Estimation of the polarity of the protein interior by optical spectroscopy
Abstract
Crystallographic studies of myoglobin have shown that the haem pocket is lined with nonpolar amino-acid residues1. In order to estimate the true polarity of the interior of proteins, certain studies have used bound fluorophores2-7, the spectroscopic properties of which reflect the polarity of their environment. These studies have most often used l-amino-8-naphthalene sulphonate (ANS) as a probe, but a more suitable probe, in principle, is 6-propionyl 2-(N,N-dimethyl)aminonaphthalene (PRODAN)8. We have synthesized a molecule with the advantageous spectroscopic properties of PRODAN but with a higher affinity for apomyo-globlin: 2'-(N,N-dimenthyl)amino-6-naphthopyl-4-trans-cyclo-hexanoic acid (DANCA), and report here its use to determine the polarity of the myoglobin haem pocket. Our results show that the pocket is actually a polar environment, and the polarity can be accounted for by peptide amide dipoles.
- Publication:
-
Nature
- Pub Date:
- January 1986
- DOI:
- 10.1038/319070a0
- Bibcode:
- 1986Natur.319...70M