Search Results (41)

Materials that store a significant amount of heat in a narrow temperature range by phase change solid–liquid or solid–solid are called Phase Change Materials (PCMs). Many PCMs are members of homologous groups of materials with similar composition and properties. Often, similarities are due to a common molecular composition with a repeating unit, e.g., for n-alkanes H-(CH₂)_n-H. An n related trend is typical in the melting temperature. Based on observations on solvents, the question arises whether such a trend also exists in eutectic binary mixtures with one component fixed while the other, from a homologous series, is varied. For verification, data from the literature were collected, specifically experimental data, each set having at least three variations from a single source. Eight data sets were collected, covering eutectic binary mixtures of n-alkanes, n-alkanols, and n-alkanoic acids. With one exception, all data sets show a systematic trend in the melting temperature and the composition. It is shown that the trends can be understood from thermodynamic theories of mixtures (Schröder–van Laar equation) combined with typical trends within homologous series. The findings offer new options in PCM development as well as the selection of PCMs for specific application temperatures. Full article

Materials that allow the storage of a significant amount of heat in a narrow temperature range by a solid–liquid or a solid–solid phase change are called Phase Change Materials (PCMs). Understanding the thermodynamics of PCMs is crucial in PCM R&D for identifying candidate materials, developing new PCMs, and optimizing known PCMs. In this work, a review of the use of entropy to understand the thermodynamics of pure substances as PCMs is performed. Among pure substances, water, alkanes, alkanols, and fatty acids are well-known. Because they give valuable information, elements are also included. While phase change enthalpy and temperature are easy to comprehend and are directly used for application, the opposite holds for entropy. Thus, entropy usually receives little attention. However, as this review shows, entropy is of central importance, and even if it is not analyzed explicitly, then it is implicitly included in the data. If explicitly used, it can reveal crucial information. This is shown by a review of analysis tools and their results from analyzing typical PCMs. The review shows that if entropy is used systematically, a significant improvement in the understanding of the thermodynamics of PCMs is possible. Full article

An excellent regioselectivity of vapor-phase catalytic transfer hydrogenation (CTH) of substituted oxiranes (methyl-, n-butyl-, and phenyloxirane) with alkanols (EtOH, 2-PrOH or 2-PeOH) as hydrogen donors in the presence of magnesium oxide as a catalyst was attained. In the vapor phase, all of these oxiranes as well as 1,2-epoxycyclohexane were hydrogenated. Moreover, it was found that primary alcohols were always the main products of CTH of methyl-, n-butyl-, and phenyloxirane with very good regioselectivity towards the alcohols: 93, 73, and 100%, respectively. It was shown that vapor-phase CTH of methyloxirane with 2-pentanol led to three products, two regioisomeric propanols, (1-PrOH and 2-PrOH), and also 1-(2-pentyloxy)-2-propanol. Their yields were 48%, 4%, and 35%, respectively. Two regioisomeric hexanols (1-HeOH, 54% yield and 2-HeOH, 20% yield) and 2-hexanone (14% yield) were found as products of the CTH of n-butyloxirane with 2-propanol as the hydrogen donor. For vapor-phase CTH of phenyloxirane, only 2-phenylethanol (95% yield) was observed together with minor amounts of phenylacetaldehyde. In vapor-phase CTH of 1,2-epoxycyclohexane, the presence of the transfer hydrogenation products (2-cyclohexenone, cyclohexanol, and cyclopentylmethanol) as well as isomerization products (cyclohexanone, 2-cyclohexenol, and 3-cyclohexenol) were found. It was noted that at 623 K, the yields of the former products were 18, 22, and 14%, respectively. Liquid-phase CTH of n-butyl- or phenyloxirane with 2-pentanol (b.p. 392 K) was unsuccessful. Full article

This study investigates the evolution of the chemical components of kombucha aroma during refrigerated storage. Two preparation methods (MT1 and MT2) were used to produce kombucha from a 1:1 mixture of black and green tea. The bottled beverages were stored at 4 °C for three months, and changes in headspace (HS) volatiles were monitored at different time points using solid-phase microextraction (SPME) and GC-MS. A total of 68 volatile substances were identified, with alcohols, acids, and esters dominating the aroma profile. The study revealed significant changes in flavor composition during cold storage, particularly in the first two weeks, with an increase in the number of esters, acids, ketones and terpenoids, as well as the total amount of esters and alkanols. While some changes contribute to the desirable “cider-like” characteristics, others, like certain volatile acids, aliphatic aldehydes and ketones, are associated with off-flavors. These findings suggest that refrigeration alone is not sufficient to completely inhibit microbial activity in freshly prepared kombucha, highlighting the need for further research to correlate chemical changes with sensory properties to establish optimal organoleptic standards and shelf life. Full article

This paper comprehensively reports experimental proof of parity violation in the ground and photoexcited states of three mirror-symmetric Si–Si bond polymers in homogeneous solutions of achiral molecules under non-stirring conditions by analyzing 370 chiroptical datasets relating to multiple second-order helix–helix transitions in the circular dichroism (CD) of poly(di-i-butylsilane) (iBS), poly(di-i-pentylsilane) (iPS), and poly(di-i-hexylsilane) (iHS) in achiral alkanols and p-dioxane-h₈/-d₈. Particularly large (–)-CD of g_abs = −3.1 × 10⁻² at 290 nm was found for iBS in i-pentanol at 25 °C. Notably, iPS in n-propanol at −5 °C generated (–)-CD with g_abs = −0.48 × 10⁻² at 300 nm, but (+)-circularly polarized luminescence (CPL) with g_lum = +0.84 × 10⁻² at 326 nm. In contrast, iHS in n-octanol at 0 °C showed only very weak (–)-CD of g_abs ~−0.03 × 10⁻² at 310 nm. The H/D isotopes of p-dioxane-h₈/-d₈ weakly affected the helix–helix transition characteristics of iBS. (–)-Sign vibrational CD signals assigned to the handed symmetric and asymmetric bending modes of the CH₃ and CH₂ groups of the solvents and other achiral molecules were observed. We assumed (i) three ¹H nuclear-spin-1/2 induced handed motions of CH₃ rotors at i-alkyl side chains and achiral alkanols, and (ii) helical main-chain Si atoms (δ⁺) coordinated by handed lone pairs at oxygen (δ⁻) in gauche-containing n- and i-alkanols induced by the CH₃ rotors. A possible origin of biomolecular handedness is proposed based on the first observation of far-UV CD and UV spectra of zwitterionic glycine bearing H₃N⁺ rotor in neutral H₂O. Full article

The diastereoselectivity of the liquid- and vapor-phase Catalytic Transfer Hydrogenation (CTH) of cyclic ketones: x-methylcyclohexanones (x = 2, 3 or 4), 4-t-butylcyclohexanone, and bicyclic ketones: 2-norbornanone, camphor, fenchone, and a tricyclic ketone (2-adamantanone) with secondary alkanols (2-propanol, 2-butanol, 2-pentanol, or 2-octanol) as hydrogen donors in the presence of ten metal oxides as the catalysts was studied. Among the oxides, only four, namely, MgO, ZrO₂·nH₂O, ZrO₂, and Al₂O₃, exhibited good or high activity. The reaction products are diastereoisomeric alcohols, the relative ratio of which depends on the structure of the ketone, mode of reaction, temperature, and, in the liquid-phase mode, reaction time. The results of vapor-phase CTH revealed that, in this mode of reaction, the diastereoselectivity to the trans isomer is lower than in the liquid phase. For the three x-methylcyclohexanones, the most pronounced difference between the experimental values and reference values was noted for x = 3. For bicyclic ketones, the implementation of heterogeneous catalysts allowed us to obtain a substantial excess of the less favorable diastereomer. In the case of 2-norbornanone, the thermodynamic equilibrium mixture contains 21% endo and 79% exo alcohols, whereas our product mixtures contained up to 79% of the endo isomer. Full article

Sargassum filipendula is a marine macroalgae, also known as brown algae. These species contain significant amounts of polysaccharides, such as alginates, and phenolic compounds, including phlorotannins, with excellent biological properties. This study evaluated the extraction of bioactive compounds from the residual biomass of Sargassum filipendula using deep eutectic solvents based on alkanol amines combined with polyols. The residual biomass presented a content of 7.36% protein, 1.11% lipids, 20.51% ash, 14.88% moisture, 50.25% total fibers, and 5.89% alginate. Preliminary screening identified N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30:1) and N, N-(dimethylamino)-ethanol:1,3-propanediol (1.83:1) as the most efficient solvents for the extraction of bioactive compounds. The optimization process showed that the temperature and solid–liquid ratio significantly influenced (p < 0.05) the extraction of total phenolic compounds, phlorotannins, and the content of photosynthetic pigments. Intermediate temperatures (74.4 °C for N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30:1) and 68.4 °C for N, N-(dimethylamino)-ethanol:1,3-propanediol (1.83:1), and a lower solid-to-liquid ratio (0.03) were optimal conditions to extract the low-pigment phlorotannins selectively. In contrast, higher temperatures (120 °C) maximized the extraction of phlorotannins and photosynthetic pigments. N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30) extracted 110.64 mg PGE/g phlorotannins and 78.15 mg GAE/g phenolics, while N, N-(dimethylamino)-ethanol:1,3-propanediol (1.83:1) produced 21.57 mg PGE/g and 72.89 mg GAE/g, respectively. The extraction of photosynthetic pigments reached a maximum yield at 120 °C, using N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30:1), with a content of 21.61 µg/g of chlorophylls and 38.11 µg/g of pheophytins, while N, N-(dimethylamino)-ethanol: 1,3-propanediol (1.83:1) provided content of 17.76 µg/g and 36.32 µg/g, respectively. The extracts exhibited antioxidant activity with 0.69 mg TE/mL in scavenging DPPH radicals, 24.42 mg TE/mL in scavenging ABTS radicals, and 2.26 mg TE/mL of iron-reducing antioxidant power. These results demonstrate the potential of DESs for the sustainable recovery of bioactive compounds from Sargassum filipendula residual biomass. Full article

Liquid and vapor phase transfer hydrogenation with 2-alkanols as hydrogen donors in the presence of MgO as a catalyst was studied. A series of dicarbonyl compounds as well as the equimolar mixtures of various monocarbonyl compounds were used as hydrogen acceptors in order to determine the chemoselectivity (ChS) in the reduction of their carbonyl groups. Thus, 1,4-diacetylbenzene was reduced to 1-(4-acetylphenyl)-1-ethanol with 89% ChS and 1,3-diacetyl-4,6-dimethylbenzene with 100% ChS. Mesitylene diacyl derivatives were unreactive in the studied reaction. CTH of an equimolar mixture of benzaldehyde and acetophenone gave benzyl alcohol and 1-PhEtOH with yields of 91 and 3%, respectively (97% ChS). An equimolar mixture of acetophenone and 6-undecanone underwent CTH with yields of the corresponding alcohols of 89 and 2%, respectively, with 98% ChS towards 1-PhEtOH. Significant differences in reactivity in CTH were reported for an equimolar mixture of regioisomeric 1- and 2-acetylnaphthalenes. The yields of the corresponding alcohols were 20 and 68% with a ChS of 77% towards 2-NphCH(OH)Me. In the case of CTH of 3-oxo-2,2-dimethylbutanal and 2,4-bis(spirocyclohexyl)-1,3-cyclobutanedione with 2-propanol, only the solvolysis of the substrates was observed. The products were methyl isopropyl ketone and isopropyl formate for the former diketone and 1-(cyclohexylcarbonyl)-1-(carboisopropoxy)cyclohexane for the latter. Full article

Many species of the genus Pseudomonas are known to be highly tolerant to solvents and other environmental stressors. Based on phylogenomic and comparative genomic analyses, several Pseudomonas species were recently transferred to a new genus named Halopseudomonas. Because of their unique enzymatic machinery, these strains are being discussed as novel biocatalysts in biotechnology. In order to test their growth parameters and stress tolerance, five Halopseudomonas strains were assessed regarding their tolerance toward different n-alkanols (1-butanol, 1-hexanol, 1-octanol, 1-decanol), as well as to salt stress and elevated temperatures. The toxicity of the solvents was investigated by their effects on bacterial growth rates and presented as EC50 concentrations. Hereby, all Halopseudomonas strains showed EC50 values up to two-fold lower than those previously detected for Pseudomonas putida. In addition, the activity of the cis-trans isomerase of unsaturated fatty acids (Cti), which is an urgent stress response mechanism known to be present in all Pseudomonas species, was monitored in the five Halopseudomonas strains. Although several of the tested species were known to contain the cti gene, no significant phenotypic activity could be detected in the presence of the assayed stressors. A bioinformatic analysis of eight cti-carrying Halopseudomonas strains examining promotor binding sites, binding motifs and signal peptides showed that most of the cti genes have a lipoprotein signal peptide and promotor regions and binding motifs that do not coincide with those of Pseudomonas. These insights represent putative reasons for the absence of the expected Cti activity in Halopseudomonas, which in turn has always been observed in cti-carrying Pseudomonas. The lack of Cti activity under membrane stress conditions when the cti gene is present has never been documented, and this could represent potential negative implications on the utility of the genus Halopseudomonas for some biotechnological applications. Full article

The process of soil genesis unfolds as pioneering microbial communities colonize mineral substrates, enriching them with biomolecules released from bedrock. The resultant intricate surface units emerge from a complex interplay among microbiota and plant communities. Under these conditions, host rocks undergo initial weathering through microbial activity, rendering them far from pristine and challenging the quest for biomarkers in ancient sedimentary rocks. In addressing this challenge, a comprehensive analysis utilizing Gas Chromatography Mass Spectrometry (GC-MS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was conducted on a 520-Ma-old Cambrian rock. This investigation revealed a diverse molecular assemblage with comprising alkanols, sterols, fatty acids, glycerolipids, wax esters, and nitrogen-bearing compounds. Notably, elevated levels of bacterial C₁₆, C₁₈ and C₁₄ fatty acids, iso and anteiso methyl-branched fatty acids, as well as fungal sterols, long-chained fatty acids, and alcohols, consistently align with a consortium of bacteria and fungi accessing complex organic matter within a soil-type ecosystem. The prominence of bacterial and fungal lipids alongside maturity indicators denotes derivation from heterotrophic activity rather than ancient preservation or marine sources. Moreover, the identification of long-chain (>C22) n-alkanols, even-carbon-numbered long chain (>C20) fatty acids, and campesterol, as well as stigmastanol, provides confirmation of plant residue inputs. Furthermore, findings highlight the ability of contemporary soil microbiota to inhabit rocky substrates actively, requiring strict contamination controls when evaluating ancient molecular biosignatures or extraterrestrial materials collected. Full article

Surface sediment samples from Al-Qahma lagoon in the southern part and Al-Wajh lagoon in the northern part of the Red Sea coast of Saudi Arabia were collected by a Van Veen grab sampler to determine the characteristics, distribution, and sources of aliphatic and cyclic hydrocarbons. The total extractable organic matter (TEOM) was extracted with a dichloromethane/methanol mixture after drying and sieving the sediments and identified by gas chromatography–mass spectrometry. The TEOM comprised n-alkanes (302.6 ± 446.7 ng·g⁻¹ and 64 ± 50 ng·g⁻¹), hopanes (29.8 ± 132.3 ng·g⁻¹ and 1.0 ± 2.5 ng·g⁻¹), steranes (0.0 and traces), n-alkanoic acids (745.8 ± 799.6 ng·g⁻¹ and 120.7 ± 92.0 ng·g⁻¹), n-alkanols (457.4 ± 1085.6 ng·g⁻¹ and 49.7 ± 32.3 ng·g⁻¹), polycyclic aromatic hydrocarbons (PAHs) (54.5 ± 96.8 ng·g⁻¹ and 7.8 ± 8.5 ng·g⁻¹), and phthalates (185.3 ± 169.9 ng·g⁻¹ and 67.4 ± 70.4 ng·g⁻¹) in the Al-Qahma and Al-Wajh lagoon sediments, respectively. The percentages of the various sources relative to total aliphatic and cyclic hydrocarbon concentrations were 6.9 ± 6% for terrestrial plants, 53.7 ± 19% for algae, 10 ± 2% for microbial, 16 ± 12% for petroleum, and 13.4 ± 7 for plasticizer inputs in Al-Qahma lagoon. In Al-Wajh lagoon, they were 9.7 ± 4% for terrestrial plants, 30.8 ± 14% for algae, 25.2 ± 5% for bacteria, 11.2 ± 3% for petroleum, and 23.1 ± 11% for plasticizers. Full article

Six previously undescribed cytosporone derivatives (phomotones A-E (1–5) and phomotone F (13)), two new spiro-alkanol phombistenes A-B (14–15), and seven known analogs (6–12) were isolated from the mangrove endophytic fungus Phomopsis sp. QYM-13. The structures of these compounds were elucidated using spectroscopic data analysis, electronic circular dichroism (ECD), and ¹³C NMR calculations. Compound 14 features an unprecedented 1,6-dioxaspiro[4.5]decane ring system. All isolates were evaluated for their inhibitory effect on nitric oxide (NO) in LPS-induced RAW264.7 cells. The results showed that compounds 1, 6, 8, and 11 exhibited potent bioactivities by comparing with positive control. Then, compound 1 displayed the anti-inflammatory effect by inhibiting the MAPK/NF-κB signaling pathways. Molecular docking further revealed the possible mechanism of compound 1 interaction with ERK protein. Full article

The spectral and dynamic properties of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) in a series of 1-alkanols ranging from methanol to 1-decanol over a temperature range 100–300 K were investigated by electron spin resonance (ESR). The main characteristic ESR temperatures connected with slow to fast motion regime transition; T_50G ‘s and T_X1^fast ‘s are situated above the corresponding glass temperatures, T_g, and for the shorter members, the T_50G ‘s lie above or close to melting point, T_m, while the longer ones the T_50G < T_m relationship indicates that the TEMPO molecules are in the local disordered regions of the crystalline media. The T_50G ‘s and especially T_X1^fast ‘s are compared with the dynamic crossover temperatures, T_X^VISC = 8.72M^0.66, as obtained by fitting the viscosity data in the liquid n-alkanols with the empirical power law. In particular, for N_C > 6, the T_X1^fast ‘s lie rather close to the T_X^VISC resembling apolar n-alkanes [PCCP 2018,20,11145-11151], while for N_C < 6, they are situated in the vicinity of T_m. The absence of a coincidence for lower1-alkanols indicates that the T_50G is significantly influenced by the mutual interaction between the polar TEMPO and the protic polar medium due to the increased polarity and proticity destroyed by the larger-scale melting transition. Full article

This study presents for the first time an analysis of the content and chemical composition of the cuticular waxes and cutin in the leaves of the widespread and important tropical species Terminalia catappa. The leaves were collected in the equatorial Atlantic islands of São Tomé and Príncipe, in the Gulf of Guinea. The epicuticular and intracuticular waxes were determined via dichloromethane extraction and their chemical composition via GC-MS analysis, and the content and monomeric composition of cutin were determined after depolymerization via methanolysis. The leaves contained an epidermal cuticular coverage of 52.8 μg cm⁻² of the cuticular waxes (1.4% of mass) and 63.3 μg cm⁻² (1.5% of mass) of cutin. Cuticular waxes include mainly n-alkanols and fatty acids, with a substantial proportion of terpenes in the more easily solubilized fraction, and sterols in the more embedded waxes. Cutin is mostly constituted by C16 fatty acids and dihydroxyacids, also including aromatic monomers, suggesting a largely linear macromolecular arrangement. The high proportion of triacontanol, α-amyrin, β-amyrin, germanicol, and lupeol in the easily solubilized cuticular fraction may explain the bioactive properties attributed to the T. catappa leaves via the popular medicine, which allows us to consider them as a potential source for the extraction of these compounds. Full article

Signal transduction by the high-affinity IgE receptor (FcεRI) depends on membrane lipid and protein compartmentalization. Recently published data show that cells treated with 1-heptanol, a cell membrane fluidizer, exhibit changes in membrane properties. However, the functional consequences of 1-heptanol-induced changes on mast cell signaling are unknown. This study shows that short-term exposure to 1-heptanol reduces membrane thermal stability and dysregulates mast cell signaling at multiple levels. Cells treated with 1-heptanol exhibited increased lateral mobility and decreased internalization of the FcεRI. However, this did not affect the initial phosphorylation of the FcεRI-β chain and components of the SYK/LAT1/PLCγ1 signaling pathway after antigen activation. In contrast, 1-heptanol inhibited SAPK/JNK phosphorylation and effector functions such as calcium response, degranulation, and cytokine production. Membrane hyperfluidization induced a heat shock-like response via increased expression of the heat shock protein 70, increased lateral diffusion of ORAI1-mCherry, and unsatisfactory performance of STIM1-ORAI1 coupling, as determined by flow-FRET. Furthermore, 1-heptanol inhibited the antigen-induced production of reactive oxygen species and potentiated stress-induced plasma membrane permeability by interfering with heat shock protein 70 activity. The combined data suggest that 1-heptanol-mediated membrane fluidization does not interfere with the earliest biochemical steps of FcεRI signaling, such as phosphorylation of the FcεRI-β chain and components of the SYK/LAT/PLCγ1 signaling pathway, instead inhibiting the FcεRI internalization and mast cell effector functions, including degranulation and cytokine production. Full article