Year: 2025
Type: preprint
Abstract: Removing solvent abolishes the hydrophobic effect, yet many proteins temporarily retain a native-like structure in the gas phase. This raises a central question: what mechanisms suppress protein denaturation in the absence of solvent? Here, we integrate tandem-trapped ion mobility spectrometry/tandem-mass spec-trometry (Tandem-TIMS) and molecular dynamics-based structure relaxation approximation (SRA) to dis-sect the unfolding of myoglobin in the absence of solvent. Experimental and computed ion mobility spec-tra agree across charge states and activation regimes, validating our integrated approach. We find that key features of myoglobin, including the hydrophobic core and noncovalent heme coordination, are metastable in the solvent-free, native-like state. Native-like myoglobin unfolds in two sequential steps: an initial coop-erative melting that disrupts native contacts yet maintains compactness through non-local salt bridges, fol-lowed by an expansion driven by gains in configurational entropy as salt-bridge networks reorganize. Our results suggest that proteins retain a native-like structure in the gas phase due to cooperative metastability: networks of non-local interactions kinetically constrain the native-like state by tethering structural elements so that disrupting native contacts in one element requires coordinated disruptions in others. Cooperative metastability provides a mechanistic framework for assessing which solvent-dependent features of protein structure persist in the gas phase and which do not, and suggests that components of a solvent-free protein that are not effectively coupled to one another may unfold independently.
Source: ChemRxiv
Institution: Florida State University
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W4415000898