Structure and conformation of linear peptides |
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Authors: | R. MURALI V. LALITHA E. SUBRAMANIAN R. PARTHASARATHY |
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Affiliation: | Department of Crystallography and Biophysics† University of Madras, Guindy Campus, Madras, India and Department of Biophysics, Roswell Park Memorial Institute, Buffalo, New York, USA |
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Abstract: | The dipeptide, (DL)-alanyl-(DL)-norvaline, crystallizes in the monoclinic space group P21/c, with a = 12.559(2)A, b = 5.265(1), c = 16.003(3), β = 103.53(2)°, Z = 4. The structure was solved by direct methods and refined to an R-value of 0.054 for 871 reflections with I > 2. The molecule exists as a zwitterion in the crystal. The peptide unit is trans and shows significant deviations from planarity (Δω = 12.4°). The peptide backbone adopts an extended conformation. The unit cell contains D-Ala-L-norval and its enantiomer. The molecular conformation and packing features show a striking resemblance to those for D-Ala-L-Met (1), and leads to the speculation that norvaline might act as an analog of methionine. |
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Keywords: | D,L-alanyl-L,D-norvaline crystal structure dipeptide X-ray analysis |
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