Organ-based chemo-profiling of Echinops echinatus Roxb. using high-performance thin-layer chromatography (HPTLC) technique

JPC – Journal of Planar Chromatography – Modern TLC - Plants contain different classes of secondary metabolites that have different levels of solubility in solvents, based on their...     

Herbal standardization of formulation containing curcuminoids,piperine and ascorbic acid by dual detection mode densitometric analysis

JPC – Journal of Planar Chromatography – Modern TLC - A dual detection mode high-performance thin-layer chromatographic (HPTLC) method has been evolved for the contemporaneous...     

Charge regulation as a stabilization mechanism for shell-like assemblies of polyoxometalates

We show that the equilibrium size of single-layer shells composed of polyoxometalate macroions is inversely proportional to the dielectric constant of the medium in which they are dispersed. This behavior is consistent with a stabilization mechanism based on Coulomb repulsion combined with charge regulation. We estimate the cohesive energy per bond between macroions on the shells to be approximately -6kT. This number is extracted from analysis based on a charge regulation model in combination with a model for defects on a sphere. The value of the cohesive bond energy is in agreement with the model-independent critical aggregate concentration. This observation points to a new class of thermodynamically stable shell-like objects. We point out the possible relevance our findings have for certain surfactant systems.     

Cobalt‐Catalyzed Intermolecular C(sp2)O Cross‐Coupling

Cobalt(II)‐catalyzed C(sp²)?O cross‐coupling between aryl/heteroaryl alcohols and vinyl/aryl halides in the presence of Cu^I has been achieved under ligand‐free conditions. In this reaction, copper plays a significant role in transmetalation rather than being directly involved in the C?O coupling. This unique Co/Cu‐dual catalyst system provides an easy access to a library of aryl–vinyl, heteroaryl–styryl, aryl–aryl, and heteroaryl–heteroaryl ethers in the absence of any ligand or additive.     

Experimental signatures of cosmological neutrino condensation

Superfluid condensation of neutrinos of cosmological origin at a low enough temperature can provide simple and elegant solution to the problems of neutrino oscillations and the accelerated expansion of the universe. It would give rise to a late time cosmological constant of small magnitude and also generate tiny masses for the neutrinos as observed from their flavor oscillations. We show that carefully prepared beta decay experiments in the laboratory would carry signatures of such a condensation, and thus, it would be possible to either establish or rule out neutrino condensation of cosmological scale in laboratory experiments.     

Hydrogenation of azides over copper nanoparticle surface using ammonium formate in water

Aryl azides undergo clean reduction by copper nanoparticles and ammonium formate in water. The surface hydrogen on copper nanoparticles is considered to be the active reducing species. A variety of functionalized aryl azides and aryl sulfonyl azides are reduced by this procedure to the corresponding amines with excellent chemoselectivity in high yields.     

Synthesis,Characterization, Covalent Binding,and Degree of Unwinding of Platinum(II) Bipyridine Complexes

The complexes [Pt(3′′‐clpbpy)Cl₂] ( 1 ) [3′′‐clpbpy = 4‐(3′′‐chlorophenyl)‐6‐phenyl‐2, 2′‐bipyridine], [Pt(4′′‐clpbpy)Cl₂] ( 2 ) [4′′‐clpbpy = 4‐(4′′‐chlorophenyl)‐6‐phenyl‐2, 2′‐bipyridine], [Pt(3′′‐brpbpy)Cl₂] ( 3 ) [3′′‐brpbpy = 4‐(3′′‐bromophenyl)‐6‐phenyl‐2, 2′‐bipyridine], and [Pt(4′′‐brpbpy)Cl₂] ( 4 ) [4′′‐brpbpy = 4‐(4′′‐bromophenyl)‐6‐phenyl‐2, 2′‐bipyridine] were synthesized and characterized. The binding of the complexes with herring sperm DNA (HS DNA) was investigated by absorption titration and viscosity measurements. It was found that the complexes have ability of interaction with DNA by covalent mode. The intrinsic binding constant K_b of the complexes with HS DNA is 8.76 × 10⁴ ( 1 ), 9.89 ×10⁴ ( 2 ), 1.52 × 10⁵ ( 3 ), and 2.31 × 10⁵ ( 4 ) M^–1. The slight depression in relative specific viscosity was observed, which also attributes to covalent binding of complexes with DNA bases. Gel electrophoresis assay demonstrated the ability of the complexes to unwind negatively supercoiled pUC19 plasmid by 14° ( 1 ), 13° ( 2 ), 13° ( 3 ), and 11° ( 4 ). The in vitro cytotoxic property of the synthesized metal complexes was also carried out against brine shrimp bioassay.     

Voltammetric studies of polyoxometalate microparticles in contact with the reactive distillable ionic liquid DIMCARB

The voltammetry of the polyoxometalate salts [Bu₄N]₄[SiW₁₂O₄₀] (α, β, γ* isomers), [Bu₄N]₄[S₂W₁₈O₆₂] (α, γ* isomers) and [Bu₄N]₄[S₂Mo₁₈O₆₂] (α isomer) has been studied in the “distillable ionic liquid” DIMCARB (a mixture of adducts, both ionic and neutral, of dimethylamine and carbon dioxide). Dissolution of these salts tended to be slow and the anions, except [α-SiW₁₂O₄₀]⁴⁻, reacted with DIMCARB. However, high quality voltammograms were obtained from microparticles of the salts adhered to a glassy carbon electrode in contact with DIMCARB. Rapid dissolution of the reduced forms of each of the polyoxometalate anions provided reversible potential data. The higher basicity of the more highly reduced anions promoted interactions with the acidic solvent component of this medium. Comparison of reversible potentials indicated that the polarity of DIMCARB is similar to CH₃CN, but smaller than that of conventional non-volatile ionic liquids and water.     

Site-selective glycosylation of hemoglobin with variable molecular weight oligosaccharides: potential alternative to PEGylation

Poly(ethylene glycol) (PEG) conjugation (i.e., PEGylation) is a commonly used strategy to increase the circulatory half-life of therapeutic proteins and colloids; however, few viable alternatives exist to replicate its functions. Herein, we report a method for the rapid site-selective glycosylation of proteins with variously sized carbohydrates, up to a molecular weight (MW) of 10,000, thus serving as a potential alternative for PEGylation. More importantly, the method developed has two unique features. First, traditional protecting group strategies that typically accompany the modification of the carbohydrate fragments are circumvented, allowing for the facile site-selective glycosylation of a desired protein with variously sized glycans. Second, the methodology employed is not limited by oligosaccharide size; consequently, glycans of MW similar to that of PEG, used in the PEGylation of therapeutic proteins, can be employed. To demonstrate the usefulness of this technology, hemoglobin (Hb) was site-selectively glycosylated with a series of carbohydrates of increasing MW (from 504 to ～10,000). Hb was selected on the basis of the vast wealth of biochemical and biophysical knowledge present in the literature and because of its use as a precursor in the synthesis/formulation of artificial red blood cell substitutes. Following the successful site-selective glycosylation of Hb, the impact of increasing the glycan MW on Hb's biophysical properties was investigated in vitro.