Abstract—Flash photolysis experiments on the complex of 8‐methoxypsoralen with calf thymus DNA have shown binding promotes the anaerobic quenching of the 8‐MOP triplet state and inhibits the accessibility to oxygen. The results indicate dark psoralen‐DNA interactions suppress the singlet oxygen generation observed in prior work.

Dialysis of hematoporphyrin derivative fraction A (HpD-A) off human serum albumin at 38°C followed the Hill equation for cooperative binding with saturation at 5 to 8. 600 dalton porphvrin units. Approximately 15% of the HpD-A was free for concentrations typical of human serum i n photoradiation therapy. Possible structures of the tumor-localizing and -photosensitizing component in HpD-A are considered. Of these. a folded-over. covalent dimer appears to be more consistent with the photophysical properties

The spectral properties and efficiency for photosensitizing the lysis of phosphatidylcholine liposomes have been measured for the components of hematoporphyrin derivative (Hpd) after alkaline hydrolysis and fractionation by polyacrylamide gel chromatography. Two malor and two minor Hpd fractions have been identified whose spectral propcrties correlate with the anoxic sensitizing cfficicncy and the oxygen enhancement ratio (OER). Thc fastest moving fraction. which is thc putative biologically active coim7onent. comprised one-third of the starting material and had OER = 2.7. Liposome lysis by this fraction was inhibited in the presence of human serum albumin at concentration ratios comparable to those employed for photoradiation therapy. The present results show that Hpd can act as an oxic and anoxic photosensitizer of a model biomembranc and suggest that scparation from serum proteins is required for in vivo photosensitization.

No abstract

Can. J. Chem. 54, 1938 (1976. The major products from the radiolysis of penicillamine in N20-saturated solutions a t p H 5 are penicillamine disulfide, penicillamine trisulfide, and valine with yields of 2.0, 1.2, and 1.5 molecules per 100 eV in lo-' M solutions and 1.8, 0.94, and 0.60 molecules per 100 eV in 10-3 M solutions respectively. These yields remain essentially the same when the major attacking radical is changed from .OH to . C H 2 0 H , .Br2-or .(CNS)?-, and it is concluded that all four species produce predominantly pens. radicals on attacking penicillamine. The formation of trisulfide and an equivalent amount of valine is attributed to secondary reactions of pens. radicals and discussed in the light of recent pulse radiolysis experiments and other work.In deaerated solutions hydrogen and H2S were observed in significant yields and the valine yield increased. These observations can be accounted for quantitatively by the reactions: [To] . The yields of minor (G < 0.5 molecules per 100 eV) products like NH3 and CH2=C(CH3)-CH(NH,+)COO-indicated that fragmentation of p e n and other secondary radicals from penSH was more important than for cys. and other radicals from cysSH.GREESH CHAND GOYAL et DAVID ANTHONY ARMSTRONG. Can. J. Chem. 54, 1938Chem. 54, (1976 Les produits majeurs de la radiolyse de la pinicillamine dans des solutions saturees de NzO 2 un p H de 5 sont le disulfure de ~Cnicillamine, le trisulfure de pCnicillamine et la valine avec des [Traduit par le journal]