Forbidden Coherence Transfer of 19F Nuclei to Quantitatively Measure the Dynamics of a CF₃-Containing Ligand in Receptor-Bound States

The dynamic property of a ligand in the receptor-bound state is an important metric to characterize the interactions in the ligand–receptor interface, and the development of an experimental strategy to quantify the amplitude of motions in the bound state is of importance to introduce the dynamic aspect into structure-guided drug development (SGDD). Fluorine modifications are frequently introduced at the hit-to-lead optimization stage to enhance the binding potency and other characteristics of a ligand. However, the effects of fluorine modifications are generally difficult to predict, owing to the pleiotropic nature of the interactions. In this study, we report an NMR-based approach to experimentally evaluate the local dynamics of trifluoromethyl (CF₃)-containing ligands in the receptor-bound states. For this purpose, the forbidden coherence transfer (FCT) analysis, which has been used to study the dynamics of methyl moieties in proteins, was extended to the ¹⁹F nuclei of CF₃-containing ligands. By applying this CF₃–FCT analysis to a model interaction system consisting of a ligand, AST-487, and a receptor, p38α, we successfully quantified the amplitude of the CF₃ dynamics in the p38α-bound state. The strategy would bring the CF₃-containing ligands within the scope of dynamic SGDD to improve the affinity and specificity for the drug-target receptors.

Asymmetric Strecker Reaction Arising from the Molecular Orientation of an Achiral Imine at the Single-Crystal Face: Enantioenriched l- and d-Amino Acids

Strecker synthesis has long been considered one of the prebiotic reactions for the synthesis of α-amino acids. However, the correlation between the origin of chirality and highly enantioenriched α-amino acids through this method remains a puzzle. In the reaction, it may be conceivable that the handedness of amino acids has been determined at the formation stage of the chiral intermediate α-aminonitrile, that is, the enantioselective addition of hydrogen cyanide to an imine. Herein, an enantiotopic crystal surface of an achiral imine acted as an origin of chirality for the enantioselective formation of α-aminonitriles by the addition of HCN. In conjunction with the amplification of the enantiomeric excess and multiplication of enantioenriched aminonitrile, a large amount of near enantiopure α-amino acids, with the l- and d-handedness corresponding to the molecular orientation of the imine, is reported.

Robust metastable skyrmions and their triangular-square lattice structural transition in a high-temperature chiral magnet

Skyrmions, topologically protected nanometric spin vortices, are being investigated extensively in various magnets. Among them, many structurally chiral cubic magnets host the triangular-lattice skyrmion crystal (SkX) as the thermodynamic equilibrium state. However, this state exists only in a narrow temperature and magnetic-field region just below the magnetic transition temperature T_c, while a helical or conical magnetic state prevails at lower temperatures. Here we describe that for a room-temperature skyrmion material, β-Mn-type Co ₈Zn ₈Mn ₄, a field-cooling via the equilibrium SkX state can suppress the transition to the helical or conical state, instead realizing robust metastable SkX states that survive over a very wide temperature and magnetic-field region. Furthermore, the lattice form of the metastable SkX is found to undergo reversible transitions between a conventional triangular lattice and a novel square lattice upon varying the temperature and magnetic field. These findings exemplify the topological robustness of the once-created skyrmions, and establish metastable skyrmion phases as a fertile ground for technological applications.

Improvement of Ligand Affinity and Thermodynamic Properties by NMR-Based Evaluation of Local Dynamics and Surface Complementarity in the Receptor-Bound State

The thermodynamic properties of a ligand in the bound state affect its binding specificity. Strict binding specificity can be achieved by introducing multiple spatially defined interactions, such as hydrogen bonds and van der Waals interactions, into the ligand-receptor interface. These introduced interactions are characterized by restricted local dynamics and improved surface complementarity in the bound state. In this study, we experimentally evaluated the local dynamics and the surface complementarity of weak-affinity ligands in the receptor-bound state by forbidden coherence transfer analysis in free-bound exchange systems (Ex-FCT), using the interaction between a ligand, a myocyte-enhancer factor 2A (MEF2A) docking peptide, and a receptor, p38α, as a model system. The Ex-FCT analyses successfully provided information for the rational design of a ligand with higher affinity and preferable thermodynamic properties for p38α.

Replication of α-amino acids via Strecker synthesis with amplification and multiplication of chiral intermediate aminonitriles

Replication of chiral l- and d-α-(p-tolyl)glycine has been achieved in combination with the asymmetric induction, amplification and multiplication of their own chiral intermediates, l- and d-aminonitriles, in the solid-phase via the Strecker reaction between three achiral components, which is a plausible prebiotic mechanism for amino acid synthesis.

Characterization of Local Structures in Flexible Polyurethane Foams by Solid-state NMR and FTIR Spectroscopy

The article examines the characterization of local structures in water-blown flexible polyurethane foams with various amine catalysts. In this study, the authors have applied solid-state nuclear magnetic resonance (NMR) relaxation, nuclear spin diffusion, and Fourier transform infrared (FTIR) microscope analysis on flexible polyurethane foams. Quantitative knowledge of the polymer structure and dynamics by these methods provides a significant insight on understanding the microphase separation and the domain structure of urethane and urea hard segments and polyether soft segments in foam.

Furthermore, the authors analyze the influence of hydrothermal degradation on the microphase structure of the foams. A detailed comparison of the fundamental results with conventional foam durability tests (e.g., humid aged compression sets) is described, and the hydrothermal degradation mechanism and the influence of catalysts on the foam stability are discussed.

Preparation of Fine Particles with Improved Solubility Using a Complex Fluidized-Bed Granulator Equipped with a Particle-Sizing Mechanism

A new type of fluidized-bed granulator equipped with a particle-sizing mechanism was used for the preparation of fine particles that improved the solubility of a poorly water-soluble drug substance. Cefteram pivoxyl (CEF) was selected as a model drug substance, and its solution with a hydrophilic polymer, hydroxypropyl cellulose (HPC-L), was sprayed on granulation grade lactose monohydrate (Lac). Three types of treated particles were prepared under different conditions focused on the spraying air pressure and the amount of HPC-L. When the amount of HPC-L was changed, the size of the obtained particles was similar. However, particle size distribution was dependent on the amount of HPC-L. Its distribution became more homogenous with greater amounts of HPC-L, but the particle size distribution obtained by decreasing the spraying air pressure was not acceptable. By processing CEF with HPC-L using a complex fluidized-bed granulator equipped with a particle-sizing mechanism, the dissolution ratio was elevated by approximately 40% compared to that of unprocessed CEF. Moreover, in the dissolution profile of treated CEF, the initial burst was suppressed, and nearly zero order release was observed up to approximately 60% in the dissolution profile. This technique may represent a method with which to design fine particles of approximately 100 µm in size with a narrow distribution, which can improve the solubility of a drug substance with low solubility.

Spontaneous formation and amplification of an enantioenriched α-amino nitrile: a chiral precursor for Strecker amino acid synthesis

Without the addition of any chiral substances, the spontaneous formation of an enantioenriched α-amino nitrile (up to 96% ee), which is a chiral precursor for Strecker amino acid synthesis, has been achieved in combination with conglomerate formation. The frequency of the formation of enantiomorphs exhibits an approximate stochastic distribution, i.e., L-form occurred 21 times and D-form occurred 22 times, which fulfils the conditions necessary for spontaneous absolute asymmetric synthesis.

Reentrant superconductivity driven by quantum tricritical fluctuations in URhGe: evidence from ^{59}Co NMR in URh_{0.9}Co_{0.1}Ge

Our measurements of the ^{59}Co NMR spin-spin relaxation in URh_{0.9}Co_{0.1}Ge reveal a divergence of electronic spin fluctuations in the vicinity of the field-induced quantum critical point at H_{R}≈13  T, around which reentrant superconductivity (RSC) occurs in the ferromagnetic heavy fermion compound URhGe. We map out the strength of spin fluctuations in the (H_{b},H_{c}) plane of magnetic field components and show that critical fluctuations develop in the same limited region near the field H_{R} as that where RSC is observed. This strongly suggests these quantum fluctuations as the pairing glue responsible for the RSC. The fluctuations observed are characteristic of a tricritical point, followed by a phase bifurcation toward quantum critical end points.

Allosteric enhancement of MAP kinase p38α's activity and substrate selectivity by docking interactions

Mitogen-activated protein kinases (MAPKs) are essential to intracellular signal transduction. MAPKs anchor their pathway-specific substrates through so-called 'docking interactions' at locations distal from the active site. Docking interactions ensure efficient substrate recognition, but their contribution to the kinase reaction itself remains unclear. Herein, we use solution NMR to analyze the interaction between dually phosphorylated, active human p38α and the C-terminal fragments of its substrate MK2. p38α phosphorylation and ATP loading collaboratively induce the active conformation; subsequently, p38α accommodates MK2 phosphoacceptor residues in its active site. The docking interaction enhances binding of ATP and the phosphoacceptor to p38α, accelerating the phosphotransfer reaction. Thus, the docking interaction enhances p38α's enzymatic activity toward pathway-specific substrates allosterically as well as by the anchor effect. These findings clarify how MAPK cascades are organized in cells, even under ATP-depleted conditions often associated with environmental stress.

Emergent antiferromagnetism out of the "hidden-order" state in URu2Si2: high magnetic field nuclear magnetic resonance to 40 T

Very high field (29)Si-NMR measurements using a fully (29)Si-enriched URu(2)Si(2) single crystal were carried out in order to microscopically investigate the "hidden order" (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the (29)Si shift, (29)K(c). Moreover, a strong enhancement of (29)K(c) develops near a critical field H(c) ≃ 35.6 T, and the ^{29}Si-NMR signal disappears suddenly at H(c), indicating the total suppression of the HO state. Nevertheless, a weak and shifted (29)Si-NMR signal reappears for fields higher than H(c) at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.

Magnetic biasing of a ferroelectric hysteresis loop in a multiferroic orthoferrite

In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign.

Abstract OT3-2-03: An efficacy and safety trial of preoperative chemo-endocrine therapy in luminal B (HER2-negative) breast cancer: A prospective multi-institutional study

Background: The St.Gallen consensus guideline recommends the sequential administration chemotherapy followed by of endocrine therapy as postoperative therapy for the higher risk ER-positive breast cancer patients based on results of a single study (Albain et al, Lancet 2009). In metastatic settings however, several trials conducted in the 1980's demonstrated that tumor response rates were higher when chemotherapy and tamoxifen were concomitantly administered, than when chemotherapy and tamoxifen administered were given sequentially. In the preoperative settings, pathological complete response (pCR) rate can be used a surrogate marker to predict event-free survival or overall survival in Luminal B(HER2-negative) breast cancer. We therefore designed a prospective randomized safety and efficacy trial in order to test a hypothesis that the concomitant administration of an aromatase inhibitor and chemotherapy improves pathological complete response(pCR) rate than chemotherapy alone in the preoperative setting.

Trial design: The trial is a prospective, multi-center, randomized comparison of chemotherapy alone versus concomitant chmo-endocrine therapy evaluating the efficacy in terms of pCR rate and safety in preoperative settings in patients with Luminal B (HER2-negative) breast cancer. 94 patients were to be accrued into this trial.

- arm A (control): 12 cycles of weekly paclitaxel(80mg/m2) followed by 4 cycles of every 3-week AC(Doxorubicine 60mg/m2, Cyclophosphamide 600mg/m2).

- arm B (experimental): The same chermotherapy as arm A and anastrozole in postmenopausal patients or anastrozole+leuprolerine in premenopansal patients.

Eligibility criteria: 1)Female patients with operable and histologically confirmed invasive breast cancer; 2)HER2-negative; 3)Either ER -positive or PgR-positive; 4)Either Ki67-LI> = 14% and NG> = 2 or NG = 3 regardless of Ki67-LI.

Endpoints : Primary endpoint is the pCR rate. Secondary endpoints are the clinical response rate(RECIST), the adverse events(CTC-AE ver.4.0), the breast conserving rate and the health related quality of life.

Statistical Considerations : The pCR rates in the control arm and the experimental arm are expected to be 10% and 25%, respectively. In order to show the superiority of the experimental arm with an alfa error at 5% and beta error at 20%, calculated number of patients needed were 96.

Present Accrual and Target Accrual: As of June 06, 2013, 18 patients were enrolled from 8 institutions.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-2-03.