稀土离子(Ⅲ)与牛血清白蛋白结合作用的研究

模拟生理条件研究了稀土离子(Ⅲ)与牛血清白蛋白(BSA)的结合性质.荧光光谱结果表明,Tb与BSA形成1∶2配合物,表观络合常数lgK=7.93,并由pH电位法得出相近结果.用平衡透析法确定Pr与BSA结合的高亲合位点数为2,低亲合位点数大于6,两类条件结合常数lgK1=5.157,lgK2=3.435.由NMR法通过²³Na弛豫时间的改变可知稀土与BSA络合后蛋白质体积膨胀,活动性增加,相关时间τ_c减小.     

A Monomer‐Micelle Model for the Formation of Simple Taurocholate Micelles

A kinetic dialysis technique was used to validate a relationship between monomer taurocholate (TC) concentration and total TC concentration in TC solutions containing 0.15 M NaCl and 0.01 M buffer (pH = 7.4). Based on the experimental data and Mukerjee's equations, the number average degree and the weight average degree of TC aggregates were estimated to be nearly the same (～5), indicating that simple TC micelles were the only aggregates. Furthermore, the TC dimer concentration was quantified to be negligible. According to the validated relationship, aggregation number of 5 for simple TC micelles, and the definition of critical micelle concentration (CMC), a modified monomer‐micelle model was used for describing simple TC micelle formation. Moreover, the CMC value was estimated to be ～6.3 mM, which is consistent with the reported value of ～6.0 mM.     

毛细管电泳电化学发光用于丙吡胺及其与血浆蛋白结合率的测定

本实验利用透析袋平衡透析、毛细管电泳Ru(bpy)2+3电化学发光检测技术测定了丙吡胺和人血浆蛋白的结合率.在恒电位1.3 V;进样电压10 kV持续10 s,分离电压15 kV,运行缓冲液30 mmol/L 磷酸盐缓冲液(pH 7.5),检测池中为5 mmol/L Ru(bpy)2+3 稀释于50 mmol/L 磷酸盐缓冲液(pH 7.5)中等最优化的条件下,丙吡胺的检出限为10 μmol/L(S/N=3).对蛋白结合率的测定结果表明,人血浆中的药物浓度为1.6～8.2 mmol/L,丙吡胺与血浆蛋白的结合是呈线性的,其线性回归方程为y=-0.07+0.93x,线性相关系数r为0.9999,丙吡胺与人血浆蛋白的结合率约为90.4%.     

Fluorimetric Determination of Aluminium Traces (ppb) in Hemodialysis Solutions Using Morin and Pontachrome Blue Black

Abstract

Two simple procedures for spectrofluorimetric microdosage of Al in dialysis fluids using Morin and Pontachrome Blue Black (PBB) dyestuffs are described. The optimum experimental conditions for both the fluorimetric reagents and for the particular kind of matrix are reported. Linearity between emission intensity and Al concentration was observed in the range 5–50 ppb for PBB and 2–30 pbb for Morin respectively. The Al amount was determined by applying the standard addition method. Both the spectrofluorimetric reagents proved to be suitable for sensitivity and accuracy to Al determination in dialysis fluids.     

Suitability of selected chromatographic columns for analysis of fatty acids in dialyzed patients

Gas chromatography–mass spectrometry is a preferred method for fatty acid (FA) analysis in biofluids from patients with metabolic diseases. Complex characteristics of FAs make their analysis particularly challenging. Selection of an appropriate chromatographic column is particularly important component of the process as it provides optimal separation and detection of possibly all FAs present in the sample. However, no accurate protocol for comparative evaluation of capillary columns for the analysis of whole serum FA profile in patients with chronic kidney disease (CKD) has been developed thus far. Therefore, in the present study four columns were examined to select the one providing optimal separation and determination of FA profiles in this group of patients. Moreover, serum FA profiles obtained with the selected column in CKD patients subjected to peritoneal dialysis and healthy controls were compared. Thirty‐seven component FAME Mix and sera from CKD patients were used to optimize chromatographic conditions and to select the most appropriate column. The ZB‐5 column turned out to be the most appropriate for the analysis of whole FA profile in CKD patients' sera. Then, this column was used to compare FA profiles in patients subjected to peritoneal dialysis and in healthy controls. The analysis demonstrated many abnormalities in the FA profile of CKD patients. Further studies involving larger groups of patients presenting with other stages of CKD are required to explain the impact of the disease progression on composition of serum FAs.     

Electric Field Enhancement of Donnan Dialysis

Abstract

Donnan dialysis of cations into simple receiver electrolytes such as NaNO₃ is inhibited by interaction between the fixed sulfonate exchange sites on the cation exchange membrane and the test cations. Application of a 5 V cm^?1 (peak-to-peak) sine wave at 1 MHz across the membrane diminishes the retardation and allows the Donnan dialysis rate to approach the diffusion limit with Cd, Cu, and Zn test metals and a 0.1 M NaNO₃ receiver. The transport to Pb is still retarded by about 25%. The use of 0.2 M Mg(II), 0.5 mM Al(III) receiver results in diffusion limited transport for all metals.     

In‐depth insight into the methods of plasma protein‐drug interaction studies: Comparison of capillary electrophoresis‐frontal analysis,isothermal titration calorimetry,circular dichroism and equilibrium dialysis

Plasma protein‐drug binding assays are routinely performed during the early stages of drug discovery and development, which creates demand for an automated high‐throughput screening assay to increase laboratory efficiency. A comprehensive comparison of the four methods typically used for determining the binding parameters is presented in this study with respect to the above demand. Capillary electrophoresis‐frontal analysis, isothermal titration calorimetry, circular dichroism and equilibrium dialysis were used to study the affinity of human serum albumin for diclofenac and lidocaine. These model drugs were chosen due to their different physico‐chemical properties and different binding sites on the albumin molecule, also resulting in different binding strength. The binding parameters estimated under the conditions as similar as possible were comparable among all these approaches as well as to the literature values. Besides this, the comparison of the results and especially other considerations demonstrated the benefits and drawbacks of the selected methods, with capillary electrophoresis‐frontal analysis being the best candidate for such studies.     

Study of the Interaction Between Trypanocide 3-Nitrobenzaldehyde Guanyl Hydrazone and Bovine Serum Albumin by Equilibrium Dialysis and Nmr

Equilibrium dialysis and NMR spin-lattice relaxation time (T¹) studies of the interaction of the trypanocidal drug 3-nitrobenzaldehyde guanyl hydrazone (3NBGH) with bovine serum albumin (BSA) were used to show that this interaction is weak and nonspecific, making 3NBGH a potential agent for the prophylaxis of Trypanosoma cruzi infected blood.     

Evaluation of partition coefficients of low molecular weight solutes between water and micelles of block copolymer of ethylene oxide based on dialysis kinetics and fluorescence spectroscopy

 Application of micelle-forming surfactants in various fields of technology and use of micelles as carriers for drug targeting requires simple evaluation of partitioning coefficients of different solutes between water solution and micellar microphase. A number of methods of partitioning evaluation have been already proposed, but most of them are applicable only for fluorescent dyes or require complicated and expensive equipment, such as NMR spectrometers. In the present work two methods of the molar fraction of solubilized material determination are compared. One of the techniques used is based on the changes in fluorescence spectra during solubilization. The other approach is based on the dialysis slowing down, which occurs if the solute is associated with large particles (e.g. micelles). Graphic method of partition coefficient (P) evaluation is proposed and P values of a widely used anti-tumor drug doxorubicin and highly hydrophobic fluorophore perylene are determined. The comparison shows that the results of both methods give very close coincidence. The solubilization data were used for the calculation of the important parameter – the ratio of micelle volume to aggregation number, which makes sense of packing density of the detergent molecules in the micelle. The comparison of this parameter calculated from the solubilization data with that obtained from light scattering experiments is discussed. It is assumed that the dialysis technique could be used for partitioning evaluation of all substances, which may be detected in solution. Received: 15 September 1997 Accepted: 3 November 1997     

Native and Hydrolyzed Fibroin of Natural Silk Modified Mechanochemically by Benzimidazolyl-2-methylcarbamate Hydrochloride

Native and hydrolyzed fibroin of natural silk modified by benzimidazolyl-2-methylcarbamate hydrochloride was studied using IR spectroscopy, electron-microscopy, X-ray structure analysis, solubility, and dialysis. Mechanical treatment of a mixture of native and hydrolyzed fibroin of natural silk with benzimidazolyl-2- methtylcarbamate hydrochloride in a 2:1 ratio was shown to form inclusion complexes.