Revealing Fast Structural Dynamics in pH-Responsive Peptides with Time-Resolved X-ray Scattering

Abstract

Many biomaterials can adapt to changes in the local biological environment (such as pH, temperature, or ionic composition) in order to regulate function or deliver a payload. Such adaptation to environmental perturbation is typically a hierarchical process that begins with a response at a local structural level and then propagates to supramolecular and macromolecular scales. Understanding fast structural dynamics that occur upon perturbation is important for rational design of functional biomaterials. However, few nanosecond time-resolved methods can probe both intra- and intermolecular scales simultaneously with a high structural resolution. Here, we utilize time-resolved X-ray scattering to probe nanosecond to microsecond structural dynamics of poly-L-glutamic acid undergoing protonation via a pH jump initiated by photoexcitation of a photoacid. Our results provide insights into the protonation-induced hierarchical changes in packing of peptide chains, formation of a helical structure, and the associated collapse of the peptide chain.

Temperature-jump solution X-ray scattering reveals distinct motions in a dynamic enzyme

“…[13][14][15][16][17][18] ). Unfortunately, the number of proteins that undergo specific photochemistry as part of their functional cycle is small, and there is a fundamental need to develop generalized methods that can be used to synchronously excite conformational transitions in any protein molecule and expand the utility of time-resolved structural experiments [19][20][21][22][23][24][25][26][27] .…”

Resolving Dynamics in the Ensemble: Finding Paths through Intermediate States and Disordered Protein Structures

“…Transient pH-jump IR spectroscopy studies have shown more transient conformational states of PGA with larger PGA systems . A pH-jump TRXSS experiment showed a transient charged intermediate in the longest (200-residue) PGA . Both studies point toward a nucleation-propagation folding mechanism, triggered by a sudden pH decrease.…”

“…70 A pH-jump TRXSS experiment showed a transient charged intermediate in the longest (200residue) PGA. 51 Both studies point toward a nucleationpropagation folding mechanism, triggered by a sudden pH decrease.…”

“…Molecular dynamics (MD) simulations offer an atomic-level description but are unsuitable for slower dynamical processes as a result of the computational cost and complexity (Figure ). − ,,,− Structurally heterogeneous proteins like IDPs and proteins with IDRs are dynamic at the same time which can intrinsically sample a multitude of diverse structures, thus providing a robust data set for testing structural refinement methodologies and kinetic pathway sampling using time-resolved techniques with molecular models.…”

“…Time scales for protein dynamics grouped by technique. − ,,,− Relevant protein time scales are plotted vs the number of residues for the system of interest for studies done using MD (purple), TRXSS (green), IR (blue), and trp-fluorescence (orange). MD studies are primarily located around smaller proteins and shorter time scales.…”