High-resolution dual-trap optical tweezers with differential detection: managing environmental noise.

Optical traps or "optical tweezers" have become an indispensable tool in understanding fundamental biological processes. The ability to manipulate and probe individual molecules or molecular complexes has led to a new, more refined understanding of the mechanical properties of the fundamental building blocks of the cell, and of the mechanism by which molecular machines function. The minimization and management of noise are the keys to building a high-resolution optical tweezers. The high degree of stability needed to observe angstrom motions of a biological system places rather stringent requirements on the environment in which the instrument operates. Specifically, environmental noise is a concern when it leads to differential movements of the optical trap relative to the second attachment point of the tether. In this article, we discuss what entails a quiet environment--what sources of noise are relevant and how they affect the instrument--and provide guidelines for choosing an appropriate location for a high-resolution instrument.