Biomedical subjects

Paul B Jones

Publications and source records attributed to Paul B Jones.

6 recordsLinked to original sources

PubMed2006

Triplet photosensitization in cyercene A and related pyrones.

Mollusks of the Sacoglossa order contain a variety of polypropionate metabolites that are characterized by a pyrone chromophore, such as cyercene A and 9,10-deoxytridachione. Most often the pyrone is a 2-methoxy-gamma-pyrone but occasionally is a 4-methoxy-alpha-pyrone or hydropyrone. Members of this class of metabolites have been shown to undergo photochemical reactions of biosynthetic importance. An example is the photochemical conversion of 9,10-deoxytridachione to photodeoxytridachione, which has been observed in several mollusks. In this report, a series of gamma-pyrones and their alpha-pyrone analogs were synthesized and analyzed for photosensitizing activity. In all cases studied, the gamma-pyrone was a more efficient triplet sensitizer than the corresponding alpha-pyrone. Included in this set of molecules was the Sacoglossan metabolite cyercene A and its alpha-pyrone isomer. When irradiated in the presence of oxygen, cyercene A produced singlet oxygen at significantly higher rate than the corresponding alpha-pyrone isomer. Furthermore, the photoisomerization of cyercene A was quenched by piperylene with con-committant isomerization of the piperylene indicating that the isomerization proceeded through a triplet excited state. In contrast, the isomerization of the alpha-pyrone analog was not quenched. The implications of these photochemical results in terms of the biosynthesis and biological activity of Sacoglossan polypropionate metabolites are discussed.

Animals↗

PubMed2005

Photosensitized conversion of 9,10-deoxytridachione to photodeoxytridachione.

[reaction: see text] The photochemical conversion of 9,10-deoxytridachione to photodeoxytridachione has been photosensitized. The conversion was also quenched by piperylene. Photodeoxytridachione was produced in good yields under conditions in which only the cyclohexadiene group is sensitized. The results show that some, and perhaps all, of the photoreactions of 9,10-deoxytridachione occur through a triplet excited state. The mechanistic and biosynthetic implications of these results are discussed.

Alkadienes↗

PubMed2005

Photochemical relationships in Sacoglossan polypropionates.

Cyercene A has been synthesized and converted to placidene A and isoplacidene A through photoisomerization with sunlight. Hydroperoxide, isolated form Placida dendritica, was synthesized both by singlet oxygenation of cyercene A using Rose Bengal and through the irradiation of cyercene A alone in aerobic solution. The observation that hydroperoxide could be made by singlet oxygenation of cyercene A and that this occurs when cyercene A alone is irradiated supported the hypothesis that gamma-pyrones may act as triplet sensitizers. This was confirmed using cyercene A and a model gamma-pyrone to sensitize the photooxidation of n-butyl sulfide. The biosynthetic implications of these observations for Sacoglossan polypropionates are discussed.

Animals↗

PubMed2004

Caged trans-4-hydroxy-2-nonenal.

[reaction: see text] A caged 4-hydroxy-2-nonenal (4-HNE) has been prepared and its photochemistry investigated. Upon photolysis, 1 releases 4-HNE in up to 100% yield. From these photolyses, 4-HNE could be isolated in up to 91% yield. 4-HNE is produced under either aerobic or anaerobic conditions. The caging strategy does not require prior preparation of 4-HNE and, therefore, represents a three-step synthetic route to the bioactive enal in 48% overall yield.

Aldehydes↗

PubMed2004

Growth, Congo Red agar colony morphotypes and antibiotic susceptibility testing of Mycobacterium avium subspecies paratuberculosis.

OBJECTIVE: Mycobacterium avium subspecies (subsp.) paratuberculosis (MAP) is the causative agent of Johne's disease in ruminants and has been associated with Crohn's disease in humans. We sought to test growth rates and susceptibilities of various strains of MAP in two available growth media. DESIGN: Paired comparison design. METHODS: Using the BACTEC macrobroth radiometric growth system and Congo Red-staining agar media, we determined inherent differences in growth characteristics of three bovine and two human strains of MAP and compared susceptibility results obtained in each growth system. RESULTS: Significant differences were observed in growth rate as well as mycobactin J dependence between strains and between a laboratory-adapted isolate of the same strain in the macrobroth system. Similarly, colonial morphology and Congo Red staining on agar media were observed. Two strains, one human and one bovine, demonstrated a 100% rough transparent colony with white coloration on Congo Red agar, while one bovine isolate exclusively grew as a smooth opaque colony with red coloration on Congo Red agar. The remaining strains exhibited mixtures of these two colonial morphotypes on agar media. Comparative susceptibility results between the BACTEC radiometric macrobroth method and the agar proportionality method showed good correlation for most antibiotics/inhibitors tested. However, erratic or poor growth in the macrobroth system prevented minimal inhibitory concentration determinations for two bovine strains by this method. CONCLUSION: This study demonstrates the variability in the colonial morphology of MAP on Congo Red agar as well as the correlation of antibiotic susceptibility results between the BACTEC macro broth method and the agar proportionality method. This study also emphasizes the need for the development of improved, standardized culture and susceptibility test methods for MAP.

Agar↗

PubMed2002

Photoreduction of benzophenones by amines in room-temperature ionic liquids.

[reaction: see text] The amine-mediated photoreduction of benzophenones in room temperature ionic liquids was investigated. Unlike the analogous reaction in organic solvents, the photoreduction produces mainly the corresponding benzhydrol in most cases. Because the reaction consumes only 1 equiv of amine and the solvent can be easily recycled, the photoreduction allows a very clean method for the conversion of benzophenones to benzhydrols.

Journal Article↗