The apomyoglobin-arylaminonaphthalenesulfonate system. Insight into fluorescent probe responses by substituent modulation

Hanna Dodiuk, Hanna Kanety, Edward M. Kosower

Research output: Contribution to journalArticlepeer-review

Abstract

Binding site "polarity" of apomyoglobin has been further probed through a study of substituent effects on complexes with 8,1-ANS (8-N-arylamino-1-naphthalenesulfonate), 6,2-ANS (6-N-arylamino-2-naphthalenesulfonate), and N-Me-6,2-ANS (N-methyl-6-N-arylamino-2-naphthalenesulfonate) derivatives. The dissociation constants for the apomyoglobin:8,1-ANS and :6,2-ANS complexes are almost independent of substituent (range 2.7-5.4 × 10-6 M for KD). The emission maximum varies in a way characterized by the Hammett ρ values of -5.3 (8,1-ANS derivatives) and -3.8 (6,2-ANS derivatives). From the relationship between ρ values and solvent polarity previously found, the binding site polarities are equivalent to ET(30) values of ca. 34 kcal/mol (8,1-ANS derivatives) or 42 kcal/mol (6,2-ANS derivatives). Fluorescent "probes" can thus not specify a binding "site polarity". The ρ values, absence of heavy atom effects and the formation of "photoproduct" imply that the excited state behavior of ANS derivatives bound to apomyoglobin is mainly determined by the restrictions on motion of the ANS molecule.

Original languageEnglish
Pages (from-to)515-521
Number of pages7
JournalJournal of Physical Chemistry
Volume83
Issue number4
DOIs
StatePublished - 1979

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