SINGLET OXYGEN YIELDS AND RADICAL CONTRIBUTIONS IN THE DYE-SENSITISED PHOTO-OXIDATION IN METHANOL OF ESTERS OF POLYUNSATURATED FATTY ACIDS (OLEIC, LINOLEIC, LINOLENIC AND ARACHIDONIC)

Abstract— The triplet state characteristics (spectrum, lifetime and quantum yield) for four dye sensi tisers [methylene blue (MB), erythrosin (ER), haematoporphyrin (HP) and riboflavin (RF)] were determined in methanol by laser flash photolysis and singlet oxygen yields (0.60 to 0.48) from time-resolved measurements of the 1270 nm near infrared emission. The reaction of singlet oxygen with four long chain unsaturated phenyl esters [oleate (18: 1), linoleate (18: 2), linolenate (18: 3) and arachidonate (20: 4)] was followed quantitatively using the singlet oxygen luminescence technique and also, after continuous420–700 nm irradiation, by HPLC and other analysis of the isomeric product monohydroperoxides. The overall quantum yield of photooxidation (∼10^-2) was shown to be consistent with the observed singlet oxygen quenching constants(2–12 times 10⁴ dm³ mol^-1 s^-1) for the four esters studied and the singlet oxygen lifetime in methanol (τ∼ 9 μs). The isomer product distribution was interpreted in terms of a dual singlet oxygen and radical mechanism, the radical contribution increasing with sensitiser in the order ER = MB < HP ≪ RF, but also showing some dependence on substrate unsaturation. Evidence is presented for singlet oxygen quenching by MB and RF ( k_O = 1.6 and 6.0 times 10⁷ dm³ mol^-1 s^-1) and for the accelerated photobleaching of the dye sensitisers in the presence of the unsaturated esters.     

Lysine peroxycarbamates: free radical-promoted peptide cleavage

Strategies are reported that combine in one step a predictable chemical-based protein digestion with mass spectrometry. Lysine residue amino groups in peptides and proteins are modified by reaction with a peroxycarbonate derived from p-nitrophenol, and tert-butyl hydroperoxide. The peroxycarbonate reacts with lysine residues in peptides and proteins, and the resulting lysine peroxycarbamates undergo homolytic fragmentation under conditions of low-energy collision-induced dissociation (CID). Observed fragmentation of the peptides involves apparent free radical processes including Hofmann-L?ffler-type rearrangements that lead to peptide chain fragmentation. Strategies for directed cleavage of peptides by free radical promoted processes are feasible, and such strategies may well simplify schemes for protein analysis.     

Analysis and interpretation of excess molar properties of amphiphile + water systems : Part 3. Excess molar volumes of isopropoxyethanol + water and isobutoxyethanol + water

Excess molar volumes at 25°C, are reported for the systems isoPrOEtOH + water and isoBuOEtOH + water across their entire composition ranges. These data have been compared to those for their normal alkyl analogs in order to assess the effects of both - and β-chain branching.

The results are discussed in terms of the relative abilities of the amphiphiles to form structured aggregates.     

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background  

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.     

Commuting point transformations

Summary The question considered is the following: If two invertible measure preserving point transformations commute, in what sense is one a function of the other? The main theorem is the following: If two invertible measure preserving transformations commute, and if the first admits of approximation by periodic transformations, then the second transformation is a piecewise power of the first, where we say that is a piecewise power of if there exists a sequence [j(n)] of positive integers such that for each measurable set A the limit of the measure of the symmetric difference of (A) and ^j(n) (A) tends to zero.Research supported in part by NSF grant GP-3752.