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The all-trans and all-cis polyenes homodisubstituted at the ends were calculated at the B3LYP/6-31G** level. The disubstitution gives rise to three end-types of the conformers: trans-trans, trans-cis, and cis-cis, denoted as EE, EZ, and ZZ. The symmetry of the EE or ZZ all-cis isomers depended on the double bond parity. Twelve substituents used: H, BeH, BH2, BF2, Br, CH3, Cl, CN, F, NH2, NO2, OH, and SiH3 were chosen to exhibit different σ- and π-electron donating and electron withdrawing properties. For polyenes composed up to ca. 20 C-atoms, the π-electron donating and withdrawing character of the end groups matters and differently acting substituents play significantly different roles. Unexpectedly, the intramolecular interactions between the substituents and the neighboring chain CH groups near appeared more decisive for the compound's stability than the substituent electron donating/withdrawing properties. The substituent-chain interplay was consonant in the all-trans and all-cis polyenes. Still, they were always more destabilizing in the latter than in all-trans isomers. [ABSTRACT FROM AUTHOR]

GRB2, or Growth Factor Receptor-Bound Protein 2, is a pivotal adaptor protein in intracellular signal transduction pathways, particularly within receptor tyrosine kinase (RTK) signaling cascades. Its crystal structure reveals a modular architecture comprising a single Src homology 2 (SH2) domain flanked by two Src homology 3 (SH3) domains, facilitating dynamic interactions critical for cellular signaling. While SH2 domains recognize phosphorylated tyrosines, SH3 domains bind proline-rich sequences, enabling GRB2 to engage with various downstream effectors. Folding and binding studies of GRB2 in its full-length form and isolated domains highlight a complex interplay between its protein-protein interaction domains on the folding energy landscape and in driving its function. Being at the crosslink of many key molecular pathways in the cell, GRB2 possesses a role in cancer pathogenesis, particularly in mediating the Ras–mitogen activated protein kinase (MAPK) pathway. Thus, pharmacological targeting of GRB2 domains is a promising field in cancer therapy, with efforts focused on disrupting protein-protein interactions. However, the dynamic interplay driving GRB2 function suggests the presence of allosteric sites at the interface between domains that could be targeted to modulate the binding properties of its constituent domains. We propose that the analysis of GRB2 proteins from other species may provide additional insights to make the allosteric pharmacological targeting of GRB2 a more feasible strategy.

The self-association of therapeutic antibodies can result in elevated viscosity and create problems in manufacturing and formulation, as well as limit delivery by subcutaneous injection. The high concentration viscosity of some antibodies has been reduced by variable domain mutations or by the addition of formulation excipients. In contrast, the impact of Fc mutations on antibody viscosity has been minimally explored. Here, we studied the effect of a panel of common and clinically validated Fc mutations on the viscosity of two closely related humanized IgG1, κ antibodies, omalizumab (anti-IgE) and trastuzumab (anti-HER2). Data presented here suggest that both Fab-Fab and Fab-Fc interactions contribute to the high viscosity of omalizumab, in a four-contact model of self-association. Most strikingly, the high viscosity of omalizumab (176 cP) was reduced 10.7- and 2.2-fold by Fc modifications for half-life extension (M252Y:S254T:T256E) and aglycosylation (N297G), respectively. Related single mutations (S254T and T256E) each reduced the viscosity of omalizumab by ~6-fold. An alternative half-life extension Fc mutant (M428L:N434S) had the opposite effect in increasing the viscosity of omalizumab by 1.5-fold. The low viscosity of trastuzumab (8.6 cP) was unchanged or increased by [Formula: see text]2-fold by the different Fc variants. Molecular dynamics simulations provided mechanistic insight into the impact of Fc mutations in modulating electrostatic and hydrophobic surface properties as well as conformational stability of the Fc. This study demonstrates that high viscosity of some IgG1 antibodies can be mitigated by Fc mutations, and thereby offers an additional tool to help design future antibody therapeutics potentially suitable for subcutaneous delivery.

We present a computational strategy based on thermodynamic cycles to predict and describe the chemical equilibrium between the 3d-transition metal ions Zn2+, Cu2+, and VO2+ and the widely used antineoplastic drug doxorubicin. Our method involves benchmarking a theoretical protocol to compute gas-phase quantities using DLPNO Coupled-Cluster calculations as reference, followed by estimating solvation contributions to the reaction Gibbs free energies using both explicit partial (micro)solvation steps for charged solutes and neutral coordination complexes, as well as a continuum solvation procedure for all solutes involved in the complexation process. We rationalized the stability of these doxorubicin-metal complexes by inspecting quantities obtained from the topology of their electron densities, particularly the bond critical points and non-covalent interaction index. Our approach allowed us to identify representative species in solution phase, infer the most likely complexation process for each case, and identify key intramolecular interactions involved in the stability of these compounds. To the best of our knowledge, this is the first study reporting thermodynamic constants for the complexation of doxorubicin with transition metal ions. Unlike other methods, our procedure is computationally affordable for medium-sized systems and provides valuable insights even with limited experimental data. Furthermore, it can be extended to describe the complexation process between 3d-transition metal ions and other bioactive ligands. [ABSTRACT FROM AUTHOR]

Operation lifetime, as an important parameter, determines the performance of phosphorescent organic light-emitting diodes (OLEDs). Unveiling the intrinsic degradation mechanism of emission material is crucial for improving the operation's lifetime. In this article, the photo-stabilities of tetradentate transition metal complexes, the popular phosphorescent materials, are explored by means of density functional theory (DFT) and time-dependent (TD)-DFT, aiming to illustrate the geometric signatures as important factors to control the photo-stabilities. Results indicate that for the tetradentate Ni(II), Pd(II), and Pt(II) complexes, the coordinate bonds of the Pt(II) complex exhibit stronger strength. It seems that the strengths of coordinate bonds are closely related to the atomic number of the metal center in the same group, which could be attributed to the various electron configurations. The effect of intramolecular and intermolecular interactions on ligand dissociation is also explored here. The large intramolecular steric hindrance and strong π-π interaction between the Pd(II) complexes caused by aggregation could effectively raise the energy barriers of the dissociation reaction, leading to an unfeasible reaction pathway. Moreover, the aggregation of Pd(II) complex can change the photo-deactivation mechanism as compared to that of monomeric Pd(II) complex, which is favored for avoiding the TTA (triplet-triplet annihilation) process. [ABSTRACT FROM AUTHOR]

Context: Dopamine (DA) is one of the most important neurotransmitters associated with numerous neural disorders. This investigation reports the intramolecular interactions present in the isomers of neutral (DA0), anionic (DA−), and cationic (DA+) dopamine isomers in gas, water, and ethanol mediums. Neutral and anion isomers have O-H∙∙∙O, C-H∙∙∙N intramolecular hydrogen bonds and N-H∙∙∙π interactions. All the interactions are electrostatic in nature. Isomers of cation dopamine show no intramolecular interactions in the solvent. Natural charges from natural bond orbital (NBO) analysis show that O-H∙∙∙O bonds and the N-H∙∙∙π interactions are the most and least polar, respectively. 1H NMR study reveals the inverse linear correlation between shielding constant and electron density in a solvent medium. HOMO-LUMO energy gap indicates higher stability for neutral and cationic forms of dopamine isomers in water and ethanol medium. Methods: We have optimized all the structural forms of dopamine molecule using the Becke three hybrid exchange and Lee-Yang-Parr correlation functional with Grimme's dispersion correction, B3LYP-D3(BJ), and aug-cc-pVTZ basis set using the Gaussian16 software. Vibrational frequency analysis with no imaginary frequencies confirms the nature of global minima. The solvent studies (water and ethanol) were carried out using the SCRF keyword and the polarisable continuum model (PCM) of Miertus and Tomasi. NBO analysis and NMR studies were also performed for all conformers. Topology analysis was explored using the software Multiwfn. [ABSTRACT FROM AUTHOR]

Operation lifetime, as an important parameter, determines the performance of phosphorescent organic light-emitting diodes (OLEDs). Unveiling the intrinsic degradation mechanism of emission material is crucial for improving the operation’s lifetime. In this article, the photo-stabilities of tetradentate transition metal complexes, the popular phosphorescent materials, are explored by means of density functional theory (DFT) and time-dependent (TD)-DFT, aiming to illustrate the geometric signatures as important factors to control the photo-stabilities. Results indicate that for the tetradentate Ni(II), Pd(II), and Pt(II) complexes, the coordinate bonds of the Pt(II) complex exhibit stronger strength. It seems that the strengths of coordinate bonds are closely related to the atomic number of the metal center in the same group, which could be attributed to the various electron configurations. The effect of intramolecular and intermolecular interactions on ligand dissociation is also explored here. The large intramolecular steric hindrance and strong π-π interaction between the Pd(II) complexes caused by aggregation could effectively raise the energy barriers of the dissociation reaction, leading to an unfeasible reaction pathway. Moreover, the aggregation of Pd(II) complex can change the photo-deactivation mechanism as compared to that of monomeric Pd(II) complex, which is favored for avoiding the TTA (triplet-triplet annihilation) process.

Baculoviruses initiate oral infection in the highly alkaline midgut of insects via a group of envelope proteins called per os infectivity factors (PIFs). To date, no high-resolution structural information has been reported for any PIF. Here, we present the crystal structure of the PIF5 ectodomain (PIF5e) from Autographa californica multiple nucleopolyhedrovirus (AcMNPV) at a 2.2-Å resolution. It revealed an open cavity between the N-terminal E1 domain and the C-terminal E2 domain and a cysteine-rich region with three pairs of disulfide bonds in the E2 domain. Multiple conserved intramolecular interactions within PIF5 are essential for maintaining its tertiary structure. Two conserved arginines (Arg8 and Arg74) play critical roles in E1-E2 interactions, and mutagenesis analysis supported their crucial role in oral infection. Importantly, the reduction in the oral infectivity of the Arg8, Arg74, or cysteine mutant viruses was related to the proteolytic cleavage of PIF5 by the endogenous protease embedded in occlusion bodies during alkaline treatment. This suggested that the structural stability of PIF5 under physiological conditions in the insect midgut is critical for baculoviral oral infectivity. IMPORTANCE Per os infection mediated by PIFs is the highly complex mechanism by which baculoviruses initiate infection in insects. Previous studies revealed that multiple PIF proteins form a large PIF complex on the envelope of virions, while PIF5 functions independently of the PIF complex. Here, we report the crystal structure of AcMNPV PIF5e, which, to our knowledge, is the first atomic structure reported for a PIF protein. The structure revealed the precise locations of three previously proposed disulfide bonds and other conserved intramolecular interactions, which are important for the structural stability of PIF5 and are also essential for oral infectivity. These findings advance our understanding of the molecular mechanism of baculovirus oral infection under alkaline conditions. [ABSTRACT FROM AUTHOR]

The energy and electronic parameters of the nitrogen atom inversion in isoelectronic Nalkylimines and N-sulfenylimines (H2C=NR, where R=Me, Et, SH, SMe) have been calculated using DFT method (B3LYP/6-311+G(d,p)) in terms of NBO. It has been established that substitution of methylene group by sulfur atom does not lead to the decrease in the inversion barriers due to the ... interactions, since total energies of the ..., ... and ... interactions in the N-sulfenylimines and of the ..., ... interactions in the N-alkylimines are almost equal. The interactions of the nitrogen lone pair with the Rydberg orbitals of the sulfur atom (...) promote the reduction of the inversion barriers of the N-sulfenylimines (by 28--33 kJ·mol-1) in comparison with the N-alkylimines. However, analysis of the total energies of all donor-acceptor and repulsive interactions between the nitrogen lone pair and the orbitals of neighboring atoms and bonds showed that they promote the increase in the inversion barriers of the N-sulfenylimines by 0.8--14.3 kJ·mol-1. The ... and ... interactions are the main factor that determines the decrease in the inversion barriers of the N-sulfenylimines relative to the N-alkylimines. These interactions, taking into account the corresponding interactions in the N-alkylimines, contribute to the barriers decrease of 64.5--71.7 kJ·mol-1. [ABSTRACT FROM AUTHOR]

The computational designing of the Li 4 N and Li 4 O as efficient dopants for Al 10 N 10 nanocage has been carried out in the present study for the applications of high-performance Nonlinear Optical materials. The density functional theory was employed with UBVP86-6-311G(++d,p)def2D2V set of functions for studying the enhanced structural, electronic, and optical properties of Al 10 N 10 nanocage after the exohedral substitution of Li 4 N and Li 4 O. The density of state calculations reveals the formation of a new high energy highest occupied molecular orbital in the combined structure of superalkali and nanocage. This seems to result in a major decrement in the band gap of the complex structure Al 10 N 10 +Li 4 N (0.878eV) and Al 10 N 10 +Li 4 O (0.872eV). The charge transfer from the metal structure towards the nanocage was supported by the natural bond orbital charges. The doping of superalkali gave an intensified value of dipole moment from 1.53 Debye (nanocage) to 10.27 and 14.93 Debye for Al 10 N 10 +Li 4 N and Al 10 N 10 +Li 4 O respectively. This supported the high electronegativities and high intramolecular charge transfer for these complexes. The vibrational spectra reveal the high-intensity modes for stretching the interconnecting bonds between the nanocage and metal structure. The first-order hyperpolarizability for nanocages was remarkably enhanced after superalkali doping. The first-order hyperpolarizability for Al 10 N 10 +Li 4 N and Al 10 N 10 +Li 4 O were computed as 173.13 × 10−30 and 172.45 × 10−30 esu respectively. Thus, the present investigation can be the basis for the experimental fabrication of highly efficient NLO materials and will attract the scientific community to design high-performance NLO materials with exceptional features for widespread applications in optoelectronics. [Display omitted] • NLO activity of super alkali-doped Al 10 N 10 nanocages is theoretically studied for the first time. • Exohedral substitution of Li 4 N and Li 4 O are investigated for electronic and NLO properties. • Decrement in the band gap was observed after the introduction of super alkali to nanocage. • Polarizability and hyperpolarizability values of Al 10 N 10 +Li 3 N are significantly high. [ABSTRACT FROM AUTHOR]

Hyperthermostable enzymes are highly desirable biocatalysts due to their exceptional stability at extreme temperatures. Recently, a hyperthermostable carboxylesterase EstD9 from Anoxybacillus geothermalis D9 was biochemically characterized. The enzyme exhibited remarkable stability at high temperature. In this study, we attempted to probe the conformational adaptability of EstD9 under extreme conditions via in silico approaches. Circular dichroism revealed that EstD9 generated new β-sheets at 80 °C, making the core of the hydrolase fold more stable. Interestingly, the profiles of molecular dynamics simulation showed the lowest scores of radius of gyration and solvent accessible surface area (SASA) at 80 °C. Three loops were responsible for protecting the catalytic site, which resided at the interface between the large and cap domains. To further investigate the structural adaptation in extreme conditions, the intramolecular interactions of the native structure were investigated. EstD9 revealed 18 hydrogen bond networks, 7 salt bridges, and 9 hydrophobic clusters, which is higher than the previously reported thermostable Est30. Collectively, the analysis indicates that intramolecular interactions and structural dynamics play distinct roles in preserving the overall EstD9 structure at elevated temperatures. This work is relevant to both fundamental and applied research involving protein engineering of industrial thermostable enzymes. [Display omitted] • Circular dichroism and fluorescence spectroscopy analysis revealed that EstD9 was relatively stable at high temperatures • High flexibility of loops and rigidity of the large domain and cap region assist in EstD9 thermal stabilization • In silico investigation confirmed that structural dynamics, flexibility, and intramolecular interactions were crucial for EstD9 stability and functionality [ABSTRACT FROM AUTHOR]

The fluorescent molecule 1,3‐di(nicotinoyloxy)‐2‐methylenepropane (L) can be a good candidate for construction of coordination polymers with photoluminescence (PL) properties. Self‐assembly of silver(I) hexafluorophosphate with this ligand in a mixture of methanol and dichloromethane produced a 1‐D helical coordination polymer consisting of [Ag(L)](PF6), whereas crystallization from an acetonitrile‐based medium afforded a 1‐D sinusoidal coordination polymer consisting of [Ag(L)(CH3CN)2](PF6) having intramolecular argentophilic Ag∙∙∙Ag and π∙∙∙π interactions arising from the eclipsed conformation of L. These findings suggest that the final structures of the two products can be controlled by the reaction solvent media rather than the crystallization method or concentration. The physicochemical properties of the present silver(I) compounds were fully characterized by means of infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, PL, single‐crystal x‐ray diffraction (XRD), and powder‐XRD measurements. [ABSTRACT FROM AUTHOR]

Electronic structural properties of the three different imidazolium-based ionic liquids, namely, 1-butyl-3-methyl imidazolium bromide (C4mimBr), 1-(4-hydroxybutyl)-3-methylimidazolium bromide (C4OHmimBr), and 1-(4-aminobutyl)-3-methylimidazolium bromide (C4NH2mimBr), were investigated with density functional theory at the B3LYP/6-311++G(d,p) level. The conformations of the mentioned cations were fully studied first using CONFLEX 8.A program. The quantum theory of atoms in molecules was used to investigate the nature of intramolecular interactions. The counterpoise-corrected ion pairs binding energies were obtained at the same level of theory. Natural bond orbital analyses show that the largest intra-molecular interaction comes from the orbital overlap between n(N1) and π* (N4–C5) in the mentioned compounds. The energy levels of frontier molecular orbitals (FMOs) are displayed. The global quantum chemical descriptors are also calculated based on the energy values of FMOs.

Herein, we report a spectroscopic study of N-acetyl-L-cysteine, an important antioxidant drug, using Fourier-transform microwave techniques and in isolated conditions. Two conformers are observed, where most stable structure adopts a cis disposition, and the second conformer has a lower abundance and adopts a trans disposition. The rotational constants and the barriers to methyl internal rotation are determined for each conformer, allowing a precise conformation identification. The results show that the cis form adopts an identical structure in the crystal, solution, and gas phases. Additionally, the structures are contrasted against those of cysteine., (© 2024 Wiley-VCH GmbH.)

GRB2, or Growth Factor Receptor-Bound Protein 2, is a pivotal adaptor protein in intracellular signal transduction pathways, particularly within receptor tyrosine kinase (RTK) signaling cascades. Its crystal structure reveals a modular architecture comprising a single Src homology 2 (SH2) domain flanked by two Src homology 3 (SH3) domains, facilitating dynamic interactions critical for cellular signaling. While SH2 domains recognize phosphorylated tyrosines, SH3 domains bind proline-rich sequences, enabling GRB2 to engage with various downstream effectors. Folding and binding studies of GRB2 in its full-length form and isolated domains highlight a complex interplay between its protein-protein interaction domains on the folding energy landscape and in driving its function. Being at the crosslink of many key molecular pathways in the cell, GRB2 possesses a role in cancer pathogenesis, particularly in mediating the Ras-mitogen activated protein kinase (MAPK) pathway. Thus, pharmacological targeting of GRB2 domains is a promising field in cancer therapy, with efforts focused on disrupting protein-protein interactions. However, the dynamic interplay driving GRB2 function suggests the presence of allosteric sites at the interface between domains that could be targeted to modulate the binding properties of its constituent domains. We propose that the analysis of GRB2 proteins from other species may provide additional insights to make the allosteric pharmacological targeting of GRB2 a more feasible strategy., Competing Interests: All the authors declare no competing interests., (© 2024 The Authors. Published by Elsevier B.V.)

The present paper deals with the correlation between intramolecular and intermolecular interactions of polycarboxybetaines. The degree of coupling between the opposite charges within the polycarboxybetaine molecules was varied by spacers of different length and by the substitution of additional alkyl chains at the quaternary nitrogen atom. In order to check intermolecular interactions between polycarboxybetaines, SANS measurements were carried out at aqueous polycarboxybetaines solutions. For getting information about the interaction with an oppositely charged polyelectrolyte, multilayers were formed by alternating adsorption of polystyrene sulfonate (PSS) and polycarboxybetaines from aqueous solutions. The occurrence of a structure peak in SANS spectra and the ability to form polyelectrolyte multilayers provide an indicator for the polyelectrolyte character of some of the studied polycarboxybetaines. Not only the charge but also the hydrophobicity of the polycarboxybetaines has a pronounced effect on the chain conformation and therefore on the thickness of the polyelectrolyte multilayers. The results show that small differences in molecular architecture lead to pronounced differences in intermolecular interactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The functional interplay between the N- and C-terminal regions of Munc13-1 was studied. • The Munc13-1 N-terminal calmodulin-binding domain inhibits the C-terminal region. • The Munc13-1 N-terminal C 2 A domain inhibits the C-terminal region. • RIM and calmodulin relieve the inhibition caused by the N-terminal domains. • An intricate set of interactions controls Munc13-1 in neurotransmitter release. Regulation of neurotransmitter release during presynaptic plasticity underlies varied forms of information processing in the brain. Munc13s play essential roles in release via their conserved C-terminal region, which contains a MUN domain involved in SNARE complex assembly, and controls multiple presynaptic plasticity processes. Munc13s also have a variable N-terminal region, which in Munc13-1 includes a calmodulin binding (CaMb) domain involved in short-term plasticity and a C 2 A domain that forms an inhibitory homodimer. The C 2 A domain is activated by forming a heterodimer with the zinc-finger domain of αRIMs, providing a link to αRIM-dependent short- and long-term plasticity. However, it is unknown how the functions of the N- and C-terminal regions are integrated, in part because of the difficulty of purifying Munc13-1 fragments containing both regions. We describe for the first time the purification of a Munc13-1 fragment spanning its entire sequence except for a flexible region between the C 2 A and CaMb domains. We show that this fragment is much less active than the Munc13-1 C-terminal region in liposome fusion assays and that its activity is strongly enhanced by the RIM2α zinc-finger domain together with calmodulin. NMR experiments show that the C 2 A and CaMb domains bind to the MUN domain and that these interactions are relieved by the RIM2α ZF domain and calmodulin, respectively. These results suggest a model whereby Munc13-1 activity in promoting SNARE complex assembly and neurotransmitter release are inhibited by interactions of the C 2 A and CaMb domains with the MUN domain that are relieved by αRIMs and calmodulin. [ABSTRACT FROM AUTHOR]

Unconjugated bilirubin (UCB) accumulation in the blood causes several diseases, such as jaundice, and most studies in the literature focus on settling these problems. However, its yellow-orange colour, antioxidant and anti-inflammatory activities and other properties have stimulated recent research to investigate this natural pigment for medical applications. Despite its polar groups, bilirubin is insoluble in water. Herein, we discuss the self-aggregation of UCB in water to understand its collective interactions employing molecular dynamics simulations. Starting from a random distribution of UCB molecules, we observed small clusters forming in a short simulation time. After that, they merged to form a single spherical aggregate. We attributed this behaviour to the preferential interactions between acid and basic groups of UCB through intermolecular and intramolecular hydrogen bonds. The electrostatic contribution between UCBs in aggregate is 150 kJ ⋅ mol − 1 , smaller than the UCB dispersed in water. Consequently, the contact between water and UCB was three times lower. Furthermore, we found that the central methylenes that bind the UCB dipyrrinones moieties are distributed in the nanoaggregate, like regular concentric layers, with a radius of 0.42 nm. • The central methylenes of bilirubin are distributed in the aggregates as if they were in concentric layers 0.42 nm apart. • Due to the non-covalent interaction forces between bilirubin, the H-bonds between bilirubin and water are unfavourable. • The self-aggregation of bilirubin in water produces a spherical-shaped material with no water in its interior. [ABSTRACT FROM AUTHOR]

Abstract A computational analysis of a series of cationic and neutral gold imidazolylidene and benzimidizolylidene complexes is reported. The Bond Dissociation Energies of the various ligands in the complexes calculated at the PBE0‐D3/def2‐TZVP level of theory increase with increasing ligand volume, except for those of complexes containing t‐butyl‐substituted ligands, which are anomalously low particularly for the benzimidazolylidene species. Atoms in Molecules studies show the presence of a variety of weak intramolecular interactions, characterised by the presence of bond critical points with a range of different properties. Energy Decomposition Analysis and calculation of Electrostatic Surface Potentials indicate that some interactions are weakly attractive dispersion‐type interactions, while others are repulsive. The octanol/water partition coefficients (log P values) were calculated as a measure of the lipophilicities of the complexes and were found to increase with increasing volume.

The naphthalenediimide (NDI) scaffold in contrast to its higher congeners possess low-fluorescence. In spite of elegant synthetic developments, a highly emissive NDI is quite rare to find, as well as, a green-light-emitting NDI is yet to be explored. Herein, we report a novel class of symmetric and asymmetric NH2-substituted core-NDIs (1-5) with tunable fluorescence in the visible region and extending to the NIR frontier. Importantly, the bis-NH2-substituted NDI 2 revealed quantum yield, Φ of ≈81 and ≈68% in toluene and DMSO, respectively, suggesting versatility of the fluorophore in a wide range of solvent polarity. The dye 1 is shown to be the first NDI-based green-light emitter. The donor piperidine group in 5 diminish the Φf by 40-fold providing a lever to modulate the excited-state intramolecular proton transfer (ESIPT) process. Our synthetic protocol applies a Pd catalyst and a benign hydride source simplifying the non-trivial -NH2 group integration at the NDI-core. TDDFT calculations predicted strong intramolecular hydrogen bonds in the excited state in the bulk nonpolar medium and responsiveness to solvent polarity. The maximization of the NDI emission outlined here would further boost the burgeoning repertoire of applications of the NDI scaffold. [ABSTRACT FROM AUTHOR]

Human guanylate‐binding protein 1 (hGBP‐1) shows a dimer‐induced acceleration of the GTPase activity yielding GDP as well as GMP. While the head‐to‐head dimerization of the large GTPase (LG) domain is well understood, the role of the rest of the protein, particularly of the GTPase effector domain (GED), in dimerization and GTP hydrolysis is still obscure. In this study, with truncations and point mutations on hGBP‐1 and by means of biochemical and biophysical methods, we demonstrate that the intramolecular communication between the LG domain and the GED (LG:GED) is crucial for protein dimerization and dimer‐stimulated GTP hydrolysis. In the course of GTP binding and γ‐phosphate cleavage, conformational changes within hGBP‐1 are controlled by a chain of amino acids ranging from the region near the nucleotide‐binding pocket to the distant LG:GED interface and lead to the release of the GED from the LG domain. This opening of the structure allows the protein to form GED:GED contacts within the dimer, in addition to the established LG:LG interface. After releasing the cleaved γ‐phosphate, the dimer either dissociates yielding GDP as the final product or it stays dimeric to further cleave the β‐phosphate yielding GMP. The second phosphate cleavage step, that is, the formation of GMP, is even more strongly coupled to structural changes and thus more sensitive to structural restraints imposed by the GED. Altogether, we depict a comprehensive mechanism of GTP hydrolysis catalyzed by hGBP‐1, which provides a detailed molecular understanding of the enzymatic activity connected to large structural rearrangements of the protein. Database: Structural data are available in RCSB Protein Data Bank under the accession numbers: 1F5N, 1DG3, 2B92. [ABSTRACT FROM AUTHOR]

The broadband rotational spectrum of jet-cooled laser-ablated thioproline was recorded. Two conformers of this system were observed and identified with the help of DFT and ab initio computations by comparison of the observed and calculated rotational constants and 14N quadrupole coupling constants as well as the predicted energies compared to the observed relative populations. These conformers showed a mixed bent/twisted arrangement of the five-membered ring similar to that of the related compound thiazolidine with the N–H bond in axial configuration. The most stable form had the COOH group in an equatorial position on the same side of the ring as N-H. The arrangement of the C=O group close to the N-H bond led to a weak interaction between them (classified as type I) characterized by a noncovalent interaction analysis. The second form had a trans-COOH arrangement showing a type II O–H···N hydrogen bond. In thioproline, the stability of conformers of type I and type II was reversed with respect to proline. We show how the conformation of the ring depends on the function associated with the endocyclic N atom when comparing the structures of isolated thioproline with its zwitterion observed in condensed phases and with peptide forms.

The aim of this review is to summarize recent achievements in the field of (N),C,N‐coordinated group 13–15 compounds not only regarding their synthesis and structure, but mainly focusing on their potential applications. Relevant compounds contain various types of N‐coordinating ligands built up on an ortho‐(di)substituted phenyl platform. Thus, group 13 and 14 derivatives were used as single‐source precursors for the deposition of semiconducting thin films, as building blocks for the preparation of high‐molecular polymers with remarkable optical and chemical properties or as compounds with interesting reactivity in hydrometallation processes. Group 15 derivatives function as catalysts in the Mannich reaction, in the allylation of aldehydes or activation of CO2. They were used as transmetallation reagents in transition metal catalysed coupling reactions. The univalent species serve as ligands for transition metals, activate alkynes or alkenes and are utilized as catalysts in the transfer hydrogenation of azo‐compounds. [ABSTRACT FROM AUTHOR]

Tropomyosins are elongated alpha-helical proteins that form co-polymers with most actin filaments within a cell and play important roles in the structural and functional diversification of the actin cytoskeleton. How the assembly of tropomyosins along an actin filament is regulated and the kinetics of tropomyosin association with an actin filament is yet to be fully determined. A recent series of publications have used total internal reflection fluorescence (TIRF) microscopy in combination with advanced surface and protein chemistry to visualise the molecular assembly of actin/tropomyosin filaments in vitro. Here, we review the use of the in vitro TIRF assay in the determination of kinetic data on tropomyosin filament assembly. This sophisticated approach has enabled generation of real-time single-molecule data to fill the gap between in vitro bulk assays and in vivo assays of tropomyosin function. The in vitro TIRF assays provide a new foundation for future studies involving multiple actin-binding proteins that will more accurately reflect the physiological protein-protein interactions in cells. [ABSTRACT FROM AUTHOR]

By the transmetallation of ppyHgCl [ppy = 2‐(2'‐pyridyl)phenyl] (1) with SnCl4 and SbCl3, the synthesis of the monoorgano main group halides, [ppySnCl3(H2O)]·2(0.5diox) (diox = 1,4‐dioxane) [2(H2O)]·2(0.5diox) and [ppySbCl2] (3) was achieved. The reaction of 1 with BiCl3 does not give the analogous monoorganobismuth dichloride. Instead, it results in the formation of [(ppy)2Bi]+·[ppyBiCl3]– (4). Reactions of (ppy)2Te and (ppyTe)2 with SO2Cl2 and Br2 result in the formation of ppyTeCl (5) and ppyTeBr (6) respectively. All the synthesized compounds were characterized by multi‐nuclear NMR spectroscopy (1H, 13C, 119Sn, and 125Te), FT‐IR spectroscopy, ESI‐MS, CHN analysis, and single‐crystal X‐ray diffraction studies. The molecular structures of 2–6 reveal strong intramolecular coordination of the N‐atoms of the pendant arms with the main group element centers. DFT calculations; including Natural Bond Order (NBO), Electron Localization Function (ELF), Electrostatic Surface Potential (ESP) and Atoms in Molecules (AIM) infer that the stability of 2–6 relies on the σ‐hole participation of the element center with the N‐lone pair of the pyridyl arm. [ABSTRACT FROM AUTHOR]

The physicochemical properties and reactivity of macrocycles are critically shaped by their conformations. In this work, we have identified seven conformations of the macrocyclic ketone cyclododecanone using chirped-pulse Fourier transform microwave spectroscopy in combination with ab initio and density functional theory calculations. Cyclododecanone is strongly biased towards adopting a square configuration of the heavy atom framework featuring three C–C bonds per side. The substitution and effective structures of this conformation have been determined through the observation of its 13C isotopologues. The minimisation of transannular interactions and, to a lesser extent, HCCH eclipsed configurations drive conformational preferences. Our results contribute to a better understanding of the intrinsic forces mediating structural choices in macrocycles.

Intramolecular interactions are shown to be key for favoring a given structure in systems with a variety of conformers. In ortho-substituted benzene derivatives including a beryllium moiety, beryllium bonds provide very large stabilizations with respect to non-bound conformers and enthalpy differences above one hundred kJ·mol−1 are found in the most favorable cases, especially if the newly formed rings are five or six-membered heterocycles. These values are in general significantly larger than hydrogen bonds in 1,2-dihidroxybenzene. Conformers stabilized by a beryllium bond exhibit the typical features of this non-covalent interaction, such as the presence of a bond critical point according to the topology of the electron density, positive Laplacian values, significant geometrical distortions and strong interaction energies between the donor and acceptor quantified by using the Natural Bond Orbital approach. An isodesmic reaction scheme is used as a tool to measure the strength of the beryllium bond in these systems in terms of isodesmic energies (analogous to binding energies), interaction energies and deformation energies. This approach shows that a huge amount of energy is spent on deforming the donor–acceptor pairs to form the new rings.

Exploring the intricate interplay within and between nucleic acids, as well as their interactions with proteins, holds pivotal significance in unraveling the molecular complexities steering cancer initiation and progression. To investigate these interactions, a diverse array of highly specific and sensitive molecular techniques has been developed. The selection of a particular technique depends on the specific nature of the interactions. Typically, researchers employ an amalgamation of these different techniques to obtain a comprehensive and holistic understanding of inter- and intramolecular interactions involving DNA-DNA, RNA-RNA, DNA-RNA, or protein-DNA/RNA. Examining nucleic acid conformation reveals alternative secondary structures beyond conventional ones that have implications for cancer pathways. Mutational hotspots in cancer often lie within sequences prone to adopting these alternative structures, highlighting the importance of investigating intra-genomic and intra-transcriptomic interactions, especially in the context of mutations, to deepen our understanding of oncology. Beyond these intramolecular interactions, the interplay between DNA and RNA leads to formations like DNA:RNA hybrids (known as R-loops) or even DNA:DNA:RNA triplex structures, both influencing biological processes that ultimately impact cancer. Protein-nucleic acid interactions are intrinsic cellular phenomena crucial in both normal and pathological conditions. In particular, genetic mutations or single amino acid variations can alter a protein's structure, function, and binding affinity, thus influencing cancer progression. It is thus, imperative to understand the differences between wild-type (WT) and mutated (MT) genes, transcripts, and proteins. The review aims to summarize the frequently employed methods and techniques for investigating interactions involving nucleic acids and proteins, highlighting recent advancements and diverse adaptations of each technique., (Copyright © 2024. Published by Elsevier Inc.)

The self-association of therapeutic antibodies can result in elevated viscosity and create problems in manufacturing and formulation, as well as limit delivery by subcutaneous injection. The high concentration viscosity of some antibodies has been reduced by variable domain mutations or by the addition of formulation excipients. In contrast, the impact of Fc mutations on antibody viscosity has been minimally explored. Here, we studied the effect of a panel of common and clinically validated Fc mutations on the viscosity of two closely related humanized IgG 1, κ antibodies, omalizumab (anti-IgE) and trastuzumab (anti-HER2). Data presented here suggest that both Fab-Fab and Fab-Fc interactions contribute to the high viscosity of omalizumab, in a four-contact model of self-association. Most strikingly, the high viscosity of omalizumab (176 cP) was reduced 10.7- and 2.2-fold by Fc modifications for half-life extension (M252Y:S254T:T256E) and aglycosylation (N297G), respectively. Related single mutations (S254T and T256E) each reduced the viscosity of omalizumab by ~6-fold. An alternative half-life extension Fc mutant (M428L:N434S) had the opposite effect in increasing the viscosity of omalizumab by 1.5-fold. The low viscosity of trastuzumab (8.6 cP) was unchanged or increased by ≤ 2-fold by the different Fc variants. Molecular dynamics simulations provided mechanistic insight into the impact of Fc mutations in modulating electrostatic and hydrophobic surface properties as well as conformational stability of the Fc. This study demonstrates that high viscosity of some IgG 1 antibodies can be mitigated by Fc mutations, and thereby offers an additional tool to help design future antibody therapeutics potentially suitable for subcutaneous delivery.

Modern molecular spectroscopy of diatomic molecules is the precision study of the structure and dynamics of electronically excited states of isolated molecules in the gas phase. At the same time, the energy, radiation, magnetic, and electrical characteristics of excited molecules, which are of interest for different physicochemical applications, must be determined and predicted at the experimental (spectral) level of accuracy in a broad range of electron vibrational and rotational excitations. This problem cannot be solved within spectroscopy's traditional adiabatic approximation, since a large number of intramolecular interactions (so-called perturbations) inevitably distorts not only the regular energy structure of different levels but he nodal structure of the corresponding wave functions as well. The most accurate solution to both direct and inverse spectroscopic problems with respect to perturbed molecular states is based on constructing a reduced system of the coupled radial Schrödinger equations encountered in the quantum-mechanical modeling of the nonadiabatic interaction of electronic states. The nonadiabatic approach can be employed successfully only through the joint use of precision spectroscopic data and highly precise calculations of electronic structure. [ABSTRACT FROM AUTHOR]

Absorption of weak polyelectrolytes impacts on properties such as ionization, conformations, and counterion (CI) condensation that are important in several areas of applied and fundamental science. We used a weak polyelectrolyte model and Monte Carlo simulations to investigate how the mentioned properties depend on pH or the size of a spherical cavity (SC) permeable to CIs but not to polyelectrolytes; the latter have either linear or starlike topologies and may be allowed to form charged hydrogen bonds (cH‐bonds) between ionized and neutral monomers. Average ionization decreases upon increasing the number of arms at a constant number of monomers; it instead increases with the arm length in large SC due to CI screening. The way SC size, cH‐bonds, and pH values interrelate to define ionization is instead more complicate due to arm pairing or clustering when cH‐bonds are possible. These induce oscillations in the arm local ionization and impact on both monomer and CI distributions in the complete simulation cell in a way that also depends on polymer topology. The impact of ionization on the confinement free energy is also estimated; this highlighted that cH‐bonding may enhance absorption compared with neutral chains. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 491–510 Confinement of polymers inside cavities (e.g. capsids) has a direct impact on properties of chains, such as conformations or entropy, and indirectly affects the local/global ionization or spatial distribution of counterions if species possess weak acid/base groups. To better gauge such changes, linear and star‐like ionizable polymers were systematically simulated via a "primitive polyelectrolyte model" with explicit counterions, allowing, also, the formation of strong hydrogen bonds. A marked drop in Helmholtz energy variation upon confinement and counterions condensation was evidenced upon increasing the number of arms and forming hydrogen bonds. [ABSTRACT FROM AUTHOR]

A computational analysis of a series of cationic and neutral gold imidazolylidene and benzimidizolylidene complexes is reported. The Bond Dissociation Energies of the various ligands in the complexes calculated at the PBE0‐D3/def2‐TZVP level of theory increase with increasing ligand volume, except for those of complexes containing t‐butyl‐substituted ligands, which are anomalously low particularly for the benzimidazolylidene species. Atoms in Molecules studies show the presence of a variety of weak intramolecular interactions, characterised by the presence of bond critical points with a range of different properties. Energy Decomposition Analysis and calculation of Electrostatic Surface Potentials indicate that some interactions are weakly attractive dispersion‐type interactions, while others are repulsive. The octanol/water partition coefficients (log P values) were calculated as a measure of the lipophilicities of the complexes and were found to increase with increasing volume.The stuff prodrugs are made of: Calculation of the properties of a series of gold complexes containing N‐heterocyclic carbene ligands using a variety of computational methodologies shows that there is a delicate balance between steric and electronic effects in the ability of the complexes to behave as prodrugs. [ABSTRACT FROM AUTHOR]

Graphical abstract The N,C,N pincer groups 2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 were employed in the synthesis of the new compounds [2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 ] 2 Se 2 and [2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 ]SeCl (E = MeN, O). Ionic species containing the organoselenium cations [2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 Se]+ or [2,6-(Me 2 NCH 2) 2 C 6 H 3 Se]+ and the gold(I) anions [AuCl 2 ]− or [Au(C 6 F 5) 2 ]− were prepared and structurally characterized. Abstract The new diorganodiselenides [2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 ] 2 Se 2 (E = MeN, O) with N,C,N pincer groups were oxidized with SO 2 Cl 2 to the corresponding organoselenium(II) chlorides of type [2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 ]SeCl. The new chlorides, as well as the related [2,6-(Me 2 NCH 2) 2 C 6 H 3 ]SeCl, transfer easily the chlorine atom to [AuCl(tht)] (tht = tetrahydrothiophene), thus forming ionic species based on the organoselenium cations [2,6-{E(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 Se]+ or [2,6-(Me 2 NCH 2) 2 C 6 H 3 Se]+ and the [AuCl 2 ]− anion. The reaction between [2,6-(Me 2 NCH 2) 2 C 6 H 3 ] 2 Se 2 and [(C 6 F 5)Au(tht)] resulted in an ionic species as well, i.e. [2,6-(Me 2 NCH 2) 2 C 6 H 3 Se]+[Au(C 6 F 5) 2 ]−. The room temperature 1H NMR spectra suggest a fast dynamic behavior in solution for all species, except the ionic [2,6-{O(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 Se]+Cl− and [2,6-(Me 2 NCH 2) 2 C 6 H 3 Se]+[Au(C 6 F 5) 2 ]−, for which the 1H NMR resonances in the aliphatic region suggest that both N→Se intramolecular interactions are preserved in solution. The solid state structures of {[2,6-{O(CH 2 CH 2) 2 NCH 2 } 2 C 6 H 3 Se]+Cl−}·H 2 O, [2,6-(Me 2 NCH 2) 2 C 6 H 3 Se]+[AuCl 2 ]− and [2,6-(Me 2 NCH 2) 2 C 6 H 3 Se]+[Au(C 6 F 5) 2 ]− were established by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract The antibody light chain (LC) consists of two domains and is essential for antigen binding in mature immunoglobulins. The two domains are connected by a highly conserved linker that comprises the structurally important Arg108 residue. In antibody light chain (AL) amyloidosis, a severe protein amyloid disease, the LC and its N-terminal variable domain (V L) convert to fibrils deposited in the tissues causing organ failure. Understanding the factors shaping the architecture of the LC is important for basic science, biotechnology and for deciphering the principles that lead to fibril formation. In this study, we examined the structure and properties of LC variants with a mutated or extended linker. We show that under destabilizing conditions, the linker modulates the amyloidogenicity of the LC. The fibril formation propensity of LC linker variants and their susceptibility to proteolysis directly correlate implying an interplay between the two LC domains. Using NMR and residual dipolar coupling-based simulations, we found that the linker residue Arg108 is a key factor regulating the relative orientation of the V L and C L domains, keeping them in a bent and dense, but still flexible conformation. Thus, inter-domain contacts and the relative orientation of V L and C L to each other are of major importance for maintaining the structural integrity of the full-length LC. Graphical Abstract Unlabelled Image Highlights • Antibody light chains exhibit properties different from the two constituent domains. • The orientation of the two domains is regulated by the connecting linker. • Amyloid formation of variants of the variable domain is inhibited in the light chain. • The stability of the domains is affected in the context of the light chain. • Particularly, the linker residue Arg108 is of special importance. [ABSTRACT FROM AUTHOR]

• The crystal structure of chlorhexidine perchlorate (CHXPC) and hydrogen citrate (CHXHC) salts were studied using synchrotron radiation. • The oxyanions perchlorate and hydrogen citrate show mono-contacted, three-centered bifurcated and four-centered trifurcated hydrogen bonds with adjacent molecules. • The estimated pKa values for H-bonds including oxygen in CHXPC (II) is equal to ≈ 4.50 for strong H-bond (a′) and for CHXHC (III) is ≈ 1.86. • The Hershfield surface analysis showing the noncovalent interactions reveals that the H−H interatomic contacts is the strongest contribution in these molecules. Novel organic salts comprising of chlorhexidine di-cation (CHX) with perchlorate H 2 CHX(ClO 4) 2 ·2H 2 O (CHXPC) and hydrogen citrate H 2 CHX(C 6 H 6 O 7).H 2 O (CHXHC) were prepared, and their crystal structures studied. Despite extensive applications of chlorhexidine as an antimicrobial agent, CHXPC and CHXHC are amongst just a few reported crystal structures containing CHX that have been characterized so far. Exhibiting different structural patterns in their crystal packing, the CHXPC and CHXHC was distinguishable from one another with U- and S- shaped conformations, respectively. Their wide variety of hydrogen bonds were investigated from different point of views, among which were the overall structure of the salts, di-cations and oxyanions, and also their capability of forming 2D- and 3D-frameworks of hydrogen bonding. In addition, multifurcated multi-centered hydrogen bonding, such as bifurcated three-centered and trifurcated four-centered hydrogen bonds were observed in the structures of CHXPC and CHXHC as well. In comparison with normal single hydrogen bonding, the multifurcated hydrogen bonding indicated more flexibility with arrangements in their geometry. The hydrogen bonds containing oxygen-oxygen as donor and acceptor (O ̶ H···O) were employed to estimate their acidity (p K a) and strength (E HB) with different directionality. Hirshfeld surface analysis (HSA) was also used to confirm the intermolecular interactions in the structures of CHXPC and CHXHC. [Display omitted] [ABSTRACT FROM AUTHOR]

Методом DFT розраховано геометричні та електронні параметри імінів, досліджено передачу електронних ефектів і фактори, які впливають на бар’єри інверсії атома N (ΔEi¹). Установлено, що зменшення негативних зарядів на атомах N та =С під час N- і С-метилування відповідно обумовлене більшою електронегативністю атома С порівняно з атомом Н; зростання значень qN зі збільшенням ступеня С-метилування викликане збільшенням надспряження метильних груп з розпушувальними орбіталями зв’язку С=N. Розглянуто основні дво- та чотириелектронні взаємодії, які впливають на зміни бар’єрів інверсії атома N; домінуючий вплив на величину ΔEi¹ має електронегативність N-замісників та стеричне напруження, а не внутрішньомолекулярні взаємодії.

The interactions between phosphines and boranes in crystal structures have been investigated by analyzing data from the Cambridge Structural Database (CSD). The interactions between phosphines and boranes were classified into three types; two types depend on groups on the boron atom, whereas the third one involves frustrated Lewis pairs (FLPs). The data enabled geometric parameters in structures to be compared with phosphine–borane FLPs with classical Lewis pairs. Most of the crystal structures (78.1%) contain BH3 as the borane group. In these systems, the boron–phosphorus distance is shorter than systems where the boron atom is surrounded by groups other than hydrogen atoms. The analysis of the CSD data has shown that FLPs have a tendency for the longest boron–phosphorus distance among all phosphine–borane pairs, as well as different other geometrical parameters. The results show that most of the frustrated phosphine–borane pairs found in crystal structures are bridged ones. The minority of non‐bridged FLP structures contain, beside phosphorus and boron atoms, other heteroatoms (O, N, S for instance). [ABSTRACT FROM AUTHOR]

This review discusses the syntheses, structures and applications of organotelluroxanes. These compounds have found applications in many areas such as catalysis, oxidation, hydrolysis etc. Weak intermolecular O⋯Te interactions are common features in this class of compounds and play an important role in the aggregation, reactivity and properties of such compounds. However, monomeric species could be isolated by employing bulky groups or intramolecular interactions in the system. The highly polar Te=O double bond in organotelluroxanes imparts very high Lewis acidic character on the tellurium atom and is responsible for their unusual reactivity as compared with organoselenium counterparts. [ABSTRACT FROM AUTHOR]

The preferred conformations of a small polyfunctional molecule containing fluorine, chlorine and hydroxyl groups, the 1-chloro-1,1-difluoro-2-pentanol ( CDP ), were completely elucidated using 1 H, 13 C and 19 F NMR in three different solvents. While the Cl-C-C-O dihedral angle was asserted using coupling constant data for the diastereotopic fluorines, the Et-C-C-O torsional angle was analyzed by means of 1 H NMR spectra with selective irradiation of the diastereotopic hydrogens and fluorines. In addition, unusual couplings of the hydroxyl hydrogen with a diastereotopic hydrogen and fluorines provided information on the O-H orientation. The behavior of 1 J C,F when the solvents varied agrees with a weak F⋅⋅⋅HO intramolecular hydrogen bond. These findings were corroborated, and the governing interactions rationalized with the aid of high level CCSD(T) theoretical calculations. Noteworthy, hyperconjugation involving the electron-acceptor σ* C-Cl orbital drives the conformational equilibrium rather than the fluorine gauche effect. [ABSTRACT FROM AUTHOR]

The formation of new types of intramolecular B-H⋅⋅⋅X hydride-halogen and B-H⋅⋅⋅π(C≡C) hydrogen bonds in nido-carborane derivatives 9-XCH2S(Me)S-7,8-C2B9H11and 10-RC≡CCH2S(Me)S-7,8-C2B9H11as well as the role of intramolecular hydrogen bonding between the dicarbollide ligands in cobalt bis(dicarbollide) complexes [3,3′-M(1,2-C2B9H11)2]−in stabilization of their different rotational isomers (rotamers) were described based on NMR spectroscopy and single-crystal X-ray studies. [ABSTRACT FROM PUBLISHER]

The ¹JC-F coupling constant can be useful to probe the conformational landscape of organofluorine compounds and the intramolecular interactions governing the stereochemistry of these compounds. Neighboring oxygen electron lone pairs and a carbonyl group relative to a C-F bond affect this coupling constant in an opposite way, and therefore, analysis of the interactions involving these entities simultaneously indicates which effect dominates ¹JC-F. Spin- spin coupling constant calculations for a series of fluorinated tetrahydropyrans, cyclohexanones, and dihydropyran-3-ones indicated that an electrostatic/dipolar interaction between the C-F and C-O bonds is more important than the steric interaction between the C-F bond and the oxygen electron lone pairs. An intuitive consequence of such outcome is that this interaction not only drives the coupling constant but can also be taken into account when aiming at the stereochemical control of functionalized organofluorine compounds. [ABSTRACT FROM AUTHOR]

The presence of glutelin plays an important role in the textural properties of reconstituted rice, but available information is limited. Herein, a comprehensive assessment of the effects of multi-scale structure and intramolecular interactions of glutelin on the textural properties of reconstituted rice was performed. The results demonstrated that the hardness, adhesiveness, and chewiness of reconstituted rice were improved as the added ratio of glutelin increased and the internal structure changed by forming compact flake-like, fibrous branches, more α-helix and β-sheet structure, and enhanced intermolecular interactions. Furthermore, extrusion promoted the generation of special aroma substances by the Maillard reaction. Correlation analysis revealed that the hardness, adhesiveness, and chewiness of reconstituted rice were significant positive correlation with Tp, ∆H, β-turn, random coil, and free SH content, and negative correlation with α-helix of glutelin. These observations provide better insights into strategies for producing reconstituted rice by extrusion. • Effects of glutelin on the textural properties of reconstituted rice were evaluated. • The presence of glutelin improved textural properties of reconstituted rice. • Textural properties of reconstituted rice had a negative correlation with α-helix. • The hydrophobic interaction had a good positive correlation with β-sheet structure. [ABSTRACT FROM AUTHOR]

• Raman scattering linewidth depends on intra- and inter- interactions. • Acetone's 1713 cm−1 mode is more affected by CS 2 shielding as opposed to CCl 4. • CCl 4 acts as a shielding agent for high energy modes. • The wall reduces the available number of intermolecular pathways. The research focuses on Raman effects from vibrational interactions for mixed solute and solvent in binary mixed liquid for vibrational exchange from anharmonic interactions from three and four body collisions of mixed solvents from shields and cages about excited molecule of solute. The Raman linewidth were measured and theoretically fitted by varying the mole fraction (X) of solute proportions with mixed solvents, one acting as a solute and the other as a solvent. The excitation of CH 3 modes to the daughter modes and other mixed molecule modes show the effect of anharmonic many body collisions, dephasing and vibrational energy transfer. The Raman linewidth and intensity of the higher vibrational modes of solvents: Acetone and Methanol can rise in the presence of a second solvent of lower vibrational modes act as shield. Using various combinations of the solvents as acetone and methanol with carbon disulfide, and carbon tetrachloride can alter relaxation pathways due to the interruption of intermolecular energy decay routes of acetone and methanol by the low energy modes of carbon tetrachloride and carbon disulfide act as shields to energy transfer. Carbon tetrachloride is a stronger shielding agent than carbon disulfide for both acetone's high and low energy modes due to acetone's larger amphiphilic structure that is more resilient to structural hindrance of the linear carbon disulfide as opposed to the larger spherical carbon tetrachloride. Carbon disulfide is a stronger shielding agent than carbon tetrachloride for methanol except in the case of 1456 cm−1 energy mode due to the increased structural hindrance of carbon disulfide's linear structure, which methanol is more susceptible to by its smaller molecular structure, preventing intermolecular interactions with other methanol molecules. [ABSTRACT FROM AUTHOR]