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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]

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]

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.