3 research outputs found
Self-Assembly of Protein Nanofibrils Orchestrates Calcite Step Movement through Selective Nonchiral Interactions
The recognition of atomically distinct surface features by adsorbed biomolecules is central to the formation of surface-templated peptide or protein nanostructures. On mineral surfaces such as calcite, biomolecular recognition of, and self-assembly on, distinct atomic kinks and steps could additionally orchestrate changes to the overall shape and symmetry of a bulk crystal. In this work, we show through <i>in situ</i> atomic force microscopy (AFM) experiments that an acidic 20 kDa cement protein from the barnacle <i>Megabalanus rosa</i> (MRCP20) binds specifically to step edge atoms on {101Ì…4} calcite surfaces, remains bound and further assembles over time to form one-dimensional nanofibrils. Protein nanofibrils are continuous and organized at the nanoscale, exhibiting striations with a period of ca. 45 nm. These fibrils, templated by surface steps of a preferred geometry, in turn selectively dissolve underlying calcite features displaying the same atomic arrangement. To demonstrate this, we expose the protein solution to bare and fibril-associated rhombohedral etch pits to reveal that nanofibrils accelerate only the movement of fibril-forming steps when compared to undecorated steps exposed to the same solution conditions. Calcite mineralized in the presence of MRCP20 results in asymmetric crystals defined by frustrated faces with shared mirror symmetry, suggesting a similar step-selective behavior by MRCP20 in crystal growth. As shown here, selective surface interactions with step edge atoms lead to a cooperative regime of calcite modification, where templated long-range protein nanostructures shape crystals
Imaging Active Surface Processes in Barnacle Adhesive Interfaces
Surface plasmon resonance
imaging (SPRI) and voltammetry were used
simultaneously to monitor <i>Amphibalanus (=Balanus) amphitrite</i> barnacles reattached and grown on gold-coated glass slides in artificial
seawater. Upon reattachment, SPRI revealed rapid surface adsorption
of material with a higher refractive index than seawater at the barnacle/gold
interface. Over longer time periods, SPRI also revealed secretory
activity around the perimeter of the barnacle along the seawater/gold
interface extending many millimeters beyond the barnacle and varying
in shape and region with time. Ex situ experiments using attenuated
total reflectance infrared (ATR-IR) spectroscopy confirmed that reattachment
of barnacles was accompanied by adsorption of protein to surfaces
on similar time scales as those in the SPRI experiments. Barnacles
were grown through multiple molting cycles. While the initial reattachment
region remained largely unchanged, SPRI revealed the formation of
sets of paired concentric rings having alternately darker/lighter
appearance (corresponding to lower and higher refractive indices,
respectively) at the barnacle/gold interface beneath the region of
new growth. Ex situ experiments coupling the SPRI imaging with optical
and FTIR microscopy revealed that the paired rings coincide with molt
cycles, with the brighter rings associated with regions enriched in
amide moieties. The brighter rings were located just beyond orifices
of cement ducts, consistent with delivery of amide-rich chemistry
from the ducts. The darker rings were associated with newly expanded
cuticle. In situ voltammetry using the SPRI gold substrate as the
working electrode revealed presence of redox active compounds (oxidation
potential approx 0.2 V vs Ag/AgCl) after barnacles were reattached
on surfaces. Redox activity persisted during the reattachment period.
The results reveal surface adsorption processes coupled to the complex
secretory and chemical activity under barnacles as they construct
their adhesive interfaces
Imaging Active Surface Processes in Barnacle Adhesive Interfaces
Surface plasmon resonance
imaging (SPRI) and voltammetry were used
simultaneously to monitor <i>Amphibalanus (=Balanus) amphitrite</i> barnacles reattached and grown on gold-coated glass slides in artificial
seawater. Upon reattachment, SPRI revealed rapid surface adsorption
of material with a higher refractive index than seawater at the barnacle/gold
interface. Over longer time periods, SPRI also revealed secretory
activity around the perimeter of the barnacle along the seawater/gold
interface extending many millimeters beyond the barnacle and varying
in shape and region with time. Ex situ experiments using attenuated
total reflectance infrared (ATR-IR) spectroscopy confirmed that reattachment
of barnacles was accompanied by adsorption of protein to surfaces
on similar time scales as those in the SPRI experiments. Barnacles
were grown through multiple molting cycles. While the initial reattachment
region remained largely unchanged, SPRI revealed the formation of
sets of paired concentric rings having alternately darker/lighter
appearance (corresponding to lower and higher refractive indices,
respectively) at the barnacle/gold interface beneath the region of
new growth. Ex situ experiments coupling the SPRI imaging with optical
and FTIR microscopy revealed that the paired rings coincide with molt
cycles, with the brighter rings associated with regions enriched in
amide moieties. The brighter rings were located just beyond orifices
of cement ducts, consistent with delivery of amide-rich chemistry
from the ducts. The darker rings were associated with newly expanded
cuticle. In situ voltammetry using the SPRI gold substrate as the
working electrode revealed presence of redox active compounds (oxidation
potential approx 0.2 V vs Ag/AgCl) after barnacles were reattached
on surfaces. Redox activity persisted during the reattachment period.
The results reveal surface adsorption processes coupled to the complex
secretory and chemical activity under barnacles as they construct
their adhesive interfaces