A Novel Method for Measuring the Optical Activity of Biopolymers and Application in Measuring Denaturation of Type I Collagen

Optical Activity is defined as a property, in which a substance will absorb incident (optical) radiation and / or change its polarization state. Molecules of this type are known as chiral (its mirror image cannot be superimposed upon itself i.e. the molecule has a handedness). Optical Rotatory Dispersion (circular birefringence) occurs when a material exhibits a difference in its index for right-handed (n_R) or left-handed (n_L) circularly polarized light. In terms of the indices of refraction, the observed rotation is defined as: α = (πd/λ_o) (n_L − n_R). Where: n_L = index of refraction for left-handed polarization; n_R = index of refraction for right-handed polarization; d = path length (sample thickness); λ_o = wavelength of incident radiation measured in vacuum. We have developed and tested a new instrument that measures the optical rotatory properties of biopolymers. The advantage of this instrument is that it allows a real time measurement of the optical activity of biopolymers; which can be used to monitor samples for changes of state. By using a differential measurement scheme, system errors are minimized and resolution is increased over current measurement techniques. A study of the denaturation process of type I collagen will be presented.