Near-UV-induced absorbance change and photochemical decomposition of ergosterol in the plasma membrane of the yeast Saccharomyces cerevisiae

Abstract

When cells of the yeast Sacchammyces cerevisiae were exposed to near-UV (300-400 nm), their absorption spectra changed slightly within the range 220-300 nm with increasing dosage. Difference spectra, calculated by subtracting the curve recorded in cells exposed to near-UV from the curve of unexposed cells, decreased with increasing dosage over a broad band with peaks at 272,282 and 295 nm and a shoulder at 265 nm. These peaks were in agreement with the absorption maxima of ergosterol, which is one of the major components of the plasma membrane of yeast. Near-UV radiation induced a simultaneous decrease in absorption spectra and reduction of ergosterol content in the plasma membrane. Photochemical decomposition of ergosterol by near-UV radiation was revealed in who, although ergosterol is generally known to be photoconverted to previtamin D, industrially by UV radiation in witm. In order to remove photosensitizers, liposomes were prepared from phospholipids and glycolipids, with or without ergosterol from purified yeast plasma membranes. Liposomal ergosterol in the orientated state was photochemically decomposed by near-UV radiation but ergosterol in the disorientated state in a homogeneous solution was not. Near-UV radiation also induced a decrease in activity of membrane-bound ATPase. Dose-response curves for the reduction of ATPase activity were similar to that for decomposition of ergosterol, suggesting that near-UV caused membrane function damage.

Synthesis and Biological Evaluation of New 1,2,3‐Triazolyl‐Pyrazolyl‐Quinoline Derivatives as Potential Antimicrobial Agents

“…The spectrophotometric absorbance profiles between 240 and 300 nm (Figure ) give the characteristic peaks of ergosterol at 265, 274 and 282 nm in control. These peaks were in agreement with absorption maxima of ergosterol . In case of compound 7 h , no peaks were observed in comparison to characteristics peaks of ergosterol in control.…”

Effects of UV radiation on the process of wilting and application of additives at ensiling on the fermentation quality of Siberian wildrye silage on the Qinghai‐Tibetan plateau

“…Excessive UV irradiation can first damage the membrane function of LAB, cause loss of a large segment of DNA cells or can prevent cross‐linked DNA from opening and prevent replication and transcription of DNA (Ito and Ito ; Arami et al . ; Sorbrun et al . ).…”

Reduction of ATPase activity accompanied by photodecomposition of ergosterol by near-UV irradiation in plasma membranes prepared from Saccharomyces cerevisiae

“…After harvest, the yeast cells were washed twice with distilled water. Plasma membranes were isolated as described previously (Arami et al ., 1997). The yeast cells were suspended in 0.1 M Tris/HCl buffer (pH 7.2) containing 10 mM EDTA, 1.2 M sorbitol and 1 mg Zymolyase ml −1 .…”

“…A fluorescent lamp (National FL20S.BL-B) was used as the light source (intensity 14 W m −2 , wavelength range 300–400 nm). The plasma membrane was suspended in deionized distilled water to a final concentration of 0.5 mg protein ml −1 and was exposed to near-UV radiation with continuous stirring and ice cooling as previously described (Arami et al ., 1997) . When nitrogen gas or air was bubbled through during irradiation, the yeast cells were suspended in water degassed by sonication under reduced pressure.…”

“…However, the initial photochemical reactions and molecular mechanisms for these phenomena are little understood. We reported previously that ergosterol, which is one of the major components in the yeast plasma membrane, was photochemically decomposed (Arami et al ., 1997) and that cell survival and membrane functions such as the permeability barrier and active transport were sigmoidally decreased by increasing doses of near-UV irradiation in Saccharomyces cerevisiae (Arami et al ., 1993).…”