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71.
72.
K. Dworecki T. Kosztolowicz St. Mrówczynski S. Wasik 《The European physical journal. E, Soft matter》2000,3(4):389-394
The near membrane layer is a region where the concentration of the substance transported across the membrane is significantly
decreased. Its thickness is defined as a length over which the concentration drops k times with k being an arbitrary large number. The time evolution of such a layer is studied experimentally by means of the laser interferometric
method. It is shown that within the experimental errors the thickness of the near membrane layer grows in time for any k as with the coefficient a being independent of the initial concentration and the membrane permeability. Time evolution of the near membrane layers
is also analyzed theoretically. The regularities found experimentally are naturally described within the model which has been
earlier developed by one of us. In particular, a scales as .
Received 12 November 1999 and Received in final form 3 July 2000 相似文献
73.
Binding equilibrium study between Mn( Ⅱ ) and HSA or BSA 总被引:2,自引:0,他引:2
The binding of Mn( Ⅱ ) to human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by equilibrium dialysis at physiological pH (7. 43). The Scatchard analysis indicates that there are 1.8 and 1.9 strong binding sites of Mn( Ⅱ ) in HSA and BSA, respectively. The successive stability constants which are reported for the first time are obtained by non-linear least-squares methods fitting Bjerrum formula. For both Mn( Ⅱ )-HSA and Mn( Ⅱ )-BSA systems, the order of magnitude of K1 was found to be 104. The analyses of Hill plots and free energy coupling show that the positive cooperative effect was found in both Mn( Ⅱ )-HSA and Mn( Ⅱ )-BSA systems . The results of Mn ( Ⅱ ) competing with Cu ( Ⅱ ) 、 Zn(Ⅱ)、Cd( Ⅱ) or Ca( Ⅱ ) to bind to HSA or BSA further support the conjecture that there are two strong binding sites of Mn( Ⅱ) in both HSA and BSA. One is most probably located at the tripeptide segment of N- terminal sequence of HSA and BSA molecules involving four groups composed of n 相似文献
74.
Chuan Zhang Jae Woo Chung Rodney D. Priestley 《Macromolecular rapid communications》2012,33(20):1798-1803
Using a facile dialysis nanoprecipitation method, nanoparticles of several hundred nanometers have been successfully generated from a “traditional,” non‐biodegradable polymer, that is, polystyrene. The effect of initial polymer concentration inside the dialysis membrane, as well as the polymer/solvent system and the ionic strength (electrolyte concentration) of the dialysis solution, on nanoparticle size is examined. A nucleation‐aggregation mechanism has been provided to explain the observed trends. Furthermore, we determine the zeta potential as a function of ionic strength for the generated nanoparticles and show that anionic charging may be present in the system. 相似文献
75.
In this work, composite cation‐exchange membrane was prepared by chemical polymerization of pyrrole on the surface of the poly(vinylidene fluoride) (PVDF) membrane using ferric ions. The changes in the surface morphologies of non‐modified and polymer‐modified PVDF membrane were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The ion‐exchange capacity, water uptake, and fixed group concentration of the composite membrane were investigated. The polypyrrole/PVDF composite membrane was used for the removal of copper (II), chromium (III), iron (III), and aluminum (III) ions from aqueous solution with Donnan dialysis experiments. The flux values (J) and recovery factors (RF) of Cu(II), Cr(III), Fe(III), and Al(III) were obtained. Because of the smaller ion charge and hydration volume, the transport of the Cu(II) ion is higher than that of the other metals. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
76.
Kim KW Chung BH Jeon EJ Kim BM Choi BS Park CW Kim YS Cho SG Cho ML Yang CW 《Experimental & molecular medicine》2012,44(8):465-472
Most of the previous studies on immune dysregulation in end-stage renal disease (ESRD) have focused on T cell immunity. We investigated B cell subpopulations in ESRD patients and the effect of hemodialysis (HD) on B cell-associated immune profiles in these patients. Forty-four ESRD [maintenance HD patients (n = 27) and pre-dialysis patients (n = 17)] and 27 healthy volunteers were included in this study. We determined the percentage of B cell subtypes, such as mature and immature B cells, memory B cells, and interleukin (IL)-10+ cells, as well as B cell-producing cytokines (IL-10, IL-4 and IL-21) by florescent activated cell sorting (FACS). B cell-associated gene expression was examined using real-time PCR and B cell producing cytokines (IL-10, IL-4 and IL-21) were determined using an enzyme- linked immunosorbent assay (ELISA). The percentage of total B cells and mature B cells did not differ significantly among the three groups. The percentages of memory B cells were significantly higher in the pre-dialysis group than in the HD group (P < 0.01), but the percentage of immature B cells was significantly lower in the pre-dialysis group than in the other groups. The percentages of IL-10-expressing cells that were CD19+ or immature B cells did not differ significantly (P > 0.05) between the two subgroups within the ESRD group, but the serum IL-10 concentration was significantly lower in the pre-dialysis group (P < 0.01). The results of this study demonstrate significantly altered B cell-associated immunity. Specifically, an imbalance of immature and memory B cells in ESRD patients was observed, with this finding predominating in pre-dialysis patients. 相似文献
77.
Carlo Santambrogio Stefano Ricagno Frank Sobott Matteo Colombo Martino Bolognesi Rita Grandori 《Journal of mass spectrometry : JMS》2011,46(8):734-741
β2‐Microglobulin (β2m) is the light chain of the class‐I major histocompatibility complex, being also the causing agent of dialysis‐related amyloidosis, which results from its accumulation as amyloid material in the skeletal joints. This study describes conformational properties of β2m under two distinct, in vitro amyloidogenic conditions: neutral pH in the presence of 20% 2,2,2‐trifluoroethanol (TFE) and acidic pH in the absence of TFE. Species distribution analysis by electrospray ionization–mass spectrometry (ESI‐MS) is combined with information obtained by ion mobility–mass spectrometry (IM‐MS), fluorescence and circular dichroism (CD) spectroscopy. It is shown that β2m populates quite different conformational ensembles under the two conditions, but both ensembles display a minor fraction of the population in a partially folded state. In spite of similar compactness, these two partially folded forms display different conformations: helical secondary structure is predominant in the species at pH 7.4, 20% TFE, while the low‐pH form is mainly random coil. As temperature is increased, the TFE intermediate looses helical structure becoming more similar to the low‐pH intermediate. The existence of different conformational ensembles may rationalize the different aggregation propensity displayed by β2m under the two fibrillation conditions analyzed here. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
78.
《Analytical letters》2012,45(15):2635-2651
Abstract In ligand binding assays, the separation of bound and free fraction of the labeled ligand is very important. Dialysis is generally overlooked as separation technique since it requires large volumes and long analysis times. The availability of the ASTED-system (Automated Sequential Trace Enrichment of Dialysates) might open ways for a complete automation of immuno assays including the separation step. A well-documented radio-immuno assay for 3-keto-desogestrel (Org3236) was used to test the potentials of this system. The tritiated analog of Org3236 not only served as label in the immuno assay but was also used to trace this compound in the entire procedure. The dialysis efficiency increased with the dialysis time and with the flush rate of the recipient solvent (tris-HCI or phosphate buffer). Addition of methanol to recipient solvent had spectacular effects on the recovery. With tris-HCI buffer, 0.18 mL/min and 1.0 mL recipient solvent 2.5% of the label was collected. Addition of 50% methanol resulted in a 5-fold increase to 12%. Replacement of buffer by 100% methanol resulted in another 5% increase in dialysis efficiency which was accompanied by a reduction in the antibody binding in the donor compartment due to denaturation of the antibody. The commercial availability of other types of membranes is essential to find optimal conditions for each analyte. A serious problem is the carryover effect between subsequent samples. Roughly 0.25% of label was collected in the next run which may have a substantial impact on the accuracy and precision of the assay. Renewal of the dialysis membrane might exclude this carry-over effect but is not a serious option with the available instrumentation. Automated dialysis systems can be very valuable for ligand binding assays as soon as membranes become available for the analytes of interest which provide high recoveries (>40%) in 1 mL recipient solvent. Moreover their carry-over effect should be negligible or eliminated by more efficient rinsing procedures of the entire dialysis system. Temperature control is favourable for the immuno assays as well as for the dialysis process in that the kinetics are temperature dependent. 相似文献
79.
LC–MS/MS method for simultaneous determination of serum p‐cresyl sulfate and indoxyl sulfate in patients undergoing peritoneal dialysis
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Tianyi Xia Feng Zhang Shouhong Gao Wansheng Chen 《Biomedical chromatography : BMC》2016,30(11):1782-1788
p‐Cresol sulfate (pCS) and indoxyl sulfate (IS) are protein‐bound uremic toxins that accumulate in patients with chronic kidney disease (CKD). They are closely associated with the mortality rate of CKD and morbidity of cardiovascular disease. In the present study, we established a rapid method for determination of pCS and IS by HPLC‐MS/MS in serum samples from 205 CKD patients undergoing peritoneal dialysis. In brief, serum was extracted by acetonitrile and spiked with hydrochlorothiazide. The prepared sample was eluted through HPLC column (Agilent Zorbax SB‐C18, 3.5 μm, 2.1 × 100 mm) with a mobile phase of acetonitrile and 10 mm ammonium acetate solution (10:90, v/v) for subsequent detection of pCS and IS by MS/MS. The linearity ranged from 50 to 10,000 ng/mL for pCS (r > 0.99), and from 500 to 10,000 ng/mL for IS (r > 0.99). The lower limit of quantification was 50 ng/mL for pCS, and 500 ng/mL for IS. Relative standard deviation (RSD) of intra‐ and inter‐day precision was within ±15%. The results showed that pCS and IS levels were partially correlated with renal function in CKD patients, and IS was directly related to serum creatinine and estimated glomerular filtration rate. 相似文献