{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T12:01:00Z","timestamp":1790164860424,"version":"4.1.0"},"reference-count":52,"publisher":"AIP Publishing","issue":"12","license":[{"start":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T00:00:00Z","timestamp":1790121600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["EXC 2033 - 390677874 - RESOLV"],"award-info":[{"award-number":["EXC 2033 - 390677874 - RESOLV"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["278162697 - SFB 1242 - A06"],"award-info":[{"award-number":["278162697 - SFB 1242 - A06"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,9,28]]},"abstract":"<jats:p>Protein behavior at aqueous interfaces is central to many soft-matter, biological, and technological systems, yet the molecular events underlying adsorption-induced structural change remain difficult to isolate. In particular, macroscopic measurements such as surface tension cannot directly reveal how proteins reorganize during interfacial adsorption. In this study, we report a time-resolved vibrational sum-frequency generation (VSFG) spectroscopy study of lysozyme adsorption and unfolding at the air\/water interface, combined with simultaneous surface-tension measurements. By monitoring the interfacial CH-stretch response after subsurface protein injection, we directly correlate macroscopic changes in surface pressure with molecular restructuring of adsorbed lysozyme. During the first \u223c10\u00a0min\u00a0after injection, the surface tension remains essentially unchanged and no lysozyme CH resonance is detected. Together with the much shorter diffusion-only estimate, this argues against assigning the full induction period to bulk transport alone. The subsequent decrease in surface tension is accompanied by a rapid increase in the interfacial CH response, indicating adsorption-induced unfolding and exposure of hydrophobic moieties toward the vapor phase. After \u223c30\u00a0min, the CH response saturates while the surface tension continues to evolve, revealing an additional kinetic regime associated with interfacial crowding, protein\u2013protein interactions, and multilayer formation. Amide I VSFG spectra further show that interfacial lysozyme retains partial secondary structure, with enhanced beta-sheet contributions relative to the bulk solution. These results demonstrate how interface-selective nonlinear vibrational spectroscopy can resolve molecular kinetic steps that are hidden in surface-tension measurements alone, providing a detailed picture of protein structural dynamics at aqueous interfaces.<\/jats:p>","DOI":"10.1063\/5.0350259","type":"journal-article","created":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T11:12:23Z","timestamp":1790161943000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Molecular kinetics of protein unfolding at the air\/water interface probed by vibrational sum-frequency spectroscopy"],"prefix":"10.1063","volume":"165","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4084-7711","authenticated-orcid":false,"given":"Yujin","family":"Tong","sequence":"first","affiliation":[{"name":"Faculty of Physics, University of Duisburg-Essen , Lotharstr. 1, 47057 Duisburg,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7091-2991","authenticated-orcid":false,"given":"R. Kramer","family":"Campen","sequence":"additional","affiliation":[{"name":"Faculty of Physics, University of Duisburg-Essen , Lotharstr. 1, 47057 Duisburg,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2026,9,23]]},"reference":[{"key":"2026092307103096800_c1","volume-title":"Proteins at Liquid Interfaces","author":"M\u00f6bius","year":"1998"},{"key":"2026092307103096800_c2","doi-asserted-by":"publisher","first-page":"1657","DOI":"10.1126\/science.1069893","article-title":"Making a network of hydrophobic clusters","volume":"295","year":"2002","journal-title":"Science"},{"key":"2026092307103096800_c3","article-title":"Lysozyme","volume-title":"Encyclopedia of Life Sciences","year":"2001"},{"key":"2026092307103096800_c4","doi-asserted-by":"publisher","first-page":"3279","DOI":"10.1039\/a805731a","article-title":"Structural conformation of lysozyme layers at the air\/water interface studied by neutron reflection","volume":"94","year":"1998","journal-title":"J.\u00a0Chem. 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