DYNAMICS OF MEROCYANINE-540 IN MODEL BIOMEMBRANES - PHOTOISOMERIZATION STUDIES IN SMALL UNILAMELLAR VESICLES

ONGANER Y., QUITEVIS E.

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES, cilt.1192, sa.1, ss.27-34, 1994 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 1192 Sayı: 1
  • Basım Tarihi: 1994
  • Doi Numarası: 10.1016/0005-2736(94)90139-2
  • Dergi Adı: BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.27-34
  • Anahtar Kelimeler: MEROCYANINE 540, PHOSPHATIDYLCHOLINE, CHOLESTEROL, VESICLE, PHOTOISOMERIZATION, MICROVISCOSITY, SINGLET OXYGEN PRODUCTION, LIPID BILAYER-MEMBRANES, RHODAMINE-B, FLUORESCENT-PROBE, PHOSPHOLIPID-MEMBRANES, OPTICAL PROBES, POLAR-SOLVENTS, CYANINE DYES, LIPOSOMES, CELLS
  • Atatürk Üniversitesi Adresli: Evet

Özet

The fluorescence lifetime, tau(f), of merocyanine 540 (MC540) in small unilamellar vesicles was measured as a function of temperature and cholesterol content by using phase modulation fluorometry. These vesicles were formed by probe sonication of aqueous suspensions of egg phosphatidylcholine (PC) and cholesterol. The fluorescence lifetime of MC540 in these vesicles decreased with increasing temperature, but was independent of cholesterol. The decrease in tau(f) with temperature is attributed to trans-cis photoisomerization. At low temperatures, the inverse of tau(f), or the fluorescence rate constant, k(f), approaches a constant value of 0.45 +/- 0.02 ns(-1), which corresponds to the value of the radiative rate constant, k(r), of the dye. The photoisomerization rate constant, k(iso), was obtained by subtracting k(r) from k(f). The temperature dependence of k(iso) is well described by an Arrhenius equation, with an activation energy of 31.5 +/- 0.9 kJ mol(-1). This Arrhenius behavior is rationalized in terms of the Smoluchowski limit for the Kramers theory for activated barrier crossing. The electronic spectra and k(iso) for MC540 in these vesicles are consistent with the dye being located in the polar headgroup region of the lipid bilayer.