[en] A novel compound based on catalytic functional metal rhenium, pyridinium perrhenate(PyHReO₄) was synthesized and characterized. The pyridinium perrhenate was used as catalyst in two types of reactions. One is the epoxidation of cyclooctene, the other is the Baeyer-Villiger oxidation of cyclicketones to lactones. The effects of catalyst, oxidant, solvent, reaction time and temperature were investigated,which confirmed the optimum reaction conditions of the catalyst system. Both types of catalytic reactions exhibit high yields and high selectivity. (author)

[en] Biochemical markers of bone turnover has received increasing attention over the past few years, because of the need for sensitivity and specific tool in the clinical investigation of osteoporosis. Bone markers should be unique to bone, reflect changes of bone less, and should be correlated with radiocalcium kinetics, histomorphometry, or changes in bone mass. The markers also should be useful in monitoring treatment efficacy. Although no bone marker has been established to meet all these criteria, currently osteocalcin and pyridinium crosslinks are the most efficient markers to assess the level of bone turnover in the menopausal and senile osteoporosis. Recently, N-terminal telopeptide (NTX), C-terminal telopeptide (CTX) and bone specific alkaline phosphatase are considered as new valid markers of bone turnover. Recent data suggest that CTX and free deoxypyridinoline could predict the subsequent risk of hip fracture of elderly women. Treatment of postmenopausal women with estrogen, calcitonin and bisphosphonates demonstrated rapid decrease of the levels of bone markers that correlated with the long-term increase of bone mass. Factors such as circadian rhythms, diet, age, sex, bone mass and renal function affect the results of biochemical markers and should be appropriately adjusted whenever possible. Each biochemical markers of bone turnover may have its own specific advantages and limitations. Recent advances in research will provide more sensitive and specific assays

[en] Calixarenes and their derivatives in recent times have been enjoying considerable attention, for their application in areas as diverse as catalysis, enzyme mimics, host-guest chemistry, selective ion transport and sensors. Calixarenesare macrocyclic compounds comprising of phenolic units connected by methylene bridges. Different calixarenes with varied size ranging from three to twenty repeating units are known today. Chemical modifications are possible both at the upper and the lower rim in order to introduce functional groups or to change solubility of the molecule or the size of the cavity. This makes calix[n]arenes versatile molecular platforms for encapsulation and building of supramolecular structures. Due to the selective inclusion of desired molecules such as neutral, cations and anions, they serve as designable receptors

[en] Development of molecular probes for imaging various analytes in biological tissues and cells has high importance in the modern disease diagnostics, therapy monitoring and patient management. Zinc is one of the most abundant transition metals present in human body and evidence suggest that it plays crucial role in autophagy process. Herein, we report a new, rigid pentacyclicpyridinium based probe, PYD-PA having a pendant N,N-di(pyridin-2-ylmethyl)amine(DPA) for Zn²⁺ ion detection in cellular environment. The pyridinium moiety itself serves as mitochondria targeting unit and DPA act as the coordination site for Zn²⁺.The probe exhibited highly selective response to Zn²⁺ over other biological metal ions, good water solubility, photostability, pH insensitivity, and low cytotoxicity. The demonstration of bioimaging in L6 cell lines of rat confirmed intracellular Zn sensing ability of the probe. Furthermore,the probe was successfully applied for sensitively monitoring the fluctuation of intracellular free zinc ions in real time during autophagy condition

No abstract available

[en] A sensitive nanopipette sensor is established through a unique design of host–guest recognition, which could be further enhanced by the introduction of gold nanoparticles (Au NPs). Generally, the nanopipette is conjugated with caboxylatopillar[5]arenes (CP[5]) or carboxylated leaning pillar[6]arene (CLP[6]) to generate recognition sites. After the addition of pesticide molecules, they would be captured by CP[5] (or CLP[6]), resulting in a significant electronegativity change on the nanopipette’s inner surface, which could be determined by the ionic current change. The CP[5]-modified nanopipette exhibited reliable selectivity for paraquat, while the CLP[6]-modified nanopipette showed an ability of detection for both paraquat and diquat. The addition of Au NPs improved the selectivity and sensitivity of the CP[5]-Au NP-modified nanopipette for paraquat sensing. After optimization by lowering the size of the Au NPs, CP[5]-Au NPs (3 nm)-modified nanopipettes achieved lower detection limits of 0.034 nM for paraquat. Furthermore, in real sample analysis, this sensor demonstrates exceptional sensitivity and selectivity. This study provides a new strategy to develop nanopipette sensors for practical small molecule detection.

Graphical abstract

The gold nanoparticles enhanced quartz nanopipette sensor based on host-guest interaction was firstly established, which could achieve an excellent limit of detection of 3.4 × 10^-11 mol/L for paraquat.

[en] The catalytic potential of chiral proline amides and pyridinium salts in the aldol condensation in water was investigated. The aldol reactions of acetone with various aromatic aldehydes were carried out in water by using proline amide derivatives and pyridinium salts derived from chiral pyridine derivatives for the first time. The products were obtained in good yields within short reaction times. (author)

[en] We have found that the tightly convoluted polypyridinium phosphotungstate catalyst 1 efficiently promoted the chemoselective oxidation of sulfides to sulfones with hydrogen peroxide. The catalyst was reused four times without loss of catalytic activity. Sulfones have generated considerable interest due to their presence in a number of biologically active compounds and also to their utility in organic synthesis. Sulfide oxidation is one of the standard approaches to sulfones, where a stoichiometric or larger amount of hazardous oxidants such as KMnO₄, MCPBA, and MMPP is often required. If sulfides could be efficiently oxidized with hydrogen peroxide by using a recyclable catalyst, the catalytic oxidation system would provide a viable, safe, clean, and environmentally benign alternative to the conventional stoichiometric oxidations

[en] Herein, we report synthesis of cetyl pyrydinium bromide caped fluorescent gold nanoparticles (CPB-AuNPs) for the selective and sensitive detection of cysteamine. The gold nanoparticles (CPB-AuNPs) were synthesized by chemical reduction method and further were modified by using fluorescein isothiocyanate (FITC). FITC-AuNPs and their interaction with cysteamine were characterized by different analytical techniques. The reported approach was successfully employed for the selective detection of cysteamine in biomedical sample. (author)

[en] Short communication