Catalytic Enantioselective Synthesis of anti‐Vicinal Silylboronates by Conjunctive Cross‐Coupling

Chiral 1,2‐bimetallic reagents are useful motifs in synthetic chemistry. Although syn‐1,2‐bimetallic compounds can be prepared by alkene dimetallation, anti‐1,2‐bimetallics are still rare. The stereospecific 1,2‐metallate shift that occurs during conjunctive cross‐coupling is shown to enable a practical and modular approach to the catalytic synthesis of enantioenriched anti‐1,2‐borosilanes. In addition to reaction development, the synthetic utility of anti‐1,2‐borosilanes was investigated, including applications to the synthesis of anti‐1,2‐diols and anti‐1,2‐amino alcohols     

3‐O‐Sulfation of Heparan Sulfate Enhances Tau Interaction and Cellular Uptake

Prion‐like transcellular spreading of tau in Alzheimer's Disease (AD) is mediated by tau binding to cell surface heparan sulfate (HS). However, the structural determinants for tau–HS interaction are not well understood. Microarray and SPR assays of structurally defined HS oligosaccharides show that a rare 3‐O‐sulfation (3‐O‐S) of HS significantly enhances tau binding. In Hs3st1^?/? (HS 3‐O‐sulfotransferase‐1 knockout) cells, reduced 3‐O‐S levels of HS diminished both cell surface binding and internalization of tau. In a cell culture, the addition of a 3‐O‐S HS 12‐mer reduced both tau cell surface binding and cellular uptake. NMR titrations mapped 3‐O‐S binding sites to the microtubule binding repeat 2 (R2) and proline‐rich region 2 (PRR2) of tau. Tau is only the seventh protein currently known to recognize HS 3‐O‐sulfation. Our work demonstrates that this rare 3‐O‐sulfation enhances tau–HS binding and likely the transcellular spread of tau, providing a novel target for disease‐modifying treatment of AD and other tauopathies.     

Polymer Lamellae as Reaction Intermediates in the Formation of Copper Nanospheres as Evidenced by In Situ X‐ray Studies

The classical nucleation theory (CNT) is the most common theoretical framework used to explain particle formation. However, nucleation is a complex process with reaction pathways which are often not covered by the CNT. Herein, we study the formation mechanism of copper nanospheres using in situ X‐ray absorption and scattering measurements. We reveal that their nucleation involves coordination polymer lamellae as pre‐nucleation structures occupying a local minimum in the reaction energy landscape. Having learned this, we achieved a superior monodispersity for Cu nanospheres of different sizes. This report exemplifies the importance of developing a more realistic picture of the mechanism involved in the formation of inorganic nanoparticles to develop a rational approach to their synthesis.     

Portable capillary liquid chromatography for pharmaceutical and illicit drug analysis

A newly developed portable capillary liquid chromatograph was investigated for the separation of various pharmaceutical and illicit drug compounds. The system consists of two high‐pressure syringe pumps capable of delivering capillary‐scale flow rates at pressures up to 10 000 psi. Capillary liquid chromatography columns packed with sub‐2 μm particles are housed in cartridges that can be inserted into the system and easily connected through high‐pressure fluidic contact points by simply applying a specific, predetermined torque rather than using standard fittings and less precise sealing protocols. Several over‐the‐counter analgesic drug separations are demonstrated, along with a simple online measurement of tablet dissolution. Twenty illicit drug compounds were also separated across six targeted drug panels. The results described in this study demonstrate the capability of this compact liquid chromatography instrument to address several important drug‐related applications while simplifying system operation, and greatly reducing solvent usage and waste generation essential for onsite analysis.     

Planar 2‐Pyridyl‐1,2,3‐triazole Derived Metallo‐ligands: Self‐assembly with PdCl2 and Photocatalysis

Self‐assembled metallosupramolecular architectures (MSAs) with built‐in functionalities such as light‐harvesting metal centers are a promising approach for developing emergent properties within discrete molecular systems. Herein we describe the synthesis of two new but simple “click” ligands featuring a bidentate 2‐pyridyl‐1,2,3‐triazole chelate pocket linked to a monodentate pyridyl (either 3‐ or 4‐substituted, L1 and L2 ) unit. The ligands and the corresponding four Pd^IIand Pt^IImetallo‐ligands ( Pd1 , Pd2 , Pt1 and Pt2 ) were synthesized and characterized using nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI‐MS), and X‐ray crystallography. Solid‐state characterization of the series of ligands and metallo‐ligands revealed that these compounds display a co‐planar conformation of all the aryl units. The Pt^IIcontaining metallo‐ligands ( Pt1 and Pt2 ) were found to assemble into square ( Sqr ) and triangular ( Tri ) shaped architectures when combined with neutral PdCl₂ linker units. Additionally, the ability of the Pt^IImetallo‐ligands and Tri to photocatalyze the cycloaddition of singlet oxygen to anthracene was investigated.     

Collective correlations,dynamics, and behavioural inconsistencies of the cryptocurrency market over time

Nonlinear Dynamics - This paper introduces new methods to study behaviours among the 52 largest cryptocurrencies between 01-01-2019 and 30-06-2021. First, we explore evolutionary correlation...     

Demonstrating the power of extended Masing models for hysteresis through model equivalencies and numerical investigation

Nonlinear Dynamics - The extended Masing model (EMM) is a powerful model for hysteresis that is theoretically sound, physically meaningful and computationally efficient. Any such model is defined...     

Application of localized molecular orbitals to the solution of semiempirical self-consistent field equations

When conventional matrix algebra is used to solve the semiempirical self-consistent field equations for large systems, the time required rises as the third power of the size of the system. A consequence of this is that self-consistent calculations of large systems such as enzymes are impractical. By using localized molecular orbitals instead of matrix methods, the time required for these systems can be made almost proportional to the size of the system. In partial geometry optimizations, the time required depends only upon the size of the fragment being optimized and is almost independent of the size of the whole system. © 1996 John Wiley & Sons, Inc.     

Syndioselective propylene polymerizations by ansa-zirconocenium catalyst

The effect of reaction conditions, including catalyst concentration, temperature, and immobilization on support, have been investigated for syndioselective propylene polymerization by the “bare” zirconocenium ion generated from 1,1-diphenyl-methylidene(1-η⁵-cyclopentadienyl)(9-η⁵-fluorenyl)zirconium-dichloride precursor (2). Neither variation of the catalyst concentration nor immobilization of 2 on silica support affect the syndiospecificity of polymerization. The stereoregularity of the syndiotactic polypropylene, as judged from the melting transition temperature and homosteric r-pentad population by ¹³C-NMR, were found to be proportional to polymer molecular weight. These behaviors are compared with a typical isoselective catalyst ethylenebis(4,5,6,7-tetrahydroindenyl) Zr precursor (4). They are in close resemblance in the case of the S-enantiomeric complex of 4, but the racemic mixture of 4 is markedly inferior. The origins of stereo- and regio-errors are discussed. © 1996 John Wiley & Sons, Inc.     

Cyclic antiautomorphisms of directed triple systems

A transitive triple, (a,b,c), is defined to be the set {(a,b), (b,c), (a,c)} of ordered pairs. A directed triple system of order v, DTS(v), is a pair (D,β), where D is a set of v points and β is a collection of transitive triples of pairwise distinct points of D such that any ordered pair of distinct points of D is contained in precisely one transitive triple of β. An antiautomorphism of a Directed triple system, (D,β), is a permutation of D that maps β to β⁻¹, where β ⁻¹ = {(c,b,a)|(a,b,c) E β}. In this article we give necessary and sufficient conditions for the existence of a Directed triple system of order v admitting an antiautomorphism consisting of a single cycle of length d and having v − d fixed points. Further, we give a more general result for partial Directed triple systems in which the missing ordered pairs are precisely those containing two fixed points. © 1996 John Wiley & Sons, Inc.