Synchrotron radiation circular dichroism (SRCD) at ANKA: new prospects for structural biology and biomedical research

Author(s): Jochen Bürck, Siegmar Roth, David Moss, Anne. S. Ulrich

Institution: Institute for Biological Interfaces (IBG-2), SRCD research group at ANKA Synchrotron Light Source, Karlsruhe Institute of Technology (KIT)

Contact data of speaker: jochen.buerck@kit.edu

In life sciences synchrotrons are generally thought of in conjunction with X-ray techniques, but synchrotron radiation-based circular dichroism (SRCD) is beginning to play a valuable role in structural biology and biomedical research as a complementary method. SRCD can provide (i) dynamic and static structural information that supplements the structural information from crystallography and NMR, it can reveal (ii) information on the secondary structures of proteins that cannot be crystallized or resolved by NMR, and it is (iii) the last resort for characterizing precious proteins that are available only in small amounts. During the last decade SRCD is a rapidly growing technique for structure analysis especially of membrane proteins, carbohydrates and other biomaterials with currently 13 beamlines in operation worldwide [1].

UV-CD12, a high flux beamline for steady-state and time-resolved SRCD measurements, has been installed at the ANKA synchrotron in 2010 and covers the VUV to near-UV spectral range. Originally, this beamline had been 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 was open for users since 2003. Following the closure of SRS in August 2008, the relatively new beamline was transferred to Karlsruhe and is now operated by the IBG-2 to continue its working life. Dedicated to structural biology research of biomacromolecules, UV-CD12 has become active again in August 2011 for the community.

Details on the main beamline components of UV-CD12 and its experimental set-up at ANKA will be given. Examples for future applications of SRCD in structure biology research, e.g., for secondary structure and orientational analysis of membrane-active antimicrobial and cell-penetrating peptides as well as for integral membrane proteins (PDGFβ-receptor, TatA translocase) will be presented. A special focus lies on the new method of synchrotron-based oriented circular dichroism (OCD) in macroscopically aligned protein / membrane samples. This OCD method is complementary to oriented solid-state NMR structure analysis of membrane proteins and uses the same type of aligned samples. Solid-state NMR has been well established at the institute and can provide quasi-atomic resolution on the molecules of interest, provided that they are selectively labeled with NMR-active isotopes.

[1] B.A. Wallace, Protein characterization by synchrotron radiation circular dichroism spectroscopy, Quarterly Reviews of Biophysics 42, 4 (2009) 317–370, Cambridge University Press.