Synthetic peptide helices in crystals: Structure and antiparallel and skewed packing motifs for α-helices in two isomeric decapeptides

✍ Scribed by Isabella L. Karle; Judith L. Flippen-Anderson; K. Uma; P. Balaram

• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 824 KB
• Volume: 30
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360300707

✦ Synopsis

I11

) , are predominantly a-helical with little effect on the conformation with interchange of Aib/Ala residues or Aib/Leu residues. The packing motif of helices in crystal I1 is antiparallel, whereas the helices pack in a skewed fashion in crystal 111, with a 40" angle between neighboring helix axes. Crystal I11 contains a water molecule in a hydrophobic hole that forms hydrogen bonds with two carbonyl oxygens that also participate in 5 + 1 type hydrogen bonds. Values for helical torsional angles and + assume a much wider range than anticipated. Crystal 11: C49HB8N10013, space group P21, with a = 16.625(2) A, b = 9.811 ( 5 ) A, c = 18.412(3) A, p = 99.79( l)", 2 = 2, R = 5.7% for 4338 data with I Fol > 3 u ( F ) . Crystal 111: C,,H,N,oO13. 1 /2H20, space group P21 with a = 11.072 ( 2 ) A, b = 34.663( 5) A, c = 16.446( 3 ) A, = 107.85( 1 ) ", 2 = 4, R = 8.3% for 6087 data with 1 Fo I > 3 u ( F ) .

* Supplementary material consisting of bond lengths, bond angles, anisotropic thermal parameters, and coordinates for hydrogen atoms will be deposited with the Cambridge Crystallographic Data File. Observed and calculated structure factors are available from ILK or JFA.