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Graphical method for force analysis: Macromolecular mechanics with atomic force microscopy
Author(s) -
Qian Hong,
Shapiro Bruce E.
Publication year - 1999
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/(sici)1097-0134(19991201)37:4<576::aid-prot8>3.0.co;2-o
Subject(s) - energy landscape , atomic force microscopy , intermolecular force , stiffness , macromolecule , titin , chemical physics , nanotechnology , statistical physics , chemistry , classical mechanics , materials science , physics , molecule , thermodynamics , quantum mechanics , sarcomere , medicine , biochemistry , myocyte , endocrinology
We present a graphical method for a unifying, quantitative analysis of molecular bonding‐force measurements by atomic force microscopy (AFM). The method is applied to interpreting a range of phenomena commonly observed in the experimental AFM measurements of noncovalent, weak bonds between biological macromolecules. The analysis suggests an energy landscape underlying the intermolecular force and demonstrates that many observations, such as “snaps‐on,” “jumps‐off,” and hysteresis loops, are different manifestations of a double‐well energy landscape. The analysis gives concrete definitions for the operationally defined “attractive” and “adhesive” forces in terms of molecular parameters. It is shown that these operationally defined quantities are usually functions of the experimental setup, such as the stiffness of the force probe and the rate of its movement. The analysis reveals a mechanical instability due to the multistate nature of molecular interactions and provides new insight into macromolecular viscosity. The graphical method can equally be applied to a quantitative analysis of multiple unfolding of subunits of the giant muscle protein titin under AFM. Proteins 1999;37:576–581. ©1999 Wiley‐Liss, Inc.