Zhang D.-X.,University of Kentucky |
Zhang D.-X.,Institute for Bioscience and Biotechnology Research IBBR |
Nagabhyru P.,University of Kentucky |
Blankenship J.D.,University of Kentucky |
Schardl C.L.,University of Kentucky
Plant Signaling and Behavior | Year: 2010
Many cool-season grasses (Poaceae, subfam. Pooideae) possess seedborne fungal symbionts, the epichloae, known for their bioprotective properties and especially for production of antiinsect alkaloids such as lolines. Asexual epichloae (Neotyphodium species) are primarily or entirely transmitted vertically, whereas the sexual structures (stromata) of the related Epichloë species give rise to horizontally transmissible spores (ascospores). In certain grass-Neotyphodium species symbiota, levels of lolines are extremely high and apparently limited by availability of precursor amino acids, whereas sexual epichloae generally produce much lower levels. This may reflect the inherent conflict between the vertical and horizontal transmission; although the plant and seeds may be protected by the alkaloids, the sexual cycle depends on anthomyiid flies for cross-fertilization. Given this insect role, we predicted that loline biosynthesis would be downregulated in the stromata relative to the corresponding asymptomatic tissues (inflorescences) of the same symbiota. This prediction was substantiated, and RNA-seq and RT-qPCR analysis indicated that the loline biosynthesis genes are dramatically upregulated in asymptomatic inflorescences compared to stromata. The fundamental difference between asexual and sexual epichloae in regulation of loline alkaloid levels is in keeping with evolutionary trends for greater host control on metabolism of their vertically transmitted symbionts compared to contagious symbionts. © 2010 Landes Bioscience.
Javvaji V.,University of Maryland University College |
Baradwaj A.G.,University of Maryland University College |
Payne G.F.,University of Maryland University College |
Payne G.F.,Institute for Bioscience and Biotechnology Research IBBR |
Raghavan S.R.,University of Maryland University College
Langmuir | Year: 2011
Biopolymers such as alginate and pectin are well known for their ability to undergo gelation upon addition of multivalent cations such as calcium (Ca 2+). Here, we report a simple way to activate such ionic gelation by UV irradiation. Our approach involves combining an insoluble salt of the cation (e.g., calcium carbonate, CaCO 3) with an aqueous solution of the polymer (e.g., alginate) along with a third component, a photoacid generator (PAG). Upon UV irradiation, the PAG dissociates to release H + ions, which react with the CaCO 3 to generate free Ca 2+. In turn, the Ca 2+ ions cross-link the alginate chains into a physical network, thereby resulting in a hydrogel. Dynamic rheological experiments confirm the elastic character of the alginate gel, and the gel modulus is shown to be tunable via the irradiation time as well as the PAG and alginate concentrations. The above approach is easily extended to other biopolymers such as pectin. Using this approach, a photoresponse can be imparted to conventional biopolymers without the need for any chemical modification of the molecules. Photoresponsive alginate gels may be useful in creating biomaterials or tissue mimics. As a step toward potential applications, we demonstrate the ability to photopattern a thin film of alginate gel onto a glass substrate under mild conditions. © 2011 American Chemical Society.
Vaish A.,U.S. National Institute of Standards and Technology |
Vaish A.,University of Maryland University College |
Vanderah D.J.,U.S. National Institute of Standards and Technology |
Vanderah D.J.,Institute for Bioscience and Biotechnology Research IBBR |
And 9 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2014
As part of an effort to develop biointerfaces for structure-function studies of integral membrane proteins (IMPs) a series of oligo(ethylene oxide) self-assembled monolayers (OEO-SAMs) were evaluated for their resistance to protein adsorption (RPA) of IMPs on Au and Pt. Spectroscopic ellipsometry (SE) was used to determine SAM thicknesses and compare the RPA of HS(CH2)3O(CH2CH2O)6CH3 (1), HS(CH2)3O(CH2CH2O)6H (2), [HS(CH2)3]2CHO(CH2CH2O)6CH3 (3) and [HS(CH2)3]2CHO(CH2CH2O)6H (4), assembled from water. For both substrates, SAM thicknesses for 1 to 4 were found to be comparable indicating SAMs with similar surface coverages and OEO chain order and packing densities. Fibrinogen (Fb), a soluble plasma protein, and rhodopsin (Rd), an integral membrane G-protein coupled receptor, adsorbed to the SAMs of 1, as expected from previous reports, but not to the hydroxy-terminated SAMs of 2 and 4. The methoxy-terminated SAMs of 3 were resistant to Fb but, surprisingly, not to Rd. The stark difference between the adsorption of Rd to the SAMs of 3 and 4 clearly indicate that a hydroxy-terminus of the OEO chain is essential for high RPA of IMPs. The similar thicknesses and high RPA of the SAMs of 2 and 4 show the conditions of protein resistance (screening the underlying substrate, packing densities, SAM order, and conformational mobility of the OEO chains) defined from previous studies on Au are applicable to Pt. In addition, the SAMs of 4, exhibiting the highest resistance to Fb and Rd, were placed in contact with undiluted fetal bovine serum for 2h. Low protein adsorption (≈12.4ng/cm2), obtained under these more challenging conditions, denote a high potential of the SAMs of 4 for various applications requiring the suppression of non-specific protein adsorption. © 2014.