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A novel and versatile peptide-based bio-logic system capable of regulating cell function is developed using sortase A (SrtA), a peptide ligation enzyme, as a generic processor. By modular peptide design, we demonstrate that mammalian cells apoptosis can be programmed by peptide-based logic operations, including binary and combination gates (AND, INHIBIT, OR, and AND-INHIBIT), and a complex sequential logic circuit (multi-input keypad lock). Moreover, a proof-of-concept peptide regulatory circuit was developed to analyze the expression profile of cell-secreted protein biomarkers and trigger cancer-cell-specific apoptosis.

We report here a label-free and sensitive electrochemical method for probing Citrate synthase (CS) activity based on detailed investigations into the nucleic acid-mimicking coordination polymer (CP) formed from the coenzyme A (CoA)-Ag(I) repeat units. Our biosensing approach provides an especial and significant detection mechanism: CS can catalyze the essential condensation reaction between acetyl-coenzyme A (Ac-CoA) and oxaloacetate (OAA) to form citrate and CoA; then, in the presence of Ag(I), CoA-Ag(I) CP can be in situ formed because of the strong complexation ability of thiol groups of CoA toward Ag(I). The generated CoA-Ag(I) CP attaches to graphene-modified glassy carbon electrode surface by multiple adenine bases deriving from CoA and acting as the side groups along the polymeric backbone, which displays efficient H 2 O 2 -electrocatalyzing activity. More importantly, by using the formed polymer as signal output, the process is implemented to quantitatively analyze the activity of CS. Under the optimal conditions, CS with a detection limit as low as 0.00165 U/µL could be sensitively probed with a wide linear range from 0.0033 to 0.264 U/µL. Furthermore, with the character of label-free detection, high sensitivity and excellent selectivity, this strategy offers a convenient and specific method for CS activity detection and relevant inhibitors screening, which holds a promising potential in the practical application of CS-based biochemical research, disease diagnosis and drug discovery.

A novel inductance-based sensing technique is presented for remote query measurement in different liquid media including organic solvents and inorganic solutions. The inorganic solutions tested included salt solutions of different concentrations, and the organic solvents detected included 1,4-dioxane and tetrahydrofuran. To extend the application of the sensor, bacterial culture media were also detected, and the growth of Escherichia coli (E. coli) was controlled. The influential factors which may affect the inductance responses were studied in detail. It was found that quantitative relationships exist between the sensor’s inductance response and the physico-chemical parameters of the liquid media. The sensor’s inductance response (L) decreases with the increase of salt concentration (C) and its ionic valence (e) according to a semi-logarithmic equation LgL = aeC + b, where a and b are constants, which is in accordance with the theoretically deduced equation. The inductance variation rate (K)

A reversed-phase high-performance liquid chromatography (RP-HPLC) method with fluorescence detection for simultaneous determination of five anthraquinones in Rhubarb collected from nine different locations in China, Polygonum cuspidatum, Polygoni multiflori and three pharmaceutical preparations is proposed and validated. Chromatography was carried out at 25 degrees C on a Hypersil C18 column with the isocratic mobile phase of methanol-0.1% aqueous formic acid (85:15, v/v) at a flow rate of 1.0 ml/min. The excitation and emission wavelengths were set at 440 and 540 nm, respectively. A comprehensive validation of the method included tests of sensitivity, linearity, precision and accuracy. The linear regressions were acquired with r>0.999. Satisfactory intra- and inter-day precisions were achieved with R.S.D.s less than 3.95% and the average recovery factors obtained were in the range of 93.2-103.8%.

Piezoelectric fibre optic reflection spectroelectrochemistry (SEC), a new technique of SEC in combination with quartz crystal microbalance (QCM) detection by using a fibre optic bundle, is proposed. The simultaneous measurements have been performed during the growth of polynaphthylamine film on the platinum electrode of the QCM in acetonitrile. Results show that this technique can provide substantial in situ information of the electrochemical process from SEC and QCM. This novel technique is recommended to find wider applications in the electrochemical study on surface phenomena. In addition, a pH fibre optic sensor based on the polynaphthylamine film as a sensitive membrane is developed.

A piezoelectric sensor is used for the determination of sulpha-drugs, as pure substances and in their dosage forms, by an indirect micro method based on reaction of the sulpha-drug with bromine and reduction of the resultant N-bromoderivative with iodide to form iodine, which after extraction is monitored with a piezoelectric quartz sensor. The response of the sensor is linear from 2 x 10(-5) to 4 x 10(-4)M sulpha-drug.

In this text we present a series of LC-MS/UV-based strategies for on-line structure identification of unknown flavone glycosides in Dracocephalum tanguticum. The aglycone portion, the glycosylation position, the order of sugars and the identity of sugars of each glycoside were unambiguously identified. The new strategy--identifying the partial structure of a molecule by comparison with a different compound possessing the same assumed partial structure--is quite effective for structure identification of the aglycone of 1-4; the unusual non-radical [Y(0)-H-CH(2)](-) ion observed for the methoxylated flavonoid glycoside 8 is quite useful for structure elucidation of the aglycone of 5-8; the UV data obtained on-line with post-column addition of UV-shift reagents are powerful for determination of the glycosylation and methoxylation positions for each flavone glycoside. Finally, isolation and subsequent individual analysis by NMR were performed to provide complementary information for the configurations of each sugar and the linkage types of each disaccharide. Thus, the structures of the eight detected flavone glycosides, which all have never been reported in D. tanguticum before, were positively identified.

The construction and general performance characteristics of three piezoelectric quartz crystal sensors responsive to the pentoxyverine are described here. This kind of non-potentiometric sensing method is based on use of ion-pair complexes of the pentoxyverine cation with three counter anions, namely, tungstophosphate, tetraphenylborate and picrolonate. The complexes were embedded in a PVC matrix. Adsorption of the pentoxyverine ion on the complex caused a frequency decrease of the crystal. The frequency decrease was proportional to the amount of adsorbed analyte. The influencing factors were investigated in detail, and then optimized. The proposed sensors exhibit reasonable selectivity and a higher sensitivity than the potentiometric sensors. For a sensor modified with pentoxyverine-phosphotungstate, the calibration graph was linear over concentration of 1.0 x 10(-7) - 5.0 x 10(-5) M with a detection limit of 6 x 10(-8) M at pH 5.4.

Quaternary ammonium, phosphonium and arsonium membrane electrodes sensitive to benzylpenicillin, ampicillin and oxacillin have been investigated. The order of merit of electrode performance is cetyltrioctylammonium > cetyltrioctylphosphonium > cetyltrioctylarsonium. The electrodes are suggested for use in rapid determination of penicillin drugs by direct potentiometry.

Cetyltrioctylammonium sulphathiazole, sulphadoxine and sulphadimethoxine membrane electrodes are proposed for the potentiometric determination of sulpha-drugs. The construction and basic characteristics of the electrodes are discussed.

An electrode selective for trimethoprim is based on the ion-pair complex of trimethoprim with silicotungstate, and gives rapid response to change in trimethoprim concentration over the range 3 x 10(-5)-2 x 10(-2)M with a response slope of 51.0 +/- 1.5 mV/decade. No significant interferences are caused by sulpha-drugs. The electrode can be used for the potentiometric determination of trimethoprim.

Liquid-membrane and PVC-membrane glycopyrronium-selective electrodes have been developed. They are based on the ion-pair complexes of glycopyrronium with dicyclohexylnaphthalenesulphonate, di-isopentylnaphthalenesulphonate, di-isobutylnaphthalenesulphonate and tetraphenylborate. Their response is nearly Nernstian over the pH-range 4–8, and the detection limits range from 10−6M to 10−5M. For the liquid-membrane electrodes, with homologous membrane solvents, the response slopes are linearly related to the inverse of the dielectric constant of the membrane solvent, according to the formula S = Co − C1/ϵ. A similar relation exists between the slopes for both types of electrode and the dielectric constants of mixed-solvent backgrounds. The electrodes can be used in the potentiometric determination of glycopyrrolate.