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51.
Phototropins (phot1 and phot2), the plant blue-light receptors for phototropism, chloroplast movement, and stomatal opening, are flavoproteins that contain two approximately 12 kDa FMN-binding domains, LOV1 and LOV2, at their N-terminus, and a serine/threonine protein kinase domain at their C-terminus. The light-activated LOV2 domain forms a metastable intermediate which has been shown to be a protein-chromophore cysteinyl adduct (Cys39) at C(4a) of FMN. This species thermally relaxes back to the ground state in the dark. We measured the light-minus-dark FTIR difference spectra for the LOV2 domain of oat phot1. These spectra show the disappearance of bands at 1580, 1550, and 1350 cm(-1) that originate from, or are strongly coupled to, the N5=C(4a) stretching vibrations, consistent with the perturbations expected upon C(4a) adduct formation. Assignment of these negative difference FTIR bands to native chromophore vibrations is based on the alignment with resonance Raman bands of FMN. Prominent positive bands include a doublet at 1516 and 1536 cm(-1) and one at 1375 and 1298 cm(-1). Normal-mode vibrational-frequency calculations for both lumiflavin and lumiflavin with a sulfur attached at the C(4a) position agree with many of the positive and negative bands observed in the difference spectra. Both calculated and experimental difference FTIR spectra for deuterium isotope substitutions at exchangeable positions in the flavin chromophore are consistent with the assignment of the above positive bands to vibrational modes involving both the newly formed tetrahedral geometry of C(4a) and the N5-H bond in the long-lived LOV2(S)(390) cysteinyl species. 相似文献
52.
Walter J. Fitz Walter W. Wenzel Gottfried Wieshammer Blaž Istenič 《Plant and Soil》2003,256(2):455-462
Experimental data on rhizosphere characteristics at high spatial resolution are required to improve our knowledge on phytoavailability of nutrients and pollutants. In numerous studies, sectioning using refrigerated microtomes has been employed to obtain thin soil layers at defined distances from the root surface. In this study, we assessed the effect of thin slicing and freezing on soil chemical characteristics. Two experimental soils were frozen at –20°C and sliced using a refrigerated microtome. In general, chemical changes relative to the non-sliced control were more pronounced as the trim thickness (thickness of a single slice) decreased. Maximum increases in pH and electrical conductivity (EC) for the smallest trim thickness used (20 m) were 0.9 units and 50%, respectively. Extractable fractions of P (0.5 M NaHCO3) K, Mg, Mn, Na and Si (1 M NH4NO3) increased up to 40, 91, 19, 621, 50 and 100%, respectively. Based on these results, we suggest to use a trim thickness of 200 m. Apart from slicing, freezing (a prerequisite for the microtome technique) was found to bias soil chemical parameters. To circumvent microtome-related artifacts we present a home-made slicing device as a cost-effective alternative, which allows sectioning of non-frozen rhizosphere soil employing one single slice. 相似文献
53.
We sought to understand better the impact of genetic testing and counseling in a group of women who had early breast cancer (age <50) or ovarian cancer and a family history of cancer. Thirty-five women underwent genetic counseling and genetic testing for BRCA1/2 at the University of Colorado Cancer Center, Hereditary Cancer Clinic. Psychological assessment (IES and Hopkins Symptom Checklist) was made before counseling, and 1 month after genetic test results were reported to women. A statistically significant decrease in anxiety was evidenced 1 month after results were given (p = 0.024). Decreased intrusive thoughts related to genetic testing were seen only for those testing negative (p = 0.0003). Women diagnosed with cancer less than 1 year prior to genetic testing experienced the greatest cancer-specific distress (p = 0.01) and distress related to genetic testing (p = not significant). Satisfaction with the counseling and testing process was high. In conclusion, genetic testing and counseling can occur with little anxiety and stress. However, women less than 1 year from a cancer diagnosis will experience the greatest distress associated with genetic testing and counseling. Women who are considering genetic testing and counseling close to a diagnosis of cancer may require greater psychological support. 相似文献
54.
We conducted kinematic and cytological studies on "between vein" epidermal cells of the gibberellin (GA)-deficient M489 dwarf mutant of barley (Hordeum vulgare L. Himalaya). GAs affect radial and axial components of cell expansion and cortical microtubule orientation. Adaxial cells in particular expand radially after leaving the elongation zone (EZ), probably as part of leaf unrolling. Exogenous gibberellic acid corrects the mutant's short, wide blades, short EZ, and slow elongation rate. Cell production rates increase more on the adaxial than on the abaxial surface. Cells spend equal periods of time elongating in dwarf and tall plants, but relative elemental growth rates start to decline sooner in the dwarf. GA increased the rate at which longitudinal wall area increased because the increased axial growth more than compensated for reduced radial growth. In dwarf leaves, increased radial expansion was detected in basal parts of the EZ before cortical microtubules lost transverse orientation in the distal elongation zone. We conclude that loss of microtubule orientation is not required for low GA levels to reduce growth anisotropy. 相似文献
55.
Ype Elgersma Minetta Elgersma-Hooisma Thibaut Wenzel J. Michael McCaffery Marilyn G. Farquhar Suresh Subramani 《The Journal of cell biology》1998,140(4):807-820
Abstract. Using a new screening procedure for the isolation of peroxisomal import mutants in Pichia pastoris, we have isolated a mutant (pex7) that is specifically disturbed in the peroxisomal import of proteins containing a peroxisomal targeting signal type II (PTS2). Like its Saccharomyces cerevisiae homologue, PpPex7p interacted with the PTS2 in the two-hybrid system, suggesting that Pex7p functions as a receptor. The pex7Δ mutant was not impaired for growth on methanol, indicating that there are no PTS2-containing enzymes involved in peroxisomal methanol metabolism. In contrast, pex7Δ cells failed to grow on oleate, but growth on oleate could be partially restored by expressing thiolase (a PTS2-containing enzyme) fused to the PTS1. Because the subcellular location and mechanism of action of this protein are controversial, we used various methods to demonstrate that Pex7p is both cytosolic and intraperoxisomal. This suggests that Pex7p functions as a mobile receptor, shuttling PTS2-containing proteins from the cytosol to the peroxisomes. In addition, we used PpPex7p as a model protein to understand the effect of the Pex7p mutations found in human patients with rhizomelic chondrodysplasia punctata. The corresponding PpPex7p mutant proteins were stably expressed in P. pastoris, but they failed to complement the pex7Δ mutant and were impaired in binding to the PTS2 sequence. 相似文献
56.
57.
We have developed an all-atom free-energy force field (PFF01) for protein tertiary structure prediction. PFF01 is based on physical interactions and was parameterized using experimental structures of a family of proteins believed to span a wide variety of possible folds. It contains empirical, although sequence-independent terms for hydrogen bonding. Its solvent-accessible surface area solvent model was first fit to transfer energies of small peptides. The parameters of the solvent model were then further optimized to stabilize the native structure of a single protein, the autonomously folding villin headpiece, against competing low-energy decoys. Here we validate the force field for five nonhomologous helical proteins with 20-60 amino acids. For each protein, decoys with 2-3 A backbone root mean-square deviation and correct experimental Cbeta-Cbeta distance constraints emerge as those with the lowest energy. 相似文献
58.
Jeppe Reitan Andersen Imad Zein Gerhard Wenzel Birte Darnhofer Joachim Eder Milena Ouzunova Thomas Lübberstedt 《BMC plant biology》2008,8(1):2
Background
Forage quality of maize is influenced by both the content and structure of lignins in the cell wall. Biosynthesis of monolignols, constituting the complex structure of lignins, is catalyzed by enzymes in the phenylpropanoid pathway. 相似文献59.
Katelyn A. Provencher Madeline A. Weber Lauren A. Randall Patrick R. Cunningham Catherine F. Dignam Thomas J. Wenzel 《Chirality》2010,22(3):336-346
Cyclodextrins that are indiscriminately carboxymethylated at the 2‐, 3‐, and 6‐positions are used as chiral NMR solvating agents for cationic substrates with phenyl, naphthyl, pyridyl, indoline, and indole rings. Enantiodifferentiation with the α‐, β‐, and γ‐cyclodextrin derivatives is compared. The carboxymethylated derivatives are almost always more effective as chiral NMR solvating agents for cationic substrates than native cyclodextrins. The most effective carboxymethylated cyclodextrin varies for different substrates, and at times even different resonances of the substrate. Addition of paramagnetic praseodymium(III) or ytterbium(III) to mixtures of the carboxymethylated cyclodextrin and substrate often causes enhancements in enantiomeric discrimination and facilitates measurements of enantiomeric purity. The lanthanide ion bonds to the carboxymethyl groups and causes perturbations in the chemical shifts in the NMR spectra of substrate molecules in the cyclodextrin cavity. Chirality, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
60.
Michael CW Chan Renee WY Chan Wendy CL Yu Carol CC Ho WH Chui CK Lo Kit M Yuen Yi Guan John M Nicholls JS Malik Peiris 《Respiratory research》2009,10(1):102