Aminopeptidases selectively hydrolyze an aminoacid residue from the amino terminus of proteins and peptides resulting in their activation or inactivation. These enzymes are mainly metallo and belong, among other, to the M1 family of peptidases. One of its members, membrane glutamyl aminopeptidase (APA, EC 3.4.11.7) participates in many physiological processes, such as peptide metabolism related with blood pressure control, and last step of protein degradation. Furthermore, the up regulation of APA has been implicated in the pathogenesis of various human disorders like cancers, hypertension and glomerulosclerosis. APA is thus a target for the development of inhibitors with potential biomedical applications. We review the most important structural and functional characteristics of mammalian APA, focusing on the most recent data. Additionally, we integrate the roles of APA in physio- and pathophysio-logical processes of biomedical relevance with the development of specific APA inhibitors.

Cyclopropanes that carry an electron-accepting group react as electrophiles in polar, ring-opening reactions. Analogous reactions at cyclopropanes with additional C2 substituents allow one to access difunctionalized products. Consequently, functionalized cyclopropanes are frequently used building blocks in organic synthesis. The polarization of the C1–C2 bond in 1-acceptor-2-donor-substituted cyclopropanes not only favorably enhances reactivity toward nucleophiles but also directs the nucleophilic attack toward the already substituted C2 position. Monitoring the kinetics of non-catalytic ring-opening reactions with a series of thiophenolates and other strong nucleophiles, such as azide ions, in DMSO provided the inherent SN2 reactivity of electrophilic cyclopropanes. The experimentally determined second-order rate constants k 2 for cyclopropane ring-opening reactions were then compared to those of related Michael additions. Interestingly, cyclopropanes with aryl substituents at the C2 position reacted faster than their unsubstituted analogues. Variation of the electronic properties of the aryl groups at C2 gave rise to parabolic Hammett relationships.

Multiphoton absorption and multiple excitation can lead to the formation of highly electronically excited states of molecules. We have been applying these excitation methods to explore specific photochemical reactions, which are rather difficult to attain by normal one-photon absorption processes. In the present review, we will introduce several examples of these photochemical responses specific to highly excited state in the condensed phase, such as two-photon-gated cycloreversion, one-color control of both reactions in photochromic systems and rapid capture of an electron ejected from the higher excited state leading to rapid generation of charge-separated states at the high energy level with a lifetime much longer than microseconds.

Octaphosphonate biscavitand and self-folding deep biscavitand show strong positive and negative cooperativity, respectively. The mechanism of the cooperativity is discussed in terms of thermodynamic parameters and the detailed structure of the host-guest complexes. The two cavitand units of both biscavitands are tightly connected via four butylene linkers; thus, they are conformationally coupled, with the first guest binding information transferred to the resting-state cavities. This preorganization modulates the successive guest binding process in strong positive and negative cooperative manners, even though they display structural similarity. The first guest complexation always preorganizes the resting-state cavities where an existing water cluster and a toluene molecule are enthalpically stabilized. Successive guest complexation competes with the water cluster or a toluene molecule, reducing enthalpy gains. However, the desolvation upon successive guest binding processes liberate the solvents within the resting-state cavities. The water cluster is composed of 12 water molecules that are released upon successive guest complexation, resulting in a large entropy benefit. In contrast, toluene desolvation results in a limited entropy benefit. The difference in entropy benefits directs the strong positive or negative cooperativity of the structurally similar biscavitands.

Hydrocarbons with open-shell singlet and triplet ground states have long been studied. In contrast to studies of Kekulé hydrocarbons with an open-shell singlet ground state, studies of non-Kekulé and Kekulé hydrocarbons with a triplet ground state are quite limited, and no hydrocarbon with a triplet ground state has been isolated as single crystals. In this review, our work on the synthesis, isolation, and properties of m-quinodimethane-based non-Kekulé polycyclic hydrocarbon, a kinetically stabilized triangulene derivative, and Kekulé polycyclic hydrocarbon, a kinetically stabilized bisdibenzo[3,4:5,6]cyclohepta[1,2-a:2,1-d]benzene derivative, are described. Triplet ground states of these hydrocarbons were experimentally confirmed by ESR and magnetic measurements, and these are the first example of polycyclic hydrocarbons with a triplet ground state whose structures were characterized by X-ray crystal structural analysis. These studies will enable the development of various polycyclic hydrocarbon multi-radicals with high spin multiplicity.

Lithium-ion batteries are attractive for their use in portable electronics and electric vehicles owing to their high energy and power density. Organic materials as active materials for the positive electrode have attracted attention as an alternative to inorganic materials in sustainable batteries. However, there is a serious drawback that elution into the electrolyte solution. This article describes our attempts in the development of tetrathiafulvalene (TTF) analogs for active materials. We have developed four types of fused TTF systems; multifused TTF systems, TTF analogs extended with cyclohexene moieties, TTF analogs extended with an anthraquinoid spacer, and fused TTF and benzoquinone systems. These molecules were designed based on the idea that increasing the size and planarity of the molecules and intermolecular interactions. They were successfully synthesized and their cell performances were clarified. We also describe that a TTF analog bearing triphenylamines was applied to long-cycle-life electrodes as a recent effort. This molecule was successfully synthesized using palladium-catalyzed C-H arylation and the cycle life of the cells comprising this molecule was markedly improved by in-cell electropolymerization.

X-ray crystallography and X-ray spectroscopy using X-ray free electron lasers plays an important role in understanding the interplay of structural changes in the protein and the chemical changes at the metal active site of metalloenzymes through their catalytic cycles. As a part of such an effort, we report here our recent development of methods for X-ray absorption spectroscopy (XAS) at XFELs to study dilute biological samples, available in limited volumes. Our prime target is Photosystem II (PS II), a multi subunit membrane protein complex, that catalyzes the light-driven water oxidation reaction at the Mn4CaO5 cluster. This is an ideal system to investigate how to control multi-electron/proton chemistry, using the flexibility of metal redox states, in coordination with the protein and the water network. We describe the method that we have developed to collect XAS data using PS II samples with a Mn concentration of <1 mM, using a drop-on-demand sample delivery method.

Caged compounds, also called phototriggers are formed by a photo-removable protecting group attached to a molecule of interest, hindering its potential interactions or reaction partners. A particular chemical bond is broken when the phototrigger absorbs light of a given wavelength, yielding a non-interacting “cage” and a free interacting molecule. Numerous organic based caged compounds have been devised, and many of them have broad applications, usually in physiology research. The tunability of these phototriggers is scarce, and the common strategy consists in changing the photoremovable group. Conversely, ruthenium-polypyridine caged compounds are built around a Ru center that can accommodate six coordinated molecules or groups including the photo-releasable molecule. The design of the coordination sphere yields many ways to achieve a desired property, or modulate a property, such as hydrophilicity, redox potential, absorption, 2P capabilities, action cross section, etc. In this work we will show how the tuning of quantum yield of photorelease, absorption wavelength and thermal stability is feasible, and discuss the rationale and the limits of the ligand-tuning technique.

The paper studies thermal characteristics of new polycarbonates obtained using the bisphenol A-free technology. Thermal tests of polycarbonates were carried out in a wide temperature range using the DSC (diffrential scanning calorimetry) and TG (thermogravimetry) analyses. The DSC data confirmed that all materials are homogeneous whereas the endothermic peaks are responsible for melting. Additionally, the analysis of the released gases was made by means of the infrared spectroscopic analysis. Our research proved that the new polycarbonates are relatively heat resistant. In the range of the thermal destruction of the studied materials there can be considered, two types of degradation reactions. The first step around 200 °C and the second one around 300 °C. Gel permeation chromatography were performed to determined molar masses of polymers. XRD analysis showed that the obtained polycarbonates showed a partially crystalline structure.

Textural properties of the solid sorbents are critical to tuning their CO2 capture performance. In this work, we studied the effect of fiber density (in turn, pore size, distribution, and accessibility) on CO2 capture capacity and kinetics. CO2 solid sorbents were prepared by physisorption of tetraethylenepentamine (TEPA) molecules on dendritic fibrous nanosilica (DFNS) with varying fiber density. Among the various DFNS, the DFNS with moderate fiber density [DFNS-3] showed the best CO2 capture capacity under the flue gas condition. The maximum CO2 capture capacity achieved was 24.3 wt % (5.53 mmol/g) at 75 °C for DFNS-3 under humid gas conditions. Fiber density also played a role in the kinetics of CO2 capture. DFNS-1 with dense fiber density needed ∼10.4 min to reach 90 % capture capacity, while DFNS-3 (moderate fiber density) needed only 6.4 min, which further decreased to 5.9 min for DFNS-5 with lightly dense fibers. The DFNS-impregnated TEPA also showed good recyclability during 21 adsorption and desorption cycles under humid and dry conditions. The total CO2 capture capacity of DFNS-3 (14.7) in 21 cycles was 108.9 and 105.0 mmol/g under humid and dry conditions, respectively. Adsorption lifetime calculation and recyclability confirmed the fiber density-dependent CO2 capture performance.

Supramolecular gels are generally formed by the self-assembly of organic molecules called low-molecular-weight gelators. However, supramolecular gels can also be formed with the assistance of metal ions. These organic-inorganic hybrids are key for creating highly functional materials. Unique properties and functions that cannot be obtained from organic molecules alone are observed in the metal ion containing supramolecular gels. In this study, several examples of supramolecular gels formed with the assistance of metal ions, cholesterol derivatives, amino acids and peptides, nucleic acid derivatives, oxalic acid, and C 3-symmetric tris-urea derivatives are introduced. This provides an overview of existing supramolecular gels to better understand the scope for possible future research for their practical applications.

Atom transfer radical polymerization (ATRP) is a versatile & famous technique for the synthesis of well defined molecular architectures. In ATRP, there is a dynamic equilibrium exists between active & dormant species. Therefore, ATRP progress through a sequence of activation & deactivation cycles, ending upon complete monomer consumption & termination reactions are minimized. This paper presents a systematic computational study on kinetics & thermodynamics associates in the ATRP of itaconimide monomers & methyl methacrylate (MMA). For this, the copolymerization system is modeled as a unimer, dimer & trimer of various itaconimides & MMA monomer. The density functional theory with B3LYP functional & 6–31 + G(d)/LanL2DZ basis sets is used in the prediction of geometries & energetics associated with the dissociation of terminal R–X bond present in the unimer, dimer & trimer. The relative equilibrium constant (K ATRP) for the ATRP activation/deactivation steps is calculated from the free energy values associated with dissociation of R–X bond. The relative K ATRP values of dimer & trimer of selected monomers is compared with their respective unimer. From the transition state geometries of the dimeric propagating radical, activation energy is calculated. The gas phase rate coefficients for propagation (k p) (of itaconimides & MMA copolymerization) are calculated using the standard transition state theory. The effect of system parameters such as solvent, temperature & substituent on K ATRP & k p values of dimer is investigated systematically. The change in the initiating system & temperature has significant effect on k p values as compared to solvent & various substituent. The K ATRP values of dimer & trimer dormant species are higher as compared to their respective monomeric species. The neighboring monomer & penultimate monomer plays vital role in kinetics & thermodynamics associated with copolymerization. The obtained initial results show that the mechanism of copolymerization of itaconimide monomers & MMA follows penultimate model.

Solid-state NMR methods incorporating dynamics-based spectral editing have a remarkable versatility for resolving and separately characterizing co-existing solid and liquid phases or domains in biologically and technically relevant organic materials. While 13C spectra acquired under magic-angle spinning and 1H decoupling provide atomic resolution, the signal intensities obtained with the CP and INEPT polarization transfer techniques give qualitative information about dynamics. This mini-review covers the basics of translational and rotational motion of atoms and molecules in organic materials, theoretical aspects of the relations between C–H bond reorientation and CP and INEPT signal intensities, and applications of the methods to a broad range of heterogeneous materials comprising hydrated assemblies of surfactants, lipids, proteins, and/or carbohydrates.

Multiple factors influence chemical process design and technology selection, including technical, economic, environmental, and safety considerations. Traditionally, a techno-economic analysis has been used to select a base case design, while safety and environmental impact have been subsequently assessed. This may leave out designs that exhibit better environmental and safety performance than the selected base case at a very early stage of design, where abundant opportunities for incorporating these objectives are present. Furthermore, although safety is an integral part of the overall sustainability of a chemical plant, historically it has been addressed separately from sustainability. Thus, there is a growing awareness for simultaneous consideration of these objectives during the conceptual process design phase of a project in order to select the most sustainable process route. The key to an effective sustainability assessment method for selecting the most sustainable process route involves the parsimonious selection of adequate metrics which define the sustainability profile of the process and an integrated multi-criteria decision-making (MCDM) framework. In this context, this work investigates gaps in conceptual process design and existing sustainability assessment methods through a review of existing environmental impact and safety assessment methodologies/tools. A possible workflow that incorporates both safety and environmental impact in a holistic multi-criterion decision-making framework (MCDM) has been proposed to select the most sustainable process route. The use of this framework is illustrated through a simple case study involving assessing solvent alternatives for palm oil recovery to highlight the scope and significance of the proposed framework.

Periodicity of elements is the basis of teaching and understanding inorganic chemistry. This review exemplifies simple rules and counting procedures as heuristic algorithms yielding often-dimensionless quantities that, as such or together with auxiliary parameters, allow us to predict not only the stoichiometry and bonding of compounds, but also some of their properties or reactions.

We have investigated an approach for obtaining 1H NMR spectra of different alcohols on a large-bore (27 cm diameter), B 0 = 0.05 T (f 0 = 2 MHz) portable MRI scanner. We used a Carr–Purcell–Meiboom–Gill (CPMG) sequence to acquire multiecho data from solutions of different alcohols, focusing on ethanol, a molecule of relevance to many applications in the food and beverage industry. Our results show that the Fourier transformed J-spectra at different echo spacings fit well with simulations of the evolution of the echo train signal with excellent signal to noise ratio (SNR) for concentrations of ∼10 % within a few minutes. Spectra were also obtained from intact bottles of whiskey and wine. Finally, we show that different alcohols with similar chemical structures can be differentiated using this approach.

Dynamic helical molecules, which can undergo a reversible chirality inversion between the P and M forms, are useful as a platform for switchable chiral functional molecules. The chirality inversion of these molecules has been extensively studied. However, it has mostly been discussed from the viewpoint of the equilibrated P/M ratios before and after the inversion; control of the response speeds or kinetic profiles has rarely been explored. In order to construct helical structures with controllable kinetic profiles, triple-helical metallocryptands, LM3, have been designed and synthesized. These molecules can undergo a relatively slow dynamic P/M chirality inversion (helicity inversion) to produce an equilibrated mixture. The P/M equilibration was accelerated or decelerated based on the following two strategies. One is based on the guest binding in the cryptand cavity. The P/M racemization kinetics of LNi3 was significantly decelerated by recognition of guanidinium ion in the cavity. The other strategy is based on the ligand exchange reactions at the octahedral cobalt(III) centers in LCo3(amine)6. The P/M chirality inversion speeds were controlled by changing the initial and entering amine ligands. In addition, a unique transient chirality inversion behavior was observed when chiral amine ligands were removed from the metallocryptand by the ligand exchange reaction with piperidine.

Bis-periazulene (cyclohepta[def]fluorene) is one of the seven possible non-alternant isomers of pyrene. Different from the other isomers, bis-periazulene had remained an uncharacterized hydrocarbon until 2022, since it was first reported in 1955. This paper documents our recent achievements in synthesizing and characterizing bis-periazulene derivatives. Its triaryl derivatives 5c‒e exhibited the superimposed electronic structures of peripheral, polarized, and open-shell π-conjugated systems. Furthermore, in contrast to previous theoretical predictions, bis-periazulene derivatives showed the singlet ground state.

Lipids in the Ready-to-use Therapeutic Food (RUTF) comprise various types of triglycerides such as palmitic, oleic and linoleic acids. Dynamic studies of the dielectric properties such as impedance, permittivity and loss tangent of the triglycerides at different temperatures ranging from 25 to −30 °C and frequencies from 10−2 Hz to 5 × 106 Hz were performed by electrochemical impedance spectroscopy (EIS). The outcomes of EIS were associated together with the analysis of Fourier-transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) in order to analyse the dielectric signals obtained. As expected, FTIR results suggest the presence of saturated and unsaturated triglycerides of the palmitic, oleic and linoleic acids. Besides, there are absorbance bands of functional groups that reflect the presence of proteins. The dielectric relaxation and dielectric constant were evaluated from the impedance and permittivity spectra, respectively. The results imply the RUTF possesses long-range motion of dipoles against lower temperatures. The phase transitions observed in RUTF as indicated by the DSC cooling curve (crystallization), lead to the shifting of dielectric properties in impedance and permittivity.

We have disclosed that 3,5-dimethyl-4-(2′-phenylethynylphenyl)phenyl (EPP) glycosides could be employed as glycosylation donors via an unprecedented activation mechanism. Here we report that the EPP glycosides without the 3,5-dimethyl groups, which were previously installed to prevent the plausible Friedel-Crafts-type side reactions, can also undergo glycosylation effectively. Employing such an EPP 2-azidoglucoside as donor, the construction of the challenging α-GlcN-(1→4)-GlcA linkage is realized, leading to a heparin trisaccharides precursor.