Tyrosinase reactivity in a model complex: an alternative hydroxylation mechanism

The binuclear copper enzyme tyrosinase activates O2 to form a mu-eta2:eta2-peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic mu-eta2:eta2-peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at -80 degrees C. Upon phenolate addition at extreme temperature in solution (-120 degrees C), a reactive intermediate consistent with a bis-mu-oxodicopper(III)-phenolate complex, with the O-O bond fully cleaved, is observed experimentally. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O-O bond cleavage and C-O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O-O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase.     

Mathematical modeling of planar cell polarity to understand domineering nonautonomy

Planar cell polarity (PCP) signaling generates subcellular asymmetry along an axis orthogonal to the epithelial apical-basal axis. Through a poorly understood mechanism, cell clones that have mutations in some PCP signaling components, including some, but not all, alleles of the receptor frizzled, cause polarity disruptions of neighboring wild-type cells, a phenomenon referred to as domineering nonautonomy. Here, a contact-dependent signaling hypothesis, derived from experimental results, is shown by reaction-diffusion, partial differential equation modeling and simulation to fully reproduce PCP phenotypes, including domineering nonautonomy, in the Drosophila wing. The sufficiency of this model and the experimental validation of model predictions reveal how specific protein-protein interactions produce autonomy or domineering nonautonomy.     

Studies of the human c-myb gene and its product in human acute leukemias

The myb gene is the transforming oncogene of the avian myeloblastosis virus (AMV); its normal cellular homolog, c-myb, is conserved across a broad span of evolution. In humans, c-myb is expressed in malignant hematopoietic cell lines and in primary hematopoietic tumors. Partial complementary DNA clones were generated from blast cells of patients with acute myelogenous leukemia. The sequences of the clones were compared to the c-myb of other species, as well as the v-myb of AMV. In addition, the carboxyl terminal region of human c-myb was placed in an expression vector to obtain protein for the generation of antiserum, which was used to identify the human c-myb gene product. Like v-myb, this protein was found within the nucleus of leukemic cells where it was associated with the nuclear matrix. These studies provide further evidence that c-myb might be involved in human leukemia.     

Recognition of a ubiquitous self antigen by prostate cancer-infiltrating CD8+ T lymphocytes

Substantial evidence exists that many tumors can be specifically recognized by CD8+ T lymphocytes. The definition of antigens targeted by these cells is paramount for the development of effective immunotherapeutic strategies for treating human cancers. In a screen for endogenous tumor-associated T cell responses in a primary mouse model of prostatic adenocarcinoma, we identified a naturally arising CD8+ T cell response that is reactive to a peptide derived from histone H4. Despite the ubiquitous nature of histones, T cell recognition of histone H4 peptide was specifically associated with the presence of prostate cancer in these mice. Thus, the repertoire of antigens recognized by tumor-infiltrating T cells is broader than previously thought and includes peptides derived from ubiquitous self antigens that are normally sequestered from immune detection.     

Wafer-scale graphene integrated circuit

A wafer-scale graphene circuit was demonstrated in which all circuit components, including graphene field-effect transistor and inductors, were monolithically integrated on a single silicon carbide wafer. The integrated circuit operates as a broadband radio-frequency mixer at frequencies up to 10 gigahertz. These graphene circuits exhibit outstanding thermal stability with little reduction in performance (less than 1 decibel) between 300 and 400 kelvin. These results open up possibilities of achieving practical graphene technology with more complex functionality and performance.     

Marcy: A chipping variety with resistance to common scab and the golden nematode

‘Marcy’ is a white-skinned, white-fleshed potato cultivar notable for its high yield, good chip color, and resistance to common scab and race Ro1 of the golden cyst nematode. It was selected from a cross made at Cornell University in 1990 between ‘Atlantic’ and Q155-3. Full-season marketable yields of Marcy have averaged 15% to 20% greater than Atlantic in 83 trials across New York, Maine, and Pennsylvania. Specific gravity of Marcy has averaged 0.008 less than Atlantic. Chip color out of 7 C storage in New York has been similar to ‘Pike’, but not as light as ‘Snowden’. Marcy tubers have an attractive oval shape, shallow eyes, and highly textured skin. Marcy was jointly released by the New York and Pennsylvania Agricultural Experiment Stations in 2002.     

Root diseases, weeds, and nematodes with poultry litter and conservation tillage in a sweet corn–snap bean double crop

The effect of continuous applications of poultry litter on root diseases, nematodes, and weeds with different tillage practices in vegetable production in Georgia was investigated. Litter treatments (noncomposted and composted broiler or breeder litter) applied 3–5 weeks before planting were compared with no litter. In sweet corn and snap bean there were differences among years, and tillage and litter treatments had a variable effect on yield, post-emergence damping-off and plant stand. Crown and brace root rot in corn induced by Rhizoctonia solani AG 2-2 increased after 3 years conservation tillage, but there were no differences among litter treatments. Population densities of R. solani AG-4 were increased by conservation tillage before planting snap bean the first year but not in later years, while litter treatments had no effect. After 3 years, populations of Pythium spp., Fusarium solani, and Fusarium spp. did not differ among treatments, but noncomposted broiler litter increased populations of saprophytic fungi in soil compared with no litter. Population densities of stylet-bearing nematodes were low and usually not different among treatments. After 3 years of sweet corn populations of Meloidogyne incognita increased with conventional tillage compared with conservation tillage, populations of Paratrichodorus christiei were reduced by litter treatments and populations of Helicotylenchus dihystera were reduced by noncomposted broiler litter compared with no litter. Weed infestation increased in both tillage systems with time, but in snap bean there was a greater infestation in conservation tillage than in conventional tillage. Litter treatments had little effect on weed infestation.     

Specificity of feruloyl esterases for water-extractable and water-unextractable feruloylated polysaccharides: influence of xylanase

Representatives of three types of feruloyl esterases were examined for their ability to release mono- and di-meric ferulic acid from water-extractable and water-unextractable cereal cell wall material, either alone or in the presence of a family 10 or family 11 xylanase. A type-C feruloyl esterase from Talaromyces stipitatus (TsFaeC) released 100% of the ferulic acid from water-extractable wheat endosperm arabinoxylan when acting in combination with a xylanase from Trichoderma longibrachiatum. The type-A esterase from Aspergillus niger, AnFaeA, was most effective in releasing ferulic acid from wheat bran and brewers' spent grain, with over 50% of the available ferulic acid being released from wheat bran in the presence of a xylanase from Bacillus subtilis. In general, family 11 xylanases were the preferred synergistic partners with feruloyl esterases for the release of ferulic acid, while family 10 xylanases were preferred for the liberation of diferulic acid, with only the 5,5′ form being released by the action of AnFaeA alone. This suggests that ferulic acid may be located in regions of low substitution on arabinoxylans while the 5,5′ diferulate moiety is located in more branched regions of the xylan chain.