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Yuan H, He Z, Chen X, Ge T, Zhang L, Wang J. Rapid, sensitive analysis method for determining the nitrogen stable isotope ratio of total free amino acids in soil. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9390. [PMID: 36056455 DOI: 10.1002/rcm.9390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 08/20/2022] [Accepted: 08/30/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE The amino acid-nitrogen (AA-N) isotope analysis of naturally abundant or isotope-labeled samples is indispensable for tracing nitrogen transfer in soil nitrogen biogeochemical cycling processes. Despite the usefulness of AA-N isotope analysis, the preparation methods are complex and time-consuming, and necessitate the use of toxic reagents. METHODS We present an improved, rapid method for AA-N isotope analysis with high precision. At a high pH, AA-N was released and oxidized to N2 O using ClO- under vacuum. Additionally, purge-and-trap isotope ratio mass spectrometry was used to analyze N2 O. Moreover, we investigated the effect of various factors on the N2 O conversion process with glycine and applied the results to seven representative single-N AAs (alanine, serine, cysteine, aspartic acid, glutamic acid, leucine, and phenylalanine) and five poly-N AAs (lysine, arginine, histidine, tryptophan, and asparagine), as well as side-chain analogs, blank reagent, and other N forms. RESULTS The concentration of ClO- and the pH were determined to be crucial factors for achieving desirable AA-N to N2 O conversion efficiencies. Glycine-N had the highest N2 O yield of 70%, with isotopic results consistent with those of the reference values at a high precision (within 0.5‰ for natural abundance and 0.01 atom% for 15 N-enrichment) at the nanomolar N level. Additionally, the α-NH2 AAs were labile, and the single-N AAs were more easily converted to N2 O than poly-N AAs. With the exception of γ-aminobutyric acid, the N2 O conversion efficiencies of the side-chain N analogs were very low (below 5%). This method was also applicable to the 15 N analysis of the total free AAs in complex soil samples without interference from analytical blanks and other forms of N. CONCLUSIONS Our method is highly selective for the α-NH2 groups of an amino acid, and the oxidation of the side chain is difficult. In addition, the method is sensitive, rapid, and convenient, and does not require toxic reagents.
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Affiliation(s)
- Hongzhao Yuan
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Mapoling, Changsha, Hunan, China
| | - Zhen He
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Mapoling, Changsha, Hunan, China
| | - Xiangbi Chen
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Mapoling, Changsha, Hunan, China
| | - Tida Ge
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection of Ministry of Agriculture and Zhejiang Province, Institute of Plant Virology, Ningbo University, Ningbo, Zhejiang, China
| | - Liping Zhang
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Mapoling, Changsha, Hunan, China
| | - Jiurong Wang
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Mapoling, Changsha, Hunan, China
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Effects of amino acid-derived chiral ionic liquids on cyclodextrin-mediated capillary electrophoresis enantioseparations of dipeptides. J Chromatogr A 2021; 1652:462342. [PMID: 34174715 DOI: 10.1016/j.chroma.2021.462342] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 06/03/2021] [Accepted: 06/08/2021] [Indexed: 11/20/2022]
Abstract
The synergistic effect of chiral ionic liquids composed of tetraalkylammonium ions and the amino acids Asn, Asp or Pro on the enantioseparations of dipeptides mediated by β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin in capillary electrophoresis was studied. Addition of a chiral ionic liquid resulted in a concentration-dependent increase in the enantioresolutions compared to the sole presence of a cyclodextrin in the background electrolyte. The extent varied with the tetraalkylammonium cation (tetramethylammonium versus tetrabutylammonium) as well as the amino acid component of the ionic liquid. The presence of a chiral ionic liquid did not counteract the pH-dependent reversal of the enantiomer migration order of the dipeptides Ala-Phe, Ala-Tyr and Phe-Phe when increasing the pH of the background electrolyte from 2.5 to 3.5. Comparing the effect of a chiral ionic liquid based on Asp with the addition of equimolar concentrations of the individual components of the ionic liquid, a diverse picture was observed. In some cases, higher resolution values were obtained with the chiral ionic liquid, while for other cases superior enantioseparations were obtained upon separate addition of the amino acid component and a tetraalkylammonium chloride. With regard to the stereochemistry of the amino acid, a superior effect was typically observed using the l-configured amino acid, but in some cases higher resolution values were found in the presence of d-Asp. The rationale for the diverse observations is not obvious and may be due to the zwitterionic nature of analytes as well as the amino acid component of the chiral ionic liquid.
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Enantioseparation of alanyl-phenylalanine analogs by capillary electrophoresis using negatively charged cyclodextrins as chiral selectors. J Chromatogr A 2020; 1632:461585. [DOI: 10.1016/j.chroma.2020.461585] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/21/2020] [Accepted: 09/23/2020] [Indexed: 11/23/2022]
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Konjaria ML, Scriba GK. Enantioseparation of analogs of the dipeptide alanyl-phenylalanine by capillary electrophoresis using neutral cyclodextrins as chiral selectors. J Chromatogr A 2020; 1623:461158. [DOI: 10.1016/j.chroma.2020.461158] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 04/18/2020] [Accepted: 04/21/2020] [Indexed: 02/07/2023]
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Tsopelas F, Vallianatou T, Tsantili-Kakoulidou A. Advances in immobilized artificial membrane (IAM) chromatography for novel drug discovery. Expert Opin Drug Discov 2016; 11:473-88. [DOI: 10.1517/17460441.2016.1160886] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Fotios Tsopelas
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Athens, Zografou, Athens, Greece
- Laboratory of Inorganic and Analytical Chemistry, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - Theodosia Vallianatou
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Athens, Zografou, Athens, Greece
| | - Anna Tsantili-Kakoulidou
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Athens, Zografou, Athens, Greece
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Ludewig R, Nietzsche S, Scriba GKE. A weak cation-exchange monolith as stationary phase for the separation of peptide diastereomers by CEC. J Sep Sci 2010; 34:64-9. [DOI: 10.1002/jssc.201000616] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 09/30/2010] [Accepted: 09/30/2010] [Indexed: 11/11/2022]
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7
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Terekhova IV, Hammitzsch-Wiedemann M, Shi Y, Sungthong B, Scriba GKE. Investigation of the pH-dependent complex formation between β-cyclodextrin and dipeptide enantiomers by capillary electrophoresis and calorimetry. J Sep Sci 2010; 33:2499-505. [DOI: 10.1002/jssc.201000093] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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8
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Ludewig R, Dong J, Zou H, Scriba GKE. Separation of peptide diastereomers using CEC and a hydrophobic monolithic column. J Sep Sci 2010; 33:1085-9. [DOI: 10.1002/jssc.200900739] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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9
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Testa B, Carrupt PA, Gaillard P, Tsai RS. Intramolecular Interactions Encoded in Lipophilicity: Their Nature and Significance. LIPOPHILICITY IN DRUG ACTION AND TOXICOLOGY 2008. [DOI: 10.1002/9783527614998.ch4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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de Person M, Chaimbault P, Elfakir C. Analysis of native amino acids by liquid chromatography/electrospray ionization mass spectrometry: comparative study between two sources and interfaces. JOURNAL OF MASS SPECTROMETRY : JMS 2008; 43:204-15. [PMID: 17902194 DOI: 10.1002/jms.1287] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The analytical performances of two triple-quadrupole instruments, which differ in their atmospheric-pressure sources, were evaluated for native amino acid analysis. The Applied Biosystems/Sciex API 300 instrument was equipped with a turboIon Spray source and a curtain gas interface while the Waters/Micromass Quattro Ultima instrument was characterized by its Z-spray source. Liquid chromatography/mass spectrometry analysis of native amino acids requires volatile ion-pairing mobile phase additives (mainly perfluorinated carboxylic acids). The effects of the structure and concentration of the ion-pairing reagents as well as the organic modifier percentage on the electrospray response of amino acids were studied in detail. The most favourable chromatographic conditions depend strongly on the mass spectrometer used. Several instrumental parameters were also studied, including spray voltage, transmission lens voltages, temperature of desolvation and auxiliary gas flow rates. The results show substantial qualitative differences depending on the instrument geometry. The quantitative performances of the two triple-quadrupole mass spectrometers were evaluated in terms of limits of detection and quantification. The effects of the matrix on the analyte ionization were also examined, and the long-term stability of the electrospray performance was studied over 12 h using a mobile phase containing the perfluorinated ion-pairing reagents. The study provides information on the robustness of the MS instrument and its detection sensitivity towards native amino acid analysis. It appears that each instrument has its good and bad points since one provides higher sensitivity while another is more robust.
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Affiliation(s)
- Marine de Person
- Institut de Chimie Organique et Analytique (ICOA), CNRS FR 2708, UMR 6005, Université d'Orléans, BP 6759, F-45067 Orléans Cedex 2, France
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12
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Hammitzsch-Wiedemann M, Scriba GKE. Influence of buffer substances and urea on the β-cyclodextrin-mediated chiral separation of dipeptides in CE. Electrophoresis 2007; 28:2619-28. [PMID: 17592612 DOI: 10.1002/elps.200600728] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The influence of buffering substances and urea on the beta-CD-mediated chiral separations of the dipeptides Ala-Phe and Ala-Tyr was studied in the pH range of 2.5-3.8. Only minor effects of the buffer substances on the chiral separation selectivity alpha were observed at a beta-CD concentration of 15 mg/mL. In contrast, the selectivity improved at pH 2.5 but decreased at pH 3.8 upon the addition of 2 M urea. Complexation by beta-CD resulted in a shift of the pK(a) values toward higher values which was more pronounced for the DD-enantiomers of both dipeptides than for the LL-enantiomers. Addition of urea further increased the pK(a) shift. The consequence of this pK(a) shift is an increase of the fraction of the protonated, positively charged form of the peptides which explained the improved chiral separation at pH 2.5 and the reduced selectivity at pH 3.8. A pK(a) shift by the addition of urea was also observed for N-tert-butyloxycarbonyl phenylalanine (BOC-Phe) as a model compound that is strongly complexed by beta-CD. This effect was not stereospecific. Addition of urea resulted in a decrease of the apparent complexation constants between beta-CD and the BOC-Phe enantiomers to the same extent but this did not affect the separation selectivity alpha. For chiral separations that display strong pH dependence such as peptide enantioseparations close to the pK(a) values of the compounds, urea may not solely be regarded as a solubility enhancer for beta-CD but may also influence the separation.
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13
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Carrupt PA, Testa B, Gaillard P. Computational Approaches to Lipophilicity: Methods and Applications. REVIEWS IN COMPUTATIONAL CHEMISTRY 2007. [DOI: 10.1002/9780470125885.ch5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
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14
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Maheshwari R, Dhathathreyan A. Investigation of surface properties of amino acids: polarity scale for amino acids as a means to predict surface exposed residues in films of proteins. J Colloid Interface Sci 2005; 277:79-83. [PMID: 15276041 DOI: 10.1016/j.jcis.2004.04.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Accepted: 04/14/2004] [Indexed: 10/26/2022]
Abstract
It is of great interest and importance to study how different amino acid residues contribute to and affect the properties of proteins coated as films on solid surface. This work shows that the solid/liquid interfacial energy of surface localized amino acid films and their Gibbs energies of transfer at the air/solution interface have the potential to be used as a rapid and simple method for studying the surface properties of proteins. Based on these results, a new polarity scale for amino acids has been proposed. This scale is compared with existing hydropathy scales in a benchmark test using some proteins with solved 3D structure. The proteins were characterized in terms of surface-exposed residues with a computer program, Graphical Representation and Analysis of Surface Properties (GRASP). It was also shown that each amino acid contribution is relative to the total protein surface and the other residues on the surface.
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Affiliation(s)
- R Maheshwari
- Chemical Laboratory, CLRI, Adyar, Chennai 600020, India
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15
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Binding constants for aromatic amino acids and their derivatives with sulfobutyl ether β-cyclodextrin determined using capillary electrophoresis. J Drug Deliv Sci Technol 2004. [DOI: 10.1016/s1773-2247(04)50067-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Gulaboski R, Scholz F. Lipophilicity of Peptide Anions: An Experimental Data Set for Lipophilicity Calculations. J Phys Chem B 2003. [DOI: 10.1021/jp034387e] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rubin Gulaboski
- Ernst-Moritz-Arndt-Universität Greifswald, Institut für Chemie und Biochemie, Soldmannstrasse 23, D-17489 Greifswald, Germany
| | - Fritz Scholz
- Ernst-Moritz-Arndt-Universität Greifswald, Institut für Chemie und Biochemie, Soldmannstrasse 23, D-17489 Greifswald, Germany
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Taillardat-Bertschinger A, Barbato F, Quercia M, Carrupt PA, Reist M, La Rotonda M, Testa B. Structural Properties Governing Retention Mechanisms on Immobilized Artificial Membrane (IAM) HPLC Columns. Helv Chim Acta 2002. [DOI: 10.1002/1522-2675(200202)85:2<519::aid-hlca519>3.0.co;2-q] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Sabbah S, Süss F, Scriba GK. pH-dependence of complexion constants and complex mobility in capillary electrophoresis separations of dipeptide enantiomers. Electrophoresis 2001; 22:3163-70. [PMID: 11589275 DOI: 10.1002/1522-2683(200109)22:15<3163::aid-elps3163>3.0.co;2-a] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The chiral separation of the LL- and DD-enantiomers of the dipeptides Ala-Tyr, Phe-Phe, and Asp-PheOMe has been investigated at pH 2.5 and pH 3.5 using beta-cyclodextrin (beta-CD), heptakis-(2,6-di-O-methyl)-beta-cyclodextrin, and heptakis-(2,3,6-tri-O-methyl)-beta-cyclodextrin as chiral selectors. According to electrospray mass spectrometry, heptakis-(2,6-di-O-methyl)-beta-cyclodextrin was a mixture of six isomers. Reversal of the enantiomer migration order upon increasing the buffer pH from 2.5 to 3.5 was observed for all peptides with beta-cyclodextrin, for Ala-Tyr and Phe-Phe in the presence of heptakis-(2,3,6-tri-O-methyl)-beta-cyclodextrin, and for Ala-Tyr using heptakis-(2,6-di-O-methyl)-beta-cyclodextrin. The migration behavior could be explained on the basis of the complexation constants and the mobilities of the peptide-cyclodextrin complexes. Both, the binding constants and complex mobilities decreased with increasing pH as the overall-charge of the peptides decreased. While the complexation constants primarily determined the migration order at pH 2.5, complex mobility dominated in most cases at pH 3.5.
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Affiliation(s)
- S Sabbah
- School of Pharmacy, Department of Pharmaceutical Chemistry, University of Jena, Germany
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Schiene-Fischer C, Fischer G. Direct measurement indicates a slow cis/trans isomerization at the secondary amide peptide bond of glycylglycine. J Am Chem Soc 2001; 123:6227-31. [PMID: 11427045 DOI: 10.1021/ja0042480] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Spectral differences between the cis and the trans isomer of a secondary amide peptide bond were used to follow the time course of the cis/trans isomerization of Gly-Gly, Gly-Ala, Ala-Gly, and Ala-Ala dipeptides in the UV/vis region at 220 nm. Isomerization rates and Eyring activation energies were calculated from pH- and LiCl-mediated solvent jump experiments. Rate constants were found to be in a narrow range of 0.29 to 0.64 s(-)(1) for the zwitterionic dipeptides at 25 degrees C. The isomerization rate is about 2-fold higher for the monoionic forms of Gly-Gly. The zwitterionic Gly-Gly has an activation enthalpy DeltaH() of 71.6 +/- 4.9 kJ mol(-)(1) that is in the range of the rotational barriers of aromatic side chain dipeptides that have been measured by (1)H NMR magnetization transfer experiments. Late stages of protein backbone rearrangements often involve crossing the energy barrier for rotational isomerization of imidic peptide bonds. Our findings are consistent with the idea that a wide range of secondary amide peptide bonds are also able to induce slow rate-limiting steps in protein restructuring.
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Affiliation(s)
- C Schiene-Fischer
- Max Planck Research Unit for Enzymology of Protein Folding, Weinbergweg 22, 06120 Halle/Saale, Germany.
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Sabbah S, Scriba GK. Separation of dipeptide and tripeptide enantiomers in capillary electrophoresis using carboxymethyl-beta-cyclodextrin and succinyl-beta-cyclodextrin: influence of the amino acid sequence, nature of the cyclodextrin and pH. Electrophoresis 2001; 22:1385-93. [PMID: 11379961 DOI: 10.1002/1522-2683(200105)22:7<1385::aid-elps1385>3.0.co;2-a] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The separation of the LL and DD enantiomers of dipeptides and tripeptides using cyclodextrins (CDs) containing carboxyl groups was investigated with respect to the amino acid sequence of the peptides, the nature of the cyclodextrin and the buffer pH. Compared to succinyl-beta-cyclodextrin, carboxymethyl-beta-cyclodextrin was the more universal CD for enantioseparations. Reversal of the enantiomer migration order upon increasing the buffer pH from 2.5 to 3.5 was observed in some cases. As shown for Phe-Phe reversal of the migration order also occurred between pH 3.5 and 5.3. Complexation constants and complex mobilities change with pH as both, the charge of the peptide and the charge of the CD vary depending on the pH. The complexation constants and complex mobilities of the dipeptides Ala-Phe and Phe-Phe were determined in order to explain the enantiomer migration behavior in the pH range 2.5-5.3. While the complexation constants determined the migration order at pH 2.5 and 5.3, complex mobility had a strong influence around pH 3.5-3.8.
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Affiliation(s)
- S Sabbah
- School of Pharmacy, Department of Pharmaceutical Chemistry, University of Jena, Germany
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Chaimbault P, Petritis K, Elfakir C, Dreux M. Determination of 20 underivatized proteinic amino acids by ion-pairing chromatography and pneumatically assisted electrospray mass spectrometry. J Chromatogr A 1999; 855:191-202. [PMID: 10514984 DOI: 10.1016/s0021-9673(99)00685-8] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A qualitative determination of 20 underivatized proteinic amino acids by LC-MS is reported. The need for chromatographic separation before mass spectrometry determination is demonstrated based on the study of several amino acid pairs which have some similar characteristics. Two suitable LC-MS systems are proposed for amino acid analysis. A preliminary optimization of these systems has been investigated using evaporative light scattering detection as these two detection modes have the same chromatographic requirements. The amino acid separation was achieved on a Purospher RP-18e or a Supelcosil ABZ+Plus column with tridecafluoroheptanoic acid or pentadecafluorooctanoic acid as volatile ion-pairing reagent in an acetonitrile-water mobile phase. In order to elute the most retained amino acids, an elution gradient based on simultaneously increasing the concentration of acetonitrile and decreasing the concentration of the ion-pairing reagent was used. The detection limits of the present work (without specialized optimization) varied from 0.5 to 1 mg 1(-1).
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Affiliation(s)
- P Chaimbault
- Institut de Chimie Organique et Analytique (ICOA), CNRS UPRES-A 6005, Université d'Orléans, France
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Sotomatsu-Niwa T, Ogino A. Evaluation of the hydrophobic parameters of the amino acid side chains of peptides and their application in QSAR and conformational studies. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0166-1280(97)90371-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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