Evidence for strain glass in the ferroelastic-martensitic system Ti(50-x)Ni(50+x)

We report here "strain glass," a new glassy phenomenon in ferroelastic-martensitic system of Ni-rich intermetallic Ti(50-x)Ni(50+x) (x > 1), where local strain is frozen in disordered configuration below a critical temperature Tg. The ac elastic modulus shows a minimum at Tg, which exhibits logarithmic frequency dependence following Vogel-Fulcher relationship, and the corresponding internal friction shows a frequency-dependent peak located at a lower temperature. In situ high-resolution transmission electron microscopy observations reveal uncorrelated nanoclusters of martensiticlike phase, randomly frozen in the otherwise untransformed parentlike matrix. Being parallel to spin glass and relaxor, strain glass may shed new light on the fundamental physics of glass and lead to the discovery of novel properties.     

Conformational preferences of the aglycon moiety in models and analogs of GlcNAc-Asn linkage: crystal structures and ab initio quantum chemical calculations of N-(beta-D-glycopyranosyl)haloacetamides

The biological addition of oligosaccharide structures to asparagine residues of N-glycoproteins influences the properties and bioactivities of these macromolecules. The linkage region constituents, 2-acetamino-2-deoxy-beta-D-glucopyranose monosaccharide (GlcNAc) and L-asparagine amino acid (Asn), are conserved in the N-glycoproteins of all eukaryotes. In order to gain information about the structure and dynamics of glycosylated proteins, two chloroacetamido sugars, Glc betaNAcNHCOCH2Cl and Man betaNHCOCH2Cl, have been synthesized, and their crystal structures have been solved. Structural comparison with a series of other models and analogs gives insight about the influence of the N-acetyl group at position C2 on the conformation of the glycan-peptide linkage at C1. Interestingly, this N-acetyl group also influences the packing and network of hydrogen bonds with involvement in weak hydrogen bonds C-H...X that are of biological importance. DFT ab initio calculations performed on a series of models and analogs also confirm that the GlcNAc derivatives present different preferred conformation about the N-CO-CH2-X (chi2) torsion angle of the glycan-peptide linkage, when compared to other monosaccharide derivatives. The energy profiles that have been obtained will be useful for parametrization of molecular mechanics force-field. The conjunction of crystallographic and computational chemistry studies provides arguments for the structural effect of the N-acetyl group at C2 in establishing an extended conformation that presents the oligosaccharide away from the protein surface.     

Gold nanoparticles functionalized with deep-cavity cavitands: synthesis, characterization, and photophysical studies

In this report, we present methods of functionalization of AuNP's with deep-cavity cavitands that can include organic molecules. Two types of deep-cavity cavitand-functionalized AuNP's have been synthesized and characterized, one soluble in organic solvents and the other in water. Functionalized AuNP soluble in organic solvents forms a 1:1 host-guest complex where the guest is exposed to the exterior solvents. The one soluble in water forms a 2:1 host-guest complex where the guest is protected from solvent water. Phosphorescence from thiones and benzil included within heterocapsules attached to AuNP was quenched by gold atoms present closer to the guests included within deep-cavity cavitands. During this investigation, we have synthesized four new deep-cavity cavitands. Of these, two thiol-functionalized hosts allowed us to make stable AuNP's. However, AuNP's protected with two amine-functionalized cavitands tended to aggregate within a day.     

Development of a new fluorescence ratiometric switch for endogenous hypochlorite detection in monocytes of diabetic subjects by dye release method

Increased oxidative stress in metabolic complications like type 2 diabetes, dyslipidemia and cardiovascular disorders exerts potential health hazards in many facets. Enhanced production of reactive oxygen species (ROS) due to increased oxidative stress promotes the damage of many biologically important macromolecules. Hypochlorous acid (HOCl), a microbicidal agent is also known to be an important ROS sub-species. An enhanced generation of endogenous HOCl due to diseased condition therefore can be detrimental to health. In present work, a new quinoline-diaminomaleonitrile based probe (HQMN) has been designed for the selective detection of hypochlorite. The probe in hand shows a selective ratiometric emission change towards OCl^?. The probe behaves as a highly selective and sensitive tool for the detection of OCl^? over other analytes with a fast response time (within 100 s). Bioimaging study revealed that HQMN can detect endogenous OCl^? in human monocytes and an increase in endogenous HOCl concentration has been witnessed in diabetic condition compared to healthy control. Thus HQMN can be used as an excellent fluorescent probe for dynamic tracking of hypochorite in living biological cells especially to identify diabetic conditions.     

Solvent-Dependent Nanostructures Based on Active π-Aggregation Induced Emission Enhancement of New Carbazole Derivatives of Triphenylacrylonitrile

In the present study, the carbazole and 2,3,3-triphenylacrylonitrile (TPAN) nanostructures (2-CTPAN and 2,2′-CTPAN) have been designed and synthesized by Pd-catalyzed Sonogashira cross-coupling reaction. CTPAN exhibit aggregation-induced emission enhancement (AIEE) behavior in water with high fluorescence quantum yield. Both the compounds show tunable self-assembly in water as well as in N,N-dimethylformamide (DMF) by extended π–π stacking interactions. CTPAN can be self-assembled into spherical particles in water and the structures of these self-assemblies have been investigated using X-ray diffraction. Interestingly, 2-CTPAN and 2,2′-CTPAN form organogels with a critical gelation concentration (CGC) of 11 and 15 mg mL⁻¹, respectively, in DMF and exhibit acicular and rod shaped morphology, respectively. The single-crystal structure of 2-CTPAN shows that the intermolecular C−H⋅⋅⋅π interactions lock the molecular conformation into a staircase-shaped supramolecular assembly. These AIEE active compounds reveal high water dispersibility, strong yellow fluorescence with high quantum yield, promising photostability and excellent biocompatibility, which make them potential bioimaging agents.     

Ethanolic or Aqueous Formic Acid (1:1) - A New Efficient Reagent for the Regeneration of Ketones from Phenylhydrazones

50% Ethanolic or aqueous formic acid has been found to be extremely efficacious for the regeneration of aliphatic and aromatic ketones from phenylhydrazones.     

A Triphenyl Amine‐Based Solvatofluorochromic Dye for the Selective and Ratiometric Sensing of OCl− in Human Blood Cells

A new visible‐light‐excitable fluorescence ratiometric probe for OCl^? has been developed based on a triphenylamine‐diamiomaleonitrile (TAM) moiety. The structure of the dye was confirmed by single‐crystal X‐ray analysis. It behaves as a highly selective and sensitive probe for OCl^? over other analytes with a fast response time (～100 s). OCl^? reacts with the probe leading to the formation of the corresponding aldehyde in a mixed‐aqueous system. The detection limit of the probe is in the 10^?8 M range. The probe (TAM) also exhibits solvatofluorochromism. Changing the solvent from non‐polar to polar, the emission band of TAM largely red‐shifted. Moreover, the probe shows an excellent performance in real‐life application in detecting OCl^? in human blood cells. The experimentally observed changes in the structure and electronic properties of the probe after reaction with OCl^? were studied by DFT and TDDFT computational calculations.     

A study on the order–disorder phase transformations of rapidly solidified Sm–Co-based permanent magnets

The structural transformation from the metastable, disordered TbCu₇-type SmCo₇ structure to the equilibrium, ordered Th₂Zn₁₇-type Sm₂Co₁₇ structure was revealed by X-ray diffraction analysis using Rietveld refinement. The magnetic properties depended strongly on the stage of the transformation, as the coercivity depended on the annealing temperature. The as-solidified alloys in the TbCu₇-type structure exhibited coercivity as high as 7.85 kOe, which increased to greater than 9 kOe after heat treatment. The magnetization processes were also strongly influenced by the structural state. Initially it was dominated by nucleation processes, which gave way to domain wall pinning-controlled magnetization processes with the development of the Sm₂Co₁₇ structure. Transmission electron microscopy revealed the development of antiphase domains during heat treatment, which apparently served as the domain-wall pinning sites during magnetization reversal.     

Metallic conduction through engineered DNA: DNA nanoelectronic building blocks

A novel way of engineering DNA molecules involves substituting the imino proton of each base pair with a metal ion to obtain M-DNA with altered electronic properties. We report the first direct evidence of metalliclike conduction through 15 microm long M-DNA. In contrast, measurements on B-DNA give evidence of semiconducting behavior with a few hundred meV band gap at room temperature. The drastic change of M-DNA conductivity points to a new degree of freedom in the development of future molecular electronics utilizing DNA, such as creating all-DNA junction devices for use as nanoelectronic building blocks.     

Photodimerization of hydrophobic guests within a water-soluble nanocapsule

Conducting reactions in environmentally benign conditions is one of the major objectives of “green chemistry.” In this context, developing ways to conduct reactions in water seems obvious. In this report, we present our results on photodimerization of select guest molecules placed within the rigid reaction cavity of a water-soluble cavitand, octa acid. The results presented herein highlight the value of a supramolecular approach in achieving selectivity in photoreactions and opening reaction pathways that are latent in solution chemistry.