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Biomedical subjects

M A Rodgers

Publications and source records attributed to M A Rodgers.

At least 55 records · Page 3Linked to original sources
PubMed1990

Glass and plastic photoluminescence: interaction with aqueous media and cultured mammalian cells.

Several types of glass and plastic materials were shown to exhibit intense photoluminescence when irradiated with UV. Water or phosphate buffered saline (PBS) contained within vessels of the respective materials when irradiated, also demonstrated relatively long-lived luminescence. A significant percentage (30%) of cultured mammalian cells were killed when exposed to UV-irradiated glass beads. The nature of the luminescence of water or PBS, or whether this or the photoluminescence of glass is directly responsible for cell toxicity, is unknown. However, we call attention to this phenomenon as a potential complicating factor in photobiological studies.

Animals↗
PubMed1989

Photoproperties of alkoxy-substituted phthalocyanines with deep-red optical absorbance.

Triplet-state properties of 1,4,8,11,15,18,22,25-octa-n-butoxyphthalocyanine and its zinc derivative were determined for the first time. The T1 state of the metal-free phthalocyanine was characterized by a short lifetime (tau T = 17 microseconds) and low quantum yield (phi T = 0.095), and quenching of the triplet by O2 occurred with a bimolecular rate constant (kT sigma = 1.3 x 10(8) M-1 s-1) that is indicative of an endogonic reaction. The zinc complex (ZnPc(OBu)8) was markedly better as a triplet photosensitizer with respect to both tau T (60 microseconds) and phi T (0.5). Quenching by O2 produced singlet oxygen with nearly 100% efficiency, and kT sigma (1.7 x 10(9) M-1s-1) was close to the spin-statistical diffusion-controlled limit. Phosphorescence measurements showed the energy of the T1 state of ZnPc(OBu)8 to be 100 kJ/mol, which is 6 kJ/mol above the 1 delta g state of O2. These photoproperties, together with Q-band absorption maxima in the mid-700 nm range indicate that metal-centered 1,4,8,11,15,18,22,25-octaalkoxyphthalocyanines have excellent potential as sensitizers in photodynamic therapy.

Indoles↗
PubMed1987

Steady-state and time-resolved spectroscopic studies on the hematoporphyrin-lipoprotein complex.

The interaction of hematoporphyrin (Hp) with the isolated rabbit lipoprotein fractions very low density lipoproteins, low-density lipoproteins, and high-density lipoproteins has been studied by steady-state and time-resolved spectroscopy. The porphyrin appears to be bound to both the apoprotein and the lipid phase. The two populations of lipoprotein-bound Hp molecules can be distinguished on the basis of the fluorescence excitation spectrum, decay constants of the lowest excited singlet and triplet states, and accessibility to oxygen. Upon Hp binding, the intrinsic fluorescence emission of apolipoproteins is quenched at least in part via singlet-singlet energy transfer from tryptophyl residues to the porphyrin moiety. The binding of Hp with the protein matrix can be adequately described on the basis of Scatchard analysis, whereas the interaction of Hp with the lipid core can be described as the partitioning of the dye between a hydrophobic and an aqueous phase. The Hp binding capacity of lipoproteins is maximal for very low density lipoproteins.

Animals↗
PubMed1981

Single-electron transfer from NADH analogues to singlet oxygen.

Laser flash photolysis techniques have yielded rate constants for physical and reactive quenching modes of O2(1 delta g) by nicotine, nicotinamide adenine dinucleotide (oxidized and reduced forms) and the reduced forms of nicotinamide mononucleotide, nicotinamide adenine dinucleotide phosphate and nicotinamide hypoxanthine dinucleotide. In the case of the last four named compounds, kinetic spectroscopy furnished evidence for one-electron transfers to O2(1 delta g). Specifically, production of O2 was demonstrated unequivocally by reaction with 1,4-benzoquinone. Quantitative determinations revealed the extent of reactive quenching to be near 60% in each case.

Chemical Phenomena↗