Bonds In Chain Research Articles

An efficient approach towards highly chemically stable poly(norbornene) membrane for alkaline polyelectrolyte fuel cells

The chemical stability of alkaline polymer electrolytes (APEs) is paramount for ensuring the long-term durability of alkaline polyelectrolyte fuel cells. Convenient methods for acquiring highly stable polymers are pivotal for fuel cell commercialization. Herein, we propose a novel strategy involving post-polymerization and grafting via cross-metathesis reaction to yield highly alkaline-stable quaternary ammonium polynorbornenes (QAPNBs). This method boasts mild reaction conditions, high yields, and cost-effective reactants. The yields have increased from less than 40 % to an impressive 80 %. Upon comparing the alkaline stability of APEs with different side chain structures, it was observed that the presence of unsaturated double bonds in the side chain adversely affected the cations, while saturated APEs retained over 90 % of the cations during stability tests at 80 °C and 1 M KOH for 4800 h. Employing the QAPNBs in fuel cells resulted in a peak power density of 2.32 W cm−2 and a durability of 200 h at 600 mA cm−2.

Effect of glycerol plasticizer on the structure and characteristics of bacterial cellulose-based biocomposite films

Abstract Biocomposite film was successfully produced by combining bacterial cellulose (BC) and sodium alginate (ratio of 80:20) with the addition of glycerol as conventional plasticizer at varied concentration (2, 4, 6% w/w, based on total sample weight) through solution casting method. The influence of glycerol content on structure (by FTIR), mechanical properties, optical properties (by colorimeter and spectrophotometer) and water vapor permeability (WVP, gravimetric method) of BC biocomposite film was investigated. The addition of glycerol disrupts the inter- and intramolecular hydrogen bonds in the cellulose chains, replaced by weaker BC-alginate-glycerol bonds. This resulted a decrease in film density, causing lower tensile strength, lightness, opacity and WVP of BC biocomposite film. An increase in glycerol concentration led to an increase in elongation percentage due to the effect of glycerol plasticization. Film with 4% glycerol exhibited the lowest WVP (5.08x10-13 g/m.s.Pa), highest lightness (L = 73.49), lowest opacity (3.24 Abs/mm) with tensile strength of 19.57 MPa and elongation 8.38%. The addition of glycerol significantly affects the BC biocomposite film properties. The resulting biofilm shows performance equivalent to commercial bioplastic TeloRoll.

Enhanced Stability-Based Hydroxymethyl Cellulose/Polyacrylamide Interpenetrating Dual Network Hydrogel Electrolyte for Flexible Yarn Zinc-Ion Batteries

As the field of wearable electronics continues to boom, the demand for flexible energy storage devices continues to grow. However, the development of soft energy supply devices with excellent stability is still a challenging task. Traditional hydrogel electrolytes are prone to mechanical deformation, which makes it difficult to maintain the functional stability of flexible yarn due to its short battery life and low wear resistance. Here, we developed a reversible energy-dissipating dual-network hydrogel electrolyte. The hydroxymethyl cellulose (CMC)/polyacrylamide (PAM) hydrogel electrolyte has a tensile deformation of 2700% and a high ionic conductivity of 6.37 × 10−2 S cm−1. The specific capacity of the assembled CMC/PAM-based yarn cell was 170 μAh cm−1 at 1 mA cm−1 and 73.14% after 100 cycles. The excellent performance is attributed to the crosslinked double network structure, in which the introduction of carboxyl groups is conducive to the improvement of hydrophilicity and ionic conductivity. The hydrogen bond and reversible CMC macromolecular chain can be restored after stress relief, which greatly improves the toughness of the material. Even under different bending angles and repeated bending conditions, zinc yarn batteries still have outstanding mechanical properties and cycle stability (71.28% specific capacity after 100 cycles), showing broad application prospects in wearable smart textiles.

Using ion mobility spectrometry to understand signal dilution during tandem mass spectrometry sequencing of digital polymers: Experimental evidence of intramolecular cyclization.

Optimizing the structure of digital polymers is an efficient strategy to ensure their tandem mass spectrometry (MS/MS) readability. In block-truncated poly(phosphodiester)s, homolysis of C-ON bonds in long chains permits the release of smaller blocks amenable to sequencing. Yet the dissociation behavior of diradical blocks was observed to strongly depend on their charge state. Polymers were ionized in negative mode electrospray and activated in-source so that blocks released as primary fragments can be investigated using ion mobility spectrometry (IMS) or sequenced in the post-IMS collision cell. Collision cross sections (CCS) were derived from arrival times using a calibration procedure developed for polyanions using the IMSCal software. A multistep protocol based on quantum methods and classical molecular dynamics was implemented for molecular modeling and calculation of theoretical CCS. Unlike their triply charged homologues, dissociation of diradical blocks at the 2- charge state produces additional fragments, with +1m/z shift for those holding the nitroxide α-termination and -1m/z for those containing the carbon-centered radical ω-end. These results suggest cyclization of these diradical species, followed by H• transfer on activated reopening of this cycle. This assumption was validated using IMS resolution of the cyclic/linear isomers and supported by molecular modeling. Combining IMS with molecular modeling provided new insights into how the charge state of digital blocks influences their dissociation. These results permit to define new guidelines to improve either ionization conditions or the structural design of these digital polymers for best MS/MS readability.

Silicone‐containing polyurea elastomer possessing main‐chain boron–oxygen bonds with delayed stress relaxation and improved adhesive properties

AbstractPolyurea (PU) elastomers have attracted considerable attention in the field of protective polymeric coatings. In this work, a dithiol‐terminated boronic ester was synthesized and used to incorporate dynamic boron–oxygen (B–O) bonds in the PU main chain based on thiol isocyanate while amino‐terminated polydimethylsiloxane (PDMS) was introduced to retain good chain flexibility. The modified PU elastomer was found to have a microphase‐separated structure in which the hard blocks served as physical crosslinks. The glass transition temperature (Tg) slightly increases when dynamic B–O bonds exist while further introduction of PDMS soft segment can lower Tg to −55.63 °C. The introduction of dynamic B–O bonds and diminished hydrogen bonding led to a decrease in mechanical strength and elongation at break. Interestingly, the simultaneous incorporation of PDMS and dynamic B–O bonds is favorable for strain rate dependence and suppressing stress relaxation. The potential for bond‐exchange interactions between the dynamic B–O bonds and hydroxyl groups on metal surfaces substantially improved the adhesion of the PU elastomer to metal substrates. Therefore, our work can offer valuable insights for the structural design of functional PU coatings tailored for anti‐impact applications. © 2024 Society of Chemical Industry.

New insights into how freeze-drying and cryo-milling affects the fine structure and digestibility of gelatinized starch

Freeze-drying (FD) and cryo-milling (CM) are common methods for preparing powder gelatinized starch samples. This study investigates the structural characterization of raw/gelatinized maize starches and digestibility after FD/CM processes to elucidate their effect on starch digestibility determination. Results showed that FD slightly increased digestibility, while higher initial glucose content in CM samples, especially for gelatinized samples. Only FD retained the granular morphology and relative crystallinity (RC), while gelatinized-FD decreased RC by 75%. CM decreased RC by 12%, while gelatinized-CM decreased it by 97%. Combined with short-range and chain structural results, FD tended to disrupt internal connected chains through volume stress, while CM cleaved glycosidic bonds in external chain. Stretched chains in gelatinized starch promoted the breakage of chains during shearing and their efficient binding with digestive enzymes. These findings would provide a basis for pre-treatment of powder samples and processes of starch- rich foods.

Systematic Characterization of Triterpenoids in Ganoderma lucidum by UHPLC-Q/TOF MS

Background: Ganoderma lucidum, which is widely used as “Ganoderma” in China or other Asian countries (Japan, Korea, etc), exerts an important role in tonifying qi and calming the mind in clinical applications. Triterpenoids are the main active components in Ganoderma lucidum, with significant biological activities of hepatoprotective, anticancer, and anti-tumor, etc. However, the current analysis of triterpenoids in Ganoderma lucidum by mass spectrometry is limited, restricting its quality control and elucidation of its functional basis. Objective: This work aimed to systematically characterize the triterpenoids in Ganoderma lucidum. Methods: The Ganoderma lucidum powder was extracted by 50% ethanol/water and separated by Waters ACQUITY UPLC HSS T3 column (2.1 mm×100 mm, 1.8 μm). The data was obtained by Waters G2-Q-TOF mass spectrometry equipped with an electrospray ionization ion (ESI) source, and the MS data under positive and negative modes was acquired and analyzed. Results: A total of 43 triterpenoids were identified or tentatively characterized from the extracts of Ganoderma lucidum, including 32 known compounds and 11 potential new compounds. Among them, five triterpenoids were unambiguously identified by comparison with reference standards, including ganoderic acid A(28), ganoderic acid D(36), ganoderenic acid D(34), ganoderic acid F(43), and ganoderic acid G(16). The profiled triterpenoids could be divided into eight types according to the substituents at the C3, C7 and C15 positions of the parent structure. The mass fragmentation rules of Ganoderma lucidum triterpenoids were summarized. Under the positive ion mode, Ganoderma lucidum triterpenoids easily lost CH3 at the C10 position and H2O at C3, C7, and C15 positions, and the side chain bond at the C22(23) position was easily split. Under the negative ion mode, the split of the C and D rings was the characteristic feature. result: A total of 43 triterpenoids were identified or tentatively characterized from the extracts of Ganoderma lucidum, including 32 known compounds and 11 potential new compounds. Among them, five triterpenoids were unambitiously identified by comparison with reference standards, including ganoderic acid A(28), ganoderic acid D(36), ganoderenic acid D(34), ganoderic acid F(43), and ganoderic acid G(16). These triterpenoids could be divided into eight types according to the substituents at the C3, C7 and C15 positions of the parent structure. The mass fragmentation rules of Ganoderma lucidum triterpenoids were summarized. Under the positive ion mode, Ganoderma lucidum triterpenoids easily lost CH3 at the C10 position and H2O at C3, C7, C15 position, and the side chain bond at C22(23) position was easily cracked. Under the negative ion mode, the crack of the C and D rings was the characteristic feature. Conclusion: The mass fragmentation behaviors of Ganoderma lucidum triterpenoids under positive ion mode were summarized and emphasized, and reliable scientific data and methods for systematic characterization of Ganoderma lucidum triterpenoids were also supplied.

Varying the position of phospholipid acyl chain unsaturation modulates hopanoid and sterol ordering

The cell membrane must balance mechanical stability with fluidity to function as both a barrier and an organizational platform. Key to this balance is the ordering of hydrocarbon chains and the packing of lipids. Many eukaryotes synthesize sterols, which are uniquely capable of modulating the lipid order to decouple membrane stability from fluidity. Ancient sterol analogs known as hopanoids are found in many bacteria and proposed as ancestral ordering lipids. The juxtaposition of sterols and hopanoids in extant organisms prompts us to ask why both pathways persist, especially in light of their convergent ability to order lipids. In this work, simulations, monolayer experiments, and cellular assays show that hopanoids and sterols order unsaturated phospholipids differently based on the position of double bonds in the phospholipid acyl chain. We find that cholesterol and diplopterol’s methyl group distributions lead to distinct effects on unsaturated lipids. In Mesoplasma florum, diplopterol’s constrained ordering capacity reduces membrane resistance to osmotic stress, unlike cholesterol. These findings suggest that cholesterol’s broader lipid-ordering ability may have facilitated the exploration of a more diverse lipidomic landscape in eukaryotic membranes.

The role of dietary fats on cognition and sarcopenia in the elderly.

To elucidate the role of dietary fats on the relationship between mild cognitive impairment and sarcopenia and help identifying and preventing the decline of cognitive and muscle function in elderly individuals. The study conducted involving a group of 1812 individuals between the ages of 61 and 92. Body composition and BMR were assessed by bioelectrical impedance analysis. Cognitive function and dietary nutrition were evaluated by neuropsychological assessments and questionnaire of food intake frequency. Lipidomics analysis was performed using UHPLC-Qtrap-MS/MS. MCI and SA are mutual influencing factors, lower intake of MUFA, PUFA and higher intake of fat was associated with cognitive dysfunction and/or SA (p < 0.05). PUFA was important for MCI combined with SA (Compared with Q1, Q4 OR: 0.176, 95%CI: 0.058,0.533). Lipidomics analysis revealed that triacylglycerol (TAG) contain more carbon chains with saturated double bonds may be closely related to cognitive impairment and the progression of SA (p < 0.05). While, DAG with carbon chains of unsaturated double bonds is opposite. Insufficient intake of unsaturated fatty acids was associated with the development of cognitive decline and the progression of SA. MUFA affecting muscle health, fats and PUFA has a greater impact on MCI combined with SA. Less MUFA intake and increasing saturated double-bonded fatty acid intake might be the key factors on promoting cognitive impairment and SA in the elderly. They have the potential to serve as prospective biomarkers indicating a higher risk of cognitive decline and/or SA in the elderly population.

Direct site-selective C(sp&lt;sup&gt;3&lt;/sup&gt;)–H functionalization of unprotected non-activated alcohols

Free alcohols are ubiquitous in nature, drugs, bulk chemicals, and various complex molecules. The abundantly available free aliphatic alcohols, being inexpensive, are sustainable starting materials in organic synthesis to construct value-added scaffolds. Direct C(sp&lt;sup&gt;3&lt;/sup&gt;)–H functionalization of inert bonds in aliphatic alcoholic chain is challenging due to their inactive nature towards chemical reactions and also multiple similar C–H bonds are available for functionalization reaction at a time. Barton process, which is a classical method for generating alkoxyl radicals, has been widely used for the remote functionalization of alcoholic chain using the strategy of 1,5-hydrogen atom transfer (1,5-HAT). However, the requirement for the pre-activation of alcohols not only adds extra and tedious steps but also, these precursors are challenging to prepare and handle. Generating desired alkoxyl radicals from these precursors is a difficult task and also affects the atom economy of reactions. Numerous methods covering the C(sp&lt;sup&gt;3&lt;/sup&gt;)–H functionalization of unprotected non-activated alcohols at diverse (α-, β-, γ-, δ-) positions to access functionalized alcohols are elaborated here. A precise and focused compilation will help to understand what has been established and how new methodologies can be developed for the future needs. &lt;br&gt; The bibliography includes 158 references.

Three-stage interaction mechanism of galactomannans with mucin to regulate the migration behavior of riboflavin: Effect of mannose-to-galactose ratio

The interactions between non-starch polysaccharides alter the physicochemical properties of the mucin, therefore can affect encapsulated nutrients penetrating through the mucus layer in the gastrointestinal tract. This study explored the interactions between mucin and galactomannans (GMs) with different mannose-to-galactose ratios going through contact, diffusion, and binding stages. During contact stage, the contact angle was used to characterize the interactions between mucin and GMs, and results showed that locust bean gum (4:1) with lower molecular weight had more contact area to form more hydrogen bonds with water. At diffusion and binding stage, based on the analysis of ATR-FTIR, rheology, and fluorescence spectroscopy, more galactose side chains in guar gum (2:1) had more hydrogen donors and acceptors and more space between polysaccharides to form intermolecular hydrogen bonds with mucin, which enhanced the interactions with mucin. Molecular docking results suggested that more hydrogen bonds in the main chain and less in the side chain resulted in more availability to form intramolecular hydrogen bonds and therefore reduced the strength of the interactions with mucin. Moreover, the Transwell assay revealed that enhancing the interactions of GMs with mucin, especially hydrogen bonds, slowed down the migration of the riboflavin. The current discovery laid the groundwork for designing GMs-based delivery systems that are capable to control the duration of nutrient action on the mucus by changing the molecular properties of the polysaccharide.

Design of diselenide-containing polyprodrug and its pH/redox co-triggered degradation and slow drug release for tumor-specific chemotherapy

Polyprodrugs have attracted intense interest for tumor-specific chemotherapy, by conjugating chemotherapeutic drugs via two dynamic covalent bonds in the polymer main chains. Here, pH/redox co-triggered degradable diselenide-containing polyprodrug with a high doxorubicin (DOX) content of 1.42×10−3 mmol/g was designed by linking diselenide-containing dimer of doxorubicin (D-DOXSeSe) with adipic dihydrazide. The polyprodrug could be triggered to degrade and release drug only when the hydrazone and diselenide conjugations on both sides of the drug units were cleaved, triggered by the higher acidity and higher GSH or ROS levels. Slow drug release was achieved in the simulated tumor intracellular microenvironment due to the lower solubility of the release drugs (DOX derivatives), with cumulative release of 10.3 % and 7.4 % in 96 h co-triggered with 10 mM GSH or 0.5 mM H2O2, without obvious drug mis-release in the simulated intracellular environment of the normal cells. It might provide a safe and efficient tumor-specific chemotherapy avoiding the toxic and side effects on the normal cells.

A four-in-one multifunctional self-assembly hydrogel composed of natural drugs for repairing myocardial infarction

To meet the multiple demands of myocardial repair, it would be a novel strategy for myocardial repair if multiple drugs could be constructed into an integrated multifunctional drug formulation. In this study, four drugs with different functions (thioctic acid with antioxidant effects, quercetin with anti-inflammatory and antioxidant effects, arginine with pro-angiogenic effects, and Mn2+ with imaging functions) were selected to construct a four-in-one injectable hydrogel (thioctic acid-arginine-quercetin-Mn2+) through chemical bonding and supramolecular interactions. First, thioctic acid polymerized to a redox-sensitive degradable polymer—poly(thioctic acid) containing disulfide bonds in the main chains through ring-opening polymerization. Quercetin was conjugated to the main chain of the poly(thioctic acid) molecules via thiyl radical-polyphenol Michael addition. Arginine cross-linked the carboxyl groups side chains of the poly(thioctic acid) molecules through hydrogen bonding. Mn2+ further cross-linked the carboxyl groups' side chains of the poly(thioctic acid) molecules through ionic bonding. The hydrogel has antioxidant properties, promotes neovascularization, inhibits inflammatory, improves intracellular Ca2+ overload and mitochondrial dysfunction, protects adenosine triphosphatase (ATPase) activity, and maintains intracellular energy supply, which can reduce the size of myocardial infarcts, and improves cardiac function. This construction method of preparing integrated multifunctional hydrogels from natural drugs will provide a new therapeutic strategy for myocardial repair.

Effect of the Activation Force of Mechanophore on Its Activation Selectivity and Efficiency in Polymer Networks.

In recent decades, more than 100 different mechanophores with a broad range of activation forces have been developed. For various applications of mechanophores in polymer materials, it is crucial to selectively activate the mechanophores with high efficiency, avoiding nonspecific bond scission of the material. In this study, we embedded cyclobutane-based mechanophore cross-linkers (I and II) with varied activation forces (fa) in the first network of the double network hydrogels and quantitively investigated the activation selectivity and efficiency of these mechanophores. Our findings revealed that cross-linker I, with a lower activation force relative to the bonds in the polymer main chain (fa-I/fa-chain = 0.8 nN/3.4 nN), achieved efficient activation with 100% selectivity. Conversely, an increase of the activation force of mechanophore II (fa-II/fa-chain = 2.5 nN/3.4 nN) led to a significant decrease of its activation efficiency, accompanied by a substantial number of nonspecific bond scission events. Furthermore, with the coexistence of two cross-linkers, significantly different activation forces resulted in the almost complete suppression of the higher-force one (i.e., I and III, fa-I/fa-III = 0.8 nN/3.4 nN), while similar activation forces led to simultaneous activations with moderate efficiencies (i.e., I and IV, fa-I/fa-IV = 0.8 nN/1.6 nN). These findings provide insights into the prevention of nonspecific bond rupture during mechanophore activation and enhance our understanding of the damage mechanism within polymer networks when using mechanophores as detectors. Besides, it establishes a principle for combining different mechanophores to design multiple mechanoresponsive functional materials.

Synthesis, structure, hirshfeld surface analysis and antibacterial activities of [Cd(2-ampy)3(NCS)(μ1,5-SCN)]2 and [Cd(4-ampy)2(μ1,5-dca)2]n complexes (2-ampy = 2-aminopyridine, 4-ampy = 4-aminopyridine, NCS = thiocyanate, dca = dicyanamide)

The complexes [Cd(2-ampy)3(NCS)(μ-SCN)]2 (1) and [Cd(4-ampy)2(μ1,5-dca)2]n (2) were synthesized and characterized using single crystal XRD. Complex 1 has a dimer structure with a triclinic crystal system and space group P1¯, whereas complex 2 has a polymer structure with a monoclinic crystal system and space group P21/c. Hirshfeld surface analysis of complex 1 showed the presence of S⋯N–H and N–H–S interactions between dimer molecules and intramolecular hydrogen bonds N–H⋯N. In complex 2, the analysis showed the polymer coordination chain bonds between Cd(II) ions with N atoms from dicyanamide and intermolecular hydrogen bonds of N–H⋯N. In vitro antibacterial testing for both complexes against Escherichia coli (gram-negative) and Staphylococus aureus (gram-positive) showed a higher inhibition zone diameter than the constituent reactants, where complex 2 had the a higher antibacterial activity.

DISCUSSION OF THE MECHANISM OF THE ELECTRICAL CONDUCTIVITY OF PURE WATER IN THE FRAMEWORK OF THE BJERRUM MODEL

An alternative mechanism of electrical conductivity and ionization of molecules in pure water is considered. Calculation of the temperature dependence for the activation energy of ionization of water molecules was carried out using data on the value of its ionic product. The calculated activation energies for the ionization and flow processes show the presence of a certain proportionality between them. This suggests that the ionization of water is caused by intermolecular forces rather than intramolecular forces. Accordingly, the electrical conductivity of water is associated with the appearance and movement in it of L and D defects of hydrogen bonds between water molecules, which have significant electrical pseudo charges and are considered in the Bjerrum model for ice. This work proposes a new interpretation of the mechanism of ionization (pseudoionization) of molecules and generation of L and D defects in water. Rotation is considered not for one, but for two of its molecules in opposite directions with partial compensation of their angular momentum, and the breaking of not three bonds for one molecule, but four bonds with neighbors for two molecules. Moreover, these four neighbors do not include molecules from water clusters that have stronger bonds, since neighboring molecules with weaker bonds can be found for the process of rotation activation. Accordingly, the exponential contribution made by molecules from water clusters is absent or small in the ionization activation energy. In this way, the activation energy for the flow, which occurs throughout the entire volume of the liquid and automatically includes molecules from clusters, differs from the activation energy of electrical conductivity, which occurs for individual molecules in chains of bonds. The presence of a maximum in the ionic product of water near 250 ⁰C can be explained by the rapid decrease in the lifetime of L and D defects with heating, which prevents the use of the standard equation for accurate calculation of the ionization activation energy above 100...200 ⁰C. However, the presence of this maximum contradicts the generally accepted model of proton hopping between neighboring hydronium and water molecules in the mechanism of its electrical conductivity.

Stability of Ti3C2-MXene/Waterborne polyurethane composite emulsion and investigation of visible light-driven film self-healing performance

Intrinsic self-healing waterborne polyurethane (WPU) is an environmentally friendly, economically viable, and practical novel intelligent material. However, the key to achieving practical applications lies in the remote activation of repair in self-healing materials and the excellent mechanical properties of the matrix. In this study, we introduce quadruple hydrogen bonding in the polyurethane backbone. We have incorporated a novel two-dimensional sheet-like material, MXene, to achieve visible light remote-driven self-healing of material hydrogen bonds while enhancing the material’s mechanical properties. By utilizing the MXene supernatant, this approach not only resolves the issues of poor stability and easy sedimentation of MXene nanosheets in water-based polymers but also helps to prevent resource wastage. Our research results demonstrate that the composite film exhibits a tensile strength of 6.55 MPa and a fracture elongation of 604%. Additionally, quadruple hydrogen bonds in the WPU chains enable rapid self-healing of microcracks under visible light irradiation at 300 mW/cm2, with complete disappearance within 80 min.

Organic-Inorganic Hybrid Materials: Tailoring Carbon Dioxide-Based Polycarbonate with POSS-SH Crosslinking.

A novel functional polycarbonate (PAGC), characterized by the presence of double bonds within its side chain, was successfully synthesized through a ternary copolymerization of propylene oxide (PO), allyl glycidyl ether (AGE), and carbon dioxide (CO2). Polyhedral oligomeric silsesquioxanes octamercaptopropyl (POSS-SH) was employed as a crosslinking agent, contributing to the formation of organic-inorganic hybrid materials. This incorporation was facilitated through thiol-ene click reactions, enabling effective interactions between the POSS molecules and the double bonds in the side chains of the polycarbonate. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed a homogeneous distribution of silicon (Si) and sulfur (S) in the polycarbonate matrix. The thiol-ene click reaction between POSS-SH and the polycarbonate led to a micro-crosslinked structure. This enhancement significantly increased the tensile strength of the polycarbonate to 42 MPa, a notable improvement over traditional poly (propylene carbonate) (PPC). Moreover, the cross-linked structure exhibited enhanced solvent resistance, expanding the potential applications of these polycarbonates in various plastic materials.

Directed Assembly of Ordered Mixed-Spacer Quasi-2D Halide Perovskites through Homomeric Chains of Intermolecular Bonds.

Two-dimensional (2D) halide perovskites (HPs) are of significant interest to researchers because of their natural structural frameworks and intriguing optoelectronic properties. However, the direct fabrication of ordered mixed-spacer quasi-2D HPs remains challenging. Herein, a synthetic strategy inspired by the principle of supramolecular synthons is employed for the self-assembly of a series of ordered mixed-spacer bilayered HPs. The key innovation involves the introduction of intermolecular hydrogen bonds using a bifunctional 3-aminopropionitrile cation. Three homogeneous n = 2 structures are obtained, with a subtly ordered perovskite connected by two distinct types of organic cation layers, resulting in a recurrent ABAB' stacking sequence. These three compounds exhibit attractive semiconducting properties. Moderate bandgaps in the range of 2.70 to 2.76eV with an absorption wavelength range of 448-459nm exhibit excellent photoelectric response. Moreover, the ordered structures facilitate excellent polarization-sensitive photodetection, with an impressive on/off ratio of 103. The response speed ranged from 298 to 381 µs, and the out-of-plane polarization-related dichroism ratio is determined to be 1.19. Such ordered mixed-spacer bilayered perovskites have not been reported. These results enrich the HPs system and play a significant role in the direct assembly of novel perovskites with ordered structures.

Determination of fatty acid uptake and desaturase activity in mammalian cells by NMR-based stable isotope tracing

BackgroundMammalian cells both import exogenous fatty acids and synthesize them de novo. Palmitate, the end product of fatty acid synthase (FASN) is a substrate for stearoyl-CoA desaturases (Δ-9 desaturases) that introduce a single double bond into fatty acyl-CoA substrates such as palmitoyl-CoA and stearoyl-CoA. This process is particularly upregulated in lipogenic tissues and cancer cells. Tracer methodology is needed to determine uptake versus de novo synthesis of lipids and subsequent chain elongation and desaturation. Here we describe an NMR method to determine the uptake of 13C-palmitate from the medium into HCT116 human colorectal cancer cells, and the subsequent desaturation and incorporation into complex lipids. ResultsExogenous 13C16-palmitate was absorbed from the medium by HCT116 cells and incorporated primarily into complex glycerol lipids. Desaturase activity was determined from the quantification of double bonds in acyl chains, which was greatly reduced by ablation of the major desaturase SCD1. SignificanceThe NMR approach requires minimal sample preparation, is non-destructive, and provides direct information about the level of saturation and incorporation of fatty acids into complex lipids.