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Binding of ligands to DNA gives rise to several relevant biological and biomedical effects. Here, through the use of atomic force microscopy (AFM), we studied the consequences of drug binding on the morphology of single DNA molecules. In particular, we quantitatively analyzed the effects of three different DNA-binding molecules (doxorubicin, ethidium bromide, and netropsin) that exert various pharmacologic and therapeutic effects. The results of this study show the consequences of intercalation and groove molecular binding on DNA conformation. These single-molecule measurements demonstrate morphological features that reflect the specific modes of drug-DNA interaction. This experimental approach may have implications in the design of therapeutically effective agents. [ABSTRACT FROM AUTHOR]

Yaupon holly (hex vomitoria Ait.) is a caffeine-containing shrub native to the southeastern United States where its leaves and twigs were traditionally used to prepare a stimulating and healthful beverage by Amerindians and more recent colonists. For a variety of mostly socioeconomic and cultural reasons, widespread consumption of yaupon tea ceased by the late 19th century, but the species is widely used in ornamental horticulture. Given the environmental damage associated with other caffeine crops, we believe that disuse of this species is unfortunate, and we report on traits that consumers may consider valuable. We found that total foliar biomass, caffeine, and antioxidant production all increased with nitrogen fertilization in one common ornamental yaupon cultivar, Nana.' Increasing light availability was associated with increased antioxidant activity but not with the decreased caffeine production predicted by the carbon/nutrient balance hypothesis for secondary metabolite production. We also found the highest caffeine concentrations in another yaupon cultivar, Pendula,' but suggest that the wide range of chemical variation offered by wild-type yaupon populations renders them more suitable as sources for the development of high caffeine-producing varieties. The results of this study suggest that yaupon is a viable caffeine alternative for North Americans living within its range on the southeastern coastal plain. [ABSTRACT FROM AUTHOR]

Yaupon ( Ilex vomitoria) is a caffeine-containing dioecious shrub native to the southeastern United States that was historically brewed into a stimulating beverage. We tested predictions of the carbon/nutrient balance (CNB) hypothesis by determining whether nitrogen availability and gender influence production of caffeine and related alkaloids as well as phenolic compounds in leaves of pot-grown yaupon plants fertilized with ammonium nitrate. The CNB hypothesis predicts that additional nitrogen should result in increased alkaloid concentrations and decreased phenolic concentrations. An extension of the CNB hypothesis to dioecious plants predicts that females have higher C/N ratios and therefore higher phenolic concentrations and lower alkaloid concentrations than male conspecifics. In our study, caffeine and total alkaloid concentrations were 5–10 times higher in fertilized than control plants but did not vary by gender. Nevertheless, an observed interaction between gender and fertilization suggests that females respond more to fertilization than males in caffeine production. In addition, fertilized plants not only contained higher concentrations of alkaloids and total nitrogen but also allocated a larger proportion of their nitrogen to alkaloid production than control plants. Total phenolic concentrations were higher in control females than control males as predicted by the CNB hypothesis, but did not vary by treatment nor were there differences by gender among fertilized plants. We also found high correlations between antioxidant capacity and both classes of phenolic compounds detected in our study (cinnamic acid derivatives and flavonoids) indicating that in addition to their putative defensive function against herbivores, phenolics protect yaupon from oxidative stress. Explanation of the inconsistencies between our data and predictions of the CNB hypothesis may benefit from a re-appraisal of the physiological mechanisms by which resource availability affects secondary metabolism as well as consideration of the selective pressures to which secondary metabolism responds. [ABSTRACT FROM AUTHOR]

We evaluated the longevity of seeds of 12 common woody species buried in fresh condition in the forest floor at three forest locations in Mississippi and Louisiana. Seed samples of each species were retrieved annually for 5 years from each location. Germination and tetrazolium chloride staining tests were conducted on the samples to determine germinative capacity. When averaged across all species, seeds remained viable longer at the Alexandria, Louisiana site than at the two sites in Mississippi. Seeds of the 12 species varied widely in their response to burial. Some species, such as American beautyberry (Callicarpa americana L.), muscadine grape (Vitis rotundifolia Michx.), and sugarberry (Celtis laevigata Willd.), had relatively high germinative capacities (from 33 to 60 percent, depending on species) even after burial in the forest floor for 5 years, whereas other species, such as flowering dogwood (Cornus florida L.) and yaupon (Ilex vomitoria Ait.), had very low germinative capacities (less than 6 percent) by the end of the first year after burial. Species were classified into five groups based on their similarity of response. [ABSTRACT FROM AUTHOR]

Indigenous people of southeastern North America drank cassina, a stimulant and emetic decoction that the colonial British termed "black drink" Though most authors cite hex vomitoria Ait. as the botanical source of cassina, confusion persists because some researchers identify the source as I. cassine L. To clarify the link between plant and product, the methylxanthine alkaloid contents of I. vomitoria and I. cassine were compared. Since methylxanthines (i.e., caffeine, theobromine, and theophylline) have pharmacological properties congruent with the recorded effects of cassina consumption, the alkaloids provide a chemical basis for the evaluation of both taxa as sources of the beverage. Methylxanthine levels are higher in I. vomitoria than in I. cassine, and the principal alkaloid of the former is caffeine. Based on its alkaloid content, I. vomitoria is the best-supported candidate source of cassina. [ABSTRACT FROM AUTHOR]