Die Struktur des Ubichinons aus Schweineherzen

The interaction between 1,2-dipalmitoyl phosphatidylcholine and ubiquinone-10 in aqueous systems was studied by difference i.r. spectroscopy. Binary mixtures of the two lipids in proportions of 2, 5 and 15 mol% were investigated in the spectral regions reporting on the hydrocarbon chains of the phospholipid and the polar phosphate group. No spectral shifts or significant broadening of any absorbances due to the phospholipid were detected at temperatures of 20 or 54 degrees C. Changes in the frequency of the maximum of the CH2 antisymmetric C-H stretching vibration with temperature indicated that the gel-to-liquid-crystal-line phase-transition temperature of the phospholipid was lowered by about 2 degrees C in the presence of between 2 and 15 mol% ubiquinone-10. Absorbance by the benzoquinone substituent of ubiquinone-10 was detected by spectral subtraction of dispersions of phospholipid alone. Bands due to C = O stretching and ester group vibrations of ubiquinone-10 in co-dispersion with phospholipid were compared with the same spectral region when ubiquinone-10 was dissolved in solvents or as a crystalline solid. Spectral changes could be detected when ubiquinone-10 in phospholipid was compared with solution in dodecane and chloroform. These may indicate that the benzoquinone ring system is located within a hydrocarbon domain in dispersions with dipalmitoyl phosphatidylcholine. It was concluded from the study that when ubiquinone-10 is co-dispersed with dipalmitoyl phosphatidylcholine in water the two lipids phase-separate. There is no evidence that ubiquinone-10 intercalates between phospholipid molecules, which undergo a gel-liquid-crystalline phase transition in only a slightly modified form. The data suggest that the benzoquinone substituent resides in a hydrophobic domain and that aggregates spanning the bilayer are a possible arrangement of the ubiquinone in the structure.

Section: Spectral Features Associated With Polar Groupsmentioning

confidence: 99%

A difference infrared-spectroscopic study of the interaction of ubiquinone-10 with phospholipid bilayers

Ondarroa¹,

Quinn²

1986

“…This band is due to C-H stretching and deformation vibration of a ci double bond. If it is assumed that substance SC has an all-trans side chain, as in ubiquinone (Morton et al 1958), the 1302 cm.-' frequency would be due to the double bond conjugated to the aromatic ring. The band at 1466 cm.-' in substance SC is less strong than that in the cyclized product and also in perhydro-SC.…”

Section: Resultsmentioning

confidence: 99%

Substance SC (ubichromenol): a naturally-occurring cyclic isomeride of ubiquinone-50

Laidman

Morton

Paterson

et al. 1960

Self Cite

Lowe, Morton & Harrison (1953) reported that the unsaponifiable-lipid fraction from livers of vitamin A-deficient rats showed selective absorption in the ultraviolet region at 275 and 330 m,u. Two materials were concentrated by chromatography on alumina, a fraction with an absorption peak (in cyclohexane) at 275 m,u and an inflexion near 330 m,u, and a second fraction showing peaks at 275 and 332 miL with marked inflexions at 233 and 283 m,. The latter has hitherto been designated 'substance SC' and it is now proposed to call it 'ubichromenol'. The former, known provisionally as 'substance SA' is now called 'ubiquinone' (Morton, Wilson, Lowe,

“…of water followed by a few millilitres of ethyl chloride. The laevulicaldehyde was isolated from the filtrate, converted into its bis-DNP-hydrazine derivative and purified by the procedures described by Morton et al (1958).…”

Section: Biosynthesis Of Terpenoid Quinonesmentioning

confidence: 99%

Biosynthesis of the prenyl side chains of plastoquinone and related compounds in maize and barley shoots

Threlfall¹,

Griffiths²,

Goodwin³

1967

The incorporation of (14)C by etiolated maize and barley shoots exposed to light of (14)CO(2) and [2-(14)C]mevalonic acid into phylloquinone, plastoquinone, ubiquinone, alpha-tocopherolquinone and alpha-tocopherol was examined. In maize (the principal tissue studied) it was demonstrated that (14)C from [2-(14)C]mevalonic acid is incorporated into phylloquinone, plastoquinone and ubiquinone. alpha-Tocopherol and alpha-tocopherolquinone, although undoubtedly labelled from this substrate, were not purified completely. As expected, (14)C from (14)CO(2) was incorporated into all components examined. Ozonolytic degradation studies showed that (14)C from [2-(14)C]mevalonic acid was incorporated specifically into the prenyl side chains of plastoquinone and ubiquinone, and from this it was inferred that mevalonic acid can be regarded as the specific distal precursor to the prenyl portions of all terpenoid quinones occurring in plant tissues. From a comparison of the relative incorporation of (14)C from (14)CO(2) and [2-(14)C]mevalonic acid into the intra- and extra-chloroplastidic terpenoids evidence was obtained consistent with the tenet that the prenyl portions of the chloroplastidic quinones phylloquinone and plastoquinone, along with beta-carotene, are biosynthesized within the confines of the chloroplast, the side chain of the extraplastidic ubiquinone and phytosterols being synthesized elsewhere within the cell. The results obtained for the incorporation of (14)C from (14)CO(2) and [2-(14)C]mevalonic acid into alpha-tocopherol and alpha-tocopherolquinone were not readily interpretable with regard to the site of synthesis of these compounds.