Laser-induced temperature jump/time-resolved infrared study of the fast events in protein folding

Conference · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:370599

Woodruff, W H; Dyer, R B; Williams, S ^[1]; Callender, H; Gilmanshin, R ^[2]

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1. Los Alamos National Laboratory, NM (United States)
2. CUNY, NY (United States)

Laser-induced temperature jump followed by time-resolved infrared probe of reaction dynamics are used to study the temporal evolution of polypeptide structure during protein folding and unfolding. Reactions are initiated in times of 50 ps or longer by T-jumps of 10`s of degrees, obtained by laser excitation of water overtone absorbances. Observation of the Amide I transient absorbances reveal melting lifetimes of helices unconstrained by tertiary structure to be ca. 160 ns in a model 21-peptide and ca. 30 ns in {open_quotes}molten globule{close_quotes} apomyoglobin. No other processes are observed in these systems over the timescale 50 ps to 2 ms. Equilibrium data suggest the corresponding helix formation lifetimes to be ca. 16 and 1 ns, respectively. In {open_quotes}native{close_quotes} apomyoglobin two helix melting lifetimes are observed and we infer that a third occurs on a timescale inaccessible to our experiment (> 1 ms). The shorter observed lifetime, as in the molten globule, is ca. 30 ns. The longer lifetime is ca. 70 {mu}s. We suggest that the slower process is helix melting that is rate-limited by the unfolding of tertiary structure. Equilibrium data suggest a lifetime of ca. 1 {mu}s for the development of these tertiary folds.

• OSTI ID: 370599
• Report Number(s): CONF-960376--
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
EXCITATION
MELTING
MOLECULAR STRUCTURE
POLYPEPTIDES
PROTEINS