Monolayer study of plastoquinones, α-tocopherol quinone, their hydroquinone forms and their interaction with monogalactosyldiacylglycerol. Charge-transfer complexes in a mixed monolayer

Jerzy Kruk, Kazimierz Strzałka, Roger M. Leblanc

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

The surface pressure-area isotherms of pure plastoquinone-9 (PQ-9), plastoquinone-3 (PQ-3), α-tocopherol quinone (α-TQ), their reduced (hydroquinone) forms and mixtures of these molecules with monogalactosyldiacylglycerol (MGDG) have been studied by a monolayer technique. The collapse pressures of all hydroquinones (QH2) were higher than those of the corresponding quinones (Q), the difference being highest between PQ-9 and PQH2-9. The limiting molecular areas of hydroquinones were higher than those of the corresponding quinones except for α-TQH2. All Q-QH2 mixtures showed miscibility throughout the whole range of the components' ratios. There was no deviation from the addivitiy rule observed for any of the Q-QH2 mixture, as well as for the mixtures of MGDG with PQ-3, PQH2-9, α-TQ and α-TQH2. On the other hand, PQ-9/MGDG and PQH2-3/MGDG mixtures showed positive and negative deviations, respectively. All the isotherms of Q-MGDG and QH2-MGDG mixtures showed a kink point above the collapse pressure of the Q or QH2 examined, indicating that with the increase in surface pressure, Q or QH2 were gradually squeezed out from the monolayer. The percent content of Q and QH2 in the monolayer as a function of surface pressure was also calculated. The hydroquinones were more difficult to remove from monolayers than the corresponding quinones, and among the investigated quinones, PQ-9 was most easily and α-TQ most difficultly squeezed out. The surface pressure-are isotherms of the three-component mixtures of PQ-9/PQH2-9/MGDG showed a shift to lower molecular areas in comparison with the corresponding two-component mixtures, especially at higher surface pressures. This indicates that the presence of PQ-9 lowered the PQH2-9 content in the monolayer, especially at higher pressures, which was explained by charge-transfer complex formation upon interaction of PQ-9 with PQH2-9. The comparison of surface potential-area isotherms of PQ-9/PQH2-9/MGDG mixtures with those of the corresponding binary mixtures also suggest charge-transfer complex formation upon interaction of PQ-9 content in the monolayer, especially at quinones and quinols in the thylakoid membrane and significance of charge-transfer interactions in functioning of PQ-9 has been discussed.

Original languageEnglish (US)
Pages (from-to)19-26
Number of pages8
JournalBBA - Biomembranes
Volume1112
Issue number1
DOIs
StatePublished - Nov 23 1992
Externally publishedYes

Keywords

  • Charge-transfer complex
  • Monogalactosyldiacylglycerol
  • Monolayer
  • Plastoquinone
  • α-Tocopherol quinone

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology

Fingerprint Dive into the research topics of 'Monolayer study of plastoquinones, α-tocopherol quinone, their hydroquinone forms and their interaction with monogalactosyldiacylglycerol. Charge-transfer complexes in a mixed monolayer'. Together they form a unique fingerprint.

  • Cite this