Search Results (38)

This paper studies how a localized defect migrates through the $D_4$ root lattice. Its spatial slice is the face-centered cubic lattice, and the tetrahedral voids of that slice form a simple cubic sublattice, two-colored by coordinate sum modulo four. Four results follow. First, the exclusion geometry of a void closes its four face channels and leaves six edge channels open, so the coordination number six is derived and not assumed. Second, each void class admits exactly one bond-direction set, so a void carries one bit of orientation information. The matter/antimatter grading therefore cannot be the void class, and the worldline must carry it instead. This corrects an earlier identification of inversion-related voids with matter and antimatter: those classes are propagation sublattices. Third, the rotational site symmetry is $T\cong A_4$, whose double cover has faithful irreducible representations only in dimension two. Among the half-integer spins, $j=\frac{1}{2}$ alone stays irreducible on restriction. This selects a spin; it does not determine one. Fourth, a hop induces a canonical bijection on the bounding atoms by a lattice translation, and baryon species is preserved if the winding labels follow that bijection. One dynamical postulate is used. Under it a hop carries exactly one time step, no update leaves a defect in place, and a defect at rest oscillates between two adjacent voids. A closing section records the conditions under which a localized continuum solution obeys $E=\gamma E_{\mathrm{rest}}$; no such relation is derived here for the lattice defect, and that section is conditional throughout. Every geometric claim is verified by an accompanying script. Full article

In UV curing technology, traditional photoinitiators are widely used in fields such as food packaging and medical devices, but they have some issues. These include migration, volatility and toxicity of the residue photoinitiator during their useful periods. This study aims to develop specialized photoinitiators specifically for food packaging and medical devices to address this gap. A novel photoinitiator, 2-{2-[4-(2-hydroxy-2-methylpropan-oyl) phenoxy]ethoxy}ethyl 2-acetoxybenzoate (AI-2959), was synthesized via esterification between acetylsalicylic acid (aspirin) and the commercial photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2- methyl- propiophenone (I-2959). The structure was confirmed using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), and elemental analysis, and the physicochemical properties of AI-2959 and I-2959 were compared. The ultraviolet spectra revealed absorption characteristics similar to I-2959 but with a higher molar extinction coefficient, indicating superior photosensitivity. Thermogravimetric analysis demonstrated improved thermal stability, and photopolymerization kinetics studies showed enhanced resistance to oxygen inhibition and higher double-bond conversion. Coating performance tests indicated a shorter curing time, greater hardness, and excellent adhesion. Importantly, the relative migration rate of AI-2959 was only 10.2% of that of I-2959, significantly reducing potential biotoxicity risks. These properties suggest the good potential of AI-2959 for use in biomedical and pharmaceutical applications involving UV curing. Full article

Helium accumulation is a major contributor to swelling, gas release, and mechanical degradation in oxide nuclear fuels under irradiation. This study employs first-principles density functional theory (DFT) to investigate helium behavior in thorium-based mixed oxide (MOX) fuels. A series of (Th_1−xPu_x)O₂ and (Th_1−xU_x)O₂ solid solutions (x = 0, 0.25, 0.5, 0.75, and 1) was constructed, and the corresponding ground-state configurations were determined through total-energy minimization. The effects of 4.167 at.% helium incorporation on structural stability, electronic structure, elastic response, and thermal expansion were evaluated. Helium migration in ThO₂, PuO₂, and UO₂ was further investigated at octahedral interstitial, metal-vacancy, and oxygen-vacancy sites. Positive helium incorporation energies indicated that helium incorporation is energetically unfavorable for all compositions. Vegard-like behavior was preserved for lattice constants and metal–oxygen bond lengths. The 2.06 eV band gap of UO₂ disappeared after helium incorporation, whereas band-gap variations in most MOX compositions remained below 0.7 eV. Helium reduced the bulk moduli of (Th_0.75U_0.25)O₂ and UO₂ by 3.75% and 7.94%, respectively. Thermal expansion coefficients followed the order α_L-UO2 > α_L-PuO2 > α_L-ThO2, with α_L of UO₂ nearly doubling. Metal vacancies acted as helium traps, whereas adjacent oxygen vacancies provided the lowest migration barrier of 0.42 eV. These results indicate that increasing ThO₂ content improves the resistance of MOX fuels to helium-induced degradation. Full article

Ribonucleotides are frequently incorporated into DNA during the replication of genetic information and, if missed during ribonucleotide excision repair, they may undergo phosphodiester bond rearrangement or cleavage. These changes can in turn lead to deformation of the spatial geometry of the local double helix and potentially interfere with charge transfer through ds-DNA. This process is believed to support long-range communication between proteins involved in genome replication and repair. This study theoretically explores how a single embedded riboadenosine (A₃) affects the structure, electronic properties, and charge-transfer properties of double-stranded DNA ([A₁G₂A₃G₄A₅]*[T₅C₄T₃C₂T₁]). In particular, the study focuses on four products formed at the ribonucleotide site: native 3′,5′-linkage (R-DNA), the 2′,3′-cyclic phosphate intermediate (IM-R-DNA), rearranged 2′,5-linked (RE-R-DNA), and the single-strand-break cleavage product (SSB-R-DNA). This theoretical investigation was performed at the M06-2X/6-31++G**//M06-2X/D95** level of theory in the aqueous phase. Significant spatial geometry perturbations were found at the central part of ds-oligonucleotides, i.e., the A₃T₃|G₄C₂ region, where the modified linkage affected the base overlap and stacking interactions most strongly; in the rearranged and cleaved forms, stacking at this site decreased by about 7 kcal•mol⁻¹ relative to native DNA. Global electronic analysis showed that R-DNA had the highest ionisation potential and the lowest electron affinity, whereas SSB-R-DNA displayed the lowest adiabatic ionisation potential and the highest adiabatic electron affinity, indicating a much greater tendency to stabilise excess charge. At the base-pair level, G₂C₄ was usually the preferred hole sink, except in RE-R-DNA, where G₄C₂ was favoured. In contrast, electron localisation was generally favoured at G₄C₂, while, in SSB-R-DNA, the A₃T₃ pair became the most favourable electron-accepting site. Overall, the results show that even a single ribonucleotide, depending on its linkage chemistry, can substantially reshape charge migration through ds-DNA and may therefore influence lesion recognition, repair efficiency, and genome stability. Full article

To reveal the long-term anti-aging mechanisms of rubber–plastic elastomer-modified asphalt in complex service environments and overcome the inherent defects of single polymer modifiers—namely their susceptibility to degradation or phase separation—this study prepared styrene-butadiene-styrene (SBS), low Mooney rubber (LMMR), and low-density polyethylene (LDPE)-modified asphalts. Simultaneously, an LMMR-LDPE rubber–plastic thermoplastic elastomer (TPE) was fabricated utilizing twin-screw extrusion technology and subsequently used to prepare a composite-modified asphalt. Three aging protocols were simulated: short-term thermo-oxidative aging (RTFOT), long-term pressure aging (PAV), and ultraviolet light aging (UV). A multi-scale quantitative characterization was conducted using a dynamic shear rheometer, Fourier transform infrared spectroscopy, and atomic force microscopy to evaluate the rutting factor, carbonyl index, and surface microroughness of each system before and after aging. The experimental results indicate that the coupled effect of long-term stress and thermal oxidation causes the most severe damage to the colloidal structure of modified asphalt. Conventional SBS-modified asphalt, due to its abundance of unsaturated double bonds, exhibits a sharp increase in the carbonyl index and aging index of the rutting factor after aging, making it highly susceptible to oxidative chain scission. Although LDPE-modified asphalt possesses chemical inertness, it is prone to crystalline phase separation under aging conditions, resulting in a microroughness distortion rate of up to 86.36%. In contrast, the LMMR-LDPE composite system, leveraging the high chemical stability of the saturated aliphatic carbon chain and the flexibility-enhancing and crystallization-inhibiting effects of LMMR, effectively reduces active oxidation sites and improves interfacial compatibility. This composite system exhibits the lowest carbonyl increment and rheological attenuation under all aging conditions, while effectively inhibiting the free migration and agglomeration of macromolecular components. The LMMR-LDPE composite modification technology effectively overcomes the inherent drawbacks of single polymers, such as susceptibility to degradation or segregation, demonstrating excellent long-term macroscopic rheological stability and microscopic phase morphology anti-aging capability. The present findings provide laboratory-scale mechanistic support for the design of durable rubber–plastic-modified asphalt systems, while further pilot-scale, economic, and field validation is still required before practical engineering application can be fully assessed. Full article

Earthen immovable cultural relics, such as murals and painted clay sculptures, are prone to deterioration (e.g., efflorescence, flaking, and cracking) under long-term preservation conditions. While conventional restoration materials primarily offer reinforcement, they fail to regulate the migration of soluble salts within the relics, which is the main cause of such damage. Herein, aimed at protecting the painted sculptures and murals of the Yungang Grottoes, nano calcium-aluminum layered double hydroxides (Ca-Al LDHs) were prepared, and their effectiveness in regulating salt crystallization within the earthen ground layer, as well as their reinforcement performance were investigated. Simulated salt crystallization tests revealed that coating the ground layer with Ca-Al LDHs delayed salt-induced damage time by 150%. This can be attributed to the ability of Ca-Al LDHs to adsorb sulfate ions from soluble salts, thereby inhibiting the crystallization of magnesium sulfate on the surface of the ground layer. After curing Ca-Al LDHs-coated samples at 35 °C and 55% relative humidity (RH) for 7 days, their surface Leeb hardness increased by 3.1%, and the weight loss rate (measured via tape peeling test) decreased by 38.3%. These results indicate that the surface bonding strength was enhanced following Ca-Al LDHs coating, with the underlying mechanism being the transformation of part of the LDHs into calcium carbonate under the influence of water and carbon dioxide. This study demonstrates that Ca-Al LDHs not only suppress magnesium sulfate crystallization but also provide effective surface consolidation, showing promising potential for application in conserving painted sculptures and murals at the Yungang Grottoes. Full article

In this study, a series of (Z)- and (E)-2-substituted-3-ferrocene-acrylonitrile derivatives were synthesized, characterized, and evaluated in vitro for their anticancer and anti-migration properties. The compounds were synthesized via the Knoevenagel condensation of the appropriate benzyl cyanide or benzoyl acetonitrile with ferrocenecarboxaldehyde 1, producing isolated yields of 99 to 23%. The structures of the compounds were analyzed using IR, ¹H NMR, ¹³C{¹H} NMR, GC-MS, and UV/Vis spectroscopic methods. Single-crystal X-ray diffraction analysis of representative compounds 21, 27, and 29 demonstrated that the geometry of the double bond was that of the (Z)-isomer. For representative compound 33, the geometry of the double bond was that of the (E)-isomer. Additionally, the electrochemistry of the compounds was investigated using cyclic voltammetry. The cytotoxic and anti-migratory effects of these compounds were evaluated in the MCF-7 and MDA-MB-231 breast cancer cell lines, providing insight into the structure–activity relationships. Preliminary investigations of their anticancer activity revealed that several compounds exhibit moderate antiproliferative effects on cancer cell lines, with GI₅₀ values ranging from 23 to 44 μM for the MCF-7 cell line and from 9 to 41 μM for the MDA-MB-231 cell line. Moreover, compound (Z)-25 inhibited 13% of the migration activity of the metastatic MDA-MB-231 cell line. Full article

The genome is continuously exposed to different harmful factors whose activity causes different types of lesions. On the other hand, during the DNA replication process, a ribonucleoside (rN) can be inserted more frequently than the occurrence of DNA damage in the genome. Notably, it can be expected that their presence and chemical lability change the electronic properties of the double helix. In this study, a short ds-oligo with a single rN was taken into consideration. The ground-state molecular geometry was obtained at the M06-2x/D95* level of theory in the aqueous phase, while the energy and vertical and adiabatic electron affinity and ionisation potential were obtained at M06-2x/6-31++G**. The obtained results indicate that the 3′,5′-phosphodiester bond cleavage is favourable after the adiabatic cation and anion states are achieved by ds-DNA. Moreover, the lowest ionisation potential and highest electron affinity of 2.76 and 5.55 eV, respectively, which make it a suitable endpoint for electrons and holes, have been found for the final product that contains a single-strand break. Additionally, after the internucleotide 3′,5′→2′,5′ bond migration process, proton-coupled electron transfer was found to occur. In this article, the electronic properties of short ds-DNA fragments with ribonucleoside inserts are reported for the first time. The obtained results suggest that rNs can play a significant role in the communication of repair and replication proteins via electron transfer, especially after rearrangement. Moreover, the discussed internucleotide bond stability changes after one-electron oxidation or reduction and can support new radiotherapy strategies that are safer and more effective. Further theoretical and experimental studies are highly warranted. Full article

The effect of low-molecular-weight dissolved organic matter (LDOM) on antimony enrichment in groundwater remains unclear. In this study, the spectroscopic and molecular characteristics of high- and low-Sb groundwater are compared using optical spectrophotometry, ultrafiltration, and Fourier transform ion cyclotron resonance mass spectrometry. The results demonstrated that although the mean DOM concentration in LDOM groundwater (3.98 mg/L) accounted for only 69.22% of the mean DOM concentration, the proportion of Sb(V) within the total Sb varied between 80.29% and 99.56%. LDOM was characterized by higher biological and fluorescence index values, a greater H/C ratio, and reduced double-bond equivalent values compared with high-molecular-weight dissolved organic matter. High abundances of LDOM can enhance the primary enrichment of Sb(V) within the total Sb concentration via competitive adsorption and, as energy and electron acceptors for microbial communities facilitate Sb(III), oxidation within groundwater systems. This study provides new perspectives on understanding how DOM influences the migration and speciation transformation of Sb in groundwater environments. Full article

Spirocalcaridines A and B are among the most challenging members of the marine invertebrate-derived Leucetta alkaloids. Approaches to the construction and elaboration of the highly compact spirocyclic core are described. The synthesis of tricyclic guanidine via tandem oxidative amination dearomatizing spirocyclization (TOADS) using hypervalent iodine set the stage for total synthesis via the migration of the C4/C8 double bond to the C4/C5 position, followed by oxidation. The undesired but not surprising propensity of the spirocyclic cyclohexadienone to undergo rearrangement to the phenol hindered the desired olefin migration. Furthermore, initial efforts to install the oxidation sequentially, first at C5 and then at C4 in the complete carbon skeleton, were fraught with unforeseen challenges and unusual outcomes. In addition, the scope and limitations of hypervalent iodine-mediated tandem oxidative dearomatizing spirocyclization on various substrates were explored. Urethanes and thiourethanes underwent spirocyclization with an excellent yield, whereas the reaction with allylic substrates and species lacking the p-methoxy substituent did not proceed. Attempts to prepare other guanidine precursors are briefly discussed. Full article

Background/Objectives: Cashew nutshell liquid (CNSL) is obtained during the industrial processing of cashew nuts. It contains anacardic acid (2-hydroxy-6-n-pentadecylbenzoic acid) and cardanol (3-n-pentadecylphenol). Therefore, CNSL provides a rich source of phenolic lipids serving as natural antioxidants or precursors for industrial uses. Here, we have analyzed in detail a commercial sample of cardanol by nuclear magnetic resonance (NMR) spectroscopy and its biological activities in the human keratinocyte cell line (HaCaT cells). Methods: The cytotoxic effects, genotoxicity, cell proliferation, and healing properties on HaCaT cells were studied using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, comet assay, proliferation assay, and scratch assay, respectively. Additionally, the modulatory effect of cardanol on the cellular fatty acid profile of HaCaT cells was analyzed by gas chromatography. Results: NMR showed the structure of cardanol as a mixture of the 8′-monoene (42%), the 8′,11′-diene (22%), and the 8′,11′,14′-triene (36%) for the pentadecyl side chain with all double bonds in Z configuration. The cytotoxic effects on HaCaT cells only occurred at high concentrations of cardanol (>10 µg/mL), which caused significant reductions in cell viability. Using the comet assay, a dose-dependent increase in DNA damage was found at concentrations above 10 µg/mL. Scratch assays revealed that cardanol achieved 99% wound closure of HaCaT cells treated with 1 µg/mL cardanol after 48 h. Cardanol at 1 and 0.1 µg/mL significantly enhanced HaCaT cell proliferation and promoted migration, contributing to accelerated wound healing processes. As shown by gas chromatography, 1 µg/mL cardanol increased the total amount of polyunsaturated fatty acids (PUFA), including ω-3, ω-6, and ω-9 fatty acids. Conclusions: Together, these findings suggest that concentrations of <10 µg/mL cardanol are safe and exhibit beneficial biological activities, particularly wound-healing effects on HaCaT cells. Further studies are necessary to explore additional potential applications of cardanol, to refine its formulations for clinical use, and to ensure its safety and action in other target cells and species. Full article

The current paradigm of low-T combustion and autoignition of hydrocarbons is based on the sequential two-step oxygenation of fuel radicals. The key chain-branching occurs when the second oxygenation adduct (OOQOOH) is isomerized releasing an OH radical and a key ketohydroperoxide (KHP) intermediate. The subsequent homolytic dissociation of relatively weak O–O bonds in KHP generates two more radicals in the oxidation chain leading to ignition. Based on the recently introduced intramolecular “catalytic hydrogen atom transfer” mechanism (J. Phys. Chem. 2024, 128, 2169), abbreviated here as I-CHAT, we have identified a novel unimolecular decomposition channel for KHPs to form their classical isomers—enol hydroperoxides (EHP). The uncertainty in the contribution of enols is typically due to the high computed barriers for conventional (“direct”) keto–enol tautomerization. Remarkably, the I-CHAT dramatically reduces such barriers. The novel mechanism can be regarded as an intramolecular version of the intermolecular relay transfer of H-atoms mediated by an external molecule following the general classification of such processes (Catal. Rev.-Sci. Eng. 2014, 56, 403). Here, we present a detailed mechanistic and kinetic analysis of the I-CHAT-facilitated pathways applied to n-hexane, n-heptane, and n-pentane models as prototype molecules for gasoline, diesel, and hybrid rocket fuels. We particularly examined the formation kinetics and subsequent dissociation of the γ-enol-hydroperoxide isomer of the most abundant pentane-derived isomer γ-C5-KHP observed experimentally. To gain molecular-level insight into the I-CHAT catalysis, we have also explored the role of the internal catalyst moieties using truncated models. All applied models demonstrated a significant reduction in the isomerization barriers, primarily due to the decreased ring strain in transition states. In addition, the longer-range and sequential H-migration processes were also identified and illustrated via a combined double keto–enol conversion of heptane-2,6-diketo-4-hydroperoxide as a potential chain-branching model. To assess the possible impact of the I-CHAT channels on global fuel combustion characteristics, we performed a detailed kinetic analysis of the isomerization and decomposition of γ-C5-KHP comparing I-CHAT with key alternative reactions—direct dissociation and Korcek channels. Calculated rate parameters were implemented into a modified version of the n-pentane kinetic model developed earlier using RMG automated model generation tools (ACS Omega, 2023, 8, 4908). Simulations of ignition delay times revealed the significant effect of the new pathways, suggesting an important role of the I-CHAT pathways in the low-T combustion of large alkanes. Full article

In this review, we focus on the one-electron oxidation of DNA, which is a multipart event controlled by several competing factors. We will discuss the oxidation free energies of the four nucleobases and the electron detachment from DNA, influenced by specific interactions like hydrogen bonding and stacking interactions with neighboring sites in the double strand. The formation of a radical cation (hole) which can migrate through DNA (hole transport), depending on the sequence-specific effects and the allocation of the final oxidative damage, is also addressed. Particular attention is given to the one-electron oxidation of ds-ODN containing G:C pairs, including the complex mechanism of the deprotonation vs. hydration steps of a G:C^•+ pair, as well as to the modes of formation of the two guanyl radical tautomers after deprotonation. Among the reactive oxygen species (ROS) generated in aerobic organisms by cellular metabolisms, several oxidants react with DNA. The mechanism of stable product formation and their use as biomarkers of guanine oxidation in DNA damage are also addressed. Full article

Reducing photoinitiator migration from photocured coatings remains a critical challenge, particularly for applications in food packaging and healthcare products. Here, we report a series of novel UV-LED sensitive oxime ester photoinitiators that possess self-anchoring ability through incorporating polymerizable double bonds into the coumarin chromophore. All photoinitiators exhibit strong absorption around 340 nm and efficient photolysis under 365 nm LED irradiation, showing good initiating efficiency in acrylates and thiol-ene formulations. Migration studies show that the incorporation of polymerizable groups at the oxime ester terminus reduces the migration rate of the residual photoinitiator from 81% to 16.3%, while introducing an allyl group into the coumarin structure further decreases it to 5% and potentially suppresses the migration of low-molecular-weight photolysis products. The dual-functionalized derivative achieves the lowest migration rate of 3%. This molecular design strategy provides an effective approach toward safe UV-LED curable coatings with minimal photoinitiator migration. Full article

Five new non-holostane di- and trisulfated triterpene pentaosides, conicospermiumosides A₃-1 (1), A₃-2 (2), A₃-3 (3), A₇-1 (4), and A₇-2 (5) were isolated from the Far Eastern sea cucumber Cucumaria conicospermium Levin et Stepanov (Cucumariidae, Dendrochirotida). Twelve known glycosides found earlier in other Cucumaria species were also obtained and identified. The structures of new compounds were established on the basis of extensive analysis of the 1D and 2D NMR spectra, as well as by the HR-ESI-MS data. The aglycones of 1–5 differed by side chains structures. Additionally, conicospermiumoside A₇-1 (4) had a 9(11)-double bond in the aglycone, while the remaining glycosides contained a 7(8)-intranuclear double bond. Eight types of carbohydrate chains known earlier from the glycosides of the sea cucumbers of the Cucumaria genus were found as part of the glycosides of C. conicospermium. The set of sugar chains of the glycosides from C. conicospermium was similar to that from C. okhotensis. The raw biogenetic series of aglycones, leading to the formation of hexa-nor-lanostane derivatives in the process of biosynthesis and a sort of functionally-structural division that was realized due to separation of biosynthetic pathways of holostane and lanostane derivatives, can be traced when the structures of the glycosides isolated from C. conicospermium are compared. The cytotoxic action against three human breast cancer cell lines (MCF-7, T-47D, MDA-MB-231), and non-tumor MCF-10A and hemolytic activity of compounds 1–5, as well as seven known glycosides were tested. Conicospermiumosides A₃-3 (3) and A₇-1 (4), having a 22-oxo-23(24)-en fragment, were strongly hemolytic despite lacking a lactone in their aglycones. Moreover, both compounds demonstrated a promising suppressing action against triple negative breast cancer cells. The cells of the MDA-MB-231 line were most sensitive to the cytotoxic action of the glycosides, while the MCF-7 cell line was most sustainable. Six glycosides were selected for further study of some aspects of anticancer action against MDA-MB-231. The selective action of the compounds 4 and 8 on the MDA-MB-231 cells without significant toxicity against the MCF-10A cells was noticeable. More importantly, the selectivity of the compounds was changed over time and maximal selectivity to cancer cells was demonstrated by glycoside 1 at 48 h of exposition. The glycosides 1, 3 and the desulfated derivative 7a strongly inhibited colony formation and growth of the TNBC cells until the process stops completely. Okhotoside B₁ (8), DS-okhotoside A₁-1 (7a), and conicospermiumoside A₃-3 (3) showed a potent cell migration-inhibiting capacity. Quantitative structure–activity relationships (QSARs) calculated on the basis of a correlational analysis of the physicochemical properties and structural features of the glycosides and their cytotoxic activity against different cell lines showed some structural features influenced differently, sometimes even in opposite ways, on the activity of glycosides toward diverse cells (erythrocytes, MCF-10A, and TNBC MDA-MB-231 cells). This observation indicated that glycosides obviously target different membrane components, such as lipids of erythrocytes and some receptors on the surface of mammary normal or tumor cells. Full article