Supporting Information
Interfacial pH during mussel adhesive plaque
formation
Nadine R. Martinez Rodrigueza, Saurabh Dasb, Yair Kaufmanb, Jacob N. Israelachvilib,c,1 and
J. Herbert Waitea,b,1
a
Department of Molecular, Cellular, and Developmental Biology, University of California
Santa Barbara, CA 93106, USA; bMaterials Research Laboratory, University of California,
Santa Barbara, California 93106, USA and cDepartment of Chemical Engineering, University
of California Santa Barbara, CA 93106, USA
1
Corresponding authors:
Email: jacob@engineering.ucsb.edu, Phone: (805) 893-8407, Fax: (805) 893-7870.
Email: waite@lifesci.ucsb.edu, Phone: (805) 893-2817.
Keywords: Dopa, mussel interfacial pH, pH sensitive surface, Oregon Green 488 DHPE
This document contains:
Methods, model parameter, supporting figures, supporting video description
Supplementary Figure S1. (a) Schematic model fluorophore (Oregon Green® 488
DHPE/DMPC, 1 mol% of total lipid composition) lipid bi-layer on a mica surface. (b)
Schematic model of lipid bi-layer on mica depicting the depth of a hole. (c) AFM image and
cross-section profile (across red line) of lipid bi-layer on mica. (d) At pH below the pKa, the
carboxyl residue in Oregon Green 488 spontaneously esterifies to a non-fluorescent lactone.
Supplementary Figure S2. Representative images of a randomly selected area within the
plaque substrate interface (A = 1.6 x 10
-6
µm2) of the lipid bi-layer was imaged for
fluorescence intensity while decreasing the pH of the buffer systematically from pH 7.7 to
2.7 (Panel a-e) in the first cycle. A small area (A = 1.4 x 10
-3
µm2) was bleached for 10
seconds (white arrow in panel a-e).
Supplementary Figure S3. Normalized fluorescence intensity of an adhesive plaque on
Oregon Green 488 DHPE/DMPC mica surface with decreasing bulk pH. The pH of the bulk
solution was decreased from a resting pH of 8.2 to 2.6. The intensity was measured at the
interface of the plaque after equilibrating with each buffer change at 5 minutes. The intensity
of the plaque/surface interface decreased up to pH 6; however, the fluorescence intensity of
the plaque/surface interface increased on decreasing the pH below 5, due to chemical
maturation of the plaque at low pH.3 Representative fluorescent images (panel (a-d)) of the
plaque surface interface under different bulk pH conditions and has been indicated on the
plot of I vs pH.
Supplementary Figure S4. Normalized intrinsic fluorescence of plaque after disengagement
from a mica surface (No Oregon Green 488 DHPE/DMPC). Figures (a) and (b) are the
fluorescent images. Figures (c) and (d) are the transmitted images.
Supplementary Figure S5. Mussels set-up. Mussels were glued onto an Oregon Green 488
DHPE/DMPC modified mica surface using epoxy glue.
Supporting video description
Mussel plaque formation
Juvenile Mytilus californianus mussel depositing an adhesive plaque onto a glass surface
magnified 40x. An inverted microscope was used to image the underside of the distal
depression during plaque formation.
References
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(6), 1632-1633.
3.
Rzepecki, L.; Waite, J. Molecular marine biology and biotechnology 1993, 2 (5),
255-266.