Papers by Chandramouli Nagula
Angewandte Chemie International Edition, 2013
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Journal of the American Chemical Society, 2012
An aromatic oligoamide sequence was designed and synthesized to fold in a single helix having a l... more An aromatic oligoamide sequence was designed and synthesized to fold in a single helix having a large cavity and to behave as a host for a dumbbell-shaped guest derived from tartaric acid. NMR, molecular modeling, and circular dichroism (CD) evidence demonstrated the rapid formation of this 1:1 host-guest complex and induction of the helix handedness of the host by the guest. This complex was found to be a long-lived kinetic supramolecular byproduct, as it slowly transformed into a 2:2 host-guest complex with two guest molecules bound at the extremities of a double helix formed by the host, as shown by NMR and CD spectroscopy and a solid-state structure. The guest also induced the handedness of the double helical host, but with an opposite bias. The chiroptical properties of the system were thus found to revert with time as the 1:1 complex formed first, followed by the 2:2 complex.
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Nature Chemistry, 2015
The ab initio design of synthetic molecular receptors for a specific biomolecular guest remains a... more The ab initio design of synthetic molecular receptors for a specific biomolecular guest remains an elusive objective, particularly for targets such as monosaccharides, which have very close structural analogues. Here we report a powerful approach to produce receptors with very high selectivity for specific monosaccharides and, as a demonstration, we develop a foldamer that selectively encapsulates fructose. The approach uses an iterative design process that exploits the modular structure of folded synthetic oligomer sequences in conjunction with molecular modelling and structural characterization to inform subsequent refinements. Starting from a first-principles design taking size, shape and hydrogen-bonding ability into account and using the high predictability of aromatic oligoamide foldamer conformations and their propensity to crystallize, a sequence that binds to β-D-fructopyranose in organic solvents with atomic-scale complementarity was obtained in just a few iterative modifications. This scheme, which mimics the adaptable construction of biopolymers from a limited number of monomer units, provides a general protocol for the development of selective receptors.
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Rapid Communications in Mass Spectrometry, 2011
... PJ Prakash, B. Jagannath, AC Kunwar. Left-handed helical twists in mixed-β-peptides derived... more ... PJ Prakash, B. Jagannath, AC Kunwar. Left-handed helical twists in mixed-β-peptides derived from alternating C-Linked carbo-β 3 -amino acids and β-hGly units. Angew. Chem. Int. Ed. 2004, 43, 3961. ... 21 G. Raju, V. Ramesh, R. Srinivas, GVM Sharma, B. Shoban Babu. ...
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Organic & Biomolecular Chemistry, 2011
Radical cyclization reactions were performed by 5-exo-dig mode to yield cis-fused bicyclic system... more Radical cyclization reactions were performed by 5-exo-dig mode to yield cis-fused bicyclic systems, leading to the synthesis of bis-butyrolactone class of natural products. The study was aimed at understanding the impact of alkyl side chains of furanoside ring systems in L-ara configuration on the radical cyclization. It was amply demonstrated by experimental studies that the increase in the length of the alkyl side chain has an effect on the cyclization: while efficient cyclization reactions could be realized with methyl and ethyl side chains, the yields were significantly reduced in the case of n-pentyl side chain. Theoretical studies using DFT and (RO)MP2 methods were carried out to analyze the influence of the substitution pattern on the cyclization barriers.
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Journal of the American Chemical Society, 2012
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Journal of the American Chemical Society, 2009
The concept of "... more The concept of "hybrid helices" as a new motif for foldamers is presented. Hybrid helices can be realized by a combination of two or more different types of homologous and hybrid peptides, for example, beta-peptides and alpha/beta- and alpha/gamma-hybrid peptides, within the same oligomer. The different helix types of the various peptide foldamer classes are maintained and form a regular helix along the sequence of the oligomer. The transition from one helix type to another was found to be rather smooth with high compatibility of the different helix types. Such hybrid helices represent novel motifs of secondary structure scaffolds. They open up the possibility to change the direction of helix propagation in a subtle manner. Hybrid helices enrich the arsenal of defined foldamer structures for a structural and functional mimicry of native peptides and proteins.
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European Journal of Organic Chemistry, 2011
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Chemistry - An Asian Journal, 2011
Novel three-residue helix-turn secondary structures, nucleated by a helix at the N terminus, were... more Novel three-residue helix-turn secondary structures, nucleated by a helix at the N terminus, were generated in peptides that have 'β-Caa-L-Ala-L-Ala,' 'β-Caa-L-Ala-γ-Caa,' and 'β-Caa-L-Ala-δ-Caa' (in which β-Caa is C-linked carbo-β-amino acid, γ-Caa is C-linked carbo-γ-amino acid, and δ-Caa is C-linked carbo-δ-amino acid) at the C terminus. These turn structures are stabilized by 12-, 14-, and 15-membered (mr) hydrogen bonding between NH(i)/CO(i+2) (i+2 is the last residue in the peptide) along with a 7-mr hydrogen bond between CO(i)/NH(i+2). In addition, a series of α/β-peptides were designed and synthesized with alternating glycine (Gly) and (S)-β-Caa to study the influence of an achiral α-residue on the helix and helix-turn structures. In contrast to previous results, the three 'β-α-β' residues at the C terminus (α-residue being Gly) are stabilized by only a 13-mr forward hydrogen bond, which resembles an α-turn. Extensive NMR spectroscopic and molecular dynamics (MD) studies were performed to support these observations. The influence of chirality and side chain is also discussed.
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Chemistry – An Asian Journal, 2008
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Papers by Chandramouli Nagula