. A2M adsorption was low or negligible on all SAMs tested, except for the positively charged surface, indicating that A2M adsorption is mainly driven by electrostatics. Evaluation of SIPC non-specific adsorption kinetics revealed that it adsorbed irreversibly and non-cooperatively on all surfaces tested.

Imaging SPR combined with stereoscopic 3D tracking to study barnacle cyprid–surface interactions

“…Using two different self-assembled monolayers (SAMs) to vary the surface chemistry, we demonstrate that both surface interactions and bulk swimming patterns vary with the surface chemistry. The surfaces were chosen since cyprids are known to interact very weakly with oligo(ethylene glycol) chains and more strongly with carboxylic acid groups (Andersson, Ekblad et al 2009, Aldred, Ekblad et al 2011, Petrone, Aldred et al 2015.…”

Biological adhesives: from biology to biomimetics

“…In barnacle larvae, one protein, SIPC (settlement-inducing protein complex), is present in the larval temporary adhesive secretion and, therefore, plays a double role in settlement and adhesion. Petrone et al [4] report on the measurement of the adsorption behaviour of SIPC to various surfaces. The establishment of the bond for biological adhesives does indeed start with the adsorption of the adhesive biopolymers to the surface.…”

Rearing Temperature Affects the Expression of Proteins in The Adhesive of the Striped Acorn Barnacle, Balanus Amphitrite

“…Preliminary investigations of the adhesive properties of SIPC examined its involvement in temporary adhesion and found that although the protein shares significant sequence homology with a family of proteins that includes the α 2 -macroglobulins (which are blood complement protease inhibitors, functioning to inactivate proteolytic enzymes in immune responses), it was in actuality more comparable to fibrinogen (clotting factor I), which shares no sequence homology (Petrone et al, 2015). Surface plasmon resonance (SPR) was used to measure protein adsorption behavior of SIPC on self-assembled monolayers (SAMs) compared to both α 2 -macroglobulin and fibrinogen and found that SIPC behaved more similarly to fibrinogen (Petrone et al, 2015).…”

“…Surface plasmon resonance (SPR) was used to measure protein adsorption behavior of SIPC on self-assembled monolayers (SAMs) compared to both α 2 -macroglobulin and fibrinogen and found that SIPC behaved more similarly to fibrinogen (Petrone et al, 2015). Thus, the authors determined that SIPC appears to behave as a 'sticky' type protein, which supports its role as a proposed temporary adhesive of barnacle larvae (Petrone et al, 2015). Since SIPC is also expressed during later developmental stages, it seems probably that these sticky characteristics may also serve an additional adhesive role in more mature barnacles.…”

“…Interestingly, more recent evidence suggests this protein may serve a dual role, both as a signaling molecule/settlement-inducer, as well as a putative adhesive (Petrone et al, 2015).…”