Sensitive voltammetric detection of yeast RNA based on its interaction with Victoria Blue B

Voltammetric studies of the interaction of yeast RNA (y-RNA) with Victoria Blue B (VBB) are described in this paper. Furthermore, a linear sweep voltammetric method for the detection of y-RNA was established. The reaction conditions, such as acidity and amount of buffer solution, the concentration of VBB, the reaction time and temperature, etc., were carefully investigated by second order derivative linear sweep voltammetry. Under the optimal conditions, the reduction peak current of VBB at –0.75 V decreased greatly after the addition of y-RNA to the solution without any shift of the reduction peak potential. Based on the decrease of the peak current, a new quantitative method for the determination of y-RNA was developed. The effects of co-existing substances on the determination were carefully investigated and three synthetic samples were determined with satisfactory results. The stoichiometry of the VBB–y-RNA complex was calculated by linear sweep voltammetry and the interaction mechanism is discussed

Spectrophotometric determination of yeast RNA with neutral red

The interaction of neutral red (NR) with yeast RNA (yRNA) was studied by UV-Vis spectrophotometry to develop a simple spectrophotometric method for the determination yRNA. NR exhibited a maximum absorption peak at 528 nm in a Britton-Robinson (B-R) buffer solution of pH 4.0. After the addition of yRNA into NR solution, the absorbance value was greatly decreased and no new absorption peaks appeared. The interaction conditions such as the buffer pH, reaction time, etc. were carefully studied. Under the optimal conditions the decrease in absorbance value was proportional to the yRNA concentration in the range from 0.2 to 20.0 mg L-1 when 8.0 × 10-5 M NR was employed. The detection limit was calculated as 0.78 mg L-1 (3σ) and three synthetic samples were determined satisfactorily. A binding ratio of NR to yRNA was found to be 1:1 by the molar ratio method. KEY WORDS: Neutral red, Yeast RNA, Interaction, UV-Vis spectrophotometry   Bull. Chem. Soc. Ethiop. 2008, 22(3), 441-444

A new electrochemical method for the determination of chondroitin sulfate based on its supramolecular interaction with cupferron-lead(II) complex

In this paper, the interaction of cupferron (Cup) and lead (II) complex [Cup-Pb (II)] with chondroitin sulfate (CS) was investigated by linear sweep voltammetric method. In the selected medium of pH 5.5 (acetic acid-hexamine buffer solution), Cup can interact with Pb (II) to form a stable complex of [Cup-Pb(II)], which has a sensitive second order derivative polarographic reductive peak at -0.64V (vs.SCE). After the addition of CS into Cup-Pb (II) complex solution, the reductive peak current decreased without any shift of the peak potential and no new peak appeared, which indicated that an unelectroactive supramolecular complex of CS with [Cup-Pb(II)] was formed. The binding reaction conditions were carefully investigated. Under the optimal conditions, the interaction mechanism was discussed. The decrease of reductive peak current was directly proportional to the CS concentration, thus a new quantitative determination method for CS was established with the linear regression equation as ΔIp″(nA)=36.97 C/mg L-1+12.45 (n=10, γ=0.995). The effects of other substances on the determination were carefully investigated and three synthetic samples were determined with satisfactory results. The binding constant (βs) and the binding number (m) of CS with [Cup-Pb(II)] complex were calculated from the voltammetric data with the results as βs=1.89×1010 and m≈2.5

Voltammetric determination of heparin based on its interaction with malachite green

In this paper malachite green (MG) was used as a bioprobe to determine heparin concentration by linear sweep voltammetry on the dropping mercury working electrode (DME). In Britton-Robinson (B-R) buffer solution of pH 1.5, MG had a well-defined second order derivative linear sweep voltammetric reductive peak at         –0.618 V (vs. SCE). After the addition of heparin into the MG solution, the reductive peak current decreased apparently without the movement of peak potential. Based on the difference of the peak current, a new voltammetric method for the determination of heparin was established. The conditions for the binding reaction and the electrochemical detection were optimized. Under the selected experimental conditions the difference of peak current was directly proportional to the concentration of heparin in the range from 0.3 to 10.0 mg/L with the linear regression equation as ∆ip″ (nA) = 360.19 C (mg/L) + 178.88 (n = 15, γ = 0.998) and the detection limit as 0.28 mg/L (3σ). The effects of coexisting substances such as metal ions, amino acids on the determination of heparin were investigated and the results showed that this method had good selectivity. This method was further applied to determine the heparin content in heparin sodium injection samples with satisfactory results and good recovery. The stoichiometry of the biocomplex was calculated by the electrochemical method and the binding mechanism was further discussed. KEY WORDS: Heparin, Malachite green, Voltammetry, Binding reaction  Bull. Chem. Soc. Ethiop. 2008, 22(2), 165-172

Voltammetric investigation on interaction of Hyaluronic Acid with crystal violet and its analytical application

In this paper, the interaction of hyaluronic acid (HA) with crystal violet (CV) was investigated carefully by linear sweep voltammetry on the dropping mercury working electrode (DME). In pH 5.0 Britton-Robinson (B-R) buffer solution, CV has a sensitive, well-defined second order derivative linear sweep voltammetric reductive wave at –0.85 V (vs. SCE). After adding a certain amount of HA into CV solution, the reductive peak current decreased without any shift of reductive peak potential. Based on the difference in the reductive peak current, a new voltammetric method for the detection of HA was established. The reaction conditions and the electrochemical determination were studied and optimized. Under the optimized conditions, the decrease of peak current showed a good linear relationship with the HA concentration in the range from 10.0 to 40.0 mg/L. The linear regression equation was got as ∆ip″(nA)= 84.07 C–527.86  (mg/L) (n=8, γ=0.997) and the detection limit was calculated as 2.65 mg/L (3σ). This new established method was further used to HA determination in the synthetic samples with satisfactory results and good recovery. The stoichiometry of CV-HA complex was calculated and the binding mechanism was also discussed by the electrochemical data

Upper Bound Limit Analysis for Seismic Stability of Rock Slope with Tunnel

The rock slopes with tunnels appear widely in the actual project, but there is no executable basis for the seismic stability calculation of the rock slope with tunnel. According to the upper bound theorem of plastic limit analysis and pseudostatic method, the upper bound solution of the safety factor of the rock slope with tunnel was rigorously derived under earthquake loading. This upper solution takes into account the design parameters of the slope and the tunnel, the horizontal and vertical seismic loads, and the physical and mechanical parameters of the rock mass. Comparing the calculated results with the existing results, the validity of the proposed method was verified. The sensitivity and influence of different parameters on the seismic stability of the slope were analyzed. The results show that the three factors such as the horizontal seismic force coefficient, the slope height, and the internal friction angle are the three key factors that influence the sensitivity of the safety factor and have a great effect on it

Electrochemical detection of heparin based on its interaction with acridine orange

476-482The interaction of acridine orange (AO) with heparin was studied by voltammetric method. In Britton-Robinson (B-R) buffer solution (pH 2.3), AO showed a sensitive linear sweep voltammetric reductive peak at -0.94 V (vs. SCE). The addition of heparin into the AO solution caused a decrease in the reductive peak current without any change in the peak potential. The results indicated that a reaction occurred between the positively charged AO and the negatively charged heparin, which led to the decrease of the free AO concentration and subsequent decrease of the reductive peak current of AO. Under the optimal conditions, the decrease of reductive peak current of AO was proportional to heparin concentration in the range of 0.8-6.0 mg L⁻¹ and the data reductive peak current were correlated as ∆ip″(nA)=807.58 C (mg L⁻¹)-542.51 (n=10, correlation coefficient ϒ=0.995) and the detection limit was calculated as 0.13 mg L⁻¹ (3 S₀/S). The new method was successfully applied to the determination of heparin content in heparin sodium injection samples with satisfactory results and good recovery. The interaction of the reactants was also confirmed by UV-Vis absorption spectrophotometric experiments

Parameter Sensitivity of Shallow-Bias Tunnel with a Clear Distance Located in Rock

In order to obtain the seismic internal force response laws of a shallow-bias tunnel with a small clear distance, the reliability of the numerical simulation is verified by the shaking table model test. The parameter sensitivity of the tunnel is studied by using MIDAS-NX finite element software. The effects of seismic wave peak (0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g, and 0.6 g), existing slope angle (30°, 45°, 60°, and 90°), clear distance (1.0 D, 1.5 D, 2.0 D, and 3.0 D), and excitation mode (X direction, Z direction, XY direction, and XYZ direction) on the internal force response law of the tunnel are studied, respectively. The results show that (1) the shear force gradually increases with the increasing of seismic peak. The amplification is different with different measuring points. (2) Under different existing slope-angle conditions, the variation trend of shear force of the tunnel is similar, but the shear force is different. The existing slope has significant effect on the shear force response of the tunnel, and the degree is different with different slope angles. (3) Under the conditions of 1.5 D and 2.0 D, the shear force response of the tunnel is stronger, but the response of other conditions is relatively weak. The tunnel with 1.5 D to 2.0 D clear distance should be avoided. Different excitation modes have a significant effect on the shear force response of the tunnel. (4) Under the same excitation mode, the different excitation directions also have a significant effect on the shear force response. (5) The shear force response of the tunnel crosssection shows nonlinear variation trend. The shear force response is strongest at the arch shoulder and arch foot of the tunnel. The research results provide a useful reference for the design of antishock and vibration resistance of the tunnel

<b>Voltammetric determination of heparin based on its interaction with malachite green</b>

In this paper malachite green (MG) was used as a bioprobe to determine heparin concentration by linear sweep voltammetry on the dropping mercury working electrode (DME). In Britton-Robinson (B-R) buffer solution of pH 1.5, MG had a well-defined second order derivative linear sweep voltammetric reductive peak at –0.618 V (vs. SCE). After the addition of heparin into the MG solution, the reductive peak current decreased apparently without the movement of peak potential. Based on the difference of the peak current, a new voltammetric method for the determination of heparin was established. The conditions for the binding reaction and the electrochemical detection were optimized. Under the selected experimental conditions the difference of peak current was directly proportional to the concentration of heparin in the range from 0.3 to 10.0 mg/L with the linear regression equation as ∆ip″ (nA) = 360.19 C (mg/L) + 178.88 (<i>n</i> = 15, <i>γ</i> = 0.998) and the detection limit as 0.28 mg/L (3<i>σ</i>). The effects of coexisting substances such as metal ions, amino acids on the determination of heparin were investigated and the results showed that this method had good selectivity. This method was further applied to determine the heparin content in heparin sodium injection samples with satisfactory results and good recovery. The stoichiometry of the biocomplex was calculated by the electrochemical method and the binding mechanism was further discussed