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Genomic DNA adopts B‐form canonically. Besides, the oligonucleotides can adopt various non‐canonical secondary structures. These are hairpins, cruciforms, triplexes, quadruplexes (G4), i‐motifs etc. G4s are usually formed by the guanine rich oligonucleotides and are found in both DNA and RNA. G4s are more frequently distributed in telomeres, promoter oncogenes, immunoglobulin switch regions, ribosomal DNA etc. Recently, it has been established that G4s are intriguingly connected with different human diseases including cancer. Stabilization of G4s by designed molecules or drugs impedes the transcription of several oncogenes and also creates encumbrance to the telomere biogenesis which is very important in impediment of cancer. G4 is treated as an important molecular target in the discovery of anti‐cancer drugs. Among the G4 targeting molecules, peptides draw sincere attention due to its small size, simple synthetic methodology, low cytotoxicity and cellular permeability. In this review, our main discussion revolves around the formation of G4, distribution of G4 in genome, structurally diverse peptides (linear, cyclic, branch, conjugated) having potential to target G4 structures and its future perspectives. [ABSTRACT FROM AUTHOR]

G‐quadruplex (G4) is one of the non‐canonical nucleic acid structures that regulate multiple key biological processes. The formation of G4 hinders the progression of cancer. The molecular entities which can stabilize the G4 structure are very important to design anticancer therapeutics. Herein, it is described that a synthetic dendron‐like peptide, Cδ3‐(YYEE)‐E co‐assembles with G4 DNA in aqueous buffer containing Na+ ions. Various orthogonal biophysical studies have established the co‐assembly phenomenon. In silico, molecular docking studies also corroborate the results obtained from biophysical experiments. Importantly, the co‐assembly enhances the thermal stability of G4 DNA compared to free G4 DNA. The peptide inhibits the activity of telomerase enzyme which is found to be over‐expressed in most of the cancer cells and also down‐regulates the c‐Myc oncogenic expression. The peptide exhibits significant cytotoxic effect on cancer cells (HeLa and U2OS) compared to non‐cancer cells (HEK293) under similar experimental conditions. The study highlights the applicability of a synthetic bioactive peptide as a putative anticancer therapeutic. [ABSTRACT FROM AUTHOR]

Upregulation of utrophin, the autosomal homologue of dystrophin, can compensate dystrophin deficiency in Duchenne Muscular Dystrophy (DMD) although the therapeutic success is yet to be achieved. The present study has identified Poly (C) binding protein 2 (PCBP2) as a post-transcriptional suppresser for the expression of utrophin-A, the muscle-specific utrophin isoform. This study confirms nuclear retention of utrophin-A mRNA in C2C12 cells, which is mediated by PCBP2. Further investigation demonstrates PCBP2-dependent nuclear retention of follistatin mRNA as well. Its involvement in nuclear retention of mRNA sheds light on a novel function of PCBP2 that makes utrophin-A mRNA less available in cytosol. PCBP2, therefore, may be a target to de-repress utrophin-A expression in DMD. [ABSTRACT FROM AUTHOR]

Protein misfolding and subsequent generation of amyloid fibrils are associated with a wide range of diseases e. g. Alzheimer's, Huntington's, Parkinson's, type II diabetes, cystic fibrosis, and many others. Aromatic amino acid residues of polypeptide/protein are supposed to play a critical role in formation and stabilization of amyloid fibrils. Herein, we report a synthetic peptide, ALYLV (peptide 1), corresponding to B14‐18 of insulin, that forms nanofibrillar aggregates upon self‐association in aqueous medium. Staining with congo red (CR) and thioflavin t (ThT) establish that these organized nano‐assemblies are amyloidogenic in nature. Interestingly, the structural modification of peptide 1 replacing the centrally located tyrosine residue with valine, ALVLV (peptide 2), significantly reduces the assembly propensity as well as the amyloidogenicity of peptide 2 compared to peptide 1. MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) cell survival assay reveals the cytotoxicity of the aggregated peptides on HeLa cells upon 48 h of exposure. Overall, the study explores the aggregation potential, amyloidogenicity, and cytotoxicity of a hotspot of insulin and pinpoints the role of aromatic amino acid residue in amyloidosis. This outcome also illuminates the peptide nano‐assemblies for various biotechnological applications. [ABSTRACT FROM AUTHOR]

The ability of a synthetic, aromatic tripeptide, H-Phe-Phe-Phe-OH (FFF) to recognize the double-stranded DNA (dsDNA) has been tested with various biophysical and thermodynamic techniques. From the study, it is established that the peptide can recognize the groove of the ct-DNA and the binding constant value calculated from the isothermal titration calorimetric (ITC) study at 25C is 9.96 × 10³ M-1. From ITC data it is also noticed that the peptide-DNA complexation is favored by positive standard molar entropy contribution (TΔS°) of 13.65 kJ mol-1 and negative standard molar enthalpy contribution (ΔH°) of -9.170 kJ mol-1. The temperature-dependent ITC study also shows that the equilibrium constant value decreases gradually with increasing temperature. However, the standard molar Gibbs energy change exhibits only minor alterations suggesting the occurrence of enthalpy-entropy compensation. The studies reveal the insight into the spectroscopic and thermodynamic prospect of the FFFct-DNA interaction in vitro and hold the promise of future applications as DNA targeting drug. [ABSTRACT FROM AUTHOR]

A terminally protected acyclic tetrapeptide has been synthesized, and the crystal structure of its hydrated form, Boc-Tyr-Aib-Tyr- Ile-OMe · 2H2O (1), has been determined directly from powder X-ray diffraction data. The backbone conformation of tetrapeptide (1) exhibiting two consecutive β-turns is stabilized by two 4?1 intramolecular N?H· · ·O hydrogen bonds. In the crystalline state, the tetrapeptide molecules are assembled through water-mediated O?H· · ·O hydrogen bonds to form two-dimensional molecular sheets, which are further linked by intermolecular C?H· · ·O hydrogen bonds into a three-dimensional supramolecular framework. The molecular electrostatic potential (MEP) surface of (1) has been used to supplement the crystallographic observations. The nature of intermolecular interactions in (1) has been analyzed quantitatively through the Hirshfeld surface and twodimensional fingerprint plot. The DFT optimized molecular geometry of (1) agrees closely with that obtained fromthe X-ray structure analysis. The present structure analysis of Boc-Tyr-Aib-Tyr-Ile-OMe · 2H2O (1) represents a case where ab-initio crystal structure of an acyclic tetrapeptide with considerable molecular flexibility has been accomplished from laboratory X-ray powder diffraction data. [ABSTRACT FROM AUTHOR]

Self-assembly of amino acids and short-peptide derivatives attracted significant curiosity worldwide due to their unique self-assembly process and wide variety of applications. Amino acid is considered one of the important synthons in supramolecular chemistry. Self-assembly processes and applications of unfunctionalized native amino acids have been less reported in the literature. In this article, we are first-time reporting the self-assembly process of tyrosine (Tyr), an aromatic amino acid, in dimethyl sulfoxide (DMSO) solvent. Most of the studies related to Tyr self-assembly were reported in different aqueous solutions. In our work, we studied the self-assembly in several common organic solvents and found that Tyr could self-assemble into a supramolecular gel in dimethyl sulfoxide (DMSO) solvent. The self-assembly process was investigated by several techniques, such as UV-vis, fluorescence, FTIR, and NMR spectroscopy. Morphological features on the nanoscale were investigated through scanning electron microscopy (SEM). SEM images indicated the formation of nanofibrils with high aspect ratios. The supramolecular gel property was investigated by different rheological experiments. Computational study on the self-assembly process of Tyr in DMSO medium suggested that noncovalent interactions like hydrogen bonding and π-π stacking among the Tyr molecules played a prominent role. Finally, the charge-transfer complex formation ability of electron-rich Tyr with electron-deficient 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was studied. In the presence of DDQ due to the charge-transfer complex formation, the supramolecular gel converted into a reddish color solution, and their fibrillar nanoscale morphologies collapsed.

The report describes the synthesis, self-association and DNA binding studies of an aromatic tripeptide H-Phe-Phe-Phe-OH (FFF). The peptide backbone adopts β-sheet conformation both in solid and solution. In aqueous solution, FFF self-assembles to form nanostructured aggregates. Interactions of this peptide with calf-thymus DNA (ct-DNA) have been studied using various biophysical techniques including ultraviolet (UV) absorption spectroscopy, fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The value of mean binding constant calculated from UV and fluorescence spectroscopic data is (2.914 ± 0.74) x 10 3  M -1 which is consistent with an external binding mode. Fluorescence intercalator displacement (FID) assay, iodide quenching study, viscosity measurement and thermal denaturation study of DNA further confirm the groove binding mode of peptide, FFF with ct-DNA. MTT cell survival assay reveals very low cytotoxicity of the peptide toward human lung carcinoma cell line A549.

Self-assembling short peptides can offer an opportunity to make useful nano-/microstructures that find potential application in drug delivery. We report here the formation of multivesicular structures from self-assembling water-soluble synthetic amphiphilic dipeptides containing a glutamic acid residue at the C-terminus. These vesicular structures are stable over a wide range of pH (pH 2-12). However, they are sensitive towards calcium ions. This causes the rupturing of these vesicles. Interestingly, these vesicles can not only encapsulate an anticancer drug and a fluorescent dye, but also can release them in the presence of calcium ions. Moreover, these multivesicular structures have the potential to carry biologically important molecules like cyclic adenosine monophosphate (cAMP) within the cells keeping their biological functions intact. A MTT cell-survival assay suggests the almost nontoxic nature of these vesicles. Thus, these peptide vesicles can be used as biocompatible delivery vehicles for carrying drugs and other bioactive molecules.

The concentration dependent transformation of an oligopeptide nanostructure from nanovesicles to nanotubes at neutral pH is presented. The oligopeptide Acp-Tyr-Glu (Acp: 6-aminohexanoic acid) forms nanovesicles at a concentration of 6.9 mg mL(-1). At a concentration of 2.3 mg mL(-1) these vesicular structures completely disappear and nanotubular structures are observed. We have also successfully optimized an intermediate concentration (3.4 mg mL(-1)) where an ordered array of fused vesicular structures are formed, which actually leads to the transition from nanovesicles to nanotubes. These vesicular structures are very much sensitive toward metal ions and pH. Biocompatible calcium ions and high pH (10.7) can trigger the rupturing of these nanovesicles. One important property of these nanovesicular structures is the encapsulation of a potent anticancer drug doxorubicin, which can also be released in the presence of calcium ions promising a future use of these nanovesicles as vehicles for carrying biologically important molecules.

A water-soluble, hydrophilic tripeptide GYE, having sequence identity with the N-terminal segment of amyloid peptides Abeta(9-11), upon self-association exhibits amyloid-like fibrils and significant neurotoxicity towards the Neuro2A cell line. However, the tripeptides GFE and GWE, in which the centrally located tyrosine residue has been replaced by phenylalanine or tryptophan, fail to show amyloidogenic behavior and exhibit little or no neurotoxicity.