Treatment of lipid membranes with ionizing radiation leads to the destructive processes within both hydrophobic and hydrophilic moiety of lipids.

Precursors for the selective generation of C-2 glyceryl radicals were synthesized, and the chemical behavior of the corresponding radicals was investigated by ESR spectroscopy, product analysis, and kinetic measurements. It was found that cleavage of the β-C,O bond proceeds rapidly, if a hydroxyl group is present at the radical carbon center. The rate constant for the elimination of a β-acetoxy group from radical 30 was dependent on the solvent (k E = 4 × 105 s-1 in methanol, k E = 2 × 107 s-1 in toluene). With these results and ab initio calculations a concerted elimination mechanism is suggested. α-Methoxy-substituted C-2 glyceryl radicals 42 and 43 showed heterolytic β-C,O bond cleavage under formation of radical cations. With ester-substituted radicals 24 and 35 no elimination could be observed. To demonstrate the biological significance of these findings, C-2 lysolecithin radical 53 was generated, which led to fast β-elimination.

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a sulfonamide fragment but also conformational equilibrium among these types of intramolecular interactions are essential for the manifestation of high efficiency in suppressing HIV-infection in cell culture.Introduction. Many derivatives of aminophenols (AP) are known to be effective antioxidants that are capable of changing the course of free-radical processes [1]. These compounds also have traditional applications as stabilizers of industrial organic materials and as food preservatives [2,3]. They exhibit high efficiency for prevention and treatment of pathologies due to disorders in the human antioxidant system [4] and as antiviral agents against herpes simplex and flu A virus [5][6][7][8][9]. AP derivatives that suppress HIV-infection in cell culture were recently synthesized [10].The pharmacological properties of AP are related to their effect on the course of free-radical processes in biological systems. Steady-state radiolysis and IR spectroscopic methods found that the antioxidant properties of AP are enhanced when the hydroxyls in the molecules are free and diminished upon forming various types of intramolecular hydrogen-bonds (IHB) [11]. As a rule, reactions involving active oxygen species occur nonselectively. Their occurrence in biological systems can damage both the cells themselves and viruses incorporated into them if highly active antioxidants are used.The question of which AP derivatives that are added to biological systems can change the course of free-radical reactions so that an effective and stable antiviral effect is obtained remains open. Therefore, it is important in principle to study properties of individual molecules such as the ability to form IHB because the type of IHB found in the AP is frequently related to their antiradical and antiviral activity [12,13].Herein IR-Fourier spectroscopy is used to study intramolecular interactions (IMI) in CCl 4 solutions of five structurally similar AP derivatives, 4,6-di-tert-butyl-2-(phenylamino)phenol (AP I), N-(3,5-di-tert-butyl-2-hydroxyphenyl)acetamide (AP II), N-(2-hydroxy-3,5-di-tert-butylphenyl)-4-methylbenzenesulfonamide (AP III), N-(2-methoxy-3,5-di-tert-butylphenyl)-4-methylbenzenesulfonamide (AP IV), and N-(2-hydroxy-3,5-di-tert-butylphenyl) methanesulfo-namide (AP V):