  Atomic-resolution-imaging approaches for single molecules, such as coherent
x-ray diffraction at free-electron lasers, require the delivery of high-density
beams of identical molecules. However, even very cold beams of biomolecules
typically have multiple conformational states populated. We demonstrate the
production of very cold ($T_\text{rot}\sim2.3~\text{K}$) molecular beams of
intact dipeptide molecules, which we then spatially separate into the
individual populated conformational states. This is achieved using the
combination of supersonic expansion laser-desorption vaporisation with
electrostatic deflection in strong inhomogeneous fields. This represents the
first demonstration of a conformer-separated and rotationally-cold molecular
beam of a peptide, and will enable future single biomolecule x-ray diffraction
measurements.
