Molecular aggregation and property changes of egg yolk low-density lipoprotein induced by ethanol and high-density ultrasound

Solvent and physical treatment are widely used in egg yolk processing, but the detailed changes in the molecular structure of egg yolk proteins during processing are unclear. The aim of this study was to investigate the effects of ethanol and ultrasonic treatments on chicken egg yolk low-density lipoprotein (LDL). The solubility, emulsifying activity and emulsifying stability decreased by 74.75%, 46.91%, and 81.58% after ethanol treatment, respectively. The average particle size of ethanol-treated LDL increased 13.3-fold to 937.85 nm. These results suggested that ethanol treatment induced wide-ranging aggregation of LDL. In contrast to ethanol treatment, ultrasonic treatment promoted the solubility and emulsifying stability of LDL and enhanced its zeta-potential (119.56%) and surface hydrophobicity (10.81%). Based on particle size analysis and transmission electron microscopy, approximately 34.65% of LDL had undergone aggregation and the molecular interface became more flexible after ultrasonic treatment. These results revealed the detailed changes in egg yolk LDL structure and properties during solvent (ethanol) and physical (ultrasound) processing.

The nature of chirality induced by molecular aggregation and self-assembly

In this paper, we theoretically analyze the nature of chirality induced by molecular self-assembly with molecular dynamics and visualization methods. Firstly, the dynamics of molecular self-assembly of biphenylenes system are demonstrated in detail. Secondly, the molecular interactions for the assembled molecules are analyzed with the weak intermolecular forces. Thirdly, electron-hole coherence and charge transfer in optical absorption are demonstrated with a transition density matrix and charge difference density, respectively. The detailed visualized analysis of electric and magnetic transition dipole moment integrals reveals the nature of chirality of assembled molecules in electronic circular dichroism (ECD) spectroscopy. The Raman optical activity (ROA) spectra demonstrate that the chirality of assembled molecules is strongly dependent on the pre-resonance Raman spectra, based on the optical absorption and ECD spectroscopy. Our visualized analysis method can well reveal the nature and origin of chirality of molecular self-assembly.

Spectroscopic Studies of Fluorescence Effects in Bioactive 4-(5-Heptyl-1,3,4-Thiadiazol-2-yl)Benzene-1,3-Diol and 4-(5-Methyl-1,3,4-Thiadiazol-2-yl)Benzene-1,3-Diol Molecules Induced by pH Changes in Aqueous Solutions

This paper presents the results of stationary fluorescence spectroscopy and time-resolved spectroscopy analyses of two 1,3,4-thiadiazole analogues, i.e. 4-(5-methyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C1) and 4-(5-heptyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C7) in an aqueous medium containing different concentrations of hydrogen ions. An interesting dual florescence effect was observed when both compounds were dissolved in aqueous solutions at pH below 7 for C1 and 7.5 for C7. In turn, for C1 and C7 dissolved in water at pH higher than the physiological value (mentioned above), single fluorescence was only noted. Based on previous results of investigations of the selected 1,3,4-thiadiazole compounds, it was noted that the presented effects were associated with both conformational changes in the analysed molecules and charge transfer (CT) effects, which were influenced by the aggregation factor. However, in the case of C1 and C7, the dual fluorescence effects were visible in a higher energetic region (different than that observed in the 1,3,4-thiadiazoles studied previously). Measurements of the fluorescence lifetimes in a medium characterised by different concentrations of hydrogen ions revealed clear lengthening of the excited-state lifetime in a pH range at which dual fluorescence effects can be observed. An important finding of the investigations presented in this article is the fact that the spectroscopic effects observed not only are interesting from the cognitive point of view but also can help in development of an appropriate theoretical model of molecular interactions responsible for the dual fluorescence effects in the analysed 1,3,4-thiadiazoles. Furthermore, the study will clarify a broad range of biological and pharmaceutical applications of these compounds, which are more frequently used in clinical therapies. Graphical Abstract Upper left corner - C7 molecule at high pH, right upper corner - fluorescence emission spectrum for C7 dissolved in H₂O at high pH (7-12) - single fluorescence. Bottom left corner - C7 molecule at low pH (1-7), lower right corner - fluorescence emission spectrum for C7 dissolved in water at low pH - two fluorescence emissions. The circles indicate the group related to dissociation of molecules at low and high pH and the additional long circles indicate C1 or a molecule with a shorter acyl chain.

Investigating how the attributes of self-associated drug complexes influence the passive transport of molecules through biological membranes

Relatively little is known about how drug self-association influences absorption into the human body. This study presented two hydrophobic membranes with a series of solutions containing different types of tetracaine aggregates with the aim of understanding how the attributes of supramolecular aggregate formation influenced passive membrane transport. The data showed that aqueous solutions of the unprotonated form of tetracaine displayed a significantly higher (p < 0.05) passive membrane transport compared to solutions with mixtures of the unprotonated and protonated drug microspecies (e.g. transport through the skin was 0.96 ± 0.31 μg cm⁻² min⁻¹ and 1.59 ± 0.26 μg cm⁻² min⁻¹ respectively). However, despite an enhanced rate of drug transport and a better membrane partitioning the unionised molecules showed a significantly longer (p < 0.05) lag time to membrane penetration compared solutions rich in the ionised microspecies. Analytical characterisation of the solutions applied to the apical surface of the membranes in the transport studies showed that larger tetracaine aggregates with smaller surface charge gave rise to the longer lag times. These large aggregates demonstrated more extensive intermolecular bonding and therefore, it was suggest that it was the enhanced propensity of the unionised species to form tightly bound drug aggregates that caused the delay in the membrane penetration.

Indium-chlorine and gallium-chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir-Blodgett nanolayers--spectroscopic investigations

The paper deals with spectroscopic characterization of metallic phthalocyanines (Pc's) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate.

Spectroscopic and Theoretical Studies of Fluorescence Effects in 2-Methylamino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole Induced by Molecular Aggregation

The article presents the results of fluorescence analyses of 2-methylamino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (MDFT) in an aqueous environment. MDFT dissolved in aqueous solutions with a pH value in the range from 1 to 4.5 yielded an interesting effect of two clearly separated fluorescence emissions. In turn, a single fluorescence was observed in MDFT dissolved in water solutions with a pH value from 4.5 to 12. As it was suggested in the previous investigations of other 1,3,4-thiadiazole compounds, these effects may be associated with conformational changes in the structure of the analysed molecule accompanied by aggregation effects. Crystallographic data showed that the effect of the two separated fluorescence emissions occurred in a conformation with the –OH group in the resorcyl ring bound on the side of the sulphur atom from the 1,3,4-thiadiazole ring. The hypothesis of aggregation as the mechanism involved in the change in the spectral properties at low pH is supported by the results of (Time-Dependent) Density Functional Theory calculations. The possibility of rapid analysis of conformational changes with the fluorescence spectroscopy technique may be rather important outcome obtained from the spectroscopic studies presented in this article. Additionally, the presented results seem to be highly important as they can be easily observed in solutions and biologically important samples.

Rayleigh light scattering detection of three α1-adrenoceptor antagonists coupled with high performance liquid chromatograph

Herein, a Rayleigh light-scattering (RLS) detection method combined with high performance liquid chromatograph (HPLC) without any post-column probe was developed for the separation and determination of three α₁-adrenoceptor antagonists. The quantitative analysis is benefiting from RLS signal enhancement upon addition of methanol which induced molecular aggregation to form an hydrophobic interface between aggregates and water that produce a sort of superficial enhanced scattering effect. A good chromatographic separation among the compounds was achieved using a Gemini 5u C₁₈ reversed phase column (250 mm × 4.6 mm; 4 μm) with a mobile phase consisting of methanol and ammonium acetate-formic acid buffer solution (25 mM; pH=3.0) at the flow rate of 0.7 mL min(-1). The RLS signal was monitored at λex=λem=354 nm. A limit of detection (LOD) of 0.065-0.70 μg L(-1) was reached and a linear range was found between peak height and concentration in the range of 0.75-15 μg L(-1) for doxazosin mesylate (DOX), 0.075-3.0 μg L(-1) for prazosin hydrochloride (PRH), and 0.25-5 μg L(-1) for terazosin hydrochloride (TEH), with linear regression coefficients all above 0.999. Recoveries from spiked urine samples were 88.4-99.0% which is within acceptable limits. The proposed method is convenient, reliable and sensitive which has been used successfully in human urine samples.

Spectral investigation of phthalocyanine complexes of high-valence silver and their aggregates

Several novel silver(II) complexes ligating a tetra-substituted phthalocyaninate, [Ag(tbpc)] (where tbpc denotes tetra-tert-butylphthalocyaninate), [Ag(tppc)] (tppc = tetrakis(2,6-dimethylphenoxy)phthalocyaninate), [Ag(tObpc)] (tObpc = tetra-n-butoxyphthalocyaninate), and [Ag(tpySpc)] (tpySpc = tetrakis(4-pyridylthio)phthalocyaninate) have been synthesized and characterized by elemental analyses, MALDI-TOF MS, optical absorption, and magnetic circular dichroism (MCD) spectroscopy. Although all the compounds are well soluble in common organic solvents, concentration studies on their optical spectra in solutions have found that they are prone to strongly aggregate in a cofacial manner (i.e., H-aggregate). Silver(II) complexes, which are essentially non-fluorescent, are readily demetallated in the presence of appropriate reductant (e.g., I^- or BH₄^-) to liberate the corresponding macrocyclic ligand, which emits intense red fluorescence. Chemical oxidation by using NOBF₄ generates the corresponding silver(III) species.

Metal Organic Framework Based on Photoactivated Aggregation-Induced Emission Molecule for Achieving Photoexcitation Regulation

Ln-MOFs, composed of lanthanide ions and functional organic ligands, are porous materials with tunable structures and unique luminescent properties. However, the interplay between ligand AIE properties and the framework's "antenna effect" on MOF morphology is understudied. Here, Tb-D-Cam-TPTB was synthesized via solvothermal method using TPTB (persulfurated arene) as the primary ligand, D-Cam as the auxiliary ligand, and Tb3+ as the metal ion. Photoexcitation of TPTB, a typical AIE molecule, promotes conformational changes, enhancing molecular aggregation and luminescence. Comprehensive photophysical investigations of TPTB in solution and crystal states, Tb3+-TPTB coordination, and Tb-D-Cam-TPTB MOF were conducted using various spectroscopic and imaging techniques. This study explores the interaction between ligand AIE and the "antenna effect" on Ln-MOF luminescence and crystal structure. The results indicate that, when the ligand is a photoexcitation-induced AIE molecule, UV irradiation of the precursor solution prior to crystal growth can alter the crystal structure, luminescence intensity, and color, holding great promise for applications in anti-counterfeiting, sensing, and other related fields.

Manipulating Aggregate Electrochemistry for High-Performance Organic Redox Flow Batteries

Organic molecule in solutions is the energy storage unit in the organic redox flow batteries (ORFBs), of which the aggregation is acknowledged pivotal but has been rarely investigated. By establishing a pyridinium library, the manipulation over the aggregation in solutions is investigated at the molecular level. Both theoretical calculations and physiochemical methods are used to characterize the aggregate's structure, and salient findings are as follows. First, the singly-reduced monoradicals simultaneously aggregate in a concentrated solution, which is driven by the solvation effect, orbital overlap and dispersion interaction. Second, the aggregation can be manipulated by the molecular engineering strategy and counteracted by introducing either electrostatic repulsive force or twisted geometry. Third, the monoradical's aggregation yields a decrease in the molecular singly occupied molecular orbital energy level and a linear scaling relationship with its thermodynamic potential. As a result, the increase in the concentration lowers the battery's voltage, which counteracts its effort to increase the battery's energy density. The anti-aggregation is proven effective in breaking the scaling relationship and accordingly, a molecular strategy to manipulate aggregate electrochemistry is developed. This work provides physical insights into the electrolytic solution and chemical strategy for optimizing the flow battery.

Optimizing Molecular Packing and Interfacial Contact via Halogenated N-Glycidyl Carbazole Small Molecules for Low Energy Loss and Highly Efficient Inverted Perovskite Solar Cells

Nonideal interfacial contact and non-radiative voltage loss in self-assembled monolayers (SAMs)-based inverted perovskite solar cells (PSCs) limit their further development. Herein, two carbazole-based molecules with different halogen atoms (X-OCZ, X = Cl or Br) are developed as efficient interfacial regulators. The halogen effect not only finely modulates the molecular packing, crystallinity, and surface contact potential of the MeO-2PACz analogue via self-induced intermolecular interactions but also significantly influences the subsequent crystal growth of perovskite, thus resulting in the formation of high-quality films with enhanced crystallinity, improved energy level alignment, and depressed non-radiative recombination. Importantly, the Cl-OCZ-mediated device exhibits a minimal interfacial carrier transport energy barrier of 0.10 eV and an impressive charge collection efficiency of 93.6%. Moreover, the target device (aperture area: 0.09 cm2) shows an exceptional efficiency of 26.57% (certified 26.4%) along with enhanced thermal and operational stability. The strategy is also extended to large area devices, delivering efficiencies of 25.0% for a 1 cm2 device and 22.9% for a 12.96 cm2 minimodule. This study highlights the halogen role of interfacial small molecules in optimizing molecular packing and interfacial contact toward highly efficient PSCs with minimized energy loss and non-radiative recombination.

Morphology and molecular arrangement of perylene-3,4,9,10-(n-pentylester) in thin layers obtained by zone-casting

Liquid-crystalline perylene-3,4,9,10-tetra-(n-pentylester) zone-casted on hydrophilic glass substrates forms characteristic belt-like structures which are observed under optical microscope and atomic force microscope. Polarised Raman scattering spectra reveal the presence of anisotropic alignment of the molecules inside the obtained structures. Moreover, the absorption and fluorescence spectra confirm molecular aggregation in the belt-like structures. The research shows, that the belt-like structures are created by columns of molecules with the edge-on alignment on the glass substrate. Such organisation of the molecules is confirmed by spectroscopic methods. These structures can be interesting from the point of view of organic electronics.