Parametric Study of Girders with Sinusoidal Corrugated Web.

Recently, steel girders with sinusoidal corrugations have become increasingly popular compared to those with traditional flat webs. This paper presents the second part of the research on the application of corrugated plates with different sinusoidal profiles as webs in girders. Parametric studies have been carried out in both linear and nonlinear domains, based on a representative numerical model developed and validated by experimental results.

Synthesis, Absolute Configuration, Biological Profile and Antiproliferative Activity of New 3,5-Disubstituted Hydantoins.

Hydantoins, a class of five-membered heterocyclic compounds, exhibit diverse biological activities. The aim of this study was to synthesize and characterize a series of novel 3,5-disubstituted hydantoins and to investigate their antiproliferative activity against human cancer cell lines. The new hydantoin derivatives - were prepared as racemic mixtures of - and -isomers via a base-assisted intramolecular amidolysis of C-3 functionalized β-lactams.

Influence of heterochirality on the structure, dynamics, biological properties of cyclic(PFPF) tetrapeptides obtained by solvent-free ball mill mechanosynthesis.

Cyclic tetrapeptides c(Pro-Phe-Pro-Phe) obtained by the mechanosynthetic method using a ball mill were isolated in a pure stereochemical form as a homochiral system (all L-amino acids, sample A) and as a heterochiral system with D configuration at one of the stereogenic centers of Phe (sample B). The structure and stereochemistry of both samples were determined by X-ray diffraction studies of single crystals. In DMSO and acetonitrile, sample A exists as an equimolar mixture of two conformers, while only one is monitored for sample B.

Molecular Dynamics of Steroidal Rotors Probed by Theoretical, Spectroscopic and Dielectric Methods.

Our study focuses on molecular rotors with fast-moving rotators and their potential applications in the development of new amphidynamic crystals. Steroidal molecular rotors with a dipolar fluorine-substituted phenyl group as the rotator were synthesized and characterized. Three different rotors were investigated with varying numbers of fluorine atoms.

Differentiation of solvatomorphs of active pharmaceutical ingredients (API) by solid-state vibrational circular dichroism (VCD).

Here, we present the new application of solid-state Vibrational Circular Dichroism (VCD) spectroscopy to differentiate several dutasteride (DS) solvatomorphs - the model active pharmaceutical ingredient (API). Several crystalline DS hydrochloride hydrates solvated with methanol, ethanol, acetonitrile, acetone, and acetic acid were prepared. In contrast to almost identical IR spectra, the VCD ones were very sensitive to changes in the sample composition.

"Nature or nurture" - How environmental factors influence the conformational memory of amyloid fibrils.

Amyloid fibrils are complex protein structures with multilayered chiral architecture, that are known to self-propagate. The replication of the mother seed structure by daughter fibrils is known as conformational or templated memory. Using vibrational circular dichroism (VCD), electronic circular dichroism (ECD), transmission electron microscopy (TEM), and cryo-electron microscopy (cryo-EM) we have shown that environmental factors (here agitation) can be a competing force against the templated growth of human lysozyme fibrils.

Strong Chiroptical Effects in the Absorption and Emission of Macrocycles Based on the 2,5-Diaminoterephthalate Minimal Fluorophore.

Chiral fluorescent macrocycles consisting of two to four units of dimethyl 2,5-diaminoterephthalate can be readily synthesized in a one-pot manner from inexpensive building blocks. Depending on the concentration, either a paracyclophane-like dimer with closely stacked benzene rings or a triangular trimer is the main product of the reaction. The macrocycles exhibit fluorescence in solution as well as in the solid state with maxima that are red-shifted with decreasing size of the macrocyclic ring and are observed at wavelengths from 590 (tetramer in solution) to 700 nm (dimer in the solid state).

Chiral and Structural Polymorphism of Fibril Architectures of Homologous Lysozymes.

Amyloid fibrils are fascinating and complex structures with the multilayered chiral organization. Using the multimodal methodology, including VCD, ECD, cryo-EM, and TEM, we characterized in detail different levels of organization (secondary structure/protofilament/mesoscopic structure) of amyloid fibrils prepared from proteins highly homologous in the structure (hen egg white and human lysozymes). Our results demonstrate that small changes in the native protein structure or preparation conditions translate into significant differences in the handedness and architecture of the formed fibrils at various levels of their complexity.

A Unique and Stable Polyproline I Helix Sorted out from Conformational Equilibrium by Solvent Polarity.

Polyproline I helical structures are often considered as the hidden face of their most famous geminal sibling, Polyproline II, as PPI is generally spotted only within a conformational equilibrium. We designed and synthesized a stable Polyproline I structure exploiting the striking tendency of ()-indoline-2-carboxylic acid to drive the peptide bond conformation toward the amide isomer, when dissolved in polar solvents. The cooperative effect of only four amino acidic units is sufficient to form a preferential structure in solution.

Influence of Corrugated Web Geometry on Mechanical Properties of I-Beam: Laboratory Tests.

This paper presents the results of experimental investigations performed on beams with corrugated webs. The aim of the research was to determine the effect of the geometric parameters of the sinusoidal web on the behavior of I-beams subjected to four-point bending. Special attention was paid to the effects of web thickness and wave geometry on the deflection of beams.

A Holistic Approach to Determining Stereochemistry of Potential Pharmaceuticals by Circular Dichroism with β-Lactams as Test Cases.

This paper's main objective is to show that many different factors must be considered when solving stereochemical problems to avoid misleading conclusions and obtain conclusive results from the analysis of spectroscopic properties. Particularly in determining the absolute configuration, the use of chiroptical methods is crucial, especially when other techniques, including X-ray crystallography, fail, are not applicable, or give inconclusive results. Based on various β-lactam derivatives as models, we show how to reliably determine their absolute configuration (AC) and preferred conformation from circular dichroism (CD) spectra.

Electronic Circular Dichroism Imaging (ECDi) Casts a New Light on the Origin of Solid-State Chiroptical Properties.

Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recorded with a bench-top instrument (1 cm area).

Study on the Effect of Geometrical Parameters of a Hexagonal Trigger on Energy Absorber Performance Using ANN.

Thin-walled structures are commonly used as energy absorbers in motor vehicles. Their function is to protect the structural components of vehicles and to absorb energy completely during collisions up to 20 km/h. This paper focuses on maintaining crush axiality during research.

Enantioselective Gel Phase Synthesis of Metal-Organic Materials.

We report the asymmetric synthesis of homochiral metal-organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates.

Synthesis and Characterization of Bis[( or )--1-(X-CH)ethyl-2-oxo-1-naphthaldiminato-κ,]-Λ/Δ-cobalt(II) (X = H, -CHO, -Br) with Symmetry- and Distance-Dependent Vibrational Circular Dichroism Enhancement and Sign Inversion.

The enantiopure Schiff bases ( or )--1-(X-CH)ethyl-2-hydroxy-1-naphthaldimine {X = H [( or )-HL1], -CHO [( or )-HL2], and -Br [(- or )-HL3]} react with cobalt(II) acetate to give bis[( or )--1-(X-CH)ethyl-2-oxo-1-naphthaldiminato-κ,]-Λ/Δ-cobalt(II) {X = H [Λ/Δ-Co-( or )-L1], -CHO [Λ/Δ-Co-( or )-L2], and -Br [Λ/Δ-Co-( or )-L3]} (-), respectively. Induced Λ and Δ chirality originates at the metal center of the -symmetric molecule in pseudotetrahedral geometry. Differential scanning calorimetry analyses explored the thermal stability of the complexes, which undergo reversible phase transformation from crystalline solid to isotropic liquid phase for and but irreversible phase transformation for .

Base-Catalyzed, Solvent-Free Synthesis of Rigid V-Shaped Epoxydibenzo[,][1,5]diazocines.

A novel method for the synthesis of epoxydibenzo[,][1,5]diazocines exhibiting a V-shaped molecular architecture is reported. The unique approach is based on unprecedented base-catalyzed, solvent-free autocondensation and cross-condensation of fluorinated -aminophenones. The structure of the newly synthesized diazocines was confirmed independently by X-ray analysis and chiroptical methods.

New camptothecin derivatives for generalized oncological chemotherapy: Synthesis, stereochemistry and biology.

Derivatives of SN38 were synthesized that were either monosubstituted at C-5 or C-9 or disubstituted at both C-5 and C-9. Substitution to C-5 led to the generation of pairs of diastereomers (2c-2 h) in a one-pot reaction and was readily separable by HPLC. The absolute configurations of C-5 were established by electronic circular dichroism experiments.

Fluorescent Molecular Cages with Sucrose and Cyclotriveratrylene Units for the Selective Recognition of Choline and Acetylcholine.

The synthesis of four fluorescent diastereoisomeric molecular cages containing cyclotriveratrylene and sucrose moieties connected the naphthalene linkers is reported. These diastereoisomers were found to be selective and efficient receptors for acetylcholine and choline. Compound has a better affinity for choline over acetylcholine, while cage exhibits a higher association constant for acetylcholine over choline.

Isolation and Self-Association Studies of Beta-Lactoglobulin.

The aim of this study was to investigate isolated β-lactoglobulin (β-LG) from the whey protein isolate (WPI) solution using the column chromatography with SP Sephadex. The physicochemical characterization (self-association, the pH stability in various salt solutions, the identification of oligomeric forms) of the protein obtained have been carried out. The electrophoretically pure β-LG fraction was obtained at pH 4.

Steroidal Molecular Rotors with 1,4-Diethynylphenylene Rotators: Experimental and Theoretical Investigations Toward Seeking Efficient Properties.

Properly designed molecular rotors with sizable stators and a fast-moving rotator could provide efficient building blocks for amphidynamic crystals. Herein, we report the synthesis of steroidal compounds , , and and their deuterated analogues , , and envisioned to work as molecular rotors. The obtained compounds were characterized by attenuated total reflection-infrared, Raman, and circular dichroism (CD) spectroscopy measurements.

Novel Potent Muscarinic Receptor Antagonists: Investigation on the Nature of Lipophilic Substituents in the 5- and/or 6-Positions of the 1,4-Dioxane Nucleus.

A series of novel 1,4-dioxane analogues of the muscarinic acetylcholine receptor (mAChR) antagonist was synthesized and studied for their affinity at M-M mAChRs. The 6-cyclohexyl-6-phenyl derivative , with a configuration between the CHN(CH) chain in the 2-position and the cyclohexyl moiety in the 6-position, showed p values for mAChRs higher than those of and a selectivity profile analogous to that of the clinically approved drug oxybutynin. The study of the enantiomers of and the corresponding tertiary amine revealed that the eutomers are (2,6)-(-)- and (2,6)-(-)-, respectively.

Gigantelline, gigantellinine and gigancrinine, cherylline- and crinine-type alkaloids isolated from Crinum jagus with anti-acetylcholinesterase activity.

Three undescribed Amarylidaceae alkaloids, named gigantelline, gigantellinine and gigancrinine, were isolated from Crinum jagus (syn. = Crinum giganteum) collected in Senegal, together with the already known sanguinine, cherylline, lycorine, crinine, flexinine and the isoquinolinone derivative hippadine. Gigantelline, gigantellinine and gigancrinine were characterized as 4-(6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-yl)-phenol, its 7-O-demethyl-5ꞌ-hydroxy-4ꞌ-methoxy derivative and 5,6a,7,7a,8a,9-hexahydro-6,9a-ethano[1,3]dioxolo[4,5-j]oxireno[2,3-b]phenanthridin-9-ol, respectively, by using spectroscopic (1D and 2D H and C NMR and HRESIMS) and chemical methods.

Chiral Diketopyrrolopyrrole-Helicene Polymer With Efficient Red Circularly Polarized Luminescence.

Chiral diketopyrrolopyrrole (DPP)-helicene polymers were synthesized to develop efficient red circularly polarized (CP) light emitters. These original chiral dyes display intense electronic circular dichroism (ECD) and CP luminescence (CPL) in the far-red spectral region owing to the presence of excitonic coupling between achiral DPPs within the chiral environment of the polymeric structure. This work affords an interesting example illustrating the potential of π-conjugated helical polymers for chiral optoelectronic applications.

An approach to new chiral bicyclic imines and amines Horner-Wadsworth-Emmons reaction.

New chiral bicyclic imines, enamines and amines were prepared Horner-Wadsworth-Emmons reaction of hexahydroquinoxalin-2(1)-one-derived phosphonate, as the source of a phosphonate carbanion, and a wide range of structurally diverse carbonyl substrates. The simplicity of the synthetic protocol, high selectivity, and broad substrate scope are the main advantages of the presented methodology.

Higginsianins D and E, Cytotoxic Diterpenoids Produced by .

Two new diterpenoids with tetrasubstituted 3-oxodihydrofuran substituents, named higginsianins D () and E (), were isolated from the mycelium of the fungus grown in liquid culture. They were characterized as methyl 2-[6-hydroxy-5,8a-dimethyl-2-methylene-5-(4-methylpent-3-enyl)-decahydronaphthalen-1-ylmethyl]-4,5-dimethyl-3-oxo-2,3-dihydrofuran-2-carboxylate and its 21-epimer by using NMR, HRESIMS, and chemical methods. The relative configurations of higginsianins D and E, which did not afford crystals suitable for X-ray analysis, were determined by NOESY experiments and by comparison with NMR data of higginsianin B.