Crystal structure and a twisted β‐sheet conformation of the tripeptide L‐leucyl‐L‐leucyl‐L‐leucine monohydrate trimethanol solvate: Conformation analysis of tripeptides

Abstract

In order to test the helical preference of short oligo-L-leucines, we crystallized the tripeptide L-leucyl-L-leucyl-L-leucine (LLL) and carried out x-ray diffraction studies of it (L-leucyl-L-leucyl-Lleucine)2. 3CH3OH. H2O, (C39H84N6O12), crystallized in the monoclinic system, space group P2(1), cell parameters: a = 12.031(2), b = 15.578(3), c = 14.087(2) A, alpha = 90 degrees, beta = 97.29(1) degrees, gamma = 90 degrees, V = 2618.6 A3, MW = 829.1, Dc = 1.051 g cm-3, R index of 0.057 for 4213 reflections (lambda CuK alpha = 1.5418 A) > 2 sigma. LLL takes up the beta-sheet rather than a helical conformation in the crystalline state. The three methanol molecules and the water molecule that constitute the solvent of crystallization form a network of hydrogen bonds to the LLL molecules and to one another. It is rather remarkable that though A and L have stronger helical preferences than G, neither AAA nor LLL form the crystalline helix but GAL does, indicating that the helical preferences depend on the sequence context. The residue L2 in molecule A and the residues L1 and L3 of molecule B do not show the preferred conformation for forming helices. Further, very remarkably, LLL exhibits a unique supersecondary feature of the protein folding topology, namely the twisted beta-sheet, whereas most short peptides show only the classical beta-sheet conformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of lengthening of peptide backbone by insertion of chiral ?-homo amino acid residues: Conformational behavior of linear peptides containing alternatingL-leucine and ?-homoL-leucine residues

“…25 It is worth noting that the tripeptide does not show in the solid state any intramolecular H bonds. Furthermore, the overall structure is similar to that observed for the unblocked NH 2 -Leu-Leu-Leu-OH tripeptide, 26 which crystallized with two crystallographic independent molecules. The superimposition between the corresponding atoms of Leu 1 and Leu 3 NC ␣ CЈ atoms of the Boc-Leu-␤-HLeu-Leu-OMe and NH 2 -Leu-LeuLeu-OH (one of the two independent units) is depicted as a stereo view in Figure 2.…”

Adsorption and self-assembly of bio-organic molecules at model surfaces: A route towards increased complexity

“…Designing such peptides is not only a dream. Some authors have indeed shown that site selectivity in biomolecules can be reproduced in relatively short peptides, not requiring the entire and complex scaffolds of natural proteins [346]; even tripeptides were shown to bear topological characteristics of much larger proteins [347]. The ultimate goal is, of course, to elucidate the relationship between chemistry, structure and functionality of these peptides/proteins, in particular to explain the mystery of specific molecular recognition or metal binding.…”

Interaction of l‐leucyl‐l‐leucyl‐l‐leucine thin film with water and organic vapors: receptor properties and related morphology

“…In present work, these structure–property relationships were studied for tripeptide l ‐leucyl‐ l ‐leucyl‐ l ‐leucine (LLL). This tripeptide forms well‐defined monoclinic or triclinic crystals with β ‐sheet structures when crystallized from methanol ; pyridine; or α ‐picoline, β ‐picoline and γ ‐picoline solutions. An ability of various guests to destroy such LLL crystals was studied using AFM.…”