Abstract
Binding of caffeine in aqueous solutions has been achieved for the first time by using water-soluble, tetracationic peptide-porphyrin conjugates Zn-1 as the receptor molecules. The association constant for caffeine with receptor Zn-1 is in some cases as high as 6000 M-1, only 5-6 times lower than the highest binding constant reported for an artificial caffeine receptor in low polarity aprotic solvents. The binding mechanism has been studied by a combination of experimental techniques such as UV-visible and NMR spectroscopy and microcalorimetry. Recognition of caffeine involves both stacking with the porphyrin ring and metal coordination. Subtle variations of the receptor structure affect the complexation. Receptors Zn-1 have also been investigated for the recognition of molecules structurally related to caffeine, for example, 1-methylimidazole. Selectivity towards oxopurine derivatives (caffeine and theophylline) have been found.
Original language | Undefined |
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Pages (from-to) | 784-792 |
Number of pages | 9 |
Journal | Chemistry : a European journal |
Volume | 9 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2003 |
Keywords
- water chemistry
- METIS-215563
- IR-40871
- Caffeine
- Noncovalent interactions
- Sensors
- porphyrinoids