Ultrafast Reorientational Dynamics of Leucine at the Air-Water Interface

TY - JOUR

T1 - Ultrafast Reorientational Dynamics of Leucine at the Air-Water Interface

AU - Donovan, Michael A

AU - Yimer, Yeneneh Y

AU - Pfaendtner, Jim

AU - Backus, Ellen H G

AU - Bonn, Mischa

AU - Weidner, Tobias

PY - 2016

Y1 - 2016

N2 - Ultrafast dynamics of protein side chains are involved in important biological processes such as ligand binding, protein folding, and hydration. In addition, the dynamics of a side chain can report on local environments within proteins. While protein side chain dynamics have been probed for proteins in solution with nuclear magnetic resonance and infrared methods for decades, information about side chain dynamics at interfaces is lacking. At the same time, the dynamics and motions of side chains can be particularly important for interfacial binding and protein-driven surface manipulation. We here demonstrate that ultrafast reorientation dynamics of leucine amino acids at interfaces can be recorded in situ and in real time using polarization- and time-resolved pump-probe sum frequency generation (SFG). Combined with molecular dynamics simulations, time-resolved SFG was used to probe the reorientation of the isopropyl methyl groups of l-leucine at the air-water interface. The data show that the methyl units reorient diffusively at an in plane rate of D= 0.07 rad 2/ps and an out of plane rate of D θ = 0.05 rad 2/ps.

AB - Ultrafast dynamics of protein side chains are involved in important biological processes such as ligand binding, protein folding, and hydration. In addition, the dynamics of a side chain can report on local environments within proteins. While protein side chain dynamics have been probed for proteins in solution with nuclear magnetic resonance and infrared methods for decades, information about side chain dynamics at interfaces is lacking. At the same time, the dynamics and motions of side chains can be particularly important for interfacial binding and protein-driven surface manipulation. We here demonstrate that ultrafast reorientation dynamics of leucine amino acids at interfaces can be recorded in situ and in real time using polarization- and time-resolved pump-probe sum frequency generation (SFG). Combined with molecular dynamics simulations, time-resolved SFG was used to probe the reorientation of the isopropyl methyl groups of l-leucine at the air-water interface. The data show that the methyl units reorient diffusively at an in plane rate of D= 0.07 rad 2/ps and an out of plane rate of D θ = 0.05 rad 2/ps.

KW - Journal Article

UR - http://www.scopus.com/inward/record.url?scp=84966359140&partnerID=8YFLogxK

U2 - 10.1021/jacs.6b01878

DO - 10.1021/jacs.6b01878

M3 - Journal article

C2 - 27057584

SN - 0002-7863

VL - 138

SP - 5226

EP - 5229

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 16

ER -