Rapid and Reliable Excitation Wavelength-Dependent Detection of 2,6-Dipicolinic Acid Based on a Luminescent Cd(II)-Tb(III) Nanocluster.

A Cd(II)-Tb(III) nanocluster {[Cd10Tb9L8(OH)16(OAc)23(H2O)3][Cd10Tb9L8(OH)16(OAc)23(H2O)4]}·3H2O (1), which contains two crystallographically independent components, was constructed from a tridentate ligand (HL, 3-ethoxysalicylaldehyde). It exhibits rapid and reliable excitation wavelength-dependent luminescence response to 2,6-dipicolinic acid (DPA) [limit of detection = 0.23 nM], which is not influenced by aromatic carboxylates, amino acids, and ions. The test papers of 1 can be used to check DPA in solution. The equation IEx272nm/IEx329nm = 0.0109 × [DPA]2 + 0.106 × [DPA] + 2.39 of 1 for the luminescence response could be used to quantitatively measure the concentration of DPA in tap water. 1 displays rapid and stable luminescence response to DPA, with the sensing times shorter than 5 s and no changes for the lanthanide luminescence over 24 h.

The function of glucose metabolism in embryonic diapause of annual killifish.

Annual killifish could survive as diapaused embryos buried in soil during dry seasons. When the embryos in diapause III were incubated in water, the larvae could be hatched quickly. However, the mechanism of diapause and hatching of annual killifish was ambiguous. In the present study, Nothobranchius guentheri were used as the model to clarify the physiological mechanism of diapause and hatching of annual killifish. The results indicated that incubation with water could significantly enhance the heart rate and blood circulation of embryos. To clarify the molecular mechanism, the transcriptomic analysis was used to compare the embryos in diapause I, diapause III, and hatching period. The results showed that DNA replication-related genes, cell division cycle 45 and proliferating cell nuclear antigen were more highly expressed in diapause I compared to diapause III. In addition, the transcript levels of glucagon, glucokinase and phosphofructokinase were more abundantly detected in hatching period compared to diapause III, but insulin receptor and insulin-like growth factor-binding protein were lower. These results indicated glucose metabolism might play an important role in diapause and hatching of killifish. To further confirm this result, several reagents involved in glucose metabolism were used to incubate embryos in diapause III. The results displayed that glucose and glucagon could both shorten the hatching time of embryos. In contrast, 2-deoxy-d-glucose, metformin, and insulin could prolong the hatching time and reduce the hatching rate. The results further confirmed that glucose metabolism played an important role in the diapause and hatching of annual killifish.

Ratiometric fluorescent detection of dipicolinic acid as an anthrax biomarker based on a high-nuclearity Yb18 nanoring.

An 18-metal lanthanide nanoring [Yb18(L1)8(HL2)2(OAc)20(MeOH)8(EtOH)6(H2O)4] (1), which shows a ratiometric fluorescent response to DPA, was constructed through the strategy of using two types of polydentate organic ligands. The addition of DPA increases the visible ligand-centered emission, but decreases the NIR lanthanide luminescence of 1. The limit of luminescent detection of 1 for DPA is 1.5 µM. The high fluorescence sensitivity of 1 to DPA is not affected by the existence of interferents such as aromatic carboxylates and ions.

Construction of a high-nuclearity Nd(III) nanoring for the NIR luminescent detection of antibiotics.

One NIR luminescent 14-metal Nd(iii) nanoring (1, molecular size: 1.0 × 2.2 × 2.6 nm) was obtained from a rigid tridentate ligand, which can absorb and transfer light energy to the Nd(iii) ions. 1 shows interesting luminescence sensing activity to antibiotics, in particular to NFAs with high sensitivity due to the inner filter effect. The quenching constants and the limits of detection of 1 to NFAs are 1.05 × 104 M-1-2.33 × 104 M-1 and 3.05 µM-6.75 µM, respectively. The high fluorescence sensitivities of 1 to NFAs are not changed by the existence of other antibiotics. It also exhibits high sensitivity in the luminescent detection of NFAs contained in real antibiotic drugs.

Construction of Zn(II)/Cd(II)-Yb(III) Schiff Base Complexes for the NIR Luminescent Sensing of Fluoroquinolone Antibiotics.

Two NIR luminescent Zn(II)/Cd(II)-Yb(III) complexes were obtained by the use of a Schiff base ligand with a binaphthyl backbone. Cd(II)-Yb(III) complex 2 has a triangular structure and exhibits interesting luminescent sensing activity to antibiotics, in particular to ciprofloxacin (CPFX) and norfloxacin (NFX) due to the inner filter effect. The limits of the detection of 2 to CPFX and NFX are 0.18 and 0.36 µM, respectively, and the fluorescence sensitivity is not changed with the existence of other antibiotics tested in this study.

Kinetic analysis of the weak affinity interaction between tris and lysozyme.

The biosensor based on total internal reflection imaging ellipsometry (TIRIE), regarded as an automotive real-time research approach for biomolecular interaction, is introduced to analyze the kinetic process of the weak interaction between tris and lysozyme. The experiment is performed by delivering lysozyme solution diluted to different concentrations to the biosensor substrate interface immobilized with tris. By applying pseudo-first-order interaction kinetics model, we are able to obtain the kinetic parameters from fitting experimental data. The calculated association rate constant and dissociation rate constant of tris and lysozyme interaction are in 10(-2) mol(-1) s(-1) and 10(3)s(-1) magnitude, respectively. To further improve TIRIE's ability for kinetically characterizing biomolecular interaction, a theoretical method to deduce associate rate constant before experiment is proposed.

Analysis of interactions between SNARE proteins using imaging ellipsometer coupled with microfluidic array.

The soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins are small and abundant membrane-bound proteins, whose specific interactions mediate membrane fusion during cell fusion or cellular trafficking. In this study, we report the use of a label-free method, called imaging ellipsometer to analyze the interactions among three SNAREs, namely Sec22p, Ykt6p and Sso2p. The SNAREs were immobilized on the silicon wafer and then analyzed in a pairwise mode with microfluidic array, leading us to discover the interactions between Ykt6p and Sso2p, Sec22p and Sso2p. Moreover, by using the real-time function of the imaging ellipsometer, we were able to obtain their association constants (K(A)) of about 10(4) M(-1). We argue that the use of imaging ellipsometer coupled with microfluidic device will deepen our understanding of the molecular mechanisms underlying membrane fusion process.