{"doi":"10.1039/d1sc06562a","title":"Direct observation of peptide hydrogel self-assembly","abstract":"The characterization of self-assembling molecules presents significant experimental challenges, especially when associated with phase separation or precipitation. Transparent window infrared (IR) spectroscopy leverages site-specific probes that absorb in the \"transparent window\" region of the biomolecular IR spectrum. Carbon-deuterium (C-D) bonds are especially compelling transparent window probes since they are non-perturbative, can be readily introduced site selectively into peptides and proteins, and their stretch frequencies are sensitive to changes in the local molecular environment. Importantly, IR spectroscopy can be applied to a wide range of molecular samples regardless of solubility or physical state, making it an ideal technique for addressing the solubility challenges presented by self-assembling molecules. Here, we present the first continuous observation of transparent window probes following stopped-flow initiation. To demonstrate utility in a self-assembling system, we selected the MAX1 peptide hydrogel, a biocompatible material that has significant promise for use in drug delivery and medical applications. C-D labeled valine was synthetically introduced into five distinct positions of the twenty-residue MAX1 β-hairpin peptide. Consistent with current structural models, steady-state IR absorption frequencies and linewidths of C-D bonds at all labeled positions indicate that these side chains occupy a hydrophobic region of the hydrogel and that the motion of side chains located in the middle of the hairpin is more restricted than those located on the hairpin ends. Following a rapid change in ionic strength to initiate self-assembly, the peptide absorption spectra were monitored as function of time, allowing determination of site-specific time constants. We find that within the experimental resolution, MAX1 self-assembly occurs as a cooperative process. These studies suggest that stopped-flow transparent window FTIR can be extended to other time-resolved applications, such as protein folding and enzyme kinetics.","journal":"Chemical Science","year":2022,"id":255614,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":20,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9583,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":582934,"name":"Erika Olson","orcid":null,"position":1,"is_corresponding":false},{"id":293982,"name":"Tania L. Lopez‐Silva","orcid":"0000-0002-0537-9393","position":2,"is_corresponding":false},{"id":833474,"name":"Zhengwen Lian","orcid":null,"position":3,"is_corresponding":false},{"id":904445,"name":"Audrey Y. Kim","orcid":null,"position":4,"is_corresponding":false},{"id":833141,"name":"Matthew Holcomb","orcid":"0000-0002-8409-4344","position":5,"is_corresponding":false},{"id":833142,"name":"Jörg Zimmermann","orcid":"0000-0002-1210-9471","position":6,"is_corresponding":false},{"id":833143,"name":"Ramkrishna Adhikary","orcid":"0000-0003-0569-7890","position":7,"is_corresponding":false},{"id":342712,"name":"Philip E. Dawson","orcid":"0000-0002-2538-603X","position":8,"is_corresponding":false},{"id":833140,"name":"Zoë C. Adams","orcid":"0000-0001-6459-4264","position":0,"is_corresponding":true}],"reference_count":66,"raw_metadata":null,"created_at":"2026-07-19T00:25:17.224217Z","pmid":"36128231","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}