A CD spectrum with broad minimum at 211 nm suggests:
Far-ultraviolet CD profiles distinguish secondary elements. Alpha-helix shows twin minima at 208 and 222 nanometers with large positive near 193 nanometers. Random coil exhibits strong negative near 195 nanometers. Beta-sheet, composed of extended strands forming twisted pleats, produces broader weaker negative band centered around 211 to 218 nanometers and positive band near 195 nanometers. A spectrum dominated by broad minimum at 211 nanometers with reduced helical signals suggests substantial beta-sheet content, observed in amyloid or beta-rich proteins under native conditions.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.