Constrained and unconstrained chirality functions. A new method, going from discrete to continuous space, to find the best overlap between enantiomer atoms

This paper provides two different functions for quantifying geometric chirality. Both are based on Euclidean distances between enantiomer atoms and the best associated RMS, but, depending on the function, atoms are paired without or with constraint. In the first, the best match between the enantiomer atoms is sought by means of a completely new method in which one enantiomer is fitted onto a spline approximation of the other. This method reestablishes the continuity between similarity and dissimilarity, broken in discrete space by atom-per-atom shape recognition treatments. In the second, each enantiomer atom is paired with its mirror image and only the mirror location is optimized. Congruity-based chirality measures are grouped into two classes according to whether the discrimination function between the chiral object and the reference object takes some constraint into account (second class) or does not (first class). In this paper, our constrained or unconstrained chirality function is compared with the continuous chirality measure (second class). It is inferred that only chirality scales of the same class can be correlated.     

Inter and intramolecular copper(I)-catalyzed 1,3-dipolar cycloaddition of azido-alkynes: synthesis of furanotriazole macrocycles

The Cu(I)-catalyzed cycloaddition of azido-alkynes (click reaction) of furanose sugar substrates provides a facile approach for the construction of macrocyclic molecules via an inter and/or intramolecular cycloaddition based on the functionality between alkyne and azide.     

Visible‐Light‐Induced Efficient Selective Oxidation of Nonactivated Alcohols over {001}‐Faceted TiO2 with Molecular Oxygen

In the presence of molecular oxygen, a {001}‐faceted nanocrystalline anatase TiO₂ catalyst enabled the selective oxidation of nonactivated aliphatic alcohols to the corresponding aldehydes or ketones under visible light. The reaction shows excellent conversion and selectivity towards the formation of the carbonyl products without over‐oxidation to the corresponding carboxylic acids. The exceptional reactivity of the catalyst is possibly due to the absorption of visible light originating from a stronger interaction of alcohol with the {001} facet, which facilitates the modification of the band structure of TiO₂, thus facilitating the photogenerated hole transfer and subsequent oxidation processes. The experimental results have also been corroborated by first‐principles quantum chemical DFT calculations.     

Advanced electrocatalytic materials based biosensors for cancer cell detection – A review

Herein, we have highlighted the latest developments on biosensors for cancer cell detection. Electrochemical (EC) biosensors offer several advantages such as high sensitivity, selectivity, rapid analysis, portability, low-cost, etc. Generally, biosensors could be classified into other basic categories such as immunosensors, aptasensors, cytosensors, electrochemiluminescence (ECL), and photo-electrochemical (PEC) sensors. The significance of the EC biosensors is that they could detect several biomolecules in human body including cholesterol, glucose, lactate, uric acid, DNA, blood ketones, hemoglobin, and others. Recently, various EC biosensors have been developed by using electrocatalytic materials such as silver sulfide (Ag₂S), black phosphene (BPene), hexagonal carbon nitrogen tube (HCNT), carbon dots (CDs)/cobalt oxy-hydroxide (CoOOH), cuprous oxide (Cu₂O), polymer dots (PDs), manganese oxide (MnO₂), graphene derivatives, and gold nanoparticles (Au-NPs). In some cases, these newly developed biosensors could be able to detect cancer cells with a limit of detection (LOD) of 1 cell/mL. In addition, many remaining challenges have to be addressed and validated by testing more real samples and confirm that these EC biosensors are more accurate and reliable to measure cancer cells in the blood and salivary samples.     

A density functional theory study of vibrational coupling in the amide I band of beta-sheet models

We report the first molecular orbital/density functional theory (DFT) calculations on the vibrational frequencies involved in the amide I band of completely geometrically optimized models for beta-sheet peptides based upon (up to 16) glycine residues. These calculations use the B3LYP/D95** level of DFT. The primary means of vibrational coupling occurs through H bond, rather than through space, interactions, which is consistent with a previous report on alpha-helical polyalanines and H-bonding chains of both formamides and 4-pyridones. We decoupled the C=O stretching vibrations using selected 14C substitutions to probe the coupling mechanism and to determine "natural" frequencies for individual 14C=Os. The intermolecular H-bonding interactions affect the geometries of the amide groups. Those near the center of H-bonding chains have long C=O bonds. The C=O bond lengths correlate with these "natural" frequencies, The frequencies obtained from the DFT calculations are generally more coupled, and the most intense are more red shifted than those calculated by transition dipole coupling (TDC). TDC inverts the order of the shifted frequencies compared to DFT in several cases.     

Photoacoustic study of the thermal and optical properties of hippuric acid

Photoacoustic spectroscopy (PAS) is a recently developed, non‐destructive testing (NDT) tool, used for analyzing the physical properties of materials. This method is used here to determine the thermal diffusivity and conductivity of the gel‐grown single crystals of hippuric acid, a minor constituent of urinary calculi and also a non‐linear optical (NLO) material. Optical absorption of the specimen was studied using its PA spectrum and compared with UV‐visible absorption spectra. Second harmonic generation (SHG) conversion efficiency was also carried out. Characterization of the crystals was made using X‐ray powder diffraction and density determination. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An efficient total synthesis of (+)-Cladospolide C

The asymmetric synthesis of (+)-Cladospolide C has been achieved in 11 steps with 26% overall yield. Key steps in the sequence involve KAPA-promoted alkyne Zipper reaction, TPP-promoted enyne ester (ynoate) to diene ester (dienoate) isomerization, Sharpless asymmetric dihydroxylation and Yamaguchi macrolactonization.     

On the lattice of stratified principal L-topologies

We investigate the lattice structure of the set of all stratified principal L-topologies on a given set X. It proves that the lattice of stratified principal L-topologies S p(X) has atoms and dual atoms if and only if L has atoms and dual atoms respectively. Moreover, it is complete and semi-complemented. We also discuss some other properties of the lattice.     

Defects in ion-implanted hcp-titanium: A first-principles study of electronic structures

The electronic structures of hexagonal closed-packed (h.c.p) titanium containing a vacancy and krypton impurity atoms at various insertion sites are calculated by first-principles methods in the framework of the density-functional theory (DFT). The density of states (DOS) for titanium containing a vacancy defect shows resonance-like features. Also, the bulk electron density decreases from ∼0.15/ų to ∼0.05/ų at the vacancy centre. Electronic structure calculations have been performed to investigate what underlies the krypton site preference in titanium. The DOS of the nearest-neighbour (NN) titanium atoms to the octahedral krypton appears to be less distorted (relative to pure titanium) when compared to the NN titanium atoms to the tetrahedral krypton. The electronic density deformation maps show that polarization of the titanium atoms is stronger when the krypton atom is located at the tetrahedral site. Since krypton is a closed-shell atom, thus precluding any bonding with the titanium atoms, we may conclude that the polarization of the electrons in the vicinity of the inserted krypton atoms and the distortion of the DOS of the NN titanium atoms to the krypton serve to indicate which defect site is preferred when a krypton atom is inserted into titanium. Based on these considerations, we conclude that the substitutional site is the most favourable one, and the octahedral is the preferred interstitial site, in agreement with recent DFT calculations of the energetics of krypton impurity sites.     

Effective electro-chemo-therapy for proliferation control of adult human mesenchymal stem cells

Clinically chemo-resistant types of cancers do not respond well to conventional therapies. To treat and enhance the efficacy of drug delivery for these cancers, we have developed an in vitro model of a combination therapy using adult human mesenchymal stem cells, electrical pulses and chemo drug. Adult Mesenchymal stem cells were used because they are similar to cancer stem cells which cause the tumor to be chemo- and radiation resistant. These cells, derived from human adult bone marrow were subjected to low voltage, long duration (200 V/cm, 40 ms and 450 V/cm, 25 ms) and high voltage, short duration (1200 V/cm, 100 μs) pulses. The effect of these voltages on the viability and proliferation ability of these cells in the presence and absence of Bleomycin (chemodrug used for treating various cancers, FDA approved in US and other respective medical agencies in other countries,) indicate the potential of transfer of this technique to clinical practice for effective electro-targeted stem cell therapy.