SOLID-STATE NMR CONSTRAINTS ON MOLECULAR ORGANIZATION WITHIN MAX8
DESIGNER PEPTIDE NANOFIBERS
Sarah R. Leonard1,2, Maxwell I. Zimmerman1,2, Xiaodong Pang3, Huan-Xiang Zhou3,
Anant K. Paravastu1,2
1
Department of Chemical and Biomedical Engineering, Florida State University, 2525 Pottsdamer
Street, Tallahassee, FL 32310 USA
2
National High Magnetic Field Laboratory, Florida State University, 1800 E Paul Dirac Dr,
Tallahassee, FL 32310
3
Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL
32306
MAX8, a designer peptide known to undergo self-assembly following changes in temperature, pH, and
ionic strength, has demonstrated utility for tissue engineering and drug delivery. Here, we report evidence
from solid-state NMR spectroscopy that supports the presence of the hypothesized β-hairpin
conformation and constrains the arrangement of MAX8 molecules within nanofibers. Specifically, 13C13
C 2-dimensional correlation spectroscopy indicates spatial proximity between V3 and K17 residues, and
13
C-13C dipolar coupling measurements reveal proximity between the V3 and V18 backbone carbonyls.
Moreover, isotopic dilution of labeled MAX8 nanofibers did not result in a loss of the 13C-13C dipolar
couplings, showing that these couplings are primarily intramolecular. Additional MAX8 samples were
synthesized to differentiate between two possible arrangements of MAX8 molecules: 1) the “syn”
configuration, with all β-hairpin hinges aligned along the same edge of the β-sheet, and 2) the “anti”
configuration, with alternating β-hairpin hinges aligned along opposite edges of the β-sheet. 13C-13C
dipolar coupling measurements indicate weak interactions between neighboring V5 backbone carbonyls,
consistent with the syn configuration. Intermolecular 15N-13C dipole-dipole couplings indicate spatial
proximity between the V5 backbone carbonyl and the V16 backbone nitrogen, also consistent with the
syn configuration. A lack of contact between the V3 and T12 residues with 13C-13C 2-dimensional
correlation spectroscopy is indicative of a syn-parallel between-sheet conformation with all β-hairpin
hinges aligned along the same edge of the stacked β-sheet. Combined, these results led to the
development of an all-atom molecular model of MAX8 nanofibers consistent with current NMR
experimental constraints.
8|Page