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

Area of Science:

• Biochemistry
• Marine Biology
• Surface Science

Background:

• Gregarious settlement in barnacle larvae (cyprids) is mediated by a contact pheromone, the settlement-inducing protein complex (SIPC).
• SIPC is present in adult barnacle cuticle and cyprid footprints, suggesting roles in both settlement induction and adhesion.
• Understanding SIPC's adsorption behavior is key to elucidating barnacle settlement mechanisms.

Purpose of the Study:

• To investigate the adsorption behavior of SIPC on various surfaces.
• To compare SIPC adsorption with that of fibrinogen and α2-macroglobulin (A2M).
• To analyze the kinetics and stability of SIPC adsorption.

Main Methods:

• Surface plasmon resonance (SPR) was used to monitor SIPC adsorption.
• Experiments were conducted on a series of self-assembled monolayers (SAMs) at pH 8.3.
• Fibrinogen and A2M served as positive and negative controls, respectively.

Main Results:

• SIPC mass uptake was comparable to fibrinogen, adsorbing even on protein-resistant surfaces.
• SIPC exhibited a kinetic overshoot on positively charged SAMs, indicating metastable adsorption.
• A2M adsorption was primarily electrostatic, with minimal binding except on positively charged surfaces.
• SIPC demonstrated irreversible and non-cooperative adsorption across all tested surfaces.

Conclusions:

• SIPC adsorption is robust and occurs on diverse surfaces, including protein-resistant ones.
• The adsorption kinetics suggest a complex interaction mechanism, potentially involving metastable states.
• SIPC's irreversible adsorption contributes significantly to barnacle adhesion and gregarious settlement.