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A pair of furan-based cyclic homooligopeptides is prepared to specifically target G-quadruplexes and UV melting has shown that these ligands have effectively induced G-quadruplex structures in the G-rich 22-mer c-MYC DNA sequence and have stabilized the structure. The studies have shown that the present molecules are effective in specifically binding and stabilizing quadruplexes and have provided a suitable scaffold to develop into a quadruplex-targeting therapeutic agent.

Cyclo-(Taa1-Leu-Val)2, cyclo-(Taa2-Leu-Val)2, and cyclo-(Taa2-Phe-Leu)2 displayed well-defined distorted beta-beta corner structures. Such oligomeric assemblies, with intramolecularly hydrogen-bonded structures could play significant roles in recognizing and binding to suitable ligands mimicking biological systems.

Objective: Analysis of shaping ability of four different rotary endodontic instruments using spiral computed tomography (CT). Materials and Methods: Eighty freshly extracted human mandibular first molars were used in the present study. Samples were randomly divided into four experimental groups with twenty samples in each group. Images of mesiobuccal canal of each sample were obtained pre- and post-operatively using spiral CT. All samples were prepared using their respective endodontic file systems (group I - ProTaper, group II - K3, group III - RaCe, and group IV - Mtwo). Image analyses were done using image analysis software for evaluation of canal transportation and centering ability. Data was then statistically analyzed using analysis of variance. Results: There was no statistically significance in transportation in their intergroup difference at any of the three locations (coronal, middle, and apical third). In centering ability there was no statistically significance in the coronal and middle third of the intergroup. However, there was a statistically significance of (P = 0.044) at the apical third between all the groups. Conclusion: Canals prepared with ProTaper had more canal transportation at all the three levels of root canal (coronal, middle, and apical third). Canals prepared with Mtwo were well centered at coronal and middle third whereas with RaCe canals were centered only at the apical third. All instruments showed some degree of canal aberrations in terms of shaping ability. [ABSTRACT FROM AUTHOR]

Structural and electronic properties of diastereomers of tetrahydrofuran amino acids (TAA) derived tripeptide, Boc‐TAA‐Leu‐Val‐OMe, are studied using density functional theory. Predicted secondary folding patterns with hydrogen bonded pseudocycles of different sizes in peptides containing (2R,5S)‐cis‐TAA and (2S,5R)‐cis‐TAA are confirmed by detailed NMR studies of both, and single crystal X‐ray analysis of the former. A novel unusual folding pattern emanating from three‐centered hydrogen bond is found in peptide with (2R,5S)‐cis relationship. Stereochemical control on the orientation of interacting sites is substantiated by structural analysis of the peptides. Using natural bonding orbital and atoms in molecules analyses, charge transfer interactions are analyzed. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Theoretical insights have been provided for the observed preference of cyclodimerization over intramolecular cyclization reactions in linear tripeptides containing “2,5-cis” (2S,5R)-tetrahydrofuran amino acid as well as in those containing “2,5-trans” (2S,5S)-tetrahydrofuran amino acid, using quantum chemical methods. The geometries of species involved as well as the feasibility of cyclization reactions are studied at the B3LYP/6-31G(d,p) level of theory in gas phase as well as in solvent phase. Thermodynamic data from Hessian calculations favor the intermolecular cyclization. Analysis of optimized geometries reveals the existence of additional stabilizing hydrogen bonding interactions in intermolecularly cyclized products. The existence of these second-order interactions is substantiated by topological (atoms in molecules (AIM)) and natural bond orbital (NBO) analyses. Such interactions are absent in the intramolecular cyclization products. Further justification for the presence of stabilizing interactions in intermolecularly cyclized products comes from the molecular electrostatic potentials and electron density surfaces. Kinetic control favoring the intermolecularly cyclized products due to additional entropy of activation in the intramolecular case is surmised. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]