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Author

Animesh Pramanik

Other affiliations: Indian Institute of Science
Bio: Animesh Pramanik is an academic researcher from University of Calcutta. The author has contributed to research in topics: Aryl & Ninhydrin. The author has an hindex of 21, co-authored 144 publications receiving 1460 citations. Previous affiliations of Animesh Pramanik include Indian Institute of Science.
Topics: Aryl, Ninhydrin, Catalysis, Hydrogen bond, Helix


Papers
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TL;DR: In this article, the preservation of helical structures in octa-and undecapeptides with centrally located β- and γ-amino acids in the sequence was established.
Abstract: Insertion of achiral ω-amino acids into peptide sequences results in replacement of scissile peptide bonds by proteolytically stable C−C bonds. This provides a convenient means of creating peptidomimetics. The present study establishes the preservation of helical structures in octa- and undecapeptides with centrally located β- and γ-amino acids in the sequence. X-ray diffraction analyses of single crystals and NMR studies have been used to investigate the extent of perturbations of a regular 310- or α-helix by the introduction of (−CH2−)n groups into the backbone by the use of the β-Ala-γ-Abu segment (β-Ala = β-alanine, γ-Abu = γ-aminobutyric acid), which is formally homomorphous with a (Gly)3 segment. In crystals, the octapeptide Boc-Leu-Aib-Val-β-Ala-γ-Abu-Leu-Aib-Val-OMe (1) and the undecapeptide Boc-Leu-Aib-Val-β-Ala-γ-Abu-Leu-Aib-Val-Ala-Leu-Aib-OMe (2) retain their helical motifs with minor bulges. Five new types of 4 → 1, 5 → 1, and 6 → 1 hydrogen bond rings are formed with up to three extra CH2 mo...

112 citations

Journal ArticleDOI
TL;DR: In vitro studies reveal that the addition of micromolar concentration “curcumin” significantly reduces the formation of amyloid‐like fibrils and shows significant thermal stability along with a morphological transformation upon heat treatment.
Abstract: The small-sized molecules that have been developed from single hydrophobic amino acids (Phe, Trp, Tyr and Leu) by suitably protecting the –NH2 and –CO2H groups generate diverse nanoscopic structures – such as nanorods, nanofibrils, nanotubes, and nanovesicles – depending upon the protection parameters and solvent polarity. The vesicular structures get disrupted in the presence of various salts, such as KCl, CaCl2, (NH4)2SO4 and N(n-Bu)4Br. Insertion of unnatural (o/m/p)-aminobenzoic acids as a protecting group and the lack of conventional peptide bonds in the molecules give the nanostructures proteolytic stability. The nanostructures also show significant thermal stability along with a morphological transformation upon heat treatment. Our in vitro studies reveal that the addition of micromolar concentration “curcumin” significantly reduces the formation of amyloid-like fibrils. These diverse nanostructures are used as a template for fabricating silver nanoparticles on their outer surfaces as well as in the inner part, followed by calcination in air which helps to obtain a 1D silver nanostructure. Furthermore, the nanovesicles are observed to encapsulate a potent drug (curcumin) and other biologically important molecules, which could be released through salt-triggered disruption of vesicles.

67 citations

Journal ArticleDOI
TL;DR: Incorporation of easily available achiral omega-amino acid residues into an oligopeptide results in substitution of amide bonds by polymethylene units of an aliphatic chain, thereby providing a convenient strategy for constructing a peptidomimetic.
Abstract: Incorporation of easily available achiral omega-amino acid residues into an oligopeptide results in substitution of amide bonds by polymethylene units of an aliphatic chain, thereby providing a convenient strategy for constructing a peptidomimetic. The central Gly-Gly segment of the helical octapeptide Boc-Leu-Aib- Val-Gly-Gly-Leu-Aib- Val-OMe(1) has been replaced by delta-amino-valeric acid (delta-Ava) residue in the newly designed peptide Boc-Leu-Aib- Val-d-Ava-Leu-Aib-Val-OMe(2). ‘H-nmr results clearly suggest that in the apolar solvent CDC13, the delta-Ava residue is accommodated into a folded helical conformation, stabilized by successive hydrogen bonds involving the NH groups of Va1(3), delta-Ava(4), and Leu(5). The delta-Ava residue must adopt a gauche-gauche-trans-gauche-gauche conformation along the central polymethylene unit of the aliphatic segment, a feature seen in an energy-minimized model conformation based on nmr parameters. The absence of hydrogen bonding functionalities, however, limits the elongation of the helix. In fact, in CDCl3 rhe folded conformation consists of an N-terminal helix spanning residues 1-4, followed by a Type II beta-turn at residues 5 and 6, whereas in strongly solvating media like (CD,),SO, the unfolding of the N-terminal helix results in beta-turn conformations at Leu([)-Aib(2). The Type II beta-turn at the Leu(S)-Aib(6) segment remains intact even in (CD3)2S0. CD comparisons ofpeptides 1 and 2 reveal a nonhelical spectrum for 2 in 2,2,2-trifluoroethanol.

59 citations

Journal ArticleDOI
TL;DR: A new class of heterocycles of isoindole fused imidazoles with phenolic subunits has been readily synthesized by a two-step one-pot reaction and show high fluorescent properties but in protic polar solvent fluorescent intensity decreases.

56 citations

Journal ArticleDOI
TL;DR: In this article, a set of modified tripeptides containing conformationally rigid m-aminobenzoic acid (m-ABA) was used as a template at the C-terminal self-assemble to form diverse micro- and nanostructure materials such as nanoveicles, nanotubes, giant microvesicles, macroporous vesicular structures, macro-and mesoporous materials, and organo gels depending upon the solvent polarity.
Abstract: A set of two modified tripeptides containing conformationally rigid m-aminobenzoic acid (m-ABA) as a template at the C-terminal self-assemble to form diverse micro- and nanostructure materials such as nanovesicles, nanotubes, giant microvesicles, macroporous vesicular structures including macroporous films, macro- and mesoporous materials, and organo gels—depending upon the solvent polarity. A balanced participation of the hydrogen bonding and the π–π interactions mainly between aromatic rings of m-ABA is crucial for this morphological diversity. Insertion of an aromatic amino acid instead of an aliphatic one in the peptide sequence drastically changes the morphology of the nanostructures formed from a particular solvent system. Interestingly these short hydrophobic peptides form salt-responsive multilayer vesicular structures from methanolic solutions, where the diameter of the vesicles increases with an increase of concentration. The most important property of these multilayer vesicular structures is the encapsulation of a potent natural hydrophobic drug curcumin and of a fluorescent dye rhodamine B, which can be effectively released in presence of biocompatible metal ions. Moreover, the encapsulation efficiency and release profile of drug and other biologically important guest molecules have been successfully quantified. We have developed a simple modified peptide based organogelator from chloroform, where the xerogel shows the striking property of adsorbing dye rhodamine B from water, which can be utilized in water purification by removing the toxic dye from waste water. Short peptide based macroporous vesicular structures including macroporous films have been successfully fabricated through controlled self-assembly employing solvents with different chloroform–petroleum ether ratios. Furthermore, the mesoporous structures prepared from toluene can efficiently absorb I2.

54 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the utility of multicomponent reactions as methods for green synthesis is highlighted and the practical value of these type of reactions for meeting many of the criteria set by the green chemistry philosophy.

873 citations

Journal ArticleDOI
TL;DR: Examination of protein 3-dimensional structures suggests that complex tertiary folds and quaternary associations can be deconstructed into a limited number of secondary structural elements, such as strands, helices, and turns, which are assembled using loosely structured loops.
Abstract: The construction of complex protein folds relies on the precise conversion of a linear polypeptide chain into a compact 3-dimensional structure. The interplay of forces that link sequence and folding is intricate and yet to be firmly elucidated. Examination of protein 3-dimensional structures suggests that complex tertiary folds and quaternary associations can be deconstructed into a limited number of secondary structural elements, such as strands, helices, and turns, which are assembled using loosely structured loops (Figure 1). The stability of a specific fold is determined by tertiary interactions between residues which are distant in sequence. De novo design of existing or novel protein folds demands a thorough understanding of the rules that underlie protein structure and stability.

612 citations

Journal ArticleDOI
TL;DR: An overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals.
Abstract: Life-threatening infectious diseases are on their way to cause a worldwide crisis, as treating them effectively is becoming increasingly difficult due to the emergence of antibiotic resistant strains. Antimicrobial peptides (AMPs) form an ancient type of innate immunity found universally in all living organisms, providing a principal first-line of defense against the invading pathogens. The unique diverse function and architecture of AMPs has attracted considerable attention by scientists, both in terms of understanding the basic biology of the innate immune system, and as a tool in the design of molecular templates for new anti-infective drugs. AMPs are gene-encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially, which exhibit broad spectrum antimicrobial activity. AMPs have been the subject of natural evolution, as have the microbes, for hundreds of millions of years. Despite this long history of co-evolution, AMPs have not lost their ability to kill or inhibit the microbes totally, nor have the microbes learnt to avoid the lethal punch of AMPs. AMPs therefore have potential to provide an important breakthrough and form the basis for a new class of antibiotics. In this review, we would like to give an overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals, in addition to pharmaceutical aspects and the additional functions of AMPs.

589 citations

Journal ArticleDOI
TL;DR: This work reviews the advantages of these molecules in clinical applications, their disadvantages including their low in vivo stability, high costs of production and the strategies for their discovery and optimization.
Abstract: Antibiotic resistance is increasing at a rate that far exceeds the pace of new development of drugs. Antimicrobial peptides, both synthetic and from natural sources, have raised interest as pathogens become resistant against conventional antibiotics. Indeed, one of the major strengths of this class of molecules is their ability to kill multidrug-resistant bacteria. Antimicrobial peptides are relatively small (6 to 100 aminoacids), amphipathic molecules of variable length, sequence and structure with activity against a wide range of microorganisms including bacteria, protozoa, yeast, fungi, viruses and even tumor cells. They usually act through relatively non-specific mechanisms resulting in membranolytic activity but they can also stimulate the innate immune response. Several peptides have already entered pre-clinical and clinical trials for the treatment of catheter site infections, cystic fibrosis, acne, wound healing and patients undergoing stem cell transplantation. We review the advantages of these molecules in clinical applications, their disadvantages including their low in vivo stability, high costs of production and the strategies for their discovery and optimization.

568 citations