E. Lazoura M.J. McLeish M.-I. Aguilar Authors’ affiliations: E. Lazoura and M.-I. Aguilar, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia. M.J. McLeish, Department of Medicinal Chemistry, Victorian College of Pharmacy, Monash University, Parkville, Victoria, Australia; present address: College of Pharmacy, University of Michigan, 428 Church Street, Ann Arbor, MI 48109-1065, USA. Correspondence to: M.-I. Aguilar Department of Biochemistry and Molecular Biology PO Box 130 Monash University Victoria 3800 Australia Tel: +61-3-9905-3723 Fax: +61-3-9905-5882 E-mail: mibel.aguilar@med.monash.edu.au Dates: Received 16 July 1999 Revised 3 September 1999 Accepted 27 October 1999 To cite this article: Lazoura, E., McLeish, M.J. & Aguilar, M.-I. Studies on the conformational properties of CP-10 42–55 , the hinge region of CP-10, using circular dichroism and RP-HPLC. J. Peptide Res., 2000, 55, 411–418. Copyright Munksgaard International Publishers Ltd, 2000 ISSN 1397-002X Studies on the conformational properties of CP-10 42–55 , the hinge region of CP-10, using circular dichroism and RP-HPLC Key words: a-helix; binding affinity; RP-HPLC; hydrophobic contact area; CP-10 Abstract: The conformational properties of CP-10 42–55 , a peptide corresponding to the hinge region of CP-10, were investigated using circular dichroism spectroscopy and reverse-phase high- performance liquid chromatography (RP-HPLC). The circular dichroism studies indicated that CP-10 42–55 formed considerable secondary structure in the presence of hydrophobic solution environments including 50% acetonitrile, 50% trifluoroethanol and 200 mM sodium dodecyl sulfate, which comprised a mixture of a-helix and b-sheet. The effect of temperature on the conformation of CP-10 42–55 was investigated between 5 and 408C, with very small changes in the spectra being observed. RP-HPLC was then used to investigate the effect of temperature on the conformation of CP-10 42–55 in the presence of a hydrophobic surface. Using a C 18 -adsorbent, CP-10 42–55 exhibited a conformational transition at 258C, which was associated with an increase in the chromatographic contact area and the binding affinity of the peptide for the stationary phase. In addition, near-planar bandbroadening behaviour indicated that conformational species interconverted with rapid rate constants compared with the chromatographic time scale. These results indicated that the conformational change at 258C in the RP-HPLC system most likely corresponds to the unfolding of an a-helical and/or b-sheet structure to an extended coil structure. Therefore, the strong chemotactic properties of this peptide may be attributed to its ability to form considerable secondary structure in the presence of a hydrophobic environment. Abbreviations: Boc, tert-butyloxycarbonyl; CD, circular dichroism; LPL, low-density lipoprotein; LSS, linear solvent strength; MeCN, acetonitrile; PHE 5 , penta-L-phenylalanine; RP-HPLC, reverse-phase high-performance liquid chromatography; SDS, sodium dodecyl sulfate; TFA, trifluoroacetic acid; TFE, trifluoroethanol. 411