Side Chain Research Articles

Comparative analysis of bio-based amino acid surfactants obtained via Diels–Alder reaction of cyclic anhydrides

Abstract Current changes in environmental legislation and customer demands set an urge for the development of more sustainable surfactants. Thus, the objective of this work was the development of novel environmentally friendly amino acid surfactants. Combining Diels–Alder cyclization of myrcene with maleic or citraconic anhydride followed by ring opening with amino acids enabled a synthesis route with a principal 100% atom economy. Variation of amino acids resulted in a large structural variety of anionic and amphoteric surfactants. Lysine gave access to either a mono-acylated product bearing a cationic side chain or a bi-acylated gemini surfactant. First, anhydride precursors were synthesized in yields of >90% in a Diels–Alder reaction under microwave radiation and subsequent amino acid coupling in aqueous environment gave fully bio-based surfactants in good yields and purity. Physicochemical characterization showed an enhanced decrease in surface tension upon addition of amino acids to the myrcene–anhydride backbone, resulting in a minimal value of 31 mN·m−1 for gemini–lysine. Foamabilitiy and foam stability were significantly increased at skin-friendly pH 5.5 by incorporation of amino acids. The carboxylic groups of surfactants with arginine were esterified with ethanol to access cationic compounds. Comparative analysis revealed moderate antimicrobial effects against yeast, Gram-positive bacteria, and Gram-negative bacteria.

Leaf developmental patterns of two species of Baccharis (Asteraceae): an analysis based on cell wall pectins

The cell wall plays a primary role in plant growth, which is regulated by cellulose microfibrils, proteins, and pectins. Regarding pectins, the rate of homogalacturonan (HG) methylesterification and the type of rhamnogalacturonan side chains can mediate leaf development. Herein, we evaluated pectic compounds of the cell walls by immunocytochemistry during the leaf development of Baccharis dracunculifolia DC. and Baccharis platypoda DC. Leaves in different maturation stages (from leaf bud to 9th node) were collected in a rupestrian field and fixed in formalin, acetic acid for anatomical and immunocytochemical analyses using monoclonal antibodies (JIM5, JIM7, LM5, and LM6). Both species showed similar anatomical structures based on peculiar cell wall pectic matrices. Baccharis platypoda leaves reach precocious maturation in the 3rd node, while B. dracunculifolia reaches maturation in the 6th node. These results seem to be related to HGs already de-methylesterified in the leaf primordia located in the leaf bud of B. platypoda. Epitopes of (1→5) α-l-arabinan occurred only in the collenchyma of B. platypoda, supporting cell wall stability. (1→4) β-D-galactans showed different fluorescence intensities in the two species, which changed during leaf development. The different rates of leaf tissue maturation between the two Baccharis species are influenced by variations in the pectic compounds of the cell walls, especially regarding the rate of HG methylesterification.

Structure and ligand binding in the putative anti-microbial peptide transporter protein, YejA.

YejABEF is an ATP-binding cassette transporter that is implicated in the sensitivity of Escherichia coli to anti-microbial peptides, the best-characterized example being microcin C, a peptide-nucleotide antibiotic that targets aspartyl-tRNA synthetase. Here the structure of the extracellular solute binding protein, YejA, has been determined, revealing an oligopeptide-binding protein fold enclosing a ligand-binding pocket larger than those of other peptide-binding proteins of known structure. Prominent electron density in this cavity defines an undecapeptide sequence LGEPRYAFNFN, an observation that is confirmed by mass spectrometry. In the structure, the peptide interactions with the protein are mediated by main chain hydrogen bonds with the exception of Arg5 whose guanidinium side chain makes a set of defining polar interactions with four YejA residues. More detailed characterization of purified recombinant YejA, by a combination of ESI and MALDI-mass spectrometry as well as thermal shift assays, reveals a set of YejA complexes containing overlapping peptides 10-19 residues in length. All contain the sequence LGEPRYAFN. Curiously, these peptides correspond to residues 8-26 of the mature YejA protein, which belong to a unique N-terminal extension that distinguishes YejA from other cluster C oligopeptide binding proteins of known structure. This 35-residue extension is well-ordered and packs across the surface of the protein. The undecapeptide ligand occupies only a fraction of the enclosed pocket volume suggesting the possibility that much larger peptides or peptide conjugates could be accommodated, though thermal shift assays of YejA binding to antimicrobial peptides and peptides unrelated to LGEPRYAFNFN have not provided evidence of binding. While the physiological significance of this 'auto-binding' is not clear, the experimental data suggest that it is not an artefact of the crystallization process and that it may have a function in the sensing of periplasmic or membrane stress.

Preparation and properties of highly flexible cholesteric side-chain liquid crystalline elastomers with selective reflective properties in the visible region

ABSTRACT In this paper, we have synthesised cholesteryl 4-allyloxybenzoate (MB), crosslinking agent dodecane-1,12-diyl bis(undec-10-enoate) (MG), and A’BGF series liquid crystalline elastomer (LCE) films which take polymethylhydrosiloxane (A’) as the backbone, MB as the cholesteric liquid crystal (LC) monomer, and MG and bis-vinyl silicone oil (MF) with different reactivities as cross-linking agent for exploring the effect of the change of MF content on the properties of the elastomeric films. The experimental results show that the synthesised MB, MG, and the LCE films are all consistent with the molecular design; MB is an enantiotropic cholesteric LC. The synthesised LCE films are cholesteric LCs, have certain selective reflection characteristic, higher thermal stability, and their Tg decreased down to 3.9°C as MF increasing. During the heating and cooling, the liquid crystalline properties of the LCE films have a good reversibility. Among the synthesised LCE films, A’BGF-2 has stretching radio of 264.8% at room temperature, with the best elastic properties. By adjusting the ratio of MF, the content of small-molecule MB remained in the films can be changed, which will affect the optical properties and elasticity of the LCE films. The experiments provide a method for the preparation of highly elastic side chain LCE film.

Interplay between the β-lactam side chain and an active-site mobile loop of NDM-1 in penicillin hydrolysis as a potential target for mechanism-based inhibitor design

Metallo-β-lactamases (MβLs) stand as significant resistant mechanism against β-lactam antibiotics in Gram-negative bacteria. The worldwide dissemination of New Delhi metallo-β-lactamases (NDMs) intensifies antimicrobial resistance, posing severe threats to human health due to the absence of inhibitors available in clinical therapy. L3, a flexible β-hairpin loop flanking the active site in MβLs, has been proven to wield influence over the reaction process by assuming a crucial role in substrate recognition and intermediate stabilization. In principle, it potentially retards product release from the enzyme, consequently reducing the overall turnover rate although the details regarding this aspect remain inadequately elucidated. In this study, we crystallized NDM-1 in complex with three penicillin substrates, conducted molecular dynamics simulations, and measured the steady-state kinetic parameters. These analyses consistently unveiled substantial disparities in their interactions with loop L3. We further synthesized a penicillin V derivative with increased hydrophobicity in the R1 side chain and co-crystallized it with NDM-1. Remarkably, this compound exhibited much stronger dynamic interplay with L3 during molecular dynamics simulation, showed much lower Km and kcat values, and demonstrated moderate inhibitory capacity to NDM-1 catalyzed meropenem hydrolysis. The data presented here may provide a strategic approach for designing mechanism-based MβL inhibitors focusing on structural elements external to the enzyme's active center.

Antioxidant Polymers with Phenolic Pendants for the Mitigation of Cellular Oxidative Stress.

Overproduction of reactive oxygen species (ROS) in cells is a major health concern as it may lead to various diseases through oxidative damage of biomolecules. Commonly used traditional small molecular antioxidants (polyphenols, carotenoids, vitamins, etc.) have inadequate efficacy in lowering excessive levels of ROS due to their poor aqueous solubility and bioavailability. In response to the widespread occurrence of antioxidant polyphenols in various biorenewable resources, we aimed to develop water-soluble antioxidant polymers with side chain phenolic pendants. Four different types of copolymers (P1-P4) containing phenyl rings with different numbers of hydroxy (-OH) substituents (0: phenylalanine, 1: tyrosyl, 2: catechol, or 3: gallol) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization with a desired molar mass (8500-10000 g/mol) and a narrow dispersity (Đ ≤ 1.3). After successful characterizations of P1-P4, their in vitro antioxidant properties were analyzed by different methods, including 2,2-diphenyl-1-picrylhydrazyl (DPPH•), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+), 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl (TMB), and β-carotene (βC) assays. Our results revealed that the gallol pendant polymers can effectively scavenge ROS. Furthermore, electron paramagnetic resonance (EPR) spectroscopy with DPPH• also confirmed the radical quenching ability of the synthesized polymers. The gallol pendant polymers, at a well-tolerated concentration, could effectively penetrate the macrophage cells and restore the H2O2-induced ROS to the basal level. Overall, the present approach demonstrates the efficacy of water-soluble antioxidant polymers with gallol pendants toward the mitigation of cellular oxidative stress.

DNA three-way junction structures with amino acid side chains prepared via post-synthetic amide condensation

DNA three-way junction (3WJ) structures with three amino acid side chains in the core have been synthesized via post-synthetic DNA modification. Amide condensation reactions of oligonucleotides containing 2′-aminouridine with activated esters yielded DNA strands modified with His, Cys and Asp side chains to form modified 3WJs. Even a 3WJ with three negatively charged Asp side chains formed stably at room temperature. Furthermore, DNA hybridization alone placed two (His and Asp) and three (His, Cys, and Asp) side chains within the 3WJs, indicating that the DNA 3WJs are a useful platform for spatial arrangement of amino acid side chains.

Alcohol‐Soluble n‐Type Polythiophenes as Cathode Interlayer in Organic Photodetectors for Hole Blocking

AbstractFor organic photodetectors (OPDs), cathode interlayer (CIL) with low‐lying highest occupied molecular orbital (EHOMO) energy level is required to reduce dark current density (Jd). In this study, toward application as CIL in OPDs, an alcohol‐processable n‐type conjugated polymer (n‐PT8) based on imide/cyano‐substituted polythiophene backbone and branched oligo(ethylene glycol) side chain is developed. Owing to the electron‐accepting imide/cyano groups on the backbone, n‐PT8 exhibits deep‐lying EHOMO of −5.80 eV and a high conductivity of 5.12 × 10−6 S cm−1. OPD with n‐PT8 as CIL exhibits dark current density one order of magnitude lower than that with the state‐of‐the‐art CIL material because of the large energy barrier for reverse hole injection. Moreover, the device performance is insensitive to the n‐PT8 layer thickness, which is very desirable for the mass production of OPDs. The near‐infrared (NIR) OPDs based on n‐PT8 exhibit an ultra‐low dark current density of 1.76 × 10−9 A cm−2 and a specific detectivity of 2.88 × 1012 cm Hz1/2 W−1 at −1 V. To the best knowledge, this is the first report on n‐type polythiophene derivatives as CIL in organic opto‐electronic devices.

Constructing high-performance fluoropoly(aryl piperidinium) ion exchange membranes via side-chain engineering for efficient vanadium flow batteries

Vanadium flow batteries (VFBs) have demonstrated significant potential for large-scale energy storage technology. However, the lack of a highly ion-selective and stable ion exchange membrane (IEM) is a major dilemma for developing high-performance VFBs. Herein, we present a new insight to prepare high-performance fluoropoly(aryl piperidinium) IEMs by side-chain engineering modifications. Benefiting from the synergistic effect between the fluorine-containing structure and the functional side chains, distinct microphase-separated structures are formed within the membrane and the prepared IEMs exhibit lower area resistance (0.16–0.41 Ω cm2) compared to Nafion115 (0.57 Ω cm2). The repulsive effect generated by the intrinsic alkaline cation groups inhibits the cross-penetration of vanadium ions, contributing to the ultra-low VO2+ permeability (∼8.63 × 10−9 cm2 min−1, 96 times lower than Nafion115) of the resultant IEMs. Moreover, the unique fluorinated structure effectively suppresses membrane swelling while enabling excellent mechanical and chemical stability. Consequently, the assembled AMPFMP battery achieves excellent efficiency (coulombic efficiency = 99.23% and energy efficiency = 82.15% at a high current density of 200 mA cm−2) and outstanding cycling performance (no significant decay in efficiency during 1000 cycles at 120 mA cm−2), outperforming Nafion 115. These results indicate that the side-chain engineering design of fluorinated IEM provides a valuable strategy for developing efficient and durable VFB diaphragms.

Structural Characterization of 5-Substituted Pyrrolo[3,2-d]pyrimidine Antifolate Inhibitors in Complex with Human Serine Hydroxymethyl Transferase 2.

We previously discovered first-in-class multitargeted 5-substituted pyrrolo[3,2-d]pyrimidine antifolates that inhibit serine hydroxymethyltransferase 2 (SHMT2), resulting in potent in vitro and in vivo antitumor efficacies. In this report, we present crystallographic structures for SHMT2 in complex with an expanded series of pyrrolo[3,2-d]pyrimidine compounds with variations in bridge length (3-5 carbons) and the side chain aromatic ring (phenyl, thiophene, fluorine-substituted phenyl, and thiophene). We evaluated structural features of the inhibitor-SHMT2 complexes and correlations to inhibitor potencies (i.e., Kis), highlighting conserved polar contacts and identifying 5-carbon bridge lengths as key determinants of inhibitor potency. Based on the analysis of SHMT2 structural data, we investigated the impact of mutation of Tyr105 in SHMT2 kinetic analysis and studies with HCT116 cells with inducible expression of wild-type and Y105F SHMT2. Increased enzyme inhibition potency by the pyrrolo[3,2-d]pyrimidine inhibitors with Phe105 SHMT2 accompanied an increased growth inhibition of Phe105-expressing HCT116 cells compared to wild-type SHMT2. Pyrrolo[3,2-d]pyrimidine inhibitors with polyglutamate modifications were evaluated for potencies against SHMT2. We determined the crystal structures of SHMT2 in complex with our lead antifolate AGF347 lacking L-glutamate, or as a diglutamate and triglutamate, for comparison with parent AGF347. These data provide the first insights into the influence of antifolate polyglutamylation on SHMT2:inhibitor interactions. Collectively, our results provide new insights into the critical structural determinants of SHMT2 binding by pyrrolo[3,2-d]pyrimidine inhibitors as novel antitumor agents, as well as the first structural characterization of human SHMT2 in complex with polyglutamates of an SHMT2-targeted antifolate.

A Convenient Oligonucleotide Conjugation via Tandem Staudinger Reaction and Amide Bond Formation at the Internucleotidic Phosphate Position.

Staudinger reaction on the solid phase between an electronodeficit organic azide, such as sulfonyl azide, and the phosphite triester formed upon phosphoramidite coupling is a convenient method for the chemical modification of oligonucleotides at the internucleotidic phosphate position. In this work, 4-carboxybenzenesulfonyl azide, either with a free carboxy group or in the form of an activated ester such as pentafluorophenyl, 4-nitrophenyl, or pentafluorobenzyl, was used to introduce a carboxylic acid function to the terminal or internal internucleotidic phosphate of an oligonucleotide via the Staudinger reaction. A subsequent treatment with excess primary alkyl amine followed by the usual work-up, after prior activation with a suitable peptide coupling agent such as a uronium salt/1-hydroxybenzotriazole in the case of a free carboxyl, afforded amide-linked oligonucleotide conjugates in good yields including multiple conjugations of up to the exhaustive modification at each phosphate position for a weakly activated pentafluorobenzyl ester, whereas more strongly activated and, thus, more reactive aryl esters provided only single conjugations at the 5'-end. The conjugates synthesized include those with di- and polyamines that introduce a positively charged side chain to potentially assist the intracellular delivery of the oligonucleotide.

Synthesis and Identification of decarbamoyloxySaxitoxins in Toxic Microalgae and their Reactions with the Oxygenase, SxtT, Reveal Saxitoxin Biosynthesis.

Saxitoxin (STX, 1) is a representative compound of paralytic shellfish toxins (PSTs) that are produced by marine dinoflagellates and freshwater cyanobacteria. Although several pathways have been proposed for the biosynthesis of STX, the order of ring and side chain hydroxylation, and formation of the tricyclic skeleton have not been well established. In this study, 12,12-dideoxy-decarbamoyloxySTX (dd-doSTX, 2), the most reduced STX analogue having the tricyclic skeleton, and its analogues, 12β-deoxy-doSTX (12β-d-doSTX, 3), 12α-deoxy-doSTX (12α-d-doSTX, 4), and doSTX (5), were synthesized, and these compounds were screened in the toxic microalgae using high-resolution LCMSMS. dd-doSTX (2) and 12β-d-doSTX (3) were identified in the PSTs-producing dinoflagellates (Alexandrium catenella, A. pacificum, and/or Gymnodinium catenatum) and in the cyanobacterium Dolichospermum circinale (TA04). doSTX (5), previously isolated from the dinoflagellate G. catenatum, was also identified in D. circinale (TA04). Furthermore, the conversion of 2 to 3, and 4 to 5, by SxtT with VanB, a reported Rieske oxygenase and its redox partner in STX biosynthesis, was confirmed. These results support that 2 is a possible biosynthetic precursor of STX, and that ring and side-chain hydroxylations proceed after cyclization.

Mesocellular Silica Foam as Immobilization Carrier for Production of Statin Precursors.

The employment of 2-deoxyribose-5-phosphate aldolase (DERA) stands as a prevalent biocatalytic route for synthesizing statin side chains. The main problem with this pathway is the low stability of the enzyme. In this study, mesocellular silica foam (MCF) with different pore sizes was used as a carrier for the covalent immobilization of DERA. Different functionalizing and activating agents were tested and kinetic modeling was subsequently performed. The use of succinic anhydride as an activating agent resulted in an enzyme hyperactivation of approx. 140%, and the stability almost doubled compared to that of the free enzyme. It was also shown that the pore size of MCF has a decisive influence on the stability of the DERA enzyme.

Meticulous Molecular Engineering of Crystal Orientation and Morphology in Conjugated Polymer Thin Films for Field-Effect Transistors.

The ability to precisely tailor molecular packing and film morphology in conjugated polymers offers a robust means to control their optoelectronic properties. This, however, remains a grand challenge. Herein, we report the dependency of molecular packing of an important conjugated polymer, poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), on a set of intrinsic parameters and unveil the correlation between their crystalline structures and charge transport characteristics. Specifically, a family of PBTTT with varying side chains (i.e., hexyl, octyl, decyl, dodecyl, tetradecyl, and hexadecyl referred to as C6, C8, C10, C12, C14, and C16, respectively) and molecular weights (MWs) with a focus on C14 are judiciously designed and synthesized. Various crystalline structures are yielded by tuning the alkyl chain and MW of PBTTT together with thermal annealing. It reveals that extending the alkyl chain length of PBTTT to C14, along with a larger MW and heating at 180 °C, promotes the formation of edge-on crystallites with significantly improved orientation and ordering. Furthermore, these distinct crystalline structures greatly impact their charge mobilities. This study sheds light on the tailored design of crystalline structures in PBTTT through a synergetic approach, which paves the way for potential applications of PBTTT and other conjugated polymers in optoelectronic devices with enhanced performance.

Enhancing lathyrane structural diversity and MDR activity by combinatorial modification of lathyrane nucleus and ester side chain: A case study of Euphorbia Factor L1 and Euphorbia Factor L3

The chemical transformation of lathyrane nucleus through reduction and oxidation reactions using Euphorbia Factor L1 (EFL1) and Euphorbia Factor L1 (EFL3) as examples were investigated, along with a co-modification strategy of lathyrane nucleus and its side ester chain. A total of 38 lathyrane derivatives (5–42) including 34 new compounds were obtained, which greatly enriched the structural diversity of the lathyrane-type diterpenoids. Cytotoxicity against drug-sensitive and drug (adriamycin, ADM) resistant MCF-7 cells showed that 23 out of 38 transformed derivatives possessed obvious cytotoxic activity with IC50 values ranging from 7.0 to 41.1 μM and 3.2 to 45.5 μM, respectively, against both cells, compared to the noncytotoxic EFL1 and EFL3. The multidrug resistance (MDR) reversing activities of these lathyrane derivatives were further evaluated in MCF-7/ADM. Three transformed compounds (reversal fold, RF = 151.33, 62.94 and 47.3 for 27, 37 and 42) showed markedly higher activity than EFL1 (RF = 32.92) and EFL3 (RF = 39.68). Structure-activity relationship study revealed an essential role of C-6/17 and C-12/13 double bonds on lathyrane nucleus for exerting MDR reversal activity. Western blotting analysis showed that 42 could reduce the expression level of P-glycoprotein (P-gp) in MCF-7/ADM cells; however, the most active compound 27 with an unnatural 5/7/7/4 fused-ring diterpenoid skeleton, had no inhibitory effect on P-gp expression.

Strategic Design of Hemi-Isoindigo Polymer for a Highly Sensitive and Selective All-Printed Flexible Nitrogen Dioxide Chemiresistive Sensor.

The study has developed two hemi-isoindigo (HID)-based polymers for printed flexible resistor-type nitrogen oxide (NO2 ) sensors: poly[2-ethylhexyl 3-((3'",4'-bis(dodecyloxy)-3,4-dimethoxy-[2,2':5',2'"-terthiophen]-5-yl)methylene)-2-oxoindoline-1-carboxylate] (P1) and poly[2-ethylhexyl 2-oxo-3-((3,3'",4,4'-tetrakis(dodecyloxy)-[2,2':5',2'"-terthiophen]-5-yl)methylene)indoline-1-carboxylate] (P2). These polymers feature thermally removable carbamate side chains on the HID units, providing solubility and creating molecular cavities after thermal annealing. These cavities enhance NO2 diffusion, and the liberated unsubstituted amide ─C(═O)NH─ groups readily form robust double hydrogen bonds (DHB), as demonstrated by computer simulations. Furthermore, both polymers possess elevated highest occupied molecular orbital (HOMO) energy levels of -4.74 and -4.77eV, making them highly susceptible to p-doping by NO2 . Gas sensors fabricated from P1 and P2 films, anneal under optimized conditions to partially remove carbamate side chains, exhibit remarkable sensitivities of +1400% ppm-1 and +3844% ppm-1 , and low detection limit (LOD) values of 514 ppb and 38.9 ppb toward NO2 , respectively. These sensors also demonstrate excellent selectivity for NO2 over other gases.

Tailoring the Position of Ester Group on N-Alkyl Chains of Benzotriazole-based Small Molecule Acceptors for High-Performance Organic Solar Cells.

Side chain engineering plays a vital role in exploring high-performance small molecule acceptors (SMAs) for organic solar cells (OSCs). In this work, we designed and synthesized a series of A-DA'D-A type SMAs by introducing different N-substituted alkyl and ester alkyl side chains on benzotriazole (BZ) central unit and aimed to investigate the effect of different ester substitution positions on photovoltaic performances. All the new SMAs with ester groups exhibit lower the lowest unoccupied molecular orbital (LUMO) energy levels and more blue-shifted absorption, but relatively higher absorption coefficients than alkyl chain counterpart. After blending with the donor PM6, the ester side chain-based devices demonstrate enhanced charge mobility, reduced amorphous intermixing domain size and long-lived charge transfer state compared to the alkyl chain counterpart, which are beneficial to achieve higher short-circuit current density (Jsc ) and fill factor (FF), simultaneously. Thereinto, the PM6 : BZ-E31 based device achieves a higher power conversion efficiency (PCE) of 18.33 %, which is the highest PCE among the OSCs based on the SMAs with BZ-core. Our work demonstrated the strategy of ester substituted side chain is a feasible and effective approach to develop more efficient SMAs for OSCs.

Enhancing flame retardancy and optical functionality in multifunctional devices through advanced design of phosphorus‐containing copoly(imide‐oxadiazole)s

AbstractThe combination of flame retardance and optical functionality in phosphorus‐containing copoly(imide‐oxadiazole)s offers a remarkable opportunity for the development of advanced and multifunctional devices, including organic light‐emitting diodes, sensors, and photovoltaics. In this context, a series of phosphorus‐containing copoly(imide‐oxadiazole)s were synthesized through a polycondensation reaction. This involved an aromatic commercial dianhydride, 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), a diamine with phosphorus in the main and side chains, and various aromatic diamines with 1,3,4‐oxadiazole rings. To achieve this, a solution imidization method was employed, which effectively converted the poly(amic acid) intermediates into the corresponding polyimides with high efficiency. The chemical structure and thermal properties of the resulting polymers were investigated. All polymers exhibited high thermal stability. Moreover, the absorption bands observed in dichloromethane, N,N‐dimethylformamide, methanol, and N‐methyl‐2‐pyrrolidone exhibited weak intensities, appearing as shoulders, with maximum values around 270, 303, and 310 nm. In most solvents, the photoluminescence spectra of the polymers showed a single emission band. However, one of the polymers exhibited two emission bands due to pendant groups that disrupted the molecular structure. The fluorescence of these derivatives was influenced by the polarity and proticity of the solvents. Furthermore, they exhibited large Stokes shifts, indicating extended conjugation and the potential to maximize luminescence efficiency. Protonation and deprotonation of polyimides alter their optical properties. These findings provide insights for the design of materials with improved optical performance.

Influence of Fluorescence Lifetime Selections and Conformational Flexibility on Brightness of FusionRed Variants.

Fluorescent proteins (FPs) for bioimaging are typically developed by screening mutant libraries for clones with improved photophysical properties. This approach has resulted in FPs with high brightness, but the mechanistic origins of the improvements are often unclear. We focused on improving the molecular brightness in the FusionRed family of FPs with fluorescence lifetime selections on targeted libraries, with the aim of reducing nonradiative decay rates. Our new variants show fluorescence quantum yields of up to 75% and lifetimes >3.5 ns. We present a comprehensive analysis of these new FPs, including trends in spectral shifts, photophysical data, photostability, and cellular brightness resulting from codon optimization. We also performed all-atom molecular dynamics simulations to investigate the impact of side chain mutations. The trajectories reveal that individual mutations reduce the flexibility of the chromophore and side chains, leading to an overall reduction in nonradiative rates.

An unusual 2-O-glyceryl-glycosyl-γ-pyrone from Erigeron annuus (L.) with potential antifungal activity: in-vitro and in-silico study

Phytochemical characterisation of the polar fraction of Erigeron annuus extract led to the isolation of glycerylerigeroside (1), a unique γ-pyrone derivative. Structure of 1 was decided by intensive study of NMR and mass spectra as 3-O-[4'-((1,3-dihydroxypropan-2-yl)oxy)-β-D-glucopyranoside)]-4H-pyran-4-one, with uncommon glyceroxy side chain attached to 4’ position of pyromeconic acid β-D-glucopyranoside. Antimicrobial potential of 1 was tested against Staphylococcus aureus, Salmonella enterica, and Candida albicans. Compound 1 strongly inhibited growth of Candida albicans (MIC = 17.24 µM/disc), compared to fluconazole (MIC = 16.33 µM/disc). Meanwhile, it moderately inhibited the growth of Staphylococcus aureus (MIC = 71.84 µM/disc) and Salmonella enterica (MIC = 71.84 µM/disc), as compared with thiophenicol (MIC = 14.05 µM/disc) and (MIC = 14.05 µM/disc), respectively. The binding mode of 1 with the active site of sterol 14α-demethylase (CYP51) from Candida albicans (PDB ID: 5TZ1), in combination with fluconazole, was predicted by molecular docking study and supported the antifungal activity.