UV-CD12 beamline

UV-CD12 is a high flux vacuum ultraviolet/ultraviolet beamline for steady-state and time-resolved synchrotron radiation circular dichroism (SRCD). SRCD can be used to investigate secondary structure of proteins and other macromolecules.

The high flux and wide wavelength range of the synchrotron radiation allows a wide range of experiments, for example:

Determination of secondary structure of proteins that cannot be crystallised.
Investigation of the effects of the binding of ligands (e.g. drugs) on protein secondary structure.
Study of dynamic processes such as protein folding.
Studies of the effects of crystallisation media on protein structure.
Determination of the secondary structure content of membrane proteins.
Study of enzyme active site changes.
Investigation of carbohydrate structure

The UV-CD12 beamline was conceived and designed by the Centre for Protein and Membrane Structure and Dynamics (CPMSD), a consortium of U.K. structural biologists. It was constructed at the SRS synchrotron facility of the Daresbury Laboratory and opened for users in 2003. Following the closure of SRS in August 2008, UV-CD12 was donated to ANKA in order to continue its working life.

ANKA is proud to have been selected to receive UV-CD12 against strong international competition, and gratefully acknowledges the U.K. Science and Technology Facilities Council for the gift of this excellent beamline.

The CD12 team

Jochen Bürck	jochen buerck ∂does-not-exist.kit edu	+49 721 608 22690
Siegmar Roth

UV-CD12 beamline

In the original UV-CD12 design at Daresbury, a plane mirror 4.1 m from the source deflects the beam vertically upwards through the storage ring roof into an experimental cabin on the upper floor. Here the beam enters the monochromator from below and is reflected back to the horizontal by the toroidal grating located 3 m above the ring plane. ANKA has no upper floor, but a near duplication of the layout could be achieved by shortening the vertical arm of the optical path to 1.2 m and lengthening the horizontal arm to 5.9 m. This brings the experimental hutch down to elevated ground floor level while preserving the 7.1 m total focus distance from source to toroidal grating. At the same time, the 45% increased distance from source to extraction mirror compensates for the additional heat load caused by ANKA’s higher electron beam energy (2.5 versus 2.0 GeV).

Characteristics

source	1.5 T Bending magnet (E_c= 6 keV)
beam divergence	30.8 mrad (horz) x 3.7 mrad (vert)
optics	planar water-cooled mirror, Al-coated silicon toroidal holographic grating, Al-coated silica
photon flux	∼ 10¹² photon/s/nm bandwidth at 200 nm
wavelength range	130 – 340 nm
energy range	3.6 – 9.5 eV
wavelength resolution	0.5 to 2.0 nm
photoelastic modulator	CaF₂, 50 kHz (Hinds Instruments PEM-90)
detector	electron tubes 9406B or solar blind PM (ET 9402B)