CH···O Hydrogen Bond Mediated Chain Reversal in a Peptide Containing a -Amino Acid Residue, Determined Directly from Powder X-ray Diffraction Data We are grateful to the EPSRC, the University of Birmingham, Purdue Pharma, Wyeth Ayerst, and the Department of Biotechnology of the Government of India (under the Drug and Molecular Design Programme) for financial support.