Maize and soybean response to phosphorus fertilization with blends of struvite and monoammonium phosphate

Plant and Soil - Struvite (MgNH4PO4·6H2O), a low water solubility (<3%) mineral that is increasingly recovered from wastewater treatment plants, has potential to be used as a slow...     

Stable isotopic signatures of carbon and nitrogen in soil aggregates following the conversion of natural forests to managed plantations in eastern China

Plant and Soil - Land cover change (LCC) from natural forest (NF) to plantations (PF) has occurred worldwide over the past several decades. However, the different LCC effects on soil aggregate C...     

A computational framework for modeling cell–matrix interactions in soft biological tissues

Biomechanics and Modeling in Mechanobiology - Living soft tissues appear to promote the development and maintenance of a preferred mechanical state within a defined tolerance around a so-called set...     

Introduction and clearance of beta-glucan in the downstream processing of monoclonal antibodies

β-Glucan process-related impurities can be introduced into biopharmaceutical products via upstream or downstream processing or via excipients. This study obtained a comprehensive process-mapping dataset for five monoclonal antibodies to assess β-glucan introduction and clearance during development and production runs at various scales. Overall, 198 data points were available for analysis. The greatest β-glucan concentrations were found in the depth-filtration filtrate (37–2,745 pg/ml). Load volume correlated with β-glucan concentration in the filtrate, whereas flush volume was of secondary importance. Cation-exchange chromatography significantly cleared β-glucans. Furthermore, β-glucan leaching from the Planova 20N virus removal filter was reduced by increasing the flush volume (1 vs. 10 L/m²). β-glucan concentrations after filter flush with 10 L/m² were consistently <10 pg/ml. No or only limited β-glucan clearance was attained via ultrafiltration/diafiltration (UF/DF). However, during the first run with monoclonal antibody (mAb) 4, β-glucan concentration in the UF/DF retentate was 10.8 pg/mg, potentially due to β-glucan leaching from the first run with a regenerated cellulose membrane. Overall, β-glucan levels in the final mAb drug substance were 1–12 pg/mg. Assuming high doses of 1,000–5,000 mg, a β-glucan contamination at 20 pg/mg would translate to 20–100 ng/dose, which is below the previously suggested threshold for product safety (≤500 ng/dose).     

Mutations of Thr169 affect substrate specificity of pyranose 2-oxidase from Trametes multicolor

Site-directed mutagenesis was used to enhance the catalytic activity of pyranose 2-oxidase (P2Ox) from Trametes multicolor with different substrates. To this end, threonine at position 169 was replaced by glycine, alanine and serine, respectively. Using oxygen as electron acceptor the mutant T169G was equally active with d-glucose and d-galactose, whereas wild-type recombinant P2Ox only showed 5.2% relative activity with the latter substrate. When d-galactose was used as electron donor in saturating concentrations, T169G showed a 4.5-fold increase in its catalytic efficiency k_cat/K_M for the alternative electron acceptor 1,4-benzoquinone and a nine-fold increased k_cat/K_M value with the ferricenium ion compared with wt recP2Ox. Variant T169S showed an increase in its catalytic efficiency both with 1,4-benzoquinone (3.7 times) as well as with the ferricenium ion (1.4 times) when d-glucose was the substrate.     

USE OF THE SODIUM SALT GLYCOSYLATION HETBOD IN NUCLEOSIDE SYNTHESIS

Abstract

A general and stereospecific method has been developed for the direct preparation of βD-ribofuranosyl, βD-arabinofuranosyl and 2-deoxy-βD-erythro-pentofuranosyl derivatives of a number of nitrogen heterocycles. The azoles thus far employed include appropriately substituted pyrrole, pyrazole, imidazole, 1,2,4-triazole, indole, imidazo[4,5-c]pyridine, pyrrolo[2,3-d]pyrimidine, pyrro10[3,2-c]pyridine, pyrrolo[4,2-c]pyrimidine, purine, pyrazolo[3,4-b]pyridine and pyrazolo-[3,4-d]pyrimidine. This simple high-yield methodology provided a facile route to the large-scale preparation of biologically significant nucleo-sides, such as 2′-deoxyribavirin, 2-chloro-2′-deoxyadenosine, tuber-cidin, Z'-deoxytubercidin, =sangivarnycin, 2′-deoxytoyocamycin, cade-guomycin, 2′-deoxycadeguomycin, G-cadeguomycin, kanagawamicin, 2′-deoxy-3-deazaguanosine, sG, brunfelsarnidine ribonucleoside and 2′-deoxyribofuranosyl derivative of the antibiotic SF-2140. This procedure appears to be considerably superior to the previously reported glycosylation methods.     

Synthesis of Brunfelsamidine Ribonucleoside and Certain Related Compounds by the Stereospecific Sodium Salt Glycosylation Procedure

Abstract

A synthesis of 2,4-dideazaribavirin ( 2 ), brunfelsamidine ribonucleoside ( 8c ) and certain related derivatives are described for the first time using the stereospecific sodium salt glycosylation procedure. Glycosylation of the sodium salt of pyrrole-3-carbonitrile ( 4 ) with 1-chloro-2, 3-O-t-isopropylidene-5-O-t-butyldimethylsilyl-α-D-ribofuranose ( 5 ) gave exclusively the corresponding blocked nucleoside ( 6 ) with β-anomeric configuration, which on deprotection provided 1-β-D-ribofuranosylpyrrole-3-carbonitrile ( 7 ). Functional group tranformation of 7 gave 2 , 8c and related 3-substituted pyrrole ribonucleosides. These compounds are devoid of any significant antiviral/antitumor activity invitro.     

Purine Nucleoside 3′,5′-Cyclic Monophosphates as Hormonal Modulators of Cellular Proliferation,Metastases and Lymphocyte Response

Abstract

A review of the potential role of cAMP and cGMP as hormonal regulators of tumor cell proliferation, metastases and lymphocyte activation reveals that several synthetic purine nucleoside 3′,5′-cyclic monophosphates are more potent and more selective in modulating certain specific responses than the parent natural cyclic nucleotides. cAMP derivatives have been prepared which will temporarily restore transformed cells to the normal phenotype. cAMP analogs may well be found which will selectively inhibit tumor metastases. Certain cGMP analogs could selectively stimulate the lymphocyte response toward the destruction of tumor cells. The synthesis of new cyclic nucleotides should provide unique nontoxic agents that could combat neoplasia on a hormonal basis.     

A New Synthesis of 7-Methyl-8-Oxoguanosine

Abstract

A new, facile synthesis of 7-methyl-8-oxoguanosine is reported. 2-Chloro-7-methylpurine-6, 8-dione (5) was silylated with hexamethyldi-silazane and the silylated intermediate, 6, glycosylated with 1-0-acetyl-2, 3, 5-tri-0-benzoyl-D-ribofuranose to yield 2-chloro-7-methyl-9-(2′, 3′,-5′-tri-0-benzoyl-β-D-ribofuranosyl) purin-6, 8-dione (8). Deprotection of 8 with sodium hydroxide in aqueous methanol gave 2-chloro-7-methyl-9-(β-D-ribofuranosyl) purine-6,8-dione (9), which was aminated with liquid ammonia or methanolic ammonia to yield 7-methyl-8-oxoguanosine (3).     

Projected climate impacts to South African maize and wheat production in 2055: a comparison of empirical and mechanistic modeling approaches

Crop model‐specific biases are a key uncertainty affecting our understanding of climate change impacts to agriculture. There is increasing research focus on intermodel variation, but comparisons between mechanistic (MMs) and empirical models (EMs) are rare despite both being used widely in this field. We combined MMs and EMs to project future (2055) changes in the potential distribution (suitability) and productivity of maize and spring wheat in South Africa under 18 downscaled climate scenarios (9 models run under 2 emissions scenarios). EMs projected larger yield losses or smaller gains than MMs. The EMs’ median‐projected maize and wheat yield changes were ?3.6% and 6.2%, respectively, compared to 6.5% and 15.2% for the MM. The EM projected a 10% reduction in the potential maize growing area, where the MM projected a 9% gain. Both models showed increases in the potential spring wheat production region (EM = 48%, MM = 20%), but these results were more equivocal because both models (particularly the EM) substantially overestimated the extent of current suitability. The substantial water‐use efficiency gains simulated by the MMs under elevated CO₂ accounted for much of the EM?MM difference, but EMs may have more accurately represented crop temperature sensitivities. Our results align with earlier studies showing that EMs may show larger climate change losses than MMs. Crop forecasting efforts should expand to include EM?MM comparisons to provide a fuller picture of crop–climate response uncertainties.