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  • 1985-1989  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Binding of 8-methoxypsoralen to human serum proteins and red blood cells (1987)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 117 (1987), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Serum binding of 8-methoxypsoralen (8-MOP) was studied by equilibrium dialysis. In therapeutic concentrations, 8-MOP binding in serum was high, 91·4%, and constant, indicating concentration-independent kinetics. This binding involved the two main proteins, human serum albumin and α-acid glycoprotein, in a saturable process with one class of binding sites (n) and affinity constants (Ka) of 1·295 × 104 mol/1 and 2·115 × 104 mol/1, respectively. Binding to lipoproteins and · globulins was negligible and non-saturable in therapeutic concentrations, with nKa values of 0·35,0·024,0·013 and 0·0004/μmol/1s for VLDL, LDL, HDL and γ globulins, respectively. Inhibition of 8-MOP serum binding was observed with salicylic acid and indomethacin, but not with diazepam, warfarin or erythromycin.Over a range of therapeutic concentrations, the ratio of 8-MOP concentration in red blood cells (RBCs) and in serum was constant at 20·3% and three times higher than would be expected if a simple diffusion of the 8-MOP plasma free fraction (fu) occurred.According to the measured and calculated parameters, simulations of 8-MOP blood binding in pathological states (hypoalbuminaemia with or without inflammation) showed variations of fu which were partially ‘buffered’ by RBCs.Simulation of 8-MOP protein binding at cutaneous interstitial fluid level showed that fu is approximately 30% and permitted prediction of a decrease of fu available to the epidermis in case of local or systemic inflammation. This may imply an increase in the minimum phototoxic dose relevant for PUVA and explain some cases of ‘poor’ responsiveness of psoriatic patients to PUVA therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2133.1987.tb04118.x
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  • 2
    Electronic Resource
    Electronic Resource
    Study of deuterium isotope effects on protein binding by gas chromatography/mass spectrometry. Caffeine and deuterated isotopomers (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 653-657 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the binding to human serum albumin (HSA) of caffeine and its deuterated isotopomers, 1-C2H3-, 3-C2H3-, 1,7-(C2H3)2-, 3,7-(C2H3)2- and 1,3,7-(C2H3)3-caffeine, was performed by equilibrium dialysis. Free and bound fractions were measured by gas chromatography/mass spectrometry. Important and significant (Fischer and Student tests) isotope effects were observed on binding parameters: sites total concentration (N = 1732) μM for 1,3,7-(C2H3)3-caffeine versus 822 μM for caffeine; number of sites (n = 3 for 1,3,7-(C2H3)3-caffeine v. 1 for caffeine); and extent of binding (46% for 1,3,7-(C2H3)3-caffeine v. 27% for caffeine).A study of competition for HSA binding between caffeine and its 1,3,7-(C2H3)3- and 3,7-(C2H3)2-isotopomers confirmed the results obtained in direct binding studies. These isotope effects are discussed in terms of (a) tools for molecular pharmacology, (b) precautions to be taken when such labelled drugs are used in clinical pharmacology.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200141115
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  • 3
    Electronic Resource
    Electronic Resource
    Study of isotope effects on protein binding by gas chromatography/mass spectrometry of theophylline-phenobarbitone and 2H, 13C, 15N isotopomers (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1988), S. 245-250 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a comparative study of human serum albumin (HSA) binding by equilibrium dialysis (pH 7.4, 37°C, 3 h) for two groups of isotopic analogues: theophylline and 1-C(2H3)theophylline; unlabelled, 5(ethyl(2H5)),-5(phenyl(2H5)) and 1,3-15N;2-13C-phenobarbitone. Bound and free drug fractions are quantified by combined gas chromatography/mass spectrometry. In three instances, protein binding parameters are greatly affected by isotopic substitution, namely for: theophylline and 1-C(2H3)theophylline with isotope effects on total binding site concentration (N), affinity constant (Ka) and extent of HSA binding (%) respectively, equal to: NL/NH=0.51; KaL/KaH = 1.78; %L/%H = 0.96 (L (light) and H (heavy) represent the unlabelled and labelled analogue respectively); phenobarbitone/-5-(phenyl(2H5))phenobarbitone, NL/NH = 1.72; KaL/KaH = 0/56; %L/%H = 1.26; phenobarbitone/1,3-15N;2-13C phenobarbitone, NL/NH = 2.95; KaL/KaH = 0.44; %L/%H = 1.32, together with a change from one (saturable) to two (saturable + non-saturable) families of albumin binding sites in the latter case. Contrasting with these data, no HSA binding isotope effect was observed on phenobarbitone C5 ethyl deuteration.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200170403
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    Paper (German National Licenses)
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