Investigation of binding behaviour of procainamide hydrochloride with human serum albumin using synchronous,3D fluorescence and circular dichroism

Interaction of procainamide hydrochloride（PAH） with human serum albumin（HSA） is of great significance in understanding the pharmacokinetic and pharmacodynamic mechanisms of the drug. Multi-spectroscopic techniques were used to investigate the binding mode of PAH to HSA and results revealed the presence of static type of quenching mechanism. The number of binding sites, binding constants and thermodynamic parameters were calculated. The results showed a spontaneous binding of PAH to HSA and hydrophobic interactions played a major role. In addition, the distance between PAH and the Trp–214 was estimated employing the F？rster＇s theory. Site marker competitive experiments indicated that the binding of PAH to HSA primarily took place in subdomain IIA（Sudlow＇s site I）. The influence of interference of some common metal ions on the binding of PAH to HSA was studied. Synchronous fluorescence spectra（SFS）, 3D fluorescence spectra and circular dichroism（CD） results indicated the conformational changes in the structure of HSA.

Multi-spectroscopic investigation of the binding interaction of fosfomycin with bovine serum albumin

The interaction between fosfomycin （FOS） and bovine serum albumin （BSA） has been investigated ef- fectively by multi-spectroscopic techniques under physiological pH 7.4. FOS quenched the intrinsic fluorescence of BSA via static quenching. The number of binding sites n and observed binding constant KA were measured by the fluorescence quenching method. The thermodynamic parameters AG0, AH0 and △S0 were calculated at different temperatures according to the van＇t Hoff equation. The site of binding of FOS in the protein was proposed to be Sudlow＇s site I based on displacement experiments using site markers viz. warfarin, ibuprofen and digitoxin. The distance r between the donor （BSA） and acceptor （FOS） molecules was obtained according to the F^rster theory. The effect of FOS on the conformation of BSA was analyzed using synchronous fluorescence spectra （SFS）, circular dichroism （CD） and 3D fluor- escence spectra. A molecular modeling study further confirmed the binding mode obtained by the ex- perimental studies.

Fluorometric Discrimination Technique of Phytoplankton Population Based on Wavelet Analysis

The discrete excitation-emission-matrix fluorescence spectra (EEMS) at 12 excitation wavelengths (400, 430, 450, 460, 470, 490, 500, 510, 525, 550, 570, and 590 nm) and emission wavelengths ranging from 600-750 nm were determined for 43 phytoplankton species. A two-rank fluorescence spectra database was established by wavelet analysis and a fluorometric discrimination technique for determining phytoplankton population was developed. For laboratory simulatively mixed samples, the samples mixed from 43 algal species (the algae of one division accounted for 25%, 50%, 75%, 85%, and 100% of the gross biomass, respectively), the average discrimination rates at the level of division were 65.0%, 87.5%, 98.6%, 99.0%, and 99.1%, with average relative contents of 18.9%, 44.5%, 68.9%, 73.4%, and 82.9%, respectively; the samples mixed from 32 red tide algal species (the dominant species accounted for 60%, 70%, 80%, 90%, and 100% of the gross biomass, respectively), the average correct discrimination rates of the dominant species at the level of genus were 63.3%, 74.2%, 78.8%, 83.4%, and 79.4%, respectively. For the 81 laboratory mixed samples with the dominant species accounting for 75% of the gross biomass (chlorophyll), the discrimination rates of the dominant species were 95.1% and 72.8% at the level of division and genus, respectively. For the 12 samples collected from the mesocosm experiment in Maidao Bay of Qingdao in August 2007, the dominant species of the 11 samples were recognized at the division level and the dominant species of four of the five samples in which the dominant species accounted for more than 80% of the gross biomass were discriminated at the genus level; for the 12 samples obtained from Jiaozhou Bay in August 2007, the dominant species of all the 12 samples were recognized at the division level. The technique can be directly applied to fluorescence spectrophotometers and to the developing of an in situ algae fluorescence auto-analyzer for phytoplankton population.

Fluorimetric analysis of paeonol in Chinese herbal medicine Cynanchi Paniculati Radix by aluminum ion-sensitized fluorescence

A novel fluorimetric method for determination of paeonol,an active component of Chinese herbal medicine,is proposed.The method is based on the reaction of paeonol with aluminum ion in pH 4.4 HAc-NaAc buffer to form a fluorescent Al(Ⅲ)-paeonol complex.The maximum excitation wavelength and emission wavelength of the complex were 296 nm and 455 nm,respectively.The fuorescence quantum yield of the complex was determined to be 0.053 at an excitation wavelength of 296 nm.A linear calibration curve covered the concentration range 0.017-1.2μg/mL.The method has been applied to the analysis of paeonol in medicinal crop Cynanchi Paniculati Radix(Xuchangqing),and the results demonstrated that this method can be used for quality evaluation of crude drug Xuchangqing.