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The Thermodynamic Dissociation Constants of Azathioprine by the Nonlinear Regression and Factor Analysis of Multiwavelength Spectrophotometric pH-Titration Data

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The mixed dissociation constant of azathioprine—chemically 6-(3-methyl-5-nitroimidazol-4-yl)sulfanyl-7H- purine at various ionic strengths I of range 0.01-0.2, and at temperatures of 25℃ and 37℃, was determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis according to a general rule. First, the number of components is determined, and then the spectral responses and concentrations of the components are calculated. Concurrently, the experimental determination of the thermodynamic dissociation constant was in agreement with its computational prediction of the PALLAS programme based on knowledge of the chemical structures of the drug. The factor analysis in the INDICES programme predicts the correct number of two light-absorbing species L- and HL. The thermodynamic dissociation constant of azathioprine was estimated by nonlinear regression of {pKa, I} data, = 8.07(1) at 25℃ and 7.84(1) at 37℃, where the figure in brackets is the standard deviation in last significant digits. The reliability of the dissociation constants of azathioprine was proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data.

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M. Meloun, Z. Ferenčíková and A. Vrána, "The Thermodynamic Dissociation Constants of Azathioprine by the Nonlinear Regression and Factor Analysis of Multiwavelength Spectrophotometric pH-Titration Data,"

*American Journal of Analytical Chemistry*, Vol. 1 No. 1, 2010, pp. 14-24. doi: 10.4236/ajac.2010.11002.

[1] | “Azathioprine,” Encyclopedia Britannica, 2009. http://www. britan-nica.com/EBchecked/topic/46740/azathioprine |

[2] | G. E. Cheney, H. Freiser and Q. Fernando, “Metal Com-plexes of Purine and some of its Derivatives,” Journal of the American Chemical Society, Vol. 81, No. 11, 1959, pp. 2611-2615. |

[3] | D. E. Duggan and E. Titus, “6-Chloropurine and 6- Chlorouric Acid as Substrates and Inhibitors of Purine- Oxidizing Enzymes,” Journal of Biological Chemistry, Vol. 234, No. 8, 1959, pp. 2100-2104. |

[4] | J. D. Davidson, “Studies on the Mechanism of Action of 6-Mercaptopurine in Sensitive and Resistant L1210 Leu-kemia in Vitro,” Cancer Research, Vol. 20, No. 2, 1960, pp. 225-232. |

[5] | U. Kela and R. Vijayvargiya, “Studies on the Mechanism of Action of 6-Mercaptopurine,” Biochemistry Journal, Vol. 193, No. 3, 1981, pp. 799-803. |

[6] | E. Mavioglu, S. Arzik and A. S. Celebi: Potentric Deter-mination of the Stability Constants of Ni(II), Co(II), Cu(II) and Zn(II) Complexes of Hypoxanthine at Physiological Conditions. JFS 27 (2004), 1-19 |

[7] | M. J. Robins and G. L. Basom, “Nucleic Acid Related Compounds. 8. Direct Conversion of 2’-Deoxyinosine to 6-Chloropurine 2’-Deoxyriboside and Selected 6-Substitued Deoxynucleosides and their Evaluation as Substrates of Adenosine Deaminase,” Canadian Journal of Chemistry, Vol. 51, No. 19, 1973, pp. 3161-3169 |

[8] | O. Bibi, J. Schwartz, Y. Eilam, E. Shohami and Z. I. Ca-bantchik, “Nucleoside Transport in Mammalian Cell. IV. Organomercurials and Organomercurial-Mercaptonucleo- side Complexes as Probes for Nucleoside Transport Sys-tems in Hamster Cells,” Journal of Membrane Biology, Vol. 39, No. 2-3, 1978, pp. 159-183 |

[9] | M. Meloun, J. Čapek, P. Mikšík and R. G. Brereton, “Critical of Methods Predicting the Number of Compo-nents in Spectroscopic Data,” Analytica Chimica Acta, Vol. 423, No. 1, 2000, pp. 51-68. |

[10] | M. Meloun and M. Pluhařová, “Thermodynamic Dissoci-ation Constants of Codeine, Ethylmorphine and Homa-tropine by Regression Analysis of Potentiometric Titration Data, Analytica Chimica Acta, Vol. 416, No. 1, 2000 pp. 55-68. |

[11] | M. Meloun and P. Černohorský, “Thermodynamic Dis-sociation Constants of Isocaine, Physostigmine and Pilo-carpine by Regression Analysis of Potentiometric Data,” Talanta, Vol. 52, No. 5, 2000, pp. 931-945. |

[12] | M. Meloun, D. Burkoňová, T. Syrový and A. Vrána: The Thermodynamic Dissociation Constants of Silychristin, Silybin, Silydianin and Mycophenolate by the Regression Analysis of Spectrophotometric Data, Analytica Chimica Acta, Vol. 486, No. 1, 2003, pp. 125-141. |

[13] | M. Meloun, T. Syrový and A. Vrána, “Determination of the Number of Light-Absorbing Species in the Protonation Equilibria of Selected Drugs,” Analytica Chimica Acta, Vol. 489, No. 2, 2003, pp. 137-151. |

[14] | M. Meloun, T. Syrový and A. Vrána, “The Thermody-namic Dissociation Constants of Ambroxol, Antazoline, Naphazoline, Oxymetazoline and Ranitidine by the Re-gression Analysis of Spectrophotometric Data,” Talanta, Vol. 62, No. 3, 2004, pp. 511-522. |

[15] | M. Meloun, T. Syrový and A. Vrána, “The Thermody-namic Dissociation Constants of Losartan, Paracetamol, Phenylephrine and Quinine by the Regression Analysis of Spectrophotometric Data,” Analytica Chimica Acta, Vol. 533, No. 1, 2005, pp. 97-110. |

[16] | M. Meloun, T. Syrový and A. Vrána, “The Thermodynamic Dissociation Constants of Haemanthamine, Lisuride, Metergoline and Nicergoline by the Regression Analysis of Spectrophotometric Data, Analytica Chimica Acta, Vol. 543, No. 1-2, 2005, pp. 254-266. |

[17] | M. Meloun, M. Javůrek and J. Militký, “Computer Esti-mation of Dissociation Constants. Part V: Regression Analysis of Extended Debye-Hückel Law,” Microchimica Acta, Vol. 109, No. 2-3, 1992, pp. 221-231. |

[18] | M. Meloun, J. Havel and E. Högfeldt, “Computation of Solution Equilibria,” Ellis Horwood, Chichester, 1988. |

[19] | M. Meloun and J. Havel, “Computation of Solution equi-libria, Part 1: Spectrophotometry,” Folia Facultatis Scientarum Naturalium Universitatis Purkynianae, Brno 1984. |

[20] | M. Meloun and J. Havel, “Computation of Solution equi-libria, Part 2: Potentiometry,” Folia Facultatis Scientarum Naturalium Universitatis Purkynianae, Brno 1985. |

[21] | M. Meloun, S. Bordovská, T. Syrový and A. Vrána, “Tu-torial on Chemical Model Building and Testing to Spec-troscopic Data with Least-Squares Regression,” Analytica Chimica Acta, Vol. 580, No. 1, 2006, pp. 107-121. |

[22] | M. Meloun, S. Bordovská and T. Syrový, “A Novel Computational Strategy for the pKa Estimation of Drugs by Nonlinear Regression of Multiwavelength Spectro-photometric pH-Titration Data Exhibiting Small Changes,” Journal of Physical Organic Chemistry, Vol. 20, 2007, pp. 690-701. |

[23] | M. Meloun, S. Bordovská and L. Galla, “The Thermody-namic Dissociation Constants of Four Non-Steroidal An-ti-Inflammatory Drugs by the Least-Squares Nonlinear Regression of Multiwavelength Spectrophotometric pH- Titration Data,” Journal of the Pharmaceutical and Bio-medical Analysis, Vol. 45, No. 4, 2007, pp. 552-564. |

[24] | M. Meloun, S. Bordovská, Benchmarking and Validating Algorithms that Estimate pKa Values of Drugs Based on their Molecular Structures,” Analytical and Bioanalytical Chemistry, Vol. 389, No. 4, 2007, pp. 1267-1281. |

[25] | M. Meloun, S. Bordovská and A. Vrána, “The Thermo-dynamic Dissociation Constants of the Anticancer Drugs Camptothecine, 7-Ethyl-10-Hydroxycamptothecine, 10- Hydroxycamptothecine, and 7-Ethylcamptothecine by the Least-Squares Nonlinear Regression of Multiwavelength Spectrophotometric pH-Titration Data, Analytica Chimica Acta, Vol. 584, No. 2, 2007, pp. 419-432. |

[26] | M. Meloun, T. Syrový, S. Bordovská and A. Vrána, Re-liability and Uncertainty in the Estimation of pKa by the Least Squares Nonlinear Regression Analysis of Multi-wavelength Spectrophotometric pH Titration Data,” Ana-lytical and Bioanalytical Chemistry, Vol. 387, No. 3, 2007, pp. 941-955. |

[27] | L. G. Sillén and B. Warnqvist, “Equilibrium Constants and Model Testing from Spectrophotometric Data, Using LETAGROP,” Acta Chemica Scandinavia, Vol. 22, 1968, pp. 3032-3034. |

[28] | D. J. Leggett, “Computational Methods for the Determi-nation of Formation Constants,” In: D. J. Leggett, Ed., Plenum Press, New York, 1985. |

[29] | J. Havel and M. Meloun, “Computational Methods for the Determination of Formation Constants,” In: D. J. Leggett, Ed., Plenum Press, New York, 1985. |

[30] | M. Meloun, M. Javůrek and J. Havel, “Multiparametric curve Fitting-X. A Structural Classification of Program for Analysing Multicomponent Spectra and their Use in Equilibrium-Model Determination,” Talanta, Vol. 33, No. 6, 1986, pp. 513-524. |

[31] | D. J. Leggett and W. A. E. McBryde, “General Computer Program for the Computation of Stability Constants from Absorbance Data,” Analytical Chemistry, Vol. 47, No. 7, 1975, pp. 1065-1070. |

[32] | D. J. Leggett, “Numerical Analysis of Multicomponent Spectra,” Analytical Chemistry, Vol. 49, No. 2, 1977, pp. 276- 281. |

[33] | D. J. Leggett, S. L. Kelly, L. R. Shiue, Y. T. Wu, D. Chang and K. M. Kadish, “A Computational Approach to the Spectrophotometric Determination of Stability Con-stants—2: Application to Metalloporphyrin Axial Ligand Interactions in Non-Aqueous Solvents,” Talanta, Vol. 30, No. 8, 1983, pp. 579-586. |

[34] | J. J. Kankare, “Computation of Equilibrium Constants for Multicomponent Systems from Spectrophoto-Metric Da-ta,” Analytical Chemistry, Vol. 42, No. 12, 1970, pp. 1322-1326. |

[35] | P. Gans, A. Sabatini and A. Vacca, “Investigation of Equilibria in Solution. Determination of Equilibrium Constants with the HYPERQUAD Suite of Programs,” Talanta, Vol. 43, No. 10, 1996, pp. 1739-1753. |

[36] | H. Gampp, M. Maeder, C. J. Mayer and A. Zuberbuhler, “Calculation of Equilibrium Constants from Multiwave-length Spectroscopic Data—I: Mathematical Considera-tions, Talanta, Vol. 32, No. 2, 1985, pp. 95-101. |

[37] | H. Gampp., M. Maeder, C. J. Meyer and A. Zuberbühler, Calculation of Equilibrium Constants from Multiwave-length Spectroscopic Data—II: Specfit: Two User-Friendly Programs in Basic and Standard Fortran 77,” Talanta, Vol. 32, No. 4, 1985, pp. 251-264. |

[38] | H. Gampp., M. Maeder, C. J. Meyer and A. Zuberbühler, “Calculation of Equilibrium Constants from Multiwave-length Spectroscopic Data—III: Model-Free Analysis of Spectrophotometric and ESR Titrations,” Talanta, Vol. 32, No. 12, 1985, pp. 1133-1139. |

[39] | H. Gampp., M. Maeder, C. J. Meyer and A. Zuberbühler, “Calculation of Equilibrium Constants from Multiwave-length Spectroscopic Data—IV: Model-Free Least-Squares Refinement by Use of Evolving Factor Analysis, Talanta, Vol. 33, No. 12, 1986, pp. 943-951. |

[40] | K. Y. Tam and K. Takács-Novák, “Multi-Wavelength Spectrophotometric Determination of Acid Dissociation Constants: A Validation Study,” Analytica Chimica Acta, Vol. 434, No. 1, 2001, pp. 157-167. |

[41] | SPECFIT/32, Spectrum Software Associates, Marlbo-rough, 2004. http://www.bio-logic.info/rapid-kinetics/specfit. html |

[42] | T. H. Scheuermann, C. Keeler and M. E. Hodson, “Con-sequences of Binding an S-Adenosylmethionine Analogue on the Structure and Dynamics of the Thiopurine Methyltransferase Protein Backbone, Biochemistry, Vol. 43, No. 38, 2004, pp. 12198-12209. |

[43] | Pallas. http://compudrug.com/show.php?id=90. http:// compudrug.com/show.php?id=36. |

[44] | M. Meloun, J. Militký and M. Forina, Chemometrics for Analytical Chemistry—Vol. 1. PC-Aided Statistical Data Analysis, Ellis Horwood, Chichester, 1992. |

[45] | M. Meloun, J. Militký and M. Forina, Chemometrics for Analytical Chemistry—Vol. 2. PC-Aided Regression and Related Methods, Ellis Horwood, Chichester, 1994. |

[46] | ORIGIN, OriginLab Corporation, Northampton. |

[47] | M. Meloun, T. Syrový and A. Vrána, “Determination of the Number of Light-Absorbing Species in the Protonation Equilibria of Selected Drugs,” Analytica Chimica Acta, Vol. 489, No. 2, 2003, pp. 137-151. |

[48] | S-PLUS. http://www.insightful.com/products/splus |

[49] | ADSTAT, ADSTAT 1.25, 2.0, 3.0 (Windows 95), Trilo-Byte Statistical Software Ltd., Pardubice. |

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