The mechanical response of biological molecules at the microscopic level contributes significantly to their function.
Optical tweezers are instruments that enable scientists to study mechanical properties at microscopic levels. They are
based on a highly focused laser beam that creates a trap for microscopic objects such as dielectric spheres, viruses,
bacteria, living cells and organelles, and then manipulates them by applying forces in the picoNewton range (a range that
is biologically relevant). In this work, mechanical properties of single collagen molecules are studied using optical
tweezers. We discuss the challenges of stretching single collagen proteins, whose length is much less than the size of the
microspheres used as manipulation handles, and show how instrumental design and biochemistry can be used to
overcome these challenges.