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Editorial |
Department of Pathology and Laboratory Medicine, University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104, fax 215-662-7529, e-mail larry kricka@path1a.med.upenn.edu
Our scientific ancestors who advanced the atomic and molecular theories of matter and the cellular basis of biological organisms would be astounded by our current ability to visualize and manipulate atoms, molecules, and cells. The new techniques of atomic force microscopy (AFM; or scanning force microscopy) (1)(2)(3)(4) and optical trapping (optical or laser tweezers) (5)(6) have allowed us to locate individual atoms and molecules on surfaces and to manipulate cells directly. In this issue Helmerson et al. (7) report one of the first studies that uses laser tweezers to detect the binding of an antigen to an immobilized antibody and applies this technique in a competitive immunoassay to determine antigen concentration.
In immunoassay, attempts to detect individual or a few antigen or antibody molecules have relied on labeling one component of the reaction with a high-specific-activity label or a label that can participate in an amplification reaction (e.g., enzymes, DNA) (8). Now the presence of a component of a ligand:binder pair can be sensed directly by using the laser-based technique of optical tweezers.
The principle of optical
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