Pressure Dependence of 15N Chemical Shifts in Model Peptides Ac-Gly-Gly-X-Ala-NH2

Abstract

High pressure NMR spectroscopy has developed into an important tool for studying conformational equilibria of proteins in solution. We have studied the amide proton and nitrogen chemical shifts of the 20 canonical amino acids X in the random-coil model peptide Ac-Gly-Gly-X-Ala-NH2, in a pressure range from 0.1 to 200 MPa, at a proton resonance frequency of 800 MHz. The obtained data allowed the determination of first and second order pressure coefficients with high accuracy at 283 K and pH 6.7. The mean first and second order pressure coefficients <B115N> and <B215N> for nitrogen are 2.91 ppm/GPa and −2.32 ppm/GPa2, respectively. The corresponding values <B11H> and <B21H> for the amide protons are 0.52 ppm/GPa and −0.41 ppm/GPa2. Residual dependent 1J1H15N-coupling constants are shown.

Impact of Hydrostatic Pressure on an Intrinsically Disordered Protein: A High‐Pressure NMR Study of α‐Synuclein

“…The change in the 15 N spin relaxation was also investigated through R 1ρ measurements. While the pressure-induced 1 H N shifts are in close agreement with those predicted for model tetrapeptides [33] and can reasonably be explained in terms of hydrogen bond compression, additional long-range factors are likely affecting the observed 15 N pressure-induced shifts. Analysis of the 13 C chemical shifts and 3 J HN-Hα couplings of α-synuclein suggests that pressure shifts the PPII-β equilibrium of the random coil towards increased PPII propensity.…”

Distinct Conformational States of the Alzheimer β‐Amyloid Peptide Can Be Detected by High‐Pressure NMR Spectroscopy

“…Before fitting, the data were corrected for the pressure dependence of random-coil shifts. [20] The deviation Dd from temperature-and pressure-corrected chemical shifts [23] was plotted as function of the pressure for a) 1 …”

“…Importantly, the observed pressure-induced chemical shift changes are completely reversible. In order to remove unspecific pressure effects occurring in random-coil structures, the corresponding pressure-dependent shift changes of random-coil model peptides [20] were always subtracted from the experimental data. Thus a random-coil structure would be characterized by vanishing pressure effects.…”

The Chemical Shift Baseline for High‐Pressure NMR Spectra of Proteins

“…Remarkably, the experimental 1 H, 13 C, and 15 N NMA slopes (0.011, 0.048, and 0.53 ppm kbar À1 ) are in the same range as the values found earlier for random coil peptides. The average values (in ppm kbar À1 ) are 0.038 [15] and 0.052 [16] for 1 H, 0.062 [17] for 13 C, and 0.29 [16] for 15 N, but show a large spread dependent on the type of amino acid studied. In proteins individual amino acids can show very different B 1 and B 2 values since they are also influenced by global conformational transitions.…”