TY  - JOUR
AB  - Multidimensional separation techniques play an increasingly important role in separation science, especially for the analysis of complex samples such as proteins. The combination of reversed-phase liquid chromatography in the nanoscale and CZE is especially beneficial due to their nearly orthogonal separation mechanism and well-suited geometries/dimensions. Here, a heart-cut nano-LC-CZE-MS setup was developed utilizing for the first time a mechanical 4-port valve as LC-CE interface. A model protein mixture containing four different protein species was first separated by nano LC followed by a heart-cut transfer of individual LC peaks and subsequent CZE-MS analysis. In the CZE dimension, various glycoforms of one protein species were separated. Improved separation capabilities were achieved compared to the 1D methods, which was exemplarily shown for ribonuclease B and its different glycosylated forms. LODs in the lower mu g/mL range were determined, which are considerably lower compared to traditional CZE-MS. In addition, this study represents the first application of an LC-CE-MS system for intact protein analysis. The nano-LC-CZE-MS system is expected to be applicable to various other analytical challenges.
AU  - Jooß, K.
AU  - Scholz, N.*
AU  - Meixner, J.*
AU  - Neusüß, C.*
C1  - 55111
C2  - 46084
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 1061-1065
TI  - Heart-cut nano-LC-CZE-MS for the characterization of proteins on the intact level.
JO  - Electrophoresis
VL  - 40
IS  - 7
PB  - Wiley
PY  - 2019
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Capillary electrophoresis (CE) offers fast and high-resolution separation of charged analytes from small injection volumes. Coupled to mass spectrometry (MS), it represents a powerful analytical technique providing (exact) mass information and enables molecular characterization based on fragmentation. Although hyphenation of CE and MS is not straightforward, much emphasis has been placed on enabling efficient ionization and user-friendly coupling. Though several interfaces are now commercially available, research on more efficient and robust interfacing with nano-electrospray ionization (ESI), matrix-assisted laser desorption/ionization (MALDI) and inductively coupled plasma mass spectrometry (ICP) continues with considerable results. At the same time, CE-MS has been used in many fields, predominantly for the analysis of proteins, peptides and metabolites. This review belongs to a series of regularly published articles, summarizing 248 articles covering the time between June 2016 and May 2018. Latest developments on hyphenation of CE with MS as well as instrumental developments such as two-dimensional separation systems with MS detection are mentioned. Furthermore, applications of various CE-modes including capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), capillary gel electrophoresis (CGE) and capillary isoelectric focusing (CIEF) coupled to MS in biological, pharmaceutical and environmental research are summarized.
AU  - Stolz, A.*
AU  - Jooß, K.
AU  - Höcker, O.*
AU  - Römer, J.*
AU  - Schlecht, J.*
AU  - Neusüß, C.*
C1  - 54754
C2  - 45831
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 79-112
TI  - Recent advances in capillary electrophoresis-mass spectrometry: Instrumentation, methodology and applications.
JO  - Electrophoresis
VL  - 40
IS  - 1
PB  - Wiley
PY  - 2019
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Comprehensive non-targeted analysis of food products normally requires two complementary chromatographic runs to achieve maximum compound coverage. In this study, we present a sensitive tandem-LC method, which combines RP and HILIC separation in a single run. The setup consists of a C18 trap column and two subsequently coupled analytical columns (HILIC and C18) which are operated in parallel. First, hydrophobic compounds are retained on the RP trap column while rather hydrophilic compounds are directly transferred onto a HILIC phase. Next, the pre-fractionated sample composition is analyzed by HILIC or RP chromatography, respectively. The presented setup allows individual and independent gradient elution as well as interfacing with mass spectrometry. The performance of the method has been proven by means of food relevant standards and analysis of complex food samples (e.g. red wine, meat extract). The simple and robust setup provides high flexibility in the selection of column combinations and does not require sophisticated instrumental setups or software. The method significantly increases the covered polarity range compared to classical one-dimensional chromatography. Our results indicate that tandem LC is a valuable and universal tool in the non-targeted screening of various types of complex food samples.
AU  - Hemmler, D.
AU  - Heinzmann, S.S.
AU  - Wöhr, K.*
AU  - Schmitt-Kopplin, P.
AU  - Witting, M.
C1  - 53295
C2  - 44546
CY  - Po Box 211, 1000 Ae Amsterdam, Netherlands
SP  - 1645-1653
TI  - Tandem HILIC-RP liquid chromatography for increased polarity coverage in food analysis.
JO  - Electrophoresis
VL  - 39
IS  - 13
PB  - Elsevier Science Bv
PY  - 2018
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Capillary Electrokinetic Fractionation (CEkF) is investigated as a new, simple and robust approach for semi-preparative and analytical sample analysis based on pKa-dependant pH-driven electrophoretic mobility. CEkF was optimized with contactless conductivity detection and conducted with 10 kV reverse voltage for 10 min, then coupled on/at-line to electrospray ionization (ESI) mass spectrometry (MS). We propose a semi-empirical model with 14 representative compounds based on the correlation between sample/medium pH regulating the partial charge, the electrokinetic loading of the capillary and intensity (I) of analytes. According to the model, an empirical function (I = f (pH)) could be derived to calculate the acid dissociation constant (pKa) of various model compounds based on their pH-dependant MS intensity profiles with the RSD less than 4.05. Using the ultrahigh resolution of ion cyclotron resonance Fourier Transform mass spectrometry (ICR-FT/MS), the pKa model was further illustrated in real samples into the structure prediction of important compounds in wine over 2 vintages. The established CEkF was successfully used to selectively fractionate sulfur compounds from the complex wine samples at pH 1.66. The proposed CEkF approach should allow in the future the simultaneous pKa evaluation of multiple constituents without complicated separation out of a complex mixture in metabolomics or environmental chemistry.
AU  - He, Y.
AU  - Harir, M.
AU  - Chen, G.*
AU  - Gougeon, R.D.*
AU  - Zhang, L.*
AU  - Huang, X.*
AU  - Schmitt-Kopplin, P.
C1  - 30857
C2  - 33999
CY  - Hoboken
SP  - 1965-1975
TI  - Capillary Electrokinetic Fractionation Mass Spectrometry (CEkF/MS): Technology setup and application to metabolite fractionation from complex samples coupled at-line with ultrahigh resolution mass spectrometry.
JO  - Electrophoresis
VL  - 35
IS  - 14
PB  - Wiley-blackwell
PY  - 2014
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The identification of fentanyl derivatives at trace levels employing capillary electrophoresis coupled to electrospray ionization tandem mass spectrometry (CE-ESI-MSn, n = 2, 3) is presented. The studied synthetic opioid fentanyl and its derivatives have an exceeding analgesic potency which can be up to 8000 times higher that of morphine. Apart from their therapeutical applications, there is an abuse of them in the drug scene as a heroin substitute. The identification of these opioids at trace levels is of further significant forensic interest with respect to recent seizures of clandestine fentanyl laboratories in Germany. In this work, a nonaqueous capillary electrophoresis (NACE)-ESI-MSn procedure was developed for the separation and identification of six fentanyl derivatives including fentanyl, cis- and trans-methylfentanyl, sufentanil, alfentanil, and carfentanil. Their fragmentation pattern in MSn experiments were investigated as well as the influence of the sheath-liquid mixture and the influence of the inside diameter of the fused silica capillary on the peak shape and the signal to noise ratio. Method validation included determination of the detection limits (about 12 nmol/L) and the repeatability of migration time (at most 0.07% relative standard deviation). The NACE-MS procedure was successfully applied for the analysis of real samples from seizures in illegal fentanyl laboratories.
AU  - Rittgen, J.*
AU  - Pütz, M.*
AU  - Zimmermann, R.
C1  - 7766
C2  - 29803
SP  - 1595-1605
TI  - Identification of fentanyl derivatives at trace levels with nonaqueous capillary electrophoresis-electrospray-tandem mass spectrometry (MSn, n = 2, 3): Analytical method and forensic applications.
JO  - Electrophoresis
VL  - 33
IS  - 11
PB  - Wiley-Blackwell
PY  - 2012
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Free-flow electrophoresis (FFE), a preparative free zone electrophoretic method, was used offline in conjunction with ultrahigh-resolution FT/ion cyclotron resonance -MS to resolve the complexity of Suwannee River fulvic acid (SRFA). Before MS, the FFE separation conditions and the compatibility with ESI were optimized. The constituents in SRFA were effectively separated based on their charge states and sizes. The obtained mass spectra were compared by means of van Krevelen diagrams and the calculated aromaticity indices of the individual constituents were used to describe the distribution of aromatic/unsaturated structures across the FFE-fractionated samples. The consolidated number of ions observed within the individual SRFA fractions were much higher than those of the bulk samples alone, demonstrating extensive ion suppression effects in bulk SRFA likely also operating in the analysis of complex biogeochemical mixtures in flow injection mode. The FFE approach allows for producing sizable amounts of sample from dilute solutions, which can be easily fractionated into dozens of individual samples with the possibility of further in-depth characterization.
AU  - Gáspár, A.
AU  - Harir, M.
AU  - Hertkorn, N.
AU  - Schmitt-Kopplin, P.
C1  - 1398
C2  - 27281
SP  - 2070-2079
TI  - Preparative free-flow electrophoretic offline ESI-Fourier transform ion cyclotron resonance/MS analysis of Suwannee River fulvic acid.
JO  - Electrophoresis
VL  - 31
IS  - 12
PB  - Wiley-Vch
PY  - 2010
SN  - 0173-0835
ER  - 

TY  - JOUR
AU  - Schmitt-Kopplin, P.
C1  - 1886
C2  - 26591
SP  - 1609
TI  - CE-MS 2009.
JO  - Electrophoresis
VL  - 30
IS  - 10
PB  - Wiley-Blackwell
PY  - 2009
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A CE-ESI/quadrupole-MS method using an ammonium acetate-based BGE (pH 4.7) was developed for the determination of isomeric benzoic acids in atmospheric aerosols and vehicular emission. UltraTrol (TM) LN was employed as the pre-coating polymer to suppress the EOF (0.3 x 10(-9) m(2) V-1 s(-1)) and achieve a baseline separation of the studied acids. Good repeatability for migration time (RSD < 1%, N = 10) was obtained without coating regeneration. The high pre-coating stability allowed coupling of CE to MS without ion suppression in the MS. In scanning mode and using field-amplified sample injection with electrokinetic injection (-5 kV for 60 s), LODs (S/N = 3) ranged from 2.5 to 6 mu g/L for standard target analytes prepared in DI water. In the presence of 100 mg/L of sulfate (added to simulate a sample matrix), LODs ranged from 8 to 90 mu g/L. Several isomeric aromatic acids could be separated in atmospheric and diesel-engine-emitted particulate matter extracts based on their different acidities. Additional measurements with a flow infusion ESI Fourier transform ion cyclotron resonance MS were used for further structural information acquisition on the unknown compounds and allowed their formula to be proposed.
AU  - Yassine, M.M.*
AU  - Dabek-Zlotorzynska, E.*
AU  - Schmitt-Kopplin, P.
C1  - 2233
C2  - 26232
SP  - 1756-1765
TI  - CE-MS: A useful tool for the identification of water-soluble polar organics in air and vehicular emitted particulate matter.
JO  - Electrophoresis
VL  - 30
IS  - 10
PB  - Wiley-VCH
PY  - 2009
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - There is increasing evidence that a large proportion of dilated cardiomyopathy (DCM) cases are mediated by autoimmune processes. Since DCM is a fatal disorder with rapid aggravation and is the leading cause of heart transplantation, further insights into disease pathogenesis are needed. Recent studies have separated the pathogenic capacity of autoantibodies and initial clinical trials removing such autoantibodies via immunoadsorption have been promising. In order to elucidate the full autoantibody repertoire involved in DCM, we applied an autoantibody screening test using ventricular and atrial proteomes as autoantigenic sources and subsequently tested the autoantibody-binding patterns of sera from dogs with spontaneous DCM. With this method, we detected five potentially DCM-related autoantigens which were identified by MS as being: myosin heavy chain cardiac muscle alpha isoform, alpha cardiac actin, mitochondrial aconitate hydratase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and brain glycogen phosphorylase (GPBB). The recovery of two known DCM autoantigens (myosin heavy chain and alpha cardiac actin) and the discovery of three novel autoantigens (mitochondrial aconitate hydratase, GADPH, and GPBB) underscore the efficacy of this experimental method and the significance of the spontaneous canine DCM model.
AU  - Buse, C.*
AU  - Altmann, F.*
AU  - Amann, B.*
AU  - Hauck, S.M.
AU  - Nautrup, C.P.*
AU  - Ueffing, M.
AU  - Stangassinger, M.*
AU  - Deeg, C. A.*
C1  - 4573
C2  - 25442
SP  - 1325-1332
TI  - Discovering novel targets for autoantibodies in dilated cardiomyopathy.
JO  - Electrophoresis
VL  - 29
IS  - 6
PB  - Wiley-Blackwell
PY  - 2008
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - CE-MS has gained further attention as a multidimensional analytical approach. The number of publications dealing with this technique is still increasing on the level of application as well as method development-oriented approaches. Additionally, 15 reviews were published the last two years focusing on CE-MS. An overview of all papers found to have been published within 2005 and 2006 is given in tabulated form. Additionally, four promising technical trends are chosen to be presented in detail: (i) chip-based CE-MS, (ii) capillary coatings in CE-MS, (iii) new trends in CEC-MS and (iv) the application of 2-D CE-MS.
AU  - Gáspár, A.
AU  - Englmann, M.
AU  - Fekete, A.
AU  - Harir, M.
AU  - Schmitt-Kopplin, P.
C1  - 17155
C2  - 30852
SP  - 66-79
TI  - Trends in CE-MS 2005-2006.
JO  - Electrophoresis
VL  - 29
IS  - 1
PB  - Wiley-VCH
PY  - 2008
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The neurotoxic effects of manganese (Mn) at elevated concentrations are well known. This raises the question, which of the Mn species can cross neural barriers and appear in cerebrospinal fluid (CSF). CSF is the last matrix in a living human organism available for analysis before a compound reaches the brain cells and therefore it is assumed to reflect best the internal exposure of brain tissue to Mn species. A previously developed CE method was modified for separation of albumin, histidine, tyrosine, cystine, fumarate, malate, inorganic Mn, oxalacetate, -keto-glutarate, nicotinamide-dinucleotide (NAD), citrate, adenosine, glutathione, and glutamine. These compounds are supposed in the literature to act as potential Mn carriers. In a first attempt, these compounds were analyzed by CZE-UV to check whether they are present in CSF. The CZE-UV method was simpler than the coupled CZE-inductively coupled plasma (ICP)-dynamic reaction cell (DRC)-MS method and it was therefore chosen to obtain a first overview information. In a second step, the coupled method (CZE-ICP-DRC-MS) was used to analyze, in detail, which of the compounds found in CSF by CZE-UV were actually bound to Mn. Finally, 13 Mn species were monitored in CSF samples, most of them being identified: Mn-histidine, Mn-fumarate, Mn-malate, inorganic Mn, Mn-oxalacetate, Mn--keto glutarate, Mn-carrying NAD, Mn-citrate and Mn-adenosine. By far the most abundant Mn species was Mn-citrate showing a concentration of 0.7 ± 0.13 µg Mn/L. Interestingly, several other Mn species can be related to the citric acid cycle.
AU  - Michalke, B.
AU  - Berthele, A.*
AU  - Mistriotis, P.*
AU  - Ochsenkühn-Petropoulou, M.*
AU  - Halbach, S.
C1  - 1063
C2  - 24413
SP  - 1380-1386
TI  - Manganese speciation in human cerebrospinal fluid using CZE coupled to inductively coupled plasma MS.
JO  - Electrophoresis
VL  - 28
IS  - 9
PB  - Wiley-VCH
PY  - 2007
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - We used a standardized electrophoresis protocol to identify differentially expressed proteins based on a sample pooling approach comparing three follicular lymphoma and three mantle cell lymphoma-derived cell lines. One hundred and seventy-five consistently differentially expressed proteins were identified out of more than 1600 protein spots per gel. Of these 175 protein spots, 38 of the 41 most highly expressed proteins were identified by MS analysis (MALDI-TOF), involving different cellular programs such as DNA repair (Rad50), cell cycle control (Mad1L1), transcription (SAFB), and apoptosis (Luca-15 protein). Expression data were confirmed by Western blot analysis of identified proteins and 2-D gel hybridization of proteins with known overexpression (G1/S-specific cyclin-D1, apoptosis regulator Bcl-2). Comparison of proteome analysis to RNA expression array data revealed only a modest correlation of RNA and protein level emphasizing the relevance of post-translational regulation in lymphomagenesis (p = 0.36). Most interestingly, additional data bank search identified 13 out of 17 referenced proteins (76%) as members of a TP53-dependent network of cell regulation.
AU  - Weinkauf, M.
AU  - Christopeit, M.
AU  - Hiddemann, W.
AU  - Dreyling, M.
C1  - 2600
C2  - 25785
SP  - 4416-4426
TI  - Proteome- and microarray-based expression analysis of lymphoma cell lines identifies a p53-centered cluster of differentially expressed proteins in mantle cell and follicular lymphoma.
JO  - Electrophoresis
VL  - 28
IS  - 23
PB  - Wiley-Blackwell
PY  - 2007
SN  - 0173-0835
ER  - 

TY  - JOUR
AU  - Fekete, A.
AU  - Hertkorn, N.
AU  - Frommberger, M.
AU  - Lahaniatis, M.R.*
AU  - Kettrup, A.*
AU  - Schmitt-Kopplin, P.
C1  - 787
C2  - 23586
SP  - 2216-2224
TI  - Development of a capillary electrophoresis mass spectrometry method for the determination of formaldehyde releasers as their hydrolysis products and amino alcohols from metal working fluids.
JO  - Electrophoresis
VL  - 27
PY  - 2006
SN  - 0173-0835
ER  - 

TY  - JOUR
AU  - Fekete, A.
AU  - Frommberger, M.
AU  - Ping, G.*
AU  - Lahaniatis, M.*
AU  - Lintelmann, J.
AU  - Fekete, J.*
AU  - Gebefügi, I.
AU  - Malik, A.K.*
AU  - Kettrup, A.
AU  - Schmitt-Kopplin, P.
C1  - 1848
C2  - 23492
SP  - 1237-1247
TI  - Development of a capillary electrophoretic method for the analysis of low-molecular-weight amines from metal working fluid aerosols and ambient air.
JO  - Electrophoresis
VL  - 27
PY  - 2006
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A quantitative, specific, and sensitive method for the determination of N-acylhomoserine lactones (HSLs – a group of bacterial semiochemicals) in the form of their hydrolysis products (N-acylhomoserines, HSs) is presented. Real samples were analyzed by capillary zone electrophoresis-mass spectrometry (CZE-MS) after alkaline lactonolysis and extraction by mixed-mode anion-exchange solid-phase extraction. The presented cleanup significantly speeds up the HSL extraction procedure, strongly reduces sample consumption, and is more selective compared to the commonly used liquid/liquid extraction. Completeness of the hydrolysis reaction was examined by nuclear magnetic resonance spectroscopy. This CZE-MS method complements recently published capillary separation techniques (nano liquid chromatography-MS, partial-filling micellar electrokinetic chromatography-MS, gas chromatography-MS) and provides a possibility to differentiate quantitatively between the homoserines (as naturally occurring degradation products) besides the intact homoserine lactones. The method was found to be quantitative down to a concentration of 0.05 µg/mL (limit of quantification), while the limit of detection was determined with 0.01 µg/mL – sufficient for the analysis of culture supernatants.
AU  - Frommberger, M.
AU  - Hertkorn, N.
AU  - Englmann, M.
AU  - Jakoby, S.
AU  - Hartmann, A.
AU  - Kettrup, A.
AU  - Schmitt-Kopplin, P.
C1  - 3090
C2  - 22764
SP  - 1523-1532
TI  - Analysis of N-acylhomoserine lactones after alkaline hydrolysis and anion-exchange solid-phase extraction by capillary zone electrophoresis-mass spectrometry.
JO  - Electrophoresis
VL  - 26
IS  - 7-8
PY  - 2005
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - This paper summarizes some basic principles of capillary electrophoresis (CE), inductively coupled plasma-mass spectrometry (ICP-MS), and coupling of both devices. Especially the interfacing is described in detail. A special focus is drawn to various interface developments reported in literature and technical problems, i.e., requirements to the interface setup and respective solutions. Nowadays, typically sheath flow-based interfaces are used. The sheath flow fulfills two requirements of hyphenation, (i) the closing of the electrical circuit of CE and (ii) the feeding of the used nebulizer with an adequate flow rate. In the beginning of CE-ICP-MS coupling predominantly home-made interface-nebulizer constructions were developed and tested for various speciation problems. Now increasingly such laboratory-constructed interfaces are left. Mostly commercial nebulizers are employed being combined with commercially available tee or cross fittings to connect the CE capillary to the electrode, the additional sheath flow, and the nebulizer. Due to the low sample amounts and low flow rates from CE, such nebulizers are typically low-flow nebulizers like, e.g., the microconcentric nebulizer (MCN) and the direct injection nebulizer (DIN). However, there are also reports on couplings using standard Meinhard systems. Still the control and reduction of a siphoning sucting flow and sufficient detection limits are the major problems in hyphenating CE to ICP-MS. Different solutions are reported on these problems and summarized here. Finally numerous applications are reported. Mostly, applications are performed on speciation of selenium, arsenic, metallothionein isoforms, mercury, or cobalt.
AU  - Michalke, B.
C1  - 1215
C2  - 22673
SP  - 1584-1597
TI  - Capillary electrophoresis-inductively coupled plasma-mass spectrometry: A report on technical principles and problem solutions, potential and limitations of this technology as well as on examples of application.
JO  - Electrophoresis
VL  - 26
IS  - 7-8
PY  - 2005
SN  - 0173-0835
ER  - 

TY  - JOUR
AU  - Schmitt-Kopplin, P.
C1  - 657
C2  - 22765
SP  - 1207
TI  - Capillary electrophoresis - mass spectrometry. Paper Symposium.
JO  - Electrophoresis
VL  - 26
IS  - 7-8
PY  - 2005
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The major developments and applications related to CE-MS over the last two years (2003–2004) and most of the reviews and applications found in the ISI Web of Science and publisher data bases are presented in a tabulated way. This article complements our previous review “Capillary electrophoresis – mass spectrometry: 15 years of developments and applications”, Electrophoresis, 2003, 24, 3837–3867 [1] for the last two years 2003–2004. All cited articles were analyzed in a way to illustrate (i) in which journals CE-MS-related papers were mostly found over the last decades and (ii) which commercial CE-, MS-instrumentations or CE-MS combinations were mostly used in the European, Asian, and American continent. Additionally, like it was done in our last review, the reader will rapidly find applications classified as forensics, environment, bioanalytics, pharmaceutics, and metabolites.
AU  - Schmitt-Kopplin, P.
AU  - Englmann, M.
C1  - 5073
C2  - 22714
SP  - 1209-1220
TI  - Capillary electrophoresis - mass spectrometry: Survey on developments and applications 2003-2004.
JO  - Electrophoresis
VL  - 26
IS  - 7-8
PY  - 2005
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A method involving self-concentration, on-column enrichment and field-amplified sample stacking for on-line concentration in capillary electrochromatography with a polymer monolithic column is presented. Since monolithic columns eliminate the frit fabrication and the problems associated with frits, the experimental conditions could be more flexibly adjusted to obtain higher concentration factor in comparison with conventional particulate packed columns. With self-concentration effect, the detection sensitivity of benzene and hexylbenzene is improved by a factor of 4 and 8, respectively. With on-column enrichment and ultralong injection, improvement as high as 22 000 times in detection sensitivity of benzoin is achieved. Furthermore, a combination of the three above-mentioned methods yields up to a 24 000-fold improvement in detection sensitivity for caffeine, a charged compound. Parameters affecting the efficiency of on-line concentration are investigated systematically. In addition, equations describing on-line concentration process are deduced.
AU  - Ping, G.*
AU  - Zhang, Y.*
AU  - Zhang, W.*
AU  - Zhang, L.*
AU  - Zhang, Li.*
AU  - Schmitt-Kopplin, P.
AU  - Kettrup, A.
C1  - 2673
C2  - 21778
SP  - 421-427
TI  - On-line concentration of neutral and charged species in capillary electrochromatography with a methacrylate-based monolithic stationary phase.
JO  - Electrophoresis
VL  - 25
IS  - 3
PY  - 2004
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A method for the analysis of N-acyl-L-homoserine lactones (AHLs) with micellar electrokinetic chromatography coupled to electrospray ionization-ion trap mass spectrometry, combining the flexibility of capillary electrophoresis with the unmatched structural information provided by mass spectrometry is presented. Different surfactants were evaluated, with sodium dodecyl sulfate (SDS) yielding the best results considering sensitivity and flexibility. We examined the interaction of AHLs with the SDS micelles at different analysis conditions and applied the optimized method to the analysis of a real bacterial sample. Two AHLs from Burkholderia cepacia colonizing the rhizosphere of traditional Indian rice cultivars could be unambiguously determined in an ethyl acetate extract with high resolution flexibility.
AU  - Frommberger, M.
AU  - Schmitt-Kopplin, P.
AU  - Menzinger, F.
AU  - Albrecht, V.
AU  - Schmid, M.
AU  - Eberl, L.*
AU  - Hartmann, A.
AU  - Kettrup, A.
C1  - 10229
C2  - 21147
SP  - 3067-3074
TI  - Analysis of N-acyl-l-homoserine lactones produced by Burkholderia cepacia with partial filling micellar electrokinetic chromatography - electrospray ionization-ion trap mass spectrometry.
JO  - Electrophoresis
VL  - 24
IS  - 17
PY  - 2003
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The separation of selected lignin/humic substance (HS) degradation compounds by capillary electrochromatography (CEC) with a methacrylate-based monolithic column and a conventional column packed with 5 μm octadecyl silica (ODS) particles is presented. The effects of organic modifier concentration, pH of the mobile phase, ionic strength, applied voltage, and temperature on the separation were investigated to determine the optimal separation conditions. With the increase of pH in the mobile phase, some of analytes start to ionize and both chromatographic partition and electrophoresis can play roles in separation simultaneously. Accordingly, different selectivity from high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) could be achieved. The performances of both kinds of columns were compared. The results showed that the peaks of compounds obtained on the former column were much wider than those on the latter one, although good separation efficiency of alkylbenzenes could be readily achieved; the most probable reasons for this behavior and method to solve this problem were briefly discussed. The CEC of a soil fulvic acid with a monolithic column produced partly resolved broad bands; by means of nuclear magnetic resonance (NMR) analysis a wide range of oxygen derived aromatic substitution patterns was found with prominent contributions from phenolic and carboxylic groups.
AU  - Ping, G.
AU  - Schmitt-Kopplin, P.
AU  - Hertkorn, N.
AU  - Zhang, W.*
AU  - Zhang, Y.*
AU  - Kettrup, A.
C1  - 10228
C2  - 20994
SP  - 958-969
TI  - Separation of selected humic degradation compounds by capillary electrochromatography with monolithic and packed columns.
JO  - Electrophoresis
VL  - 24
IS  - 6
PY  - 2003
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The separation of Suwannee River natural organic matter (NOM) with capillary zone electrophoresis hyphenated to electrospray ionization-mass spectrometry (CZE-ESI-MS) is presented. The obtained electropherograms and signal distributions are comparable to the mobility distributions obtained with more classical UV detection. A direct comparison of the results was possible with free-flow electrophoresis (FFE), which allows an upscaling of the CZE method and the analysis of the collected fractions in an off-line modus with flow-injection electrospray ionization-mass spectrometry (FI-ESI-MS). The changes of the m/z distributions with mobility are very similar with both methods and show a decrease of the m/z with increasing electrophoretic mobility in the humic hump at alkaline pH; superimposed on this hump a low-molecular-weight fraction migrates at lower mobility. The analysis of benzene carboxylic acids, glycerrhycic acid as well as oligomers of polystyrene sulfonic acid and polyacrylic acid additionally illustrates possible fragmentation, formation of adducts and multiplicity of the charges of the molecules prior to MS detection. These hardly controllable difficulties add a challenge to the interpretation of the obtained m/z distributions of NOM in terms of charge and mass distributions of molecules present in the NOM mixture.
AU  - Schmitt-Kopplin, P.
AU  - Kettrup, A.
C1  - 10230
C2  - 21148
SP  - 3057-3066
TI  - Capillary electrophoresis - electrospray ionization - mass spectrometry for the characterization of natural organic matter : An evaluation with free flow electrophoresis-off-line flow injection electrospray ionization-mass spectrometry.
JO  - Electrophoresis
VL  - 24
IS  - 17
PY  - 2003
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Since its introduction in 1987, capillary electrophoresis-mass spectrometry (CE-MS) has developed to a well accepted multidimensional analytical approach complementary and/or competitive to classical MS-hyphenated separation techniques. The threefold combination of rapid developments of an exceptional separation technique, of selective mass detection possibilities, and of very mild ionization modes first allowed these progresses. This article shows the CE specificities that need to be well controlled/known, compared to classical and more routinely used liquid chromatography in the light of its coupling to MS. The major trends and developments over the last 15 years and most of the reviews and applications found in ISI Web of science and publisher databases are presented in a tabulated way. The reader can thus rapidly find existing CE-MS analysis techniques in his field of research and application (forensics, environment, bioanalytics, pharmaceutics, and metabolites).
AU  - Schmitt-Kopplin, P.
AU  - Frommberger, M.
C1  - 10231
C2  - 21379
SP  - 3837-3867
TI  - Capillary electrophoresis-mass spectrometry : 15 years of developments and applications.
JO  - Electrophoresis
VL  - 24
IS  - 22-23
PY  - 2003
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Glycoalkaloids are naturally occurring nitrogen-containing compounds present in many species of the family Solanaceae, including cultivated and wild potatoes (Solanum spp.), tomatoes (Lycopersicon spp.), etc. These compounds have pharmacological and toxicological effects on humans due to their significant anticholinesterase activity and disruption of cell membranes. Herein is reported the development of a, capillary electrophoresis (CE) method using nonaqueous (NA) separation solutions in combination with ion trap mass spectrometry (MS and MS/MS) detection for the identification and quantification of glycoalkaloids and their relative aglycones. A mixture 90:10 v/v of MeCN-MeOH containing 50 mm ammonium acetate and 1.2 m acetic acid (applied voltage of 25.5 kV) was selected as a good compromise for the separation and detection of these compounds. The electrospray MS measurements were carried out in the positive ionization mode using a coaxial sheath liquid, methanol-water (1:1) with 1 % of acetic acid at a flow rate of 2.5 muL/min. Under optimized experimental conditions, the predominant ion was the protonated molecular ion ([M + H] ) of solanidine (m/z = 398), tomatidine (m/z = 416), chaconine (m/z = 852), solanine (m/z = 868), and tomatine (m/z = 1034). MS/MS experiments were carried out systematically by changing the relative collisional energy and monitoring the intensities of the fragment ions that were not high enough to allow better quantification than with the mother ions. The method was used for analyzing glycoalkaloids in potato extracts.
AU  - Bianco, G.*
AU  - Schmitt-Kopplin, P.
AU  - de Benedetto, G.*
AU  - Kettrup, A.
AU  - Cataldi, T.R.I.*
C1  - 10232
C2  - 20270
SP  - 2904-2912
TI  - Determination of glycoalkaloids and relative aglycones by nonaqueous capillary electrophoresis coupled with electrospray ionization-ion trap mass spectrometry.
JO  - Electrophoresis
VL  - 23
IS  - 17
PB  - Wiley-VCH
PY  - 2002
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A scale-up of analytical capillary zone electrophoresis (CZE) to preparative free-flow electrophoresis (FFE) is described. FFE allows fractionations based on charge densities in larger amounts than in CZE, enabling further off-line analysis of the fractions. Model compounds (carboxylic acids and polystyrene sulfonates) showed a similar behavior in FFE as in CZE. Diffusion and electrodynamic distortion effects are more pronounced in FFE than in CZE. A soil fulvic acid was analyzed by CZE and fractionated by FFE. A comparison of the FFE fractions with CZE measurements of the same sample using the effective mobility scale showed good agreement of the two methods.
AU  - Junkers, J.
AU  - Schmitt-Kopplin, P.
AU  - Munch, J.-C.
AU  - Kettrup, A.
C1  - 10234
C2  - 20610
SP  - 2872-2879
TI  - Up-scaling capillary zone electrophoresis separations of polydisperse anionic polyelectrolytes with preparative free-flow electrophoresis exemplified with a soil fulvic acid.
JO  - Electrophoresis
VL  - 23
IS  - 17
PY  - 2002
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A theoretical study on the velocity of electroosmotic flow (EOF) and the retention times of neutral solutes under multiple-step gradient of capillary electrochromatography (CEC) was carried out, focusing on that with three kinds of mobile phases. Through the model computations, the detaining time of the second kind of mobile phase in the column was proved to play an important role in affecting EOF. The variation speed of EOF was shown to be determined by the differences among dead times in different steps. In addition, the prediction of the retention times of 13 aromatic compounds under gradient mode was performed with the deduced equations. A relative error below 3.3% between the calculated and experimental values was obtained, which demonstrated the rationality of the theoretical deduction. Our study could not only improve the comprehension of stepwise gradient elution, but also be of significance for the further optimization of separation conditions in the analysis of complex samples.
AU  - Zhang, L.
AU  - Zhang, W.*
AU  - Ping, G.*
AU  - Zhang, Y.*
AU  - Kettrup, A.
C1  - 10233
C2  - 20353
SP  - 2417-2423
TI  - Characteristics of electroosmotic flow and migration of neutral solutes under stepwise gradient elution of capillary electrochromatography.
JO  - Electrophoresis
VL  - 23
IS  - 15
PB  - Wiley-VCH
PY  - 2002
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - By transforming the time-based x-axis of electropherograms in capillary zone electrophoresis (CZE) into the corresponding effective mobility-scale, we propose a simple and robust data representation for a better qualitative and quantitative capillary electrophoresis (CE) analysis. The time scale of the raw electrophoretic data (detection signal versus time) is transformed into an effective electrophoretic mobility scale (mu eff-scale) with account of the electroosmotic flow (EOF) peak or of an internal standard of known effective mobility. With the new scaling (detection signals versus effective mobility), the obtained electropherograms are more representative of the velocity-based electrophoretic separation and the comparison of complete electropherograms is directly possible. This is of importance when tracking peaks in real samples where alteration in EOF stability can occur or when comparing electrophoretic runs from different experimental setups (independence in column length and voltage). Beside the qualitative possibilities, a quantitative improvement is achieved in the mu eff-scale with significant better peak area reproducibility and equal to more precision in quantitative analysis than with the primary time-scale integration.
AU  - Schmitt-Kopplin, P.
AU  - Garmash, A.V.*
AU  - Kudryavtsev, A.V.*
AU  - Menzinger, F.
AU  - Perminova, I.V.*
AU  - Hertkorn, N.
AU  - Freitag, D.
AU  - Petrosyan, V.S.*
AU  - Kettrup, A.
C1  - 10227
C2  - 19591
SP  - 77-87
TI  - Quantitative and qualitative precision improvements by effective mobility-scale data transformation in capillary electrophoresis analysis.
JO  - Electrophoresis
VL  - 22 
IS  - 1
PB  - Wiley-VCH
PY  - 2001
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - We report a novel method to identify protein kinase C (PKC) substrates. Tissue lysates were fractionated by ion exchange chromatography and used as substrates in in vitro kinase reactions. The phosphorylated proteins were separated using two-dimensional gel electrophoresis. Spots that contained isolated phosphoproteins were excised and digested with trypsin. The tryptic peptides were analyzed using mass spectrometry. While several of the proteins identified using this technique represent known PKC substrates, we identified a new PKC substrate in the initial screen. This protein, sm22, is expressed in smooth muscle cells and served well as a substrate for PKC in vitro. Sm22 is predominantly associated with the actin cytoskeleton. Upon activation of PKC in vivo, sm22 dissociates from the actin cytoskeleton and is distributed diffusely in the cytoplasm. Our data strongly suggest that phosphorylation by PKC controls the intracellular localization of sm22. This demonstrates that our approach, using a complex mixture of proteins as in vitro kinase substrates and subsequently identifying the newly phosphorylated proteins by mass spectrometry, is a powerful method to identify new kinase substrates.
AU  - Dammeier, S.
AU  - Lovric, J.
AU  - Eulitz, M.
AU  - Kolch, W.*
AU  - Mushinski, J.F.*
AU  - Mischak, H.*
C1  - 22186
C2  - 20890
SP  - 2443-2453
TI  - Identification of the smooth muscle-specific protein, sm22, as a novel protein kinase C substrate using two-dimensional gel electrophoresis and mass spectrometry.
JO  - Electrophoresis
VL  - 21
IS  - 12
PY  - 2000
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The electrophoretic behavior of fourteen 4,6-diamino-s-triazines was investigated in the presence of an anionic surfactant (sodium dodecyl sulfate, SDS) using micellar capillary electrophoresis (MCE). The measurements were performed at the pH of zero charge of the hydroxytriazines and the existence of strong ionic and H-bond interactions of hydroxy-s-triazine species with the anionic micelles could be shown. Their migration behavior was compared to the n-octanol-water partition coefficients (log Kow) measured with reverse-phase HPLC and calculated with different fragment contribution methods. A partition model was proposed to understand the interactions of the three major hydroxy-s-triazine species: cationic, anionic and neutral (presenting enol and keto forms) with the charged SDS micelles taken as model for charged natural polyelectrolytes like humic substances. These results strongly indicate that hydroxy-s-triazines are polarized in the presence of the charged micelles and that they are essentially present in their keto form in the micellar phase (and enol form in the water phase), confirming previous studies suggesting the presence of zwitterionic resonance structures at a neutral pH around their isoelectric point.
AU  - Freitag, D.
AU  - Schmitt-Kopplin, P.
AU  - Simon, R.*
AU  - Kaune, A.*
AU  - Kettrup, A.
C1  - 20920
C2  - 18990
SP  - 1568-1577
TI  - Interactions of hydroxy-s-triazines with sodium dodecyl sulfate-micelles investigated by micellar capillary electrophoresis.
JO  - Electrophoresis
VL  - 20
IS  - 7
PY  - 1999
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - The commercially available and widely used flatbed electrophoresis apparatus PhastSystem and MultiPhor II (Amersham Pharmacia Biotech, Uppsala, Sweden) were checked for the possible release of significant amounts of platinum from the electrodes during isoelectric focusing (IEF) and native polyacrylamide gel electrophoresis (PAGE). Capillary electrophoresis (CE; Biofocus 3000; Bio-Rad, Munich, Germany) in zone electrophoresis (CZE) mode was investigated for the same purpose. Platinum analysis was done by inductively coupled plasma mass spectrometry (quadrupole and magnetic sector field) either “off-line” for all flatbed gels or “on-line” for the CE measurements. The buffers and process chemicals did not significantly leach platinum from the electrodes. During flatbed electrophoresis, application of the electrical field, however, released high platinum amounts exceeding by far the amount of platinum originally present in the sample. For CE, no platinum was released from the electrodes. The results are strongly dependent on the system and conditions used. The results presented in this paper underline the necessity to replace the platinum electrodes with ultrapure gold electrodes whenever investigating platinum species. Previous literature data, in which electrophoresis was used for platinum speciation without mentioning the platinum recoveries, becomes questionable.
AU  - Lustig, S.
AU  - Kimpe, J. de*
AU  - Cornelis, R.*
AU  - Schramel, P.
AU  - Michalke, B.
C1  - 20900
C2  - 18994
SP  - 1627-1633
TI  - Platinum speciation in clinical and environmental samples: Scrutiny of data obtained by using electrophoresis techniques (flatbed and capillary).
JO  - Electrophoresis
VL  - 20
IS  - 7
PY  - 1999
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - A hyphenation of capillary electrophoresis (CE) to inductively coupled plasma mass spectrometry (ICP-MS) was employed for the speciation of iodine. The separation method used a buffer sandwich of phosphate (pH 2.3), NaOH, sodium dodecyl sulfate (SDS) and borate buffer (pH 8.3) for stacking, aiming at sufficient separation of iodide, iodate, thyroxine (T4) and triiodothyronine (T3). These four iodine species were separated within 15 min and subsequently detected during a pressure-driven detection step (baseline-separated) at 19.5, 29.1, 36.6 and 42.2 s. The detection limits were determined at 0.08 μg I/L (iodide), 0.3 μg I/L (iodate), 3.5 μg I/L (thyroxine) and 2.5 μg I/L (triiodothyronine). This method was applied on iodine speciation in human serum (“healthy” and after thyroid gland operation) and urine. The serum from the healthy person contained iodide (13 μg I/L), T4 (61 μg I/L) and T3 (7.5 μg I/L), whereas the serum from the thyroid-operated person lacked T3. As no “free” I-hormones are known in serum, the role of the thyroid hormone binding globulin (TBG) was investigated. We found that spiked T4 or T3 immediately bound to TBG. Investigations on human urine showed only a peak for iodide.
AU  - Michalke, B.
AU  - Schramel, P.
C1  - 20965
C2  - 19015
SP  - 2547-2553
TI  - Iodine speciation in biological samples by capillary electrophoresis : inductively coupled plasma mass spectrometry.
JO  - Electrophoresis
VL  - 20
PY  - 1999
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Proteins of human bronchoalveolar lavage fluids, obtained by washing the epithelial lining fluid of the lungs with phosphate-buffered saline, were analyzed by two-dimensional electrophoresis under denaturating and reducing conditions. The two-dimensional pattern of bronchoalveolar lavage fluid proteins of healthy volunteers (controls) were compared with those of patients with idiopathic pulmonary fibrosis, sarcoidosis, and asbestosis. Particular interest was paid to the proteins present in minor amounts mainly in the low molecular weight region of the gels. Marked changes in single protein spots were observed. In idiopathic pulmonary fibrosis the spot intensity of the surfactant-associated protein, SP-A, showing isomeric forms both in charge and in molecular weight, was markedly decreased. In sarcoidosis, the immunoglobulins (IgG, IgA) and a group of protein spots at an isoelectric point of 4.5-5.0 and a molecular mass of 55 kDa were increased. An additional spot appeared at an isoelectric point of 4.5 and a molecular mass of 12 kDa. In particular in asbestosis, but also in some cases of idiopathic pulmonary fibrosis and sarcoidosis, the number and intensity of low molecular weight proteins were increased strongly.
AU  - Lenz, A.-G.
AU  - Meyer, B.
AU  - Costabel, U.
AU  - Maier, K.L.
C1  - 20118
C2  - 13294
SP  - 242-244
TI  - Bronchoalveolar Lavage Fluid Proteins in Human Lung Disease: Analysis by Two-Dimensional Electrophoresis.
JO  - Electrophoresis
VL  - 14
IS  - 3
PY  - 1993
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Proteins of human bronchoalveolar lavage fluids, obtained by washing the epithelial lining fluid of the lungs with phosphate-buffered saline, were analyzed by two-dimensional electrophoresis under denaturating and reducing conditions. The two-dimensional pattern of bronchoalveolar lavage fluid proteins of healthy volunteers (controls) were compared with those of patients with idiopathic pulmonary fibrosis, sarcoidosis, and asbestosis. Particular interest was paid to the proteins present in minor amounts mainly in the low molecular weight region of the gels. Marked changes in single protein spots were observed. In idiopathic pulmonary fibrosis the spot intensity of the surfactant-associated protein, SP-A, showing isomeric forms both in charge and in molecular weight, was markedly decreased. In sarcoidosis, the immunoglobulins (IgG, IgA) and a group of protein spots at an isoelectric point of 4.5–5.0 and a molecular mass of 55 kDa were increased. An additional spot appeared at an isoelectric point of 4.5 and a molecular mass of 12 kDa. In particular in asbestosis, but also in some cases of idiopathic pulmonary fibrosis and sarcoidosis, the number and intensity of low molecular weight proteins were increased strongly.
AU  - Lenz, A.-G.
AU  - Meyer, B.E.
AU  - Costabel, U.
AU  - Maier, K.L.
C1  - 40289
C2  - 38983
SP  - 242-244
TI  - Bronchoalveolar lavage fluid proteins in human lung disease: Analysis of two-dimensional electrophoresis.
JO  - Electrophoresis
VL  - 14
IS  - 3
PY  - 1993
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - In the hypusine-containing protein (HP), a specific lysine residue is modified by spermidine to form the unusual amino acid hypusine (4-amino-2-hydroxybutyllysine). The HP has been designated as an eucaryotic translation initiation factor--eIF-5A--because of its stimulating effect in the methionyl-puromycin in vitro assay. Nevertheless, the precise function of this protein remains to be elucidated. In the yeast Saccharomyces cerevisiae two genes, HYP1 and HYP2, coding for two different forms of the HP, are present. The HYP1-gene is identical to the ANB1-gene and has already been localized on chromosome X. However, the chromosomal localization of the HYP2-gene has not been elucidated. By using pulsed-field gel electrophoresis (PFGE) and subsequent Southern blotting, we determined the localization of the HYP2-gene to chromosome V. Furthermore, PFGE was used for the detection of irregular recombination events, such as misintegration or integration into a duplicated gene, and in gene disruption experiments using haploid and diploid yeast cells. The obtained data support the critical role of the HP for cell viability.
AU  - Wöhl, T.
AU  - Baur, M.
AU  - Friedl, A.A.
AU  - Lottspeich, F.
C1  - 20183
C2  - 13361
SP  - 651-653
TI  - Chromosomal Localisation of the HYP2-gene in Saccharomyces Cerevisiae and Use of Pulsed-Field Gel Electrophoresis (PFGE) for Detection of Irregular Recombination Events in Gene Disruption Experiments.
JO  - Electrophoresis
VL  - 13
IS  - 9-10
PY  - 1992
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Proteins of dog bronchoalveolar lavage fluid, obtained by washing the epithelial lining layer of lungs with phosphate-buffered saline, were separated by two-dimensional electrophoresis. Due to the low protein and high salt content of the bronchoalveolar lavage fluid, samples had to be concentrated and desalted. Following electrophoresis the protein spots were visualized by silver staining. Comparing the two-dimensional protein patterns of bronchoalveolar lavage fluid with that from serum, several lungspecific proteins were detected. The most prominent protein, most probably a surfactant-associated protein, showed isoforms with isoelectric points in the range of pH 4.2–4.8, and a molecular mass of 32 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis after reduction with dithiothreitol.
AU  - Lenz, A.-G.
AU  - Meyer, B.
AU  - Weber, H.
AU  - Maier, K.L.
C1  - 18407
C2  - 11358
SP  - 510-513
TI  - Two-dimensional Electrophoresis of Dog Bronchoalveolar Lavage Fluid Proteins.
JO  - Electrophoresis
VL  - 11
IS  - 6
PY  - 1990
SN  - 0173-0835
ER  - 

TY  - JOUR
AB  - Electrofocusing has been adapted in order to make experiments for the detection of enzyme variants more efficient. The principle of the new technique consists in making agar copies of the polyacrylamide gel by contact; the original gel and the agar copies are then developed for different enzyme systems. By doing so, the number of enzymes, i.e. loci, per test animal screened after a single electrofocusing run is increased. This method has proved to be feasible for the detection of mouse variants with altered enzyme banding patterns due to parental treatment with chemical mutagens.
AU  - Pretsch, W.
AU  - Charles, D.J.
AU  - Narayanan, K.R.
C1  - 42237
C2  - 38386
SP  - 142-145
TI  - The agar contact replica technique after isoelectric focusing as a screening method for the detection of enzyme variants.
JO  - Electrophoresis
VL  - 3
IS  - 3
PY  - 1982
SN  - 0173-0835
ER  -