Organogelation of diacetylene cholesteryl esters having two urethane linkages and their photopolymerization in the gel state.

Various diacetylene cholesteryl esters having two urethane linkages were synthesized to study the relationship between their gelation properties and chemical structures. Most of these compounds form organogels in cyclohexane, and some compounds gelatinized hexane, diethyl ether, N,N-dimethylformamide, and ethanol. The cholesteryl moieties play an important role in gel formation, but IR spectroscopic measurements show that the main driving force for gelation is hydrogen bonding of the urethane groups. Upon UV irradiation, most of the gels polymerized to give polydiacetylenes, with concomitant changes from colorless to a variety of hues, such as dark blue, orange, and pink. The polymerization proceeds efficiently in cases where the gels change color to dark blue. The polymerization reached 52% chemical yield, with the quantum yield estimated to be at least 54. Solid-state NMR spectroscopy confirmed that polymerization in the gel state proceeds via 1,4-addition.

Mass spectrometric examinations of stratum corneum lipid models exposed to ultraviolet irradiation.

Lipid model systems consisting of the major components of the stratum corneum intercellular lipid matrix were studied to investigate the ultraviolet-radiation-mediated damage of these biomolecules. Pure lipids and liposomes were irradiated using a lamp emitting a solar radiation spectrum. The influences of the irradiation and the effects of added iron ions were studied by electrospray ionization mass spectrometry (MS) with an ion trap analyser. Exact mass measurements were carried out using a time-of-flight mass spectrometer. Only linolenic acid and cholesterol were found to be subject to oxidative changes caused by UV irradiation whereas the other lipids examined (dipalmitoylphosphatidylcholine, ceramide III and cholesterol sulphate) were stable to oxidative stress. Several lipid adducts were observed upon analysis of the liposomes. The composition of these adducts was identified by MS/MS experiments.

Selective removal of cholesterol esters in an arteriosclerotic region of blood vessels with a free-electron laser.

BACKGROUND AND OBJECTIVE: In advanced atheromatous atherosclerosis, a large amount of lipids, particularly cholesterol esters, accumulates on the arterial wall. The selective removal of cholesterol esters accumulated in the intracellular or extracellular spaces has clinical significance. In the present work, the authors investigated the removal of cholesterol esters by using a free-electron laser (FEL) in an arteriosclerotic region. STUDY DESIGN/MATERIALS AND METHODS: Thin films of cholesteryl oleate and albumin and the cross section of a rabbit artery were placed on an inverted microscope stage, and the changes caused by the FEL irradiation of 5.75 microm and 6.1 microm, with 1.5-3 mW on average, were monitored continuously by using a CCD camera in real time. RESULTS AND CONCLUSION: FEL irradiation at a wavelength of 5.75 microm, which is a stretching vibrational mode of the ester, was able to ablate cholesterol esters without affecting albumin. It can also remove cholesterol esters from rabbit arteriosclerotic arterial walls.

[Synthesis of lipids in the thymocytes of irradiated rats]. / Sintez lipidov v timotsitakh obluchennykh krys.

During the first two hours following whole-body gamma-irradiation of rats with a dose of 7.5 Gy, the content of free cholesterol, phosphatidylcholine and phosphatidylethanolamine in the thymus decreases. Incorporation of 2-14C-acetate into cholesterol and fatty acids of thymus phospholipids in vitro is inhibited. At a dose of 4 Gy, incorporation of 2-14C-acetate into cholesterol and total lipids of thymocytes is activated.