Measuring molecular elasticity by atomic force microscope cantilever fluctuations.
In single-molecule mechanics experiments the molecular elasticity is usually measured from the deformation in response to a controlled applied force, e.g., via an atomic force microscope cantilever. We have tested the validity of an alternative method based on a recently developed theory. The concept is to measure the change in thermal fluctuations of the cantilever tip with and without its coupling to a rigid surface via the molecule. The new method was demonstrated by its application to the elasticity measurements of L- and P-selectin complexed with P-selectin glycoprotein ligand-1 or their respective antibodies, which showed values comparable to those measured from the slope of the force-extension curve. L- and P-selectin were found to behave as nearly linear springs capable of sustaining large forces and strains without sudden unfolding. The measured spring constants of approximately 4 and approximately 1 pN/nm for L- and P-selectin, respectively, suggest that a physiological force of approximately 100 pN would result in an approximately 200% strain for the respective selectins.
Marshall
Bryan T
BT
George W. Woodruff School of Mechanical Engineering, and Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0363, USA.
Sarangapani
Krishna K
KK
Wu
Jianhua
J
Lawrence
Michael B
MB
McEver
Rodger P
RP
Zhu
Cheng
C
D002138:Calibration; D003627:Data Interpretation, Statistical; D004548:Elasticity; D006358:Hot Temperature; D006801:Humans; D019041:L-Selectin / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods*; D015233:Models, Statistical; D019007:P-Selectin / Q000378:metabolism; D011094:Polyethyleneimine / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D012107:Research Design; D019087:Selectins; D013314:Stress, Mechanical; D013997:Time Factors
D008051:Lipid Bilayers; D019007:P-Selectin; D011108:Polymers; D019087:Selectins; D019041:L-Selectin; D011094:Polyethyleneimine