12/10‐ and 11/13‐Mixed Helices in α/γ‐ and β/γ‐Hybrid Peptides Containing C‐Linked Carbo‐γ‐amino Acids with Alternating α‐ and β‐Amino Acids.

Abstract

Peptides U 0400 12/10-and 11/13-Mixed Helices in α/γand β/γ-Hybrid Peptides Containing C-Linked Carbo-γ-amino Acids with Alternating αand β-Amino Acids. -(SHARMA*, G. V. M.; JADHAV, V. B.; RAMAKRISHNA, K. V. S.; JAYAPRAKASH, P.; NARSIMULU, K.; SUBASH, V.; KUNWAR, A. C.; J.

Differentiation of three pairs of Boc‐β,γ‐ and γ,β‐hybrid peptides by electrospray ionization tandem mass spectrometry

“…16 All the peptides were prepared from corresponding monomers of carbo-ˇ3-and 4 -amino acids (derived from D-xylose) by conventional methods using 1-(3-dimethylaminopropyl)-3-ethylcarbodimide hydrochloride (EDCI) and 1-hydroxy benzotriazole hydrate (HOBt) in dichloromethane.…”

“…Recently, Talaty et al reported an interesting mass spectral study on the influence of the presence and position of an alternative amino acid including two nonnatural amino acids viz.ˇ-alanine (X), -aminobutyric acid (X) on the formation of b n C and y n C ions from a series of protonated tetrapeptides with general sequence XAAG, AXAG, and AAXG. 39 In continuation of our studies, here we report on ESI MS/MS of a new series of hybrid peptides comprising the repeats ofˇ3-Caa- 4 -Caa (ˇ, -)/ 4 -Caa-ˇ3-Caa ( ,ˇ-) 16 (Scheme 1).…”

“…9,10 A 12/10-mixed helix unique to thě -peptides was discovered for the first time by Seebach et al 11 inˇ2/ˇ3-dipeptide repeats. As a part of an ongoing program toward developing new oligomers 12,13 of carbo-ˇand -amino acids with novel secondary structures, 14,15 one of us 16 has recently reported the synthesis of oligomers with dipeptide repeats of carbo-ˇ3-amino acid and carbo- 4 -amino acid and demonstrated novel left-handed 11/13-mixed helices.…”

Differentiation of Positional Isomers of Hybrid Peptides Containing Repeats of β-Nucleoside Derived Amino Acid (β-Nda-) and L-Amino Acids by Positive and Negative Ion Electrospray Ionization Tandem Mass Spectrometry (ESI-MSn)

“…The positive ion ESI mass spectra of all these peptides (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) + ions (Scheme 2). Fragmentation of these peptides can be explained by using the nomenclature, which was originally proposed for α-peptides by Roepstorff and Fohlman, and later modified by Biemann [18][19][20].…”

“…Oligomers of non-natural peptidic residues [4][5][6], particularly with β-amino acids [7,8] and their hybrids with natural L-amino acids have emerged as versatile structural templates (foldamers) as these exhibit predictable and welldefined secondary structures such as helices, turns, and strands, and offer a variety of possibilities for orienting functional sidechains [9][10][11][12][13]. The oligomers of these amino acids both in cisand trans-conformation have exhibited diverse helical patterns in solution [12][13][14].…”