Side Chain Moiety Research Articles

Deciphering the Selective Targeting of Noncovalent, Wild Type-sparing, and ATP-competitive Tyrosine Kinase Inhibitors to EGFR T790M Gatekeeper Mutant

Various tyrosine kinase inhibitors (TKIs) have been developed to target human epidermal growth factor receptor (EGFR) for cancer therapy. However, many patients treated with first-line TKIs are clinically observed to eventually establish a gatekeeper T790M mutation in the ATP-binding site of the EGFR kinase domain, which is primarily responsible for acquired drug resistance to cancers. Over the past decades, a number of noncovalent, wild-type-sparing and ATP-competitive inhibitors (NWAIs) were reported to selectively target the T790M mutant over wild-type kinase, which are independent of the traditional inhibitor classification system that categorizes EGFR TKIs into four generations. Here, we systematically investigated the intermolecular interaction of wild-type EGFR (EGFR[Formula: see text] and its T790M mutant (EGFR[Formula: see text] with 15 existing NWAI inhibitors, paying attention to the structural and energetic responses of inhibitor ligands to the gatekeeper mutation. It was revealed that the NWAIs can be typed into three classes I, II and III, which can form S[Formula: see text] interactions, hydrophobic (van der Waals) contacts and weak hydrogen (halogen) bonding with the side-chain thioether moiety of the mutant Met790 residue, respectively, thus conferring additional affinity and specificity to inhibitor ligands upon the T790M mutation. In addition, we further performed 2D-chemical similarity search to identify new class I NWAIs, from which two Staurosporine analogs (i.e. UCN01 and ZHD0501) were identified to have a good selectivity for EGFR[Formula: see text] over EGFR[Formula: see text]. They can be exploited as promising leading chemical scaffolds to further develop potent, selective, wild-type-sparing NWAI inhibitors of EGFR[Formula: see text] gatekeeper mutant.

水性レドックスフロー電池用アントラキノン系陽極液の機能化

Redox flow batteries (RFBs) are developed as grid-scale load-leveling technologies for renewable energy. Commercial RFBs use vanadium ions as active materials. However, their low energy density and high cost hinder wide deployment in electrical grids. To address these issues, 2,2′-(anthraquinone-2,6-diyldioxy)dipropionic acid (1Me) was reported as an aqueous anolyte to achieve two-electron redox capability, long cycle life, and high solubility.1 In this work, we improve the cycle stability by introducing a sterically bulkier substituent into the side chain of the anthraflavic acid derivative: 2,2′-(anthraquinone-2,6-diyldioxy)dibutyric acid (1Et; Figure 1). 1Et was synthesized by introducing methyl 2-bromobutyrate into anthraflavic acid, followed by saponification and subsequent neutralization with hydrochloric acid. Both 1Me and 1Et exhibit a redox potential of −0.68 V (vs. Ag/AgCl) in 1 mol L−1 KCl and 0.01 mol L−1 KOH aqueous solutions, indicating little influence of the substituent modification to a redox potential. Interestingly, 1Et shows higher solubility (1.73 mol L−1) than 1Me (1.54 mol L−1) despite an elongated hydrophobic alkyl side chain moiety. An ethyl group possesses a higher degree of freedom for rotation and vibration than a methyl group, resulting in larger dissolution entropy and hence higher solubility. Charge/discharge measurements using an H-type cell reveal that 1Et shows a higher capacity retention (0.029%/cycle) than that of 1Me (0.047%/cycle) (Figure 2) owing to a bulkier substituent preventing from nucleophilic attack on the side chain of anthraquinone. Levich analyses show comparable diffusion coefficients for 1Et (4.55×10−6 cm2 s−1) and 1Me (3.26×10− 6 cm2 s−1). These results demonstrate that introducing a bulkier substituent is an effective strategy to improve solubility in water and cycle stability without degrading other physical properties (e.g., redox potential and diffusivity).Reference[1] R. G. Godon, M. J. Aziz, et al., ACS Energy Lett. 2023, 8, 600. Figure 1

Exploring the impact of end-capped benzothiazine-based acceptors to lead the photovoltaic properties of solar cells: A DFT/TD-DFT approach

To improve the solar cells performance, usually end-capped acceptors are used in designing of new molecules. Therefore, in this study, the side-chain and end-capped moieties were modified in reference compound (BTZR) and proposed new compounds (BTZD1-BTZD6) to augment their photovoltaic and optoelectronic properties. The density functional method was employed at the M06/6-311G(d,p) level to optimize and interpret their frontier molecular orbitals (FMOs), density of states (DOS), transition density matrix (TDM), exciton binding energy (Eb), light absorption and open circuit voltage (Voc) characteristics. Their global reactivity parameters (GRPs) were calculated via the HOMO-LUMO energy band gap. Further, it was observed that all the investigated compounds showed lower band gaps (2.975–3.160 eV) and bathochromic shifts in the visible region (482.501–504.223 nm). Various plots such as the DOS, TDM and hole-electron further confirmed the efficiency of designed chromophores. Additionally, an interface of model donor–acceptor was constructed by considering the donor polymer (PBDB-T) and designed NFAs. Significant results were obtained for Voc (1.538–1.772 V). Among the selected candidates, BTZD3 and BTZD5 were obtained as high-performance non-fullerene acceptors (NFAs). They exhibited least band gaps (2.988 and 2.975 eV) and highest λmax (504.223 and 498.606, respectively). These compounds also demonstrated the least exciton binding energy values as 0.529 and 0.488 eV, respectively. Besides this, comparative study with the standard hole transport material (HTM) spiro-OMeTAD showed a reasonable agreement, suggesting that the entitled compounds could serve as effective HTMs. Overall, the findings suggested the crucial role of end-capped modification in elevating the charge mobility and photovoltaic characteristics of BTZD1-BTZD6. This study provides a valuable insight in the development of good photovoltaic materials.

Covalent penicillin-protein conjugates elicit anti-drug antibodies that are clonally and functionally restricted

Many archetypal and emerging classes of small-molecule therapeutics form covalent protein adducts. In vivo, both the resulting conjugates and their off-target side-conjugates have the potential to elicit antibodies, with implications for allergy and drug sequestration. Although β-lactam antibiotics are a drug class long associated with these immunological phenomena, the molecular underpinnings of off-target drug-protein conjugation and consequent drug-specific immune responses remain incomplete. Here, using the classical β-lactam penicillin G (PenG), we probe the B and T cell determinants of drug-specific IgG responses to such conjugates in mice. Deep B cell clonotyping reveals a dominant murine clonal antibody class encompassing phylogenetically-related IGHV1, IGHV5 and IGHV10 subgroup gene segments. Protein NMR and x-ray structural analyses reveal that these drive structurally convergent binding modes in adduct-specific antibody clones. Their common primary recognition mechanisms of the penicillin side-chain moiety (phenylacetamide in PenG)—regardless of CDRH3 length—limits cross-reactivity against other β-lactam antibiotics. This immunogenetics-guided discovery of the limited binding solutions available to antibodies against side products of an archetypal covalent inhibitor now suggests future potential strategies for the ‘germline-guided reverse engineering’ of such drugs away from unwanted immune responses.

Loratadine Derivative Lo-7: A Weapon against Drug-Resistant Enterococcus and Streptococcal Infections.

The primary obstacles in the management of Enterococcus and Streptococcal infections are drug resistance and biofilm formation. Our study revealed that loratadine at a concentration of ≥25 μM exhibited significant inhibitory effects on biofilm formation in 167 clinical strains of Enterococcus faecalis and 15 clinical isolates of Streptococcus agalactiae, Streptococcus pyogenes, and Streptococcus pneumoniae. Additionally, the antibiofilm activity against E. faecalis and Streptococcal was demonstrated by several loratadine derivatives with altered side-chain carbamate moieties. This study investigated the antibacterial activity of the loratadine derivative Lo-7 against clinical strains of S. agalactiae and S. pyogenes, with minimum inhibitory concentrations ranging from 12.5 to 25 μM. The findings revealed that a low concentration of loratadine derivative Lo-7 (3.125 μM) significantly augmented the bactericidal efficacy of vancomycin against multidrug-resistant (MDR) S. agalactiae, both in vitro and in vivo. The loratadine derivative Lo-7, even at low concentrations, demonstrated significant efficacy in eliminating intracellular MDR S. agalactiae within macrophages, potentially indicating a unique advantage over vancomycin, linezolid, and loratadine. Mechanistically, exposure to the loratadine derivative Lo-7 resulted in membrane depolarization without affecting membrane permeability in S. agalactiae. The potential targeting of the SecG subunit of the SecYEG membrane-embedded channel by the loratadine derivative Lo-7 in S. agalactiae was identified through quantitative proteomics, a drug affinity responsive target stability assay, and molecular docking.

Cation-Binding of Glutamate in Aqueous Solution.

Interactions of the cations Li+, Na+, Mg2+, and Ca2+ with L-glutamate (Glu-) in aqueous solution were studied at room temperature with dielectric relaxation spectroscopy in the gigahertz region. Spectra of ∼0.4 M NaGlu with added LiCl, NaCl, MgCl2, or CaCl2 (c(MCln) ≤ 1.5 M) were evaluated and experiments supplemented by density functional theory and 3D reference interaction site model (3D-RISM) calculations. In addition to the modes found for aqueous NaGlu, namely, the reorientation of free Glu- ions (peaking at ∼1.6 GHz), of moderately retarded H2O molecules hydrating the carboxylate moieties of Glu- (∼8.4 GHz), of the cooperative resettling of the H-bond network of bulk water (∼20 GHz), and its preceding fast H-bond flip (∼400 GHz), an additional low-frequency relaxation at ∼0.4 GHz was detected upon the addition of the four salts. In the case of NaGlu + MgCl2(aq) and NaGlu + CaCl2(aq), this mode could be unequivocally assigned to an ion pair formed by the cation and the side-chain carboxylate moiety of Glu-. For NaGlu + LiCl(aq), either this species or a backbone-[Li+-H2O-Cl--Glu-] triple ion is formed. Binding constants increase in the order Li+<Mg2+<Ca2+. For NaGlu + NaCl(aq), an assignment of the ∼0.4 GHz mode to ion pairs or triples was not plausible. Accordingly, its origin remains speculative here.

Polynorbornenes with carbocyclic substituents: A perspective approach to highly permeable gas separation membranes

Gas transport properties of two sets of polynorbornenes bearing carbocyclic substituents of different nature (cyclohexyl, norbornyl, phenyl groups, and framed oligocyclic moieties) were systematically studied. The influence of side chain carbocyclic substituents on gas permeability and separation selectivity for CO2-containing gas pairs and gaseous hydrocarbons was evaluated. It was found that the presence of carbocyclic moieties in side chains of polynorbornenes promotes the increase in gas permeability similarly to that of SiMe3 groups, with this effect being enhanced by the increase in the number of cycles in the substituents. As a result, P(CO2) of the metathesis polymer with pentacene-based substituents is equal to 1200 Barrer. Studied polynorbornenes with carbocyclic substituents displayed promising gas separation selectivities: CO2/N2 separation selectivity up to 41 (above the 2008 upper bound in the Robeson diagram) and solubility-controlled hydrocarbon separation selectivity up to 16 for the n-butane/methane gas pair. For the polymer with pentacene-based substituents, the separation of the mixture of hydrocarbons and aging were studied. The studies revealed that the mixed gas C4/C1 separation selectivity of this polymer reaches 4, and a two-time reduction of permeability occurs in 8.5 months. Therefore, the incorporation of carbocyclic groups in the side chains of polynorbornenes can be considered as an efficient strategy for the design of polymeric gas separation membrane materials.

Synthesis of a unique mannose α-1-phosphate side chain moiety found in Candida auris cell wall mannan

Candida auris is an emerging fungal pathogen that has become a world-wide public health threat. While there have been numerous studies into the nature, composition and structure of the cell wall of Candida albicans and other Candida species, much less is known about the C. auris cell wall. We have shown that C. auris cell wall mannan contains a unique phosphomannan structure which distinguishes C. auris mannan from the mannans found in other fungal species. Specifically, C. auris exhibits two unique acid-labile mannose α-1-phosphate (Manα1PO4) sidechains that are absent in other fungal mannans and fungal pathogens. This unique mannan structural feature presents an opportunity for the development of vaccines, therapeutics, diagnostic tools and/or research reagents that target C. auris. Herein, we describe the successful synthesis and structural characterization of a Manα1PO4-containing disaccharide moiety that mimics the phosphomannan found in C. auris. Additionally, we present evidence that the synthetic Manα1PO4 glycomimetic is specifically recognized and bound by cell surface pattern recognition receptors, i.e. rhDectin-2, rhMannose receptor and rhMincle, that are known to play important roles in the innate immune response to C. auris as well as other fungal pathogens. The synthesis of the Manα1PO4 glycomimetic may represent an important starting point in the development of vaccines, therapeutics, diagnostics and research reagents which target a number of C. auris clinical strains. In addition, these data provide new insights and understanding into the structural biology of this unique fungal pathogen.

Hydrazone Activation in the Aminocatalytic Cascade Reaction for the Synthesis of Tetrahydroindolizines.

In this Letter, we demonstrate the usefulness of hydrazone activation for the synthesis of biologically relevant tetrahydroindolizines. A pyrrol-derived hydrazone bearing a Michael acceptor moiety in the N-alkyl side chain has been designed with the aim of participating in the aminocatalytic cascade reaction leading to the annulation of the new six-membered heterocyclic scaffold. The application of (S)-(-)-α,α-diphenyl-2-pyrrolidinemethanol trimethylsilyl ether as the aminocatalyst allows for the iminium ion-enamine-mediated cascade to proceed in a fully stereoselective manner.

Resveratrol is converted to the ring portion of coenzyme Q10 and raises intracellular coenzyme Q10 levels in HepG2 cell

Coenzyme Q10 is an essential lipid in the mitochondrial electron transport system and an important antioxidant. It declines with age and in various diseases, there is a need for a method to compensate for the decrease in coenzyme Q10. Resveratrol, a well-known anti-aging compound, has been shown to undergo metabolism to coenzyme Q10's benzene ring moiety in cells. However, administration of resveratrol did not alter or only slightly increased total intracellular coenzyme Q10 levels in many cell types. Synthesis of coenzyme Q10 requires not only the benzene ring moiety but also the side chain moiety. Biosynthesis of the side chain portion of coenzyme Q10 is mediated by the mevalonic acid pathway. Here, we explore the impact of resveratrol on coenzyme Q10 levels in HepG2 cells, which possess a robust mevalonic acid pathway. As a results, intracellular coenzyme Q10 levels were increased by resveratrol administration. Analysis using 13C6-resveratrol revealed that the benzene ring portion of resveratrol was converted to coenzyme Q10. Inhibition of the mevalonic acid pathway prevented the increase in coenzyme Q10 levels induced by resveratrol administration. These results indicate that resveratrol may be beneficial as a coenzyme Q10-enhancing reagent in cells with a well-developed mevalonic acid pathway.

Synthesis and antitumor activity of cyclopentane-fused anthraquinone derivatives

In our pursuit of developing novel analogs of anthracyclines with enhanced antitumor efficacy and safety, we have designed a synthesis scheme for 4,11-dihydroxy-5,10-dioxocyclopenta[b]anthracene-2-carboxamides. These newly synthesized compounds exhibit remarkable antiproliferative potency against various mammalian tumor cell lines, including those expressing activated mechanisms of multidrug resistance. The structure of the diamine moiety in the carboxamide side chain emerges as a critical determinant for anticancer activity and interaction with key targets such as DNA, topoisomerase 1, and ROS induction. Notably, the introduced modification to the doxorubicin structure results in significantly increased lipophilicity, cellular uptake, and preferential distribution in lysosomes. Consequently, while maintaining an impact on anthracyclines targets, these novel derivatives also demonstrate the potential to induce cytotoxicity through pathways associated with lysosomes. In summary, derivatives of cyclic diamines, particularly 3-aminopyrrolidine, can be considered a superior choice compared to aminosugars for incorporation into natural and semi-synthetic anthracyclines or new anthraquinone derivatives, aiming to circumvent efflux-mediated drug resistance.

Redox-responsive biodegradable dendronized polymers: A side-chain modulation based fabrication of drug delivery vehicles

Among various nanomedicine platforms, stimuli-responsive biodegradable polymeric micelles offer a viable approach to address challenges in cancer therapy. Herein, we report the fabrication of redox-responsive micellar aggregates based on an amphiphilic dendron-polymer conjugate. In particular, acid-degradable hydrophobic polyester dendrons are attached as side chain moieties through a disulfide linkage on a hydrophilic copolymer. Polymers containing three generations of dendrons are synthesized using the thiol-disulfide exchange reaction and utilized to obtain micellar aggregates. The stability of the obtained aggregates, drug loading, and release characteristics in neutral, acidic, and redox environments were investigated. It was established that micelles are efficiently internalized by cells, and the highest level of cytotoxicity was observed for MDA-MB-231 breast cancer carcinoma cells under a reducing environment.

Self-Assembled Monolayers of Gemini-Type Amphiphilic Hexabenzocoronenes on Gold: Contribution of Their Triethylene Glycol Side Chains to Self-Assembly Formation.

We report on a two-dimensional self-assembled structure of a supramolecule with hydrophilic oligoethylene glycol (EG) units, which are capable of stronger electrostatic interactions than van der Waals (vdW) interactions between alkyl chains. For this purpose, hexabenzocoronene (HBC) with two hydrophobic dodecyl chains on one side of the HBC core and two hydrophilic triethylene glycol (TEG) chains on the other side of the HBC core (HBCGemini) and HBCGemini with a trinitrofluorenone (TNF) added to the end of one TEG chain (HBCTNFGemini) were employed. Scanning tunneling microscopy (STM) revealed the presence of multiple two-dimensional self-assembled structures in each of HBCGemini and HBCTNFGemini deposited on the gold substrate in vacuum. The role of polar functional groups in these observations is discussed based on semiempirical molecular orbital simulations. Two types of 2D organized structures of HBC-TEG were observed: one with rectangular and relatively dense unit cells and the other with nearly square and relatively sparse unit cells. In both organized structures, the phenyl group TEG units and alkyl chains were considered to be the main molecular interactions with each other. On the other hand, in HBCTNFGemini, three types of organized structures were observed, which could be explained by the mechanism of interdigitation of the TEG-containing side-chain moieties to form a dimeric core. The EG units are more flexible than the alkyl chains and thus can interact flexibly with the hydrophobic HBC core, and the glycol side chains facilitate the intermolecular interactions as well as the alkyl chains.

Synthesis and absolute configuration of paraconiothin I, a structurally unique sesquiterpene isolated from the endophytic fungus Paraconiothyrium brasiliense ECN258

The total synthesis and determination of the absolute configuration are described for paraconiothin I, an inhibitor against the nuclear receptor liver X receptor α, which is produced by the endophytic fungus Paraconiothyrium brasiliense ECN258. Our method for synthesizing paraconiothin I involved Evans asymmetric alkylation and Sharpless asymmetric dihydroxylation, which enabled us to develop an efficient synthetic approach for constructing the side-chain moiety of paraconiothin I. Through model synthesis, we discovered that the previously proposed relative configuration of the natural product was incorrect and determined the correct absolute configuration of the natural product by comparing the specific rotations of the synthetic and natural products.

New 2-alkoxycyanopyridine derivatives as inhibitors of EGFR, HER2, and DHFR: Synthesis, anticancer evaluation, and molecular modeling studies

New series of substituted 2-alkoxycyanopyridine derivatives were synthesized and evaluated for their in vitro and in vivo anticancer activities. Comparing the evaluated activities against cancer cell lines to the broad-spectrum anticancer doxorubicin, and the kinase inhibitor sorafenib, compounds 3a, 4b, 4c, 7a, and 8d demonstrated superior anticancer efficacy with elevated safety profiles and selectivity indices, particularly against MCF7 breast cancer. For exploration of their mechanism of action, assays for inhibition of EGFR, HER2 kinase, and DHFR were performed. The promising synthesized compounds exhibited potent dual kinase EGFR/HER2 inhibitory activity with IC50values of 0.248/0.156 μM for 4b and 0.138/0.092 μM for 4c. Additionally, with IC50 values of 0.138 and 0.193 M, respectively, 4b and 4c had the greatest DHFR inhibitory activity that was comparable to methotrexate. In the MCF7 breast cancer cell line, they caused arrest at the S phase of the cell cycle and exhibited apoptosis induction activity. With restored caspase-3 immunoexpression, the anti-breast cancer assay performed in vivo of 4b and 4c demonstrated a substantial decrease in tumor volume. Results from molecular modeling were in agreement with biological assays proving the importance of the 3-caynopyridine, two substituted phenyl rings attached to central pyridine ring, and propoxy side chain moieties for binding with the receptors. As 4c works by inhibiting both EGFR/HER2 kinase, DHFR enzymes, in addition to cellular apoptosis, it could be viewed as a model of compounds possessing a multi-targeting anticancer activity. Collectively, compounds 4b and 4c might represent prototypes for further development as anticancer molecules.

Copper catalyzed Shono-type oxidation of proline residues in peptide.

Since the initial report in 1975, the Shono oxidation has become a powerful tool to functionalize the α position of amines, including proline derivatives, by electrochemical oxidation. However, the application of electrochemical Shono oxidations is restricted to the preparation of simple building blocks and homogeneous Shono-type oxidation of proline derivatives remains challenging. The late-stage functionalization at proline residues embedded within peptides is highly important as substitutions about the proline ring are known to affect biological and pharmacological activities. Here, we show that homogenous copper-catalyzed oxidation conditions complement the Shono oxidation and this general protocol can be applied to a series of formal C-C coupling reactions with a variety of nucleophiles using a one-pot procedure. This protocol shows good tolerance toward 19 proteinogenic amino acids and was used to functionalize several representative bioactive peptides, including captopril, enalapril, Smac, and endomorphin-2. Last, peptide cyclization can also be achieved by using an appropriately positioned side-chain hydroxyl moiety.

Sirturo- a diarylquinoline (bedaquiline): a novel approach for the treatment of MDR-TB and pre-XDR TB

Sirturo (bedaquiline fumarate) is a new antitubercular class of medicine, lately, FDA, approved and indicated for use as a part of an appropriate applicable combination regimen along with other antitubercular medicines (i. e.; 2nd line anti-TB agents) for pulmonary multidrug-resistant tuberculosis (MDR TB) in grown up with age 12 years to less than 18 years of age and weighing at least 30 kg when an alternative treatment regimen cannot be considered for the reasons of resistance or tolerability. Bedaquiline, an enantiomer chemically belongs to the diarylquinoline (DAR) compound, which is nearly related to fluoroquinolones and chloroquine with differences in their side-chain moiety. Amongst all anti-TB medicines that have been approved, bedaquiline has a unique mechanism, which targets energy metabolism i. e.; adenosine triphosphate of mycobacteria, and eventually leads to bacterial cell lysis. ATP is an essential energy-producing molecule required for metabolic actions and survival of Mycobacteria and also for many other cells. Mycobacteria generally invade into well-encapsulated lung cavities and endosomes of macrophages, which can survive even under low oxygen levels leading to resistance against standard TB drugs. Bedaquiline has a spectrum of activity against drug-susceptible TB and MDR TB. Many clinical trials and studies demonstrated that bedaquiline is a crucial component of a combination regimen for multidrug-resistant TB.

Structural and Computational Analyses of the Unique Interactions of Opicapone in the Binding Pocket of Catechol O-Methyltransferase: A Crystallographic Study and Fragment Molecular Orbital Analyses.

A third-generation inhibitor of catechol O-methyltransferase (COMT), opicapone (1), has the 3-nitrocatechol scaffold as do the second-generation inhibitors such as entacapone (2) and tolcapone (3), but only 1 can sustainably inhibit COMT activity making it suitable for a once-daily regimen. These improvements should be attributed to the optimized sidechain moiety (oxidopyridyloxadiazolyl group) of 1 substituted at the 5-position of the 3-nitrocatechol ring. We analyzed the role of the sidechain moiety by solving the crystal structures of COMT/S-adenosylmethionine (SAM)/Mg/1 and COMT/S-adenosylhomocysteine (SAH)/Mg/1 complexes. Fragment molecular orbital (FMO) calculations elucidated that the dispersion interaction between the sidechains of Leu 198 and Met 201 on the β6β7-loop and the oxidopyridine ring of 1 were unique and important in both complexes. In contrast, the catechol binding site made a remarkable difference in the sidechain conformation of Lys 144. The ε-amino group of Lys 144 was outside of the catalytic pocket and was replaced by a water molecule in the COMT/SAH/Mg/1 complex. No nitrocatechol inhibitor has ever been reported to make a complex with COMT and SAH. Thus, the conformational change of Lys 144 found in the COMT/SAH/Mg/1 complex is the first crystallographic evidence that supports the role of Lys 144 as a catalytic base to take out a proton ion from the reaction site to the outside of the enzyme. The fact that 1 generated a complex with SAH and COMT also suggests that 1 could inhibit COMT twofold, as a typical substrate mimic competitive inhibitor and as a product-inhibition enhancer.

Poly(Vinyl Ketones): New Directions in Photodegradable Polymers.

Poly(vinyl ketones) (PVKs) have received considerable attention over the past few decades due to their unique photochemistry and photodegradation properties under ultraviolet (UV) light. Many PVKs rapidly undergo photodegradation under UV light. The side-chain carbonyl moieties of PVKs permit photolysis through Norrish type I or Norrish type II reaction mechanisms and can also be readily modified by nucleophilic addition reactions. These unique properties lead to this class of polymers serving as versatile scaffolds for generating functional materials. This review captures the evolution of synthetic routes to access well-defined PVKs, along with their photochemistry and photo-degradation pathways, and discusses recent and potential applications of these photodegradable materials.

Small Schiff base molecules derived from salicylaldehyde as colorimetric and fluorescent neutral-to-basic pH sensors

The development of pH sensors is very important to distinguish different pHs in several applications. In this study, we examined the change of the side chain moiety on the photophysical properties of eight pH-sensitive small Schiff bases (SBs) that can act as both, colorimetric and fluorometric probes. For that, we synthesized all SBs by condensation between salicylaldehyde with a primary amine (methyl-, ethyl-, isopropyl, propyl-, butyl-, pentyl-, cyclohexyl-, and benzyl-amine). The complete molecular structure was confirmed by 1H NMR, 13C NMR, FTIR, UV–Vis, and by GC–FID purity over 90% was confirmed for all synthesized SBs. Theoretical calculations were also performed to give support to our findings. All synthesized samples were tested as a colorimetric and fluorometric pH sensor in the range of pH 3.0–12.0. All SBs exhibited similar behavior, despite the side chain lengths. The SBs are quite long-lived in water solution, allowing their usage as pH sensor. While between pH 3.0–7.0 they are colorless due to the presence of the protonated species, HSB, above pH 7.0 they turn yellow due to the formation of SB−, indicating that the chromogenic property depends on the pH. Additionally, these SBs also exhibit fluorogenic characteristic as they show fluorescence off at acidic pH 3.0–7.0 and fluorescence on (508 nm) above pH 8.0, exhibiting a linear response between pH 7.0–9.0. The pKa value was calculated using the Henderson–Hasselbalch equation for all SBs, obtaining values from 8.20 to 8.52. All SBs act as pH-sensitive colorimetric and fluorometric probes in neutral-to-basic solutions and this process is reversible.