title: Protein hydrophobic collapse and early folding steps observed in a microfluidic mixer.
abstract: We demonstrate that the sub-millisecond protein folding process referred to as "collapse" actually consists of at least two separate processes. We observe the UV fluorescence spectrum from naturally occurring tryptophans in three well-studied proteins, cytochrome c, apomyoglobin, and lysozyme, as a function of time in a microfluidic mixer with a dead time of approximately 20 mus. Single value decomposition of the time-dependent spectra reveal two separate processes: 1), a spectral shift which occurs within the mixing time; and 2), a fluorescence decay occurring between approximately 100 and 300 micros. We attribute the first process to hydrophobic collapse and the second process to the formation of the first native tertiary contacts.
authors.affiliation: Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, USA. lapidus@msu.edu
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Lapidus
authors.forename: Shuhuai
authors.initials: S
authors.lastname: Yao
authors.forename: Kimberly S
authors.initials: KS
authors.lastname: McGarrity
authors.forename: David E
authors.initials: DE
authors.lastname: Hertzog
authors.forename: Emily
authors.initials: E
authors.lastname: Tubman
authors.forename: Olgica
authors.initials: O
authors.lastname: Bakajin
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D011506:Proteins