The interaction of collagen with the hydrophobic fluorescent probe 2-p-toluidinylnaphthalene-6-sulfonate

✍ Scribed by Hsin-Chou Chiang; Aaron Lukton

• Publisher: Wiley (John Wiley & Sons)
• Year: 1975
• Tongue: English
• Weight: 794 KB
• Volume: 14
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1975.360140809

✦ Synopsis

Abstract

Three kinds of fluorescence enhancement result from the interaction of 2‐p‐toluidinylnaphthalene‐6‐sulfonate and calf‐skin collagen. They are negatively cooperative, independent, and highly cooperative fluorescence enhancement. In the independent region at pH 3.7, the binding number is about 36 moles of 2‐p‐toluidinylnaphthalene‐6‐sulfonate per mole of tropocollagen with a binding constant of 2.0 × 10^4^ M^−1^; with Δ__G__ = −5.7 kcal/mole, Δ__H__ = −4.0 kcal/mole, and Δ__S__ = 6 e.u. The pH dependence of fluorescence of native collagen shows that the deprotonated forms of the β and γ carboxyl groups of aspartic and glutamic acid decrease the intensity, possibly by charge repulsion of the negatively charged sulfonate group of 2‐p‐toluidinylnaphthalene‐6‐sulfonate. The positive charge of lysine is found to be unimportant in the interaction of 2‐p‐toluidinylnaphthalene‐6‐sulfonate with collagen. Fluorescence enhancement is caused mainly by the hydrophobic interactions of 2‐p‐toluidinylnaphthalene‐6‐sulfonate and collagen. Salt bridge formation between basic and acidic side chains in very low salt concentration may be detectable by 2‐p‐toluidinylnaphthalene‐6‐sulfonate fluorescence.