Israel Journal of Chemistry最新文献

Conflict of interest

No conflicts to declare.

Genetically encoded peptide libraries are at the forefront of de novo drug discovery. The RaPID (Random Nonstandard Peptides Integrated Discovery) platform stands out due to the unique combination of flexible in vitro translation (FIT) and mRNA display. This enables the incorporation of non-canonical amino acids, improving chemical diversity and allowing macrocyclisation of the peptide library. The resulting constrained peptides are valued for their strong binding affinity and stability, especially in the context of protein-protein interactions. In response to SARS-CoV-2, the causative agent of the COVID-19 pandemic, the RaPID system proved valuable in identifying high-affinity ligands of viral proteins. Among many peptide ligands of SARS-CoV-2 spike and main protease (M^pro), several macrocycles stand out for their exceptional binding affinities. Structural data showcases distinct binding modes in complex with the receptor-binding domain (RBD) of the spike glycoprotein or the catalytic active site of M^pro. However, translating these in vitro findings into clinical applications remains challenging, especially due to insufficient cell permeability.

Surface characterization is essential for understanding chemical and electrochemical transformations occurring on surfaces or at interfaces. Battery electrode aging processes, biofilm growth, crystallization, and transport/signaling across cellular membranes are only a few examples of such phenomena. This special issue delves into applied electrochemistry and nonlinear optical techniques applicable to surface characterization.

Near-field techniques usually require specialized instrumentation. However, although much improvement has been made over recent years, many surface-characterization tools are still limited to samples in a vacuum; therefore, in-situ and in-operando experiments are impractical. On the other hand, optical techniques are more flexible and less demanding regarding sample handling. Still, they usually need more surface specificity and sensitivity, and in principle, they have a lower resolution compared to electron beam-based techniques.

On the other hand, optical techniques also offer different contrast modalities. For example, Second-harmonic generation (SHG) or surface-enhanced Raman spectroscopy (SERS) are versatile optical tools for probing surfaces. From symmetry considerations, SHG responses are forbidden from the bulk of metallic electrodes and observed only from the surface where the symmetry is broken. Thus, high sensitivity can be attained using SHG, and when both SHG and SERS are combined, selectivity and sensitivity can be achieved. In addition, nanofabrication of metallic surfaces can further improve the sensitivity of SHG and SERS by orders of magnitude due to local field enhancement.

In recent years, much improvement has been made in super-resolution microscopy and imaging, enabling fast yet high-resolution imaging over areas as large as half-by-half-millimeter squares. For the field of electrochemistry, such development is very important since it may open the door for real-time optical characterization of solid-liquid interfaces during charging/discharging cycles, which can potentially lead to significant improvements in the performance and durability of the electrode. These contributions not only expand the horizons of applied electrochemical science but also underline its influence on our daily lives and its pivotal role in addressing global challenges related to climate and energy.

Cucurbiturils are popular macrocyclic receptors that bind complementary guest molecules with high affinity in aqueous environments. They are recognized for their ability to selectively bind positively charged guest molecules, including ionizable ammonium cations which frequently display much higher affinity than their neutral counterparts. This selectivity for the protonated species is translated into an increase in the basicity of encapsulated guests (i. e. into complexation-induced positive pK_a shifts). However, despite being very rare, negative pK_a shifts can be observed for specific guests. Following a previous work from our group reporting slightly negative pK_a shifts for flavylium and chalcone dyes featuring N-diethylamino substituents (ΔpK_a=− 0.2), herein we report a systematic study on the complexation of N-dialkylaminochalcones with CB7. The results show that the pK_a shifts of these host-guest complexes can be rationally tuned by the nature of the N-dialkylamino groups and as well by target substitutions on the skeleton of the dye, allowing the design of a CB7 1 : 1 host-guest complex with a ΔpK_a=− 0.6.

1 Introduction

Quasicrystals exhibit long-range aperiodic order which distinguishes them from periodic crystalline materials. Since their discovery, a major research effort has been undertaken to understand their structure and properties.^{1, 2} Characterising the physical properties of atomic-scale quasicrystals poses several challenges, primarily due to the aperiodic arrangement of atoms, which complicates structure determination and requires advanced measurement techniques.³ In particular, the repertoire of quasicrystals available is limited to certain structures, such as icosahedral, decagonal, and dodecagonal systems.

Quasicrystals are grown with Czochralski, Bridgman, Floating Zone, or Self-Flux methods.^{4, 5} Growth conditions such as temperature, pressure, and composition, are carefully controlled to produce high-quality quasicrystals with desired properties. Characterising the properties of the bulk and surfaces of quasicrystals is performed with various diffraction, spectroscopic and microscopy techniques.⁶ Pseudomorphic systems of atomic overlayers on quasicrystal surfaces have also been grown.⁷ Overall, the preparation and characterisation of quasicrystals is challenging, spurring novel approaches.

Nanolithography techniques encompass artificial fabrication or manipulation of nanoscale structures to create patterns on a substrate. At the nano- to mesoscopic scale, nanolithography fabrication techniques open new possibilities for precisely engineering the size, shape, and arrangement of nanostructures, thus enabling tailored functionalities.^8-11 Quasicrystalline nanostructures have demonstrated exceptional properties with enhanced solar efficiency,^{12, 13} improved catalytic performance,¹⁴ and thermoelectric applications.^15-17

Quasiperiodic tilings model the surface of quasicrystals and have the potential to be fabricated with established nanolithography techniques.¹⁸ Broadly, there are three main nanolithography techniques described in the literature which are used to produce quasiperiodic tilings (see Table 1): scanning probe lithography (SPL), electron-beam lithography (EBL), and photolithography. In SPL a direct-write probe manipulates a substrate surface by rearranging, etching, or removing the atoms or molecules, either chemically or physically. Techniques such as thermal-scanning probe lithography (t-SPL) remove surface atoms or molecules by thermal sublimation with a heated probe.¹⁹ The resolution of SPL techniques is limited by the probe dimensions. EBL involves irradiating a surface with a focused beam of electrons through a mask covering specific areas of the substrate, or directly writing a pattern similar to SPL with e-beam resists. Resis

Introduction

The discovery of the thermally stable binary icosahedral (i) Cd−Yb¹ quasicrystal opened up a new area of research in the field of aperiodic materials. Unlike other common quasicrystals, which largely consist of three elements and are based on Al, the i-Cd−Yb quasicrystal is composed of only two elements, allowing for a complete structural determination to be made.² This material is constructed from an aperiodic array of Rhombic Triacontrahedral (RTH) clusters with adjoining glue atoms, which gives it a different structure than the Al-based quasicrystals, whose building blocks are Mackay and Bergman clusters.³

However, Cd−Yb is not suitable for surface studies under ultra-high vacuum (UHV) conditions due to the high vapor pressure of Cd. By replacing Cd with Ag and In, it has been possible to grow the isostructural Ag−In−Yb quasicrystal in a large single grain with high structural quality,⁴ enabling UHV surface studies of this phase.^5-9 It has been shown that all three high symmetry surfaces of i-Ag−In−Yb form at bulk planes that intersect the RTH cluster centers.^{5, 8, 9}

The search for aperiodic structures that possess less chemical complexity than the bulk quasicrystals has led to the discovery of novel epitaxial structures.^{10, 11} These structures include noble metal films with fivefold-twinned structure,¹⁰ magic height Bi and Ag films influenced by quantum size effects,^12-14 and quasiperiodically modulated multilayer Cu structures.^15-17 Furthermore, it has been found that the quasicrystalline structure of the substrate can be transmitted to a film of a single element. The quasicrystalline structure is not only limited to a monolayer but may extend up to a few atomic layers of the film. The observed quasicrystalline monolayers include Bi,^{18, 19} Sb,¹⁸ Sn,²⁰ and Pb^{21, 22} on various Al-based quasicrystals. A multilayer quasicrystalline structure has been observed in Pb deposited on i-Ag−In−Yb,²³ Sn deposited on i-Al−Pd−Mn²⁴ and Na on i-Al−Pd−Mn.²⁵ There has been a theoretical prediction of a quasicrystalline bilayer with a sparse second layer of alkaline metals on i-Al−Pd−Mn,²⁶ but such a structure has not been experimentally realized.

In this paper we present scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS) studies of Sb thin film growth on the fivefold i-Ag−In−Yb surface. Antimony was chosen to examine the possibility of pseudomorphic growth on i-Ag−In−Yb because of the following reason

This special issue commemorates the life and work of Prof. Richard A. Lerner. Prof. Lerner's mix of creativity, fearlessness, and unboundedness conceived and conceptualized inventions like catalytic antibodies, antibody libraries, and DNA-encoded small molecule libraries.