Locking the Dynamic Axial Chirality of Biphenyl Crown Ethers through Threading

This paper describes the syntheses of [2]rotaxanes comprising 23- and 26-membered biphenyl crown ethers as the macrocyclic components and secondary ammonium ions as the dumbbell-shaped components, and the locking of the dynamic axial chirality of the biphenyl moieties in these structures. Chiral high-performance liquid chromatography (HPLC) revealed that our [2]rotaxane featuring the 26-membered crown ether racemized at room temperature, but the racemization of the [2]rotaxane featuring the 23-membered crown ether did not proceed at room temperature over a period of three days. After separation of the enantiomers of the [2]rotaxane incorporating the 23-membered crown ether through chiral HPLC, we studied its racemization at elevated temperature. The rate of stereoinversion in dimethylsulfoxide (a polar solvent) was faster than that in o-dichlorobenzene (a nonpolar solvent), and herein we discuss these kinetic parameters.

Utilization of a Crown Ether/Amine-Type Rotaxane as a Probe for the Versatile Detection of Anions and Acids by Thin-Layer Chromatography

A crown ether/amine-type [2]rotaxane was synthesized and utilized as a probe for the detection of acids and anions. The addition of acids to the amine-type [2]rotaxane solution generated corresponding crown ether/ammonium-type [2]rotaxanes, which were purified by silica gel column chromatography as ammonium salts. The isolated yields of the [2]rotaxanes, possessing a variety of anions, depended on the acidity and polarity of the counter anions. The behaviours of the ammonium-type [2]rotaxanes on thin-layer chromatography (TLC) silica gel reflected the properties of the counter anions. The treatment of the amine-type [2]rotaxane with acids afforded the corresponding ammonium-type [2]rotaxanes bearing several different anions. The ammonium-type [2]rotaxanes behaved similarly to the purified [2]rotaxanes on the TLC silica gel. Furthermore, we succeeded in the analysis of anions using mixtures of the amine-type [2]rotaxane and salts in an appropriate solvent. We demonstrated the detection of anions by the combination of TLC and the utilization of the [2]rotaxane probe.

Control of Transcription Initiation by Biased Thermal Fluctuations on Repetitive Genomic Sequences

In the process of transcription initiation by RNA polymerase, promoter DNA sequences affect multiple reaction pathways determining the productivity of transcription. However, the question of how the molecular mechanism of transcription initiation depends on the sequence properties of promoter DNA remains poorly understood. Here, combining the statistical mechanical approach with high-throughput sequencing results, we characterize abortive transcription and pausing during transcription initiation by Escherichia coli RNA polymerase at a genome-wide level. Our results suggest that initially transcribed sequences, when enriched with thymine bases, contain the signal for inducing abortive transcription, whereas certain repetitive sequence elements embedded in promoter regions constitute the signal for inducing pausing. Both signals decrease the productivity of transcription initiation. Based on solution NMR and in vitro transcription measurements, we suggest that repetitive sequence elements within the promoter DNA modulate the nonlocal base pair stability of its double-stranded form. This stability profoundly influences the reaction coordinates of the productive initiation via pausing.

Targeting the cryptic sites: NMR-based strategy to improve protein druggability by controlling the conformational equilibrium

Cryptic ligand binding sites, which are not evident in the unligated structures, are beneficial in tackling with difficult but attractive drug targets, such as protein-protein interactions (PPIs). However, cryptic sites have thus far not been rationally pursued in the early stages of drug development. Here, we demonstrated by nuclear magnetic resonance that the cryptic site in Bcl-xL exists in a conformational equilibrium between the open and closed conformations under the unligated condition. While the fraction of the open conformation in the unligated wild-type Bcl-xL is estimated to be low, F143W mutation that is distal from the ligand binding site can substantially elevate the population. The F143W mutant showed a higher hit rate in a phage-display peptide screening, and the hit peptide bound to the cryptic site of the wild-type Bcl-xL. Therefore, by controlling the conformational equilibrium in the cryptic site, the opportunity to identify a PPI inhibitor could be improved.

A Five-layer π-Aromatic Structure Formed through Self-assembly of a Porphyrin Trimer and Two Aromatic Guests

In this study we synthesized two- and four-armed porphyrins - bearing two carboxyl and four 2-aminoquinolino functionalities, respectively, at their meso positions - as a complementary hydrogen bonding pair for the self-assembly of a D₂ -symmetric porphyrin trimer host. Two units of the two-armed porphyrin and one unit of the four-armed porphyrin self-assembled quantitatively into the D₂ -symmetric porphyrin trimer, stabilized through ammidinium-carboxylate salt bridge formation, in CH₂ Cl₂ and CHCl₃ . The porphyrin trimer host gradually bound two units of 1,3,5-trinitrobenzene between the pair of porphyrin units, forming a five-layer aromatic structure. At temperatures below -40 °C, the rates of association and dissociation of the complexes were slow on the NMR spectroscopic time scale, allowing the 1 : 1 and 1 : 2 complexes of the trimer host and trinitrobenzene guest(s) to be detected independently when using less than 2 eq of trinitrobenzene. Vis titration experiments revealed the values of K₁ (2.1±0.4×10⁵  M^-1 ) and K₂ (2.2±0.06×10⁴  M^-1 ) in CHCl₃ at room temperature.

The Provisional No-Effect Threshold of Sugar Alcohols on Oral Drug Absorption Estimated by Physiologically Based Biopharmaceutics Model

Sugar alcohols reduce oral drug bioavailability by osmotic effects, but the magnitude of these effects differs among different drugs. This study aimed to identify the drug-related critical attributes of osmotic effects and estimate the impact of a "practical" sugar alcohol dose on the pharmacokinetics of various molecules using modeling and simulation approaches. We developed a physiologically based biopharmaceutics model that considers the dose-dependent effects of sugar alcohols on the gastrointestinal physiology. The developed model captured the effects of sugar alcohols on ranitidine hydrochloride, metoprolol tartrate, theophylline, cimetidine, and lamivudine. Sensitivity analysis provided quantitative insights into the effects of sugar alcohols dependent on different drug permeability. In addition, our developed model indicated for the first time that a high systemic elimination rate is crucial for the reduction in maximum plasma concentration even for highly permeable drugs. Nonetheless, mannitol/sorbitol level of less than 400 mg had minor effects on the pharmacokinetics of the most sensitive drugs, indicating a provisional no-effect threshold dose. This mechanistic approach provides comprehensive estimation of osmotic effects on variety of drugs. Subsequently, these findings may invoke scientific discussion on the criteria for excipient changes in the context of biowaiver guidelines (e.g. biopharmaceutics classification system-based biowaiver).

Structural Fingerprints of an Intact Monoclonal Antibody Acquired under Formulated Storage Conditions via 15N Direct Detection Nuclear Magnetic Resonance

Noninvasive evaluation of tertiary structures is fundamental to the research, development, and use of the biologics. However, few methodologies are currently available for evaluating large molecular weight (MW) biologics, such as therapeutic monoclonal antibodies (mAbs; 150 kDa). Here, we have newly developed a ¹⁵N direct detection nuclear magnetic resonance (NMR) technique, the ¹⁵N direct detection CRINEPT, which allows the observation of the main chain amide resonances of a nondeuterated protein with MW 150 kDa. The technique not only substantially expands the range of proteins applicable to solution NMR studies but also allows the noninvasive structural analyses of intact mAbs in a wide range of temperature and solvent conditions. As a proof of principle, we successfully acquired the ¹⁵N-detected CRINEPT spectra of an intact mAb in its formulated solution at 4 °C. The technique was able to discriminate heterogeneous galactosylation states, demonstrating the benefit of high resolution of the ¹⁵N direct detection.

Osmostress enhances activating phosphorylation of Hog1 MAP kinase by mono-phosphorylated Pbs2 MAP2K

The MAP kinase (MAPK) Hog1 is the central regulator of osmoadaptation in yeast. When cells are exposed to high osmolarity, the functionally redundant Sho1 and Sln1 osmosensors, respectively, activate the Ste11‐Pbs2‐Hog1 MAPK cascade and the Ssk2/Ssk22‐Pbs2‐Hog1 MAPK cascade. In a canonical MAPK cascade, a MAPK kinase kinase (MAP3K) activates a MAPK kinase (MAP2K) by phosphorylating two conserved Ser/Thr residues in the activation loop. Here, we report that the MAP3K Ste11 phosphorylates only one activating phosphorylation site (Thr‐518) in Pbs2, whereas the MAP3Ks Ssk2/Ssk22 can phosphorylate both Ser‐514 and Thr‐518 under optimal osmostress conditions. Mono‐phosphorylated Pbs2 cannot phosphorylate Hog1 unless the reaction between Pbs2 and Hog1 is enhanced by osmostress. The lack of the osmotic enhancement of the Pbs2‐Hog1 reaction suppresses Hog1 activation by basal MAP3K activities and prevents pheromone‐to‐Hog1 crosstalk in the absence of osmostress. We also report that the rapid‐and‐transient Hog1 activation kinetics at mildly high osmolarities and the slow and prolonged activation kinetics at severely high osmolarities are both caused by a common feedback mechanism.

Rotaxanes comprising cyclic phenylenedioxydiacetamides and secondary mono- and bis-dialkylammonium ions: effect of macrocyclic ring size on pseudorotaxane formation

[2]Rotaxanes, stabilized through multiple and cooperative hydrogen bonding system, were synthesized from dialkylammonium ions and macrocycle possessing two phenylenedioxydiacetamide units and appropriate spacers.

Significance of Granulocyte Colony-Stimulating Factor-Combined High-Dose Cytarabine, Cyclophosphamide, and Total Body Irradiation in Allogeneic Hematopoietic Cell Transplantation for Myeloid Malignant Neoplasms

Allogeneic hematopoietic cell transplant (HCT) is a curative procedure for myeloid malignant neoplasms, but relapse after HCT remains critical. A conditioning regimen involving granulocyte colony-stimulating factor-combined high-dose cytarabine, cyclophosphamide, and total body irradiation (G-CSF-combined high-dose cytarabine/cyclophosphamide/total-body irradiation [HDCA/CY/TBI]) was reported to improve outcomes after cord blood transplant (CBT) for myeloid malignant neoplasms, but this regimen was not previously evaluated among patients undergoing bone marrow transplant (BMT) or peripheral blood stem cell transplant (PBSCT).

METHODS

We retrospectively analyzed 28 patients who underwent allogeneic HCT including BMT from a related (1 patient) or unrelated donor (9 patients), PBSCT from a related donor (7 patients), or single-unit CBT from an unrelated donor (11 patients) after a G-CSF-combined HDCA/CY/TBI regimen.

RESULTS

All patients achieved neutrophil and platelet engraftment, which were significantly more rapid in the BMT/PBSCT group than in the CBT group. Eighteen patients were alive at a median follow-up of 54.3 months. The 3-year relapse and nonrelapse mortality rates were 28.6% and 7.1%, respectively, which were similar between the BMT/PBSCT and CBT groups. Overall survival and disease-free survival at 5 years after HCT were 62.6% and 64.3%, respectively, which were also similar between the BMT/PBSCT and CBT groups. Only disease status at HCT had a significant impact on overall survival and disease-free survival (86.7% with standard risk vs 38.5% with high risk and 86.7% with standard risk vs 38.5% with high risk, respectively).

CONCLUSION

A G-CSF-combined HDCA/CY/TBI regimen is a promising conditioning in patients with myeloid malignant neoplasms who undergo not only CBT but also BMT or PBSCT.

Magnetization-polarization cross-control near room temperature in hexaferrite single crystals

Mutual control of the electricity and magnetism in terms of magnetic (H) and electric (E) fields, the magnetoelectric (ME) effect, offers versatile low power consumption alternatives to current data storage, logic gate, and spintronic devices. Despite its importance, E-field control over magnetization (M) with significant magnitude was observed only at low temperatures. Here we have successfully stabilized a simultaneously ferrimagnetic and ferroelectric phase in a Y-type hexaferrite single crystal up to 450 K, and demonstrated the reversal of large non-volatile M by E field close to room temperature. Manipulation of the magnetic domains by E field is directly visualized at room temperature by using magnetic force microscopy. The present achievement provides an important step towards the application of ME multiferroics.

Mutual control of the electric polarization and magnetization promises for low power consumption spintronic devices but remains challenging. Here the authors show reversal of non-volatile magnetization by electric field as well as the polarization switching by magnetic field in a single-component material, close to room temperature.

Absolute asymmetric Strecker synthesis in a mixed aqueous medium: reliable access to enantioenriched α-aminonitrile

Without using chiral sources, the Strecker reaction of achiral hydrogen cyanide, p-tolualdehyde and benzhydrylamine gave enantioenriched l- or d-N-benzhydryl-α-(p-tolyl)glycine nitriles with up to >99% ee in a mixed solvent of water and methanol. Therefore, total spontaneous resolution of α-aminonitriles could occur through a prebiotic mechanism of α-amino acid synthesis. Moreover, it was demonstrated that the repetition of partial dissolution and crystallization of a suspended conglomerate of aminonitrile under solution-phase racemization could generate the enantiomeric imbalance to afford, in combination with the amplification of chirality, an enantioenriched product in every case. Among the 73 experiments that were carried out, d- and l-enriched isomers occurred 36 and 37 times, respectively. This stochastic behavior, under achiral or racemic starting conditions, meets the requirements of the spontaneous absolute asymmetric Strecker synthesis. The implications of the present results for the origin of chirality of α-amino acids are discussed.

Rotational isomerism of the amide units in rotaxanes based on a cyclic tetraamide and secondary ammonium ions

We describe the synthesis of [2]rotaxanes consisting of a macrocyclic tetraamide and mono- and bis-ammonium ions and their conformational isomerism.

Synthesis of a Chiral [2]Rotaxane: Induction of a Helical Structure through Double Threading

A helically chiral [2]rotaxane featuring two ammonium ion recognition sites in the dumbbell-like component and a calix-bis-crown ether as the macrocyclic component was synthesized, but with no chirality in either individual component. The enantiomeric nature of the isomers, separated through chiral HPLC, was apparent in their CD spectra, which were mirror images for all wavelengths.

Formation of [2]- and [3]Rotaxanes through Bridging under Kinetic and Thermodynamic Control

An efficient synthesis of a doubly stranded [3]rotaxane has been developed through bridging of a pseudo[3]rotaxane featuring two axle components. Reversible azine formation was effective as the bridging reaction. Kinetic and thermodynamic conditions provided the [2]- and [3]rotaxanes, respectively.

Evidence for Spin Singlet Pairing with Strong Uniaxial Anisotropy in URu_{2}Si_{2} Using Nuclear Magnetic Resonance

In order to identify the spin contribution to superconducting pairing compatible with the so-called "hidden order", ^{29}Si nuclear magnetic resonance measurements have been performed using a high-quality single crystal of URu_{2}Si_{2}. A clear reduction of the ^{29}Si Knight shift in the superconducting state has been observed under a magnetic field applied along the crystalline c axis, corresponding to the magnetic easy axis. These results provide direct evidence for the formation of spin-singlet Cooper pairs. Consequently, results indicating a very tiny change of the in-plane Knight shift reported previously demonstrate extreme uniaxial anisotropy for the spin susceptibility in the hidden order state.

Differences in Powder Properties of Two 1,4-Dihydropyridine-Type Compounds Evaluated through Thermal Analysis

The powder properties of two 1,4-dihydropyridine type compounds, manidipine dihydrochloride (Man) and benidipine hydrochloride (Ben), which possess similar physicochemical properties, were compared through thermal and mechanical analyses. Man and Ben were compressed with lactose monohydrate (Lac) and magnesium stearate (Mgst) at different compression forces. As an index, we focused on the onset temperatures of Lac dehydration during thermal analysis and plotted them against compression forces to evaluate the differences in powder properties between Man and Ben. To discuss in detail, the Lac ratio was selected as a formulation factor and compression speed as a process factor, which would be influenced to the onset temperature or its profile. It could be represented that Man was more adherent than Ben through thermal analysis by changing these critical factors, which were consistent with the results obtained through mechanical analysis.