Molecular Environment Modulates CO Liberation from Carboxy-Biotin.

Carboxy-biotin serves as a coenzyme in certain carboxylases, exhibiting the remarkable capability to transfer a carboxy group to specific substrates. This process is made possible by the presence of biotin, a unique molecule that consists of a sulfur-containing tetrahydrothiophene ring fused to a ureido group. It is covalently attached to the enzyme via a flexible linker, allowing for its functionality.

Multicomponent synthesis and photophysical study of novel α,β-unsaturated carbonyl depsipeptides and peptoids.

Multicomponent reactions were performed to develop novel α,β-unsaturated carbonyl depsipeptides and peptoids incorporating various chromophores such as cinnamic, coumarin, and quinolines. Thus, through the Passerini and Ugi multicomponent reactions (P-3CR and U-4CR), we obtained thirteen depsipeptides and peptoids in moderate to high yield following the established protocol and fundamentally varying the electron-rich carboxylic acid as reactants. UV/Vis spectroscopy was utilized to study the photophysical properties of the newly synthesized compounds.

Comparative Study of the Removal Efficiency of Nalidixic Acid by Poly[(4-vinylbenzyl)trimethylammonium Chloride] and N-Alkylated Chitosan through the Ultrafiltration Technique and Its Approximation through Theoretical Calculations.

Emerging antibiotic contaminants in water is a global problem because bacterial strains resistant to these antibiotics arise, risking human health. This study describes the use of poly[(4-vinylbenzyl) trimethylammonium chloride] and N-alkylated chitosan, two cationic polymers with different natures and structures to remove nalidixic acid. Both contain ammonium salt as a functional group.

Formation and evolution of C-C, C-O, C[double bond, length as m-dash]O and C-N bonds in chemical reactions of prebiotic interest.

A series of prebiotic chemical reactions yielding the precursor building blocks of amino acids, proteins and carbohydrates, starting solely from HCN and water is studied here. We closely follow the formation and evolution of the pivotal C-C, C-O, C[double bond, length as m-dash]O, and C-N bonds, which dictate the chemistry of the molecules of life. In many cases, formation of these bonds is set in motion by proton transfers in which individual water molecules act as catalysts so that water atoms end up in the products.

Structural Requirements of -alpha-Mercaptoacetyl Dipeptide (NAMdP) Inhibitors of Virulence Factor LasB: 3D-QSAR, Molecular Docking, and Interaction Fingerprint Studies.

The zinc metallopeptidase elastase (LasB) is a virulence factor of (), a pathogenic bacterium that can cause nosocomial infections. The present study relates the structural analysis of 118 -alpha-mercaptoacetyl dipeptides (NAMdPs) as LasB inhibitors. Field-based 3D-QSAR and molecular docking methods were employed to describe the essential interactions between NAMdPs and LasB binding sites, and the chemical features that determine their differential activities.

Studying the phosphoryl transfer mechanism of the phosphofructokinase-2: from X-ray structure to quantum mechanics/molecular mechanics simulations.

Phosphofructokinases (Pfks) catalyze the ATP-dependent phosphorylation of fructose-6-phosphate (F6P) and they are regulated in a wide variety of organisms. Although numerous aspects of the kinetics and regulation have been characterized for Pfks, the knowledge about the mechanism of the phosphoryl transfer reaction and the transition state lags behind. In this work, we describe the X-ray crystal structure of the homodimeric Pfk-2 from , which contains products in one site and reactants in the other, as well as an additional ATP molecule in the inhibitory allosteric site adjacent to the reactants.

Understanding the nature of bonding interactions in the carbonic acid dimers.

Carbonic acid dimer, (CA), (HCO), helps to explain the existence of this acid as a stable species, different to a simple sum between carbon dioxide and water. Five distinct, well characterized types of intermolecular interactions contribute to the stabilization of the dimers, namely, C=O⋯H-O, H-O⋯H-O, C=O⋯C=O, C=O⋯O-H, and C-O⋯O-H. In many cases, the stabilizing hydrogen bonds are of at least the same strength as in the water dimer.

Insights into bonding interactions and excitation energies of 3d-4f mixed lanthanide transition metal macrocyclic complexes.

In this contribution, a computational study of equatorial bound tetranuclear macrocycle (butylene linked) [LnZn(HOM)] (Ln = La, Ce) complexes was carried out. Here, the electronic structure, bonding interaction and excitation energies were studied within the relativistic density functional theory framework. From the electronic structure analysis, the frontier molecular orbitals (FMOs) were strongly localized in the d-orbitals of the Zn centers and the f-orbitals of the lanthanide ions.

Aromatic Lateral Substituents Influence the Excitation Energies of Hexaaza Lanthanide Macrocyclic Complexes: A Wave Function Theory and Density Functional Study.

The high interest in lanthanide chemistry, and particularly in their luminescence, has been encouraged by the need of understanding the lanthanide chemical coordination and how the design of new luminescent materials can be affected by this. This work is focused on the understanding of the electronic structure, bonding nature, and optical properties of a set of lanthanide hexaaza macrocyclic complexes, which can lead to potential optical applications. Here we found that the DFT ground state of the open-shell complexes are mainly characterized by the manifold of low lying f states, having small HOMO-LUMO energy gaps.

Exploring the nature of the excitation energies in [Re6(μ3-Q8)X6](4-) clusters: a relativistic approach.

This contribution is a relativistic theoretical study to characterize systematically the main electronic transitions in a series of hexarhenium chalcogenide [Re6(μ3-Q8)X6](4-) clusters with the aim of understanding: (i) the terminal ligand substitution effect, (ii) the substitution effect of the chalcogenide ion on the [Re6(μ3-Q8)](2+)core, and finally (iii) the significance of the spin-orbit coupling (SOC) effect on the optical selection rules. In all the cases, we found characteristic bands at around 300-550 nm, where the band positions are directly determined by the terminal ligand. However, SCN(-)/NCS(-) presents a different nature of the orbitals involved in the electronic transitions, in comparison with the other studied terminal ligands, located in the near-infrared (NIR) region.

Understanding the influence of terminal ligands on the electronic structure and bonding nature in [Re6(μ3-Q8)](2+) clusters.

Since the synthesis of the first molecular cluster [Re6(μ3-Q8)X6](4-), the substitutional lability of the terminal ligands prompted new developments in their chemistry, making these molecular clusters a reasonable point of departure for building new materials. The development of novel inorganic materials of technological interest certainly requires an understanding of the electronic structure, bonding, spectroscopy, photophysical and structural properties of these clusters. Taking into account the potential applications in material sciences and the lack of systematization in the study of these kinds of clusters, the proposal of the present work is to perform a detailed theoretical study of the [Re6(μ3-Q8)X6](4-) (Q = S(2-), Se(2-), Te(2-); X = F(-), Cl(-), Br(-), I(-), CN(-), NC(-), SCN(-), NCS(-), OCN(-), NCO(-)) clusters based on the detailed description of the electronic structure of these complexes and the bonding nature between the [Re6(μ3-Q8)](2+) core and several donor-acceptor peripheral ligands.

Electron transfer from the benzophenone triplet excited state directs the photochemical synthesis of gold nanoparticles.

The rarely recognized electron donating ability of the benzophenone triplet excited state provides an unusual route for the photochemical synthesis of gold nanoparticles.

Antenna effect by organometallic chromophores in bimetallic d-f complexes.

The nature of the intermetallic bond in a series of complexes of the type [Cp2-TM-M-Cp2] (where TM = Re and M = Y, La, Lu, Yb, Ac; also TM = Os and M = Th; Cp = cyclopentadienyl ligand) have been studied by relativistic two-component density functional theory (DFT) calculations. The results obtained in this work show that the interaction between the transition metal and lanthanide atoms is mainly ionic in all cases, while for the case of actinide atoms this interaction becomes significantly more covalent. The effective direction of the electron transfer between the Re→Ac or Os→Th centers allows us to propose that the [Cp2ReAcCp2] and [Cp2OsThCp2] complexes are ideal candidates for near-infrared (NIR) technologies since their absorption spectra show some transitions over 600 nm.

Bonding nature and electron delocalization of An(COT)2, An = Th, Pa, U.

A systematic study of a series of An(COT)(2) compounds, where An = Th, Pa, U, and COT represents cyclooctatetraene, has been performed using relativistic density functional theory. The ZORA Hamiltonian was applied for the inclusion of relativistic effects, taking into account all of the electrons for the optimization and explicitly including spin-orbit coupling effects. Time-dependent density functional theory (TDDFT) was used to calculate the excitation energies with the GGA SAOP functional, and the electronic transitions were analyzed using double group irreducible representations.