Ultraviolet circular dichroism of polyproline and oriented collagen

The ultraviolet absorption, linear dichroism, circular dichroism, and oriented circular dichroism of collagen are reported and the spectra are resolved into a self‐consistent set of bands in accord with exciton theory. The parallel band at 200 nm has 40% of the π → π* intensity; the perpendicular band is placed at 189 nm yielding a splitting of 2700 cm −1 . The circular dichroism is resolved into two Gaussians at λ ∥ and λ τ (rotational strengths +14 × 10 −40 and −32 × 10 −40 esu 2 . cm 2 ) plus a large non‐Gaussian (“helix”) band with ampplitude −25,000° at 201 nm. These data appear to be in reasonably good accord with recent calculations. Measurements of the absorption, linear dichroism and circular dichroism of polyproline I and II are also reported and are resolved into their component bands. Polyproline I is in good accord with exciton theory, whereas polyproline II remains unsatisfactory.