Investigating the Role of Protein Phosphatase 2A in the Salt Stress Response in Arabidopsis thaliana

Protein Phosphatase 2A (PP2A) is a ubiquitous enzyme in eukaryotes that regulates a large array of cellular signaling processes. PP2A is composed of three subunits: catalytic C subunit, regulatory B subunit, and scaffolding/regulatory A subunit. In Arabidopsis thaliana, the A subunit has three isoforms - A1, A2, and A3 - that are highly conserved at the protein level, indicating that these proteins may be functionally interchangeable. In comparison to wildtype plants, seedlings with a mutation in the A1 gene have roots with obvious root cell file rotation or twisting under conditions of moderate salt stress. Twisted root cells result in a characteristic root curling phenotype when seedlings are grown on the surface of vertically-oriented agar plates. Mutations in the A2 and A3 genes do not result in any observable root phenotype, even though all three A subunit isoforms are expressed in roots. To test the hypothesis that differences in expression may be responsible for mutant phenotype variation, hybrid genes were constructed containing promoters from one subunit and coding regions of a different subunit, then transformed into a1mutant Arabidopsis to test for complementation. These tests showed that a1 mutants transformed with transgenes containing A1 or A3 promoters, regardless of coding region, had their mutant phenotype corrected, while the phenotypes of a1 mutants transformed with a2 promoters were only partially corrected. This supports the hypothesis that a deficit in the total A subunit pool, rather than subunit specificity, is a major contributor to the a1 mutant phenotype

Engineering Hydroxylase and Ketoreductase Activity, Selectivity, and Stability for a Scalable Concise Synthesis of Belzutifan

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Forces exerted during exercises by patients with adolescent idiopathic scoliosis wearing fiberglass braces

OBJECTIVE: To quantify and compare the forces exerted by scoliosis patients in fiberglass braces during exercises usually prescribed in departments where casts are made. The exercises are intended to increase corrective forces, activate muscles, stimulate ventilation and help the patient psychologically. SETTING: Outpatient care. PATIENTS: 17 consecutive adolescent patients wearing fiberglass brace for idiopathic scoliosis. INTERVENTIONS: Exercises (kyphotization, rotation, "escape from the pad") in different positions (sitting, supine, on all fours). MAIN OUTCOME MEASURE: Pressure detected by the F-Socket System between the rib hump and the pad of the brace. RESULTS: In static and dynamic conditions, the position adopted did not alter the total pressure exerted by the brace, although the part of the sensor stimulated did vary. Kyphotization and rotation exercises produced a significant increase of pressure (+ 58.9% and +29.8%, respectively); however, the "escape from the pad" exercise, despite its name, did not produce any significant variation of pressure. CONCLUSION: Exercises in the brace allow adjunctive forces to be applied on soft tissues and through them, presumably on the spine. Different exercises can be chosen to obtain different actions. Physical exercises and sporting activities are useful in mechanical terms, although other important actions should not be overlooked

Development of novel N-heterocyclic carbenes for asymmetric C-C bond forming reactions, The

2012 Summer.Includes bibliographical references.A variety of novel N-heterocyclic carbenes have been developed as organocatalysts for highly efficient and selective intermolecular C-C bond forming reactions. Problems associated with attaining high selectivity while retaining high efficiency in asymmetric intermolecular acyl anion pathways have been resolved through non-traditional manipulation of the catalyst architecture. In the context of the asymmetric intermolecular Stetter reaction, a new series of fluorinated triazolium salt pre-catalysts have been developed that catalyze the highly enantioselective coupling of hetaryl aldehydes and nitroalkenes. Stereoelectronic effects in the ground state suggest that conformation of the catalyst plays a role in determining selectivity. DFT calculations provide evidence for an electrostatic interaction between the fluorine-induced dipole and the electrophiles as the source of increased selectivity. The scope of the asymmetric intermolecular Stetter reaction of nitroalkenes has been further expanded to incorporate α,β-unsaturated aldehydes as partners. Mechanistic studies point to the initial proton-transfer event leading to generation of the acyl-anion equivalent as being turnover limiting. With this knowledge, an additive has been introduced that effectively increases the rate of proton transfer leading to substantially shorter reaction times and dramatically lower catalyst loadings. Further catalyst development has led to the realization of another mode of catalyst control, using the C-F bond as an additional source of substrate differentiation. This complementary fluorinated catalyst architecture substantially increases the reactivity of enolizable aldehydes in the asymmetric intermolecular Stetter reaction of nitrostyrenes, and for the first time allows for their inclusion in this transformation. An asymmetric aza-benzoin reaction of aliphatic aldehydes and N-Boc imines has been developed after identifying an extremely selective amino-indanol derived catalyst scaffold and mild reaction conditions. The direct enantioselective acylation of amines has been realized using a dual catalysis manifold, incorporating a photoactive metal complex as a catalyst to activate amines toward acyl-anion addition and a chiral NHC catalyst. This methodology has led to the isolation and full characterization of a series of aza-Breslow intermediates by X-ray crystallography. Studies of these intermediates provide crucial information about the fundamental reactivity of the Breslow intermediate and show that it is not only a catalyst resting state in these transformation but its generation is also reversible in the presence of a weak acid

Catalytic Asymmetric α-Acylation of Tertiary Amines Mediated by a Dual Catalysis Mode: N-Heterocyclic Carbene and Photoredox Catalysis

Cross-coupling reactions are among the most widely utilized methods for C–C bond formation; however, the requirement of preactivated starting materials still presents a major limitation. Methods that take direct advantage of the inherent reactivity of the C–H bond offer an efficient alternative to these methods, negating the requirement for substrate preactivation. In this process, two chemically distinct activation events culminate in the formation of the desired C–C bond with loss of H₂ as the only byproduct. Herein we report the catalytic asymmetric α-acylation of tertiary amines with aldehydes facilitated by the combination of chiral N-heterocyclic carbene catalysis and photoredox catalysis

Catalytic Asymmetric α-Acylation of Tertiary Amines Mediated by a Dual Catalysis Mode: N-Heterocyclic Carbene and Photoredox Catalysis

Cross-coupling reactions are among the most widely utilized methods for C–C bond formation; however, the requirement of preactivated starting materials still presents a major limitation. Methods that take direct advantage of the inherent reactivity of the C–H bond offer an efficient alternative to these methods, negating the requirement for substrate preactivation. In this process, two chemically distinct activation events culminate in the formation of the desired C–C bond with loss of H₂ as the only byproduct. Herein we report the catalytic asymmetric α-acylation of tertiary amines with aldehydes facilitated by the combination of chiral N-heterocyclic carbene catalysis and photoredox catalysis

Isolable Analogues of the Breslow Intermediate Derived from Chiral Triazolylidene Carbenes

Since Breslow’s initial report on the thiamine mode of action, the study of catalytic acyl carbanion processes has been an area of immense interest. With the advent of azolylidene catalysis, a plethora of reactivtiy has been harnessed, but the crucial nucleophilic intermediate proposed by Breslow had never been isolated or fully characterized. Herein, we report the isolation and full characterization of nitrogen analogues of the Breslow intermediate. Both stable and catalytically relevant, these species provide a model system for the study of acyl carbanion and homoenolate processes catalyzed by triazolylidene carbenes

Asymmetric N‑Heterocyclic Carbene Catalyzed Addition of Enals to Nitroalkenes: Controlling Stereochemistry via the Homoenolate Reactivity Pathway To Access δ‑Lactams

An asymmetric intermolecular reaction between enals and nitroalkenes to yield δ-nitroesters has been developed, catalyzed by a novel chiral N-heterocyclic carbene. Key to this work was the development of a catalyst that favors the δ-nitroester pathway over the established Stetter pathway. The reaction proceeds in high stereoselectivity and affords the previously unreported <i>syn</i> diastereomer. We also report an operationally facile two-step, one-pot procedure for the synthesis of δ-lactams

Isolable Analogues of the Breslow Intermediate Derived from Chiral Triazolylidene Carbenes

Since Breslow’s initial report on the thiamine mode of action, the study of catalytic acyl carbanion processes has been an area of immense interest. With the advent of azolylidene catalysis, a plethora of reactivtiy has been harnessed, but the crucial nucleophilic intermediate proposed by Breslow had never been isolated or fully characterized. Herein, we report the isolation and full characterization of nitrogen analogues of the Breslow intermediate. Both stable and catalytically relevant, these species provide a model system for the study of acyl carbanion and homoenolate processes catalyzed by triazolylidene carbenes

Isolable Analogues of the Breslow Intermediate Derived from Chiral Triazolylidene Carbenes

Since Breslow’s initial report on the thiamine mode of action, the study of catalytic acyl carbanion processes has been an area of immense interest. With the advent of azolylidene catalysis, a plethora of reactivtiy has been harnessed, but the crucial nucleophilic intermediate proposed by Breslow had never been isolated or fully characterized. Herein, we report the isolation and full characterization of nitrogen analogues of the Breslow intermediate. Both stable and catalytically relevant, these species provide a model system for the study of acyl carbanion and homoenolate processes catalyzed by triazolylidene carbenes