摘要:

AbstractThe influence of convection on the structure of an isotachophoretic boundary is investigated using an asymptotic method to simplify the conservation equations. To illustrate the methodology it is applied to a simple strong electrolyte system consisting of three ions and the relevant equations solved numerically. The technique, however, is of general applicability and can be useful in exploring the influence of various flow processes on analytical and preparative electrophoretic separation techniques in addition to isotachophoresis.

ISSN:0173-0835    

DOI:10.1002/elps.1150111103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents a new numerical method for computation of solutions of prototypical equations of isotachophoresis. Numerical computation is complicated because the Poisson equation, which relates electrostatic potential to space charge density, contains a small parameter. This parameter is usually assumed to have the value of zero. Under this assumption the Poisson differential equation is replaced by an algebraic equation, which is often called the equation of electroneutrality, because it indeed states that the electrolyte is electrically neutral this assumption were not studied in the past. Here we propose an iterative procedure which allows for computation of solutions without the assumption of electroneutrality. The accuracy is controlled by a number of iterations and is limited by a computer round‐off error only. The method is based on our previously published theory of existence and uniqueness of solutions of isotachophoretic equations. Details of the computational algorithm for prototypical equations of isotachophoresis are given. A numerical example and comparison with previously published data are also provide

ISSN:0173-0835    

DOI:10.1002/elps.1150111104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractFree‐flow isoelectric focusing was adapted to preparative scale separations and chemical engineering methods were used to describe the main mechanisms operating in the apparatus. A mixture of human serum albumin (pI4.6) and β‐lactoglobulin (pI5.22) was separated in pH gradients, generated with carrier ampholytes of different origin and covering the pH ranges 4‐6.5, 3.5‐5, 4‐5.5 and 4.5‐5.0. Best results were obtained in the pH 4‐5.5 range. The experimental results have validated the results obtained with a n

ISSN:0173-0835    

DOI:10.1002/elps.1150111105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe separation of proteins by free‐flow zone electrophoresis is generally impaired by a number of secondary effects which cause spreading of the protein streams with resultant loss in resolution. A strategy is outlined, based on experimental observations and numerical modeling, which allows the operating conditions and separation chamber dimensions to be chosen so as to obtain complete separation of two proteins of known mobility. This approach takes into account some dispersive phenomena such as molecular diffusion, electroosmosis and residence time gradients. In some cases, the right operating conditions cannot be achieved on earth and electrophoresis separations in microgravity may then be justifie

ISSN:0173-0835    

DOI:10.1002/elps.1150111106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractMilan Bier′s contributions to preparative electrophoresis and, in particular, his work in „recycling”︁, have had an enormous impact on the development of scaling strategies for continuous flow electrophoresis. This paper reviews my early work on the theory of recycle applied to zone electrophoresis and reports the results of several recent experiments in which proteins were purified from complex feed mixtures using recycle zone electrop

ISSN:0173-0835    

DOI:10.1002/elps.1150111107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractContinous flow zone electrophoresis (CFE) and recycling isoelectric focusing (RIEF) are two of the alternative formats for fluid phase preparative isolation of biological products in liquid separation media. The McDonnell Douglas CFE system has been used for both ground‐based and microgravity separations. The ground‐based McDonnell Douglas CFE and RIEF were compared for the ability to reslove mixtures of proteins with known charge differences. Mixtures of (1) cytochrome c, myoglobin, and ovalbumin or (2) beta‐lactoglobulin and ovalbumin were used to evaluate the resolving capabilities of CFE and RIEF. Following separation, fractions were analyzed by determining absorbance at 280 nm and by analytical isoelectric focusing (IEF) using Coomassie Brilliant Blue or silver staining to detect focused proteins. Both CFE and RIEF apparently separated the components of both mixtures into individual peaks, separated by fractions which contained little or no detectable protein. Coomassie‐stained analytical IEF gels supported this finding. However, when separated proteins were analyzed by silver staining of the analytical gels, the separation of ovalbumin from beta‐lactoglobulin by CFE was not complete. Ovalbumin was free ofbeta‐lactoglobulin but beta‐lactoglobulin was contaminated by trace amounts of ovalbumin. RIEF clearly separated each protein with no detectable contamination. These data demonstrate the superiority of RIEF over CFE for resolution of protein mixtures having only minor charge differences. RIEF may be more efficient due to the documented electrodissociation of noncovalent protein:protein complexes which occurs during RIE

ISSN:0173-0835    

DOI:10.1002/elps.1150111108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo carrier‐free electrophoretic separation methods, capillary zone electrophoresis (CZE) and continuous free‐flow zone electrophoresis (FFZE), have been applied to both microanalysis at the nanogram level and preparative fractionation, with a throughput of 30 mg/h, of synthetic growth hormone releasing peptide (GHRP). A crude product of GHRP, a hexapeptide with the sequence His‐D‐Trp‐Ala‐Trp‐D‐Phe‐Lys‐NH2, synthesized by the solid phase methodology, was desalted and analyzed by CZE. Based on the results of analytical CZE the separation was converted into a preparative purification procedure by continuous FFZE, employing the same separation medium (0.5 mol/L acetic acid, pH 2.6). The purity of peptide frcttions obtained by FFZE was reevaluated by CZE. The combination of these two techniques proved to be a valuable tool for both peptide analysis and peptide purification. A close correalation of CZE and FFZE, resulting from the fact that both methods are based on the same separation principle (zone electrophoresis) and that both are performed in a free solution of the same composition, was confirmed. However, when transforming data from CZE to FFZE, the different electroosmotic flow, temperature and electric field intensity in the capillary and in the flow‐through cell, respectively, have to be taken into account and corresponding correc

ISSN:0173-0835    

DOI:10.1002/elps.1150111109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractSeparation of the enzymes formate dehydrogenase, formaldehyde dehydrogenase and methanol oxidase fromCandida boidiniicrude extract has been explored using continuous flow zone electrophoresis in the VaP‐22 and the scaled‐up VaP‐220 electrophoresis apparatus. Yields up to 95 % and purification factors between 3 and 7 were obtained, together with separation of cell debris from the enzymes. Multiple injections of sample were used to obtain a protein throughput of 46.2 mg/h in the VaP‐22. A tenfold higher throughput was achieved using the VaP‐220. Correlation of the electrophoretic mobility in continuous flow zone electrophoresis with the elution behavior in ion‐exchange chromatography confirmed the primary role of net surface charge in the separation of biological molecules. Proteins and enzymes with differences>0.05 M elution molarities in ion‐exchange chromatography can be separated. This corresponds to a preparative scale (mg/h or g/h) separation of proteins and enzymes whose difference in apparent electrophoretic mobility is>0.70 x

ISSN:0173-0835    

DOI:10.1002/elps.1150111110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo modes of continuous isoelectric focusing are described. The development of a natural pH gradient, consisting of a mixture of three buffer solutions, and the focusing behavior of human serum albumin is investigated. The advantages of isoelectric focusing in an artificial pH gradient of three buffer solutions are demonstrated on the purification of α‐amylase from anE. coliprotein extract. Furthermore the principle of field step electrophoresis is presented. The most important factors influencing the efficiency: (i) residence time, (ii) conductivity of the sample and (iii) sample zone width, are discussed. The use of a larger sized device to allow simultaneous multiple injections of the sample demonstrates the feasibility of scaling‐up field step electrophoresis. This approach permits a throughput of about 20 mL sample solution per mi

ISSN:0173-0835    

DOI:10.1002/elps.1150111111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractBy complexing polyols with borate in recycling isoelectric focusing and by varying the ratio of polyol to borate over the useful pH range of 4.0‐6.0, it is possible to control pH. Twelve solutions of 0.1 M boric acid and varying glycerol concentration were used to vary pH in a twelve‐compartment commercial recycling isoelectric focusing (RIEF) system. Various concentrations of boric acid were tested as anolyte, and various Tris(hydroxymethylamino)methane‐borate buffer systems were tested as catholyte. Electroosmosis, hydrogen ion flow, and fluid balancing were characterized in two glycerol gradients; one was maintained at 0.06 pH/fraction and the other at 0.12 pH/fraction. In the latter case, ovalbumin (pI4.70) migrated to the pH 4.61 and 4.72 compartments. It is concluded that the borate‐glycerol system can be adequately stabilized in RIEF for isoelectric purification of certain p

ISSN:0173-0835    

DOI:10.1002/elps.1150111112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY