Amino Acid Moiety Research Articles

LC-MS analysis of the degradation products of a sprayable, biodegradable poly(ester-urethane-urea)

Biodegradable polymers must degrade completely to CO2, H2O, small and non-toxic molecules (e.g. NO3− and NH3/NH4+), and biomass on a similar timescale to classically compostable materials (3–12 months). More importantly, the degradation intermediates - the compounds that form as a polymeric material breaks down in the environment, before being mineralized or bio-assimilated also need to be non-toxic. Here, for the first time, the identity of the degradation intermediates formed from the breakdown of a sprayable, biodegradable poly(ester-urethane-urea) was investigated using a liquid chromatography mass spectrometry (LC-MS) system. This was accomplished by degrading the polymer in abiotic aqueous media for varying lengths of time and in soil media for 57 days, and analyzing the degradation media for polymer degradation intermediates. It was found that during degradation, monomers and short oligomers were formed containing amino, alcohol and carboxylic acid moieties. Interestingly, the most prominent degradation products formed during abiotic degradation (6-hydroxy hexanoic acid, and its oligomers) were not detectable when the polymer was degraded in a soil environment. Gel permeation chromatography confirmed that the polymer's molecular weight was substantially reduced during the degradation studies, but the presence of polymer fragments >1000 Da in the soil indicated that there would be an ongoing release of 6-hydroxy hexanoic acid and its oligomers. Taken together this suggests that those molecules were rapidly bio-assimilated by the soil microbial community.

Recent advances in understanding prodrug transport through the SLC15 family of proton-coupled transporters

Solute carrier (SLC) transporters play important roles in regulating the movement of small molecules and ions across cellular membranes. In mammals, they play an important role in regulating the uptake of nutrients and vitamins from the diet, and in controlling the distribution of their metabolic intermediates within the cell. Several SLC families also play an important role in drug transport and strategies are being developed to hijack SLC transporters to control and regulate drug transport within the body. Through the addition of amino acid and peptide moieties several novel antiviral and anticancer agents have been developed that hijack the proton-coupled oligopeptide transporters, PepT1 (SCL15A1) and PepT2 (SLC15A2), for improved intestinal absorption and renal retention in the body. A major goal is to understand the rationale behind these successes and expand the library of prodrug molecules that utilise SLC transporters. Recent co-crystal structures of prokaryotic homologues of the human PepT1 and PepT2 transporters have shed important new insights into the mechanism of prodrug recognition. Here, I will review recent developments in our understanding of ligand recognition and binding promiscuity within the SLC15 family, and discuss current models for prodrug recognition.

Durable, Stable, and Functional Nanopores Decorated by Self-Assembled Dipeptides.

Nanopores have become an important tool for the detection and analysis of molecules at the single-molecule level. Surface modification of solid-state nanopores can improve their durability and efficiency. Peptides are ideal for surface modifications as they allow tailoring of multiple properties by a rational design of their sequence. Here, silicon nitride nanopores were coated by a dipeptide layer where a l-3,4-dihydroxyphenylalanine (DOPA) residue is the anchoring element and the other amino acid moiety is the functional element. DOPA binds tightly to many types of surfaces and allows a one-step functionalization of surfaces by simple immersion. As a result, the lifetime of coated nanopores increased from hours to months and the current-stability has significantly improved with respect to uncoated pores. This improvement is achieved by controlling the surface wettability and charge. Peptide-coated nanopores can be utilized as sensitive sensors that can be adjusted based on the choice of the functional moiety of the coated peptide. In addition, the coating slows down dsDNA translocation because of the DNA interaction with the pore coating.

Structural Patterns and Stabilities of Hydrogen-Bonded Pairs Involving Ribonucleotide Bases and Arginine, Glutamic Acid, or Glutamine Residues of Proteins from Quantum Mechanical Calculations.

Ribonucleotide:protein interactions play crucial roles in a number of biological processes. Unlike the RNA:protein interface where van der Waals contacts are prevalent, the recognition of a single ribonucleotide such as ATP by a protein occurs predominantly through hydrogen-bonding interactions. As a first step toward understanding the role of hydrogen bonding in ribonucleotide:protein recognition, the present work employs density functional theory to provide a detailed quantum-mechanical analysis of the structural and energetic characteristics of 18 unique hydrogen-bonded pairs involving the nucleobase/nucleoside moiety of four canonical ribonucleotides and the side chains of three polar amino-acid residues (arginine, glutamine, and glutamic acid) of proteins. In addition, we model five new pairs that are till now not observed in crystallographically identified ribonucleotide:protein complexes but may be identified in complexes crystallized in the future. We critically examine the characteristics of each pair in its ribonucleotide:protein crystal structure occurrence and (gas phase and water phase) optimized intrinsic structure. We further evaluated the interaction energy of each pair and characterized the associated hydrogen bonds using a number of quantum mechanics-based relationships including natural bond orbital analysis, quantum theory atoms in molecules analysis, Iogansen relationships, Nikolaienko–Bulavin–Hovorun relationships, and noncovalent interaction–reduced density gradient analysis. Our analyses reveal rich variability in hydrogen bonds in the crystallographic as well as intrinsic structure of each pair, which includes conventional O/N–H···N/O and C–H···O hydrogen bonds as well as donor/acceptor-bifurcated hydrogen bonds. Further, we identify five combinations of nucleobase and amino acid moieties; each of which exhibits at least two alternate (i.e., multimodal) structures that interact through the same nucleobase edge. In fact, one such pair exhibits four multimodal structures; one of which possesses unconventional “amino–acceptor” hydrogen bonding with comparable (−9.4 kcal mol–1) strength to the corresponding conventional (i.e., amino:donor) structure (−9.2 kcal mol–1). This points to the importance of amino–acceptor hydrogen bonds in RNA:protein interactions and suggests that such interactions must be considered in the future while studying the dynamics in the context of molecular recognition. Overall, our study provides preliminary insights into the intrinsic features of ribonucleotide:amino acid interactions, which may help frame a clearer picture of the molecular basis of RNA:protein recognition and further appreciate the role of such contacts in biology.

Improved synthetic route for the GluN2-specific NMDA receptor glycine site agonist AICP

(R)-2-Amino-3-(4-(2-ethylphenyl)-1H-indole-2-carboxamido)propanoic acid (AICP) is a N-methyl-d-aspartate (NMDA) receptor glycine site agonist with unprecedented high potency in the low nanomolar range, and a GluN2 subunit-dependent pharmacological profile in terms of potency and agonist efficacy (Jessen et al., 2017 [1]). Here, we report a scalable, practical and cost-efficient synthetic route for AICP, which is an improvement compared to the previously reported route. This improved synthetic route includes a versatile diphenylmethylester (DPM) protection for the amino acid moiety, which can be widely used in the synthesis of other amino acid ligands. Further functional evaluation of AICP at the different ionotropic glutamate receptor (iGluR) classes demonstrates that high affinity binding of AICP to the orthosteric binding site is selective for NMDA receptors over AMPA and kainate receptors. Furthermore, high affinity binding of AICP is not observed at GluN3A, GluN3B, and GluD2 subunits, which also bind glycine and d-serine. Thus, the new approach described here enables scalable synthesis of AICP for the use as a pharmacological tool compound to study the involvement of neuronal NMDA receptor subtypes in normal brain function and disease.

Functionalization of amino acids with aryl fluorosulfate for prodrug construction by SuFEx chemistry

Sulfur (VI) Fluoride Exchange (SuFEx) chemistry is proposed as a new generation of click chemistry with potential in drug discovery and biological study. Herein we report a simple and convenient approach to synthesize amino acid derivatives functionalized with aryl fluorosulfonyl group from a simple building block. Promoted by 1,1′-Carbonyldiimidazole (CDI), methyl protected amino acids and other amines were efficiently functionalized with SO2F by the reaction with 4-((fluorosulfonyl)oxy)benzoic acid giving fluorosulfonylated amides (FSAs) as products. We also demonstrated that FSAs are useful building blocks in drug discovery. The conjugation of FSA with pharmaceutical phenols by SuFEx efficiently introduced amino acid moiety into target molecule, providing a series of prodrugs with diverse property.

Dynamics of the context-specific translation arrest by chloramphenicol and linezolid

Chloramphenicol (CHL) and linezolid (LZD) are antibiotics that inhibit translation. Both were thought to block peptide bond formation between all combinations of amino acids. Yet recently, a strong nascent peptide context-dependency of CHL- and LZD-induced translation arrest was discovered. Here, we probed the mechanism of action of CHL and LZD by using single-molecule Förster resonance energy transfer spectroscopy (smFRET) to monitor translation arrest induced by antibiotics. The presence of CHL or LZD does not significantly alter dynamics of protein synthesis until the arrest-motif of the nascent peptide is generated. Inhibition of peptide-bond formation compels the fully accommodated A-site tRNA to undergo repeated rounds of dissociation and non-productive rebinding. The glycyl amino-acid moiety on the A-site Gly-tRNA manages to overcome the arrest by CHL. Our results illuminate the mechanism of CHL and LZD action through their interactions with the ribosome, the nascent peptide and the incoming amino acid, perturbing elongation dynamics.

Light Emission in Betalains: From Fluorescent Flowers to Biotechnological Applications.

The discovery of visible fluorescence in the plant pigments betalains revealed the existence of fluorescent patterns in flowers of plants of the order Caryophyllales, where betalains substitute anthocyanins. The serendipitous initial discovery led to a systemized characterization of the role of different substructures on the photophysical phenomenon. Strong fluorescence is general to all members of the family of betaxanthins linked to the structural property that the betalamic acid moiety is connected to an amine group. This property has led to bioinspired tailor-made probes and to the development of novel biotechnological applications in screening techniques or microscopy labeling. Here, we comprehensively review the photophysics, photochemistry, and photobiology of betalain fluorescence and describe all current applications.

Synthesis and Study of Derivatives of the [B10H10]2– Anion with Amino Acids

The interaction between tetrahydrofuran, tetrahydropyran, and 1,4-dioxane derivatives of the [B10H10]2– anion and a number of amino acids (glycine, cysteine, serine, and p-aminobenzoic acid) has been studied. It has been shown that, during the reactions, the exo-polyhedral cyclic substituent is opened to form closo-decaborates containing the pendant amino acid group, while the nucleophilic reagent is attached via the oxygen atom. The nucleophilic reagents can be both amino acids (in water) and their sodium salts (in dimethylformamide). All the compounds obtained are effective polydentate ligands capable to be coordinated to the metal through the donor atoms of the amino acid moiety attached and by forming three-center two-electron bonds. The synthesized compounds have been studied by elemental analysis, IR spectroscopy, 11B, 13C, and 1H NMR spectroscopies, and ESI mass spectrometry. closo-Decaborates with pendant amino acid moieties are of interest for 10B neutron capture therapy of malignant tumors due to the high content of boron atoms and a convenient way to transport them to the cells affected.

A Non-Viral Plasmid DNA Delivery System Consisting on a Lysine-Derived Cationic Lipid Mixed with a Fusogenic Lipid.

The insertion of biocompatible amino acid moieties in non-viral gene nanocarriers is an attractive approach that has been recently gaining interest. In this work, a cationic lipid, consisting of a lysine-derived moiety linked to a C12 chain (LYCl) was combined with a common fusogenic helper lipid (DOPE) and evaluated as a potential vehicle to transfect two plasmid DNAs (encoding green fluorescent protein GFP and luciferase) into COS-7 cells. A multidisciplinary approach has been followed: (i) biophysical characterization based on zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), and cryo-transmission electronic microscopy (cryo-TEM); (ii) biological studies by fluorescence assisted cell sorting (FACS), luminometry, and cytotoxicity experiments; and (iii) a computational study of the formation of lipid bilayers and their subsequent stabilization with DNA. The results indicate that LYCl/DOPE nanocarriers are capable of compacting the pDNAs and protecting them efficiently against DNase I degradation, by forming Lα lyotropic liquid crystal phases, with an average size of ~200 nm and low polydispersity that facilitate the cellular uptake process. The computational results confirmed that the LYCl/DOPE lipid bilayers are stable and also capable of stabilizing DNA fragments via lipoplex formation, with dimensions consistent with experimental values. The optimum formulations (found at 20% of LYCl content) were able to complete the transfection process efficiently and with high cell viabilities, even improving the outcomes of the positive control Lipo2000*.

Influence of Non-natural Cationic Amino Acids on the Biological Activity Profile of Innate Defense Regulator Peptides.

Non-natural amino acids can be incorporated into synthetic host defense peptides (HDPs) to modulate their susceptibility to proteolytic degradation. However, the impact of non-natural amino acids on the antibiofilm and immunomodulatory activities of synthetic HDPs remains unclear. Using SPOT-synthesized peptide arrays, non-natural cationic amino acids of varying side chain lengths were incorporated into a synthetic HDP, IDR-1018, and the impact of these substitutions on the antibiofilm activity toward methicillin resistant Staphylococcus aureus biofilms was assessed. Multiply-substituted derivatives were designed that incorporated favorable non-natural cationic amino acid moieties throughout IDR-1018. The antibiofilm and immunomodulatory activities of these derivatives were assessed in vitro, revealing that the incorporation of non-natural amino acids modulated (either positively or negatively) these activities of IDR-1018. Furthermore, the tryptic stability of the IDR-1018 derivatives was assessed revealing that proteolytic stability was favored for shorter cationic side chains and was influenced by the primary peptide sequence.

Synthesis, DNA binding studies, and antiproliferative activity of novel Pt(II)-complexes with an L-alanyl-based ligand

An artificial alanine-based amino acid {(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoic acid, here named TioxAla}, bearing a substituted triazolyl-thione group on the side chain and able to bind RNA biomedical targets, was here chosen as a valuable scaffold for the synthesis of new platinum complexes with potential dual action owing to the concomitant presence of the metal centre and the amino acid moiety. Three new platinum complexes, obtained from the reaction of TioxAla with K2PtCl4, were characterized by mass spectrometry, nuclear magnetic resonance and UV–vis spectroscopy: one compound (Pt1, bis-{(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoate-O,S} platinum(II)) consisted of two amino acid units coordinating the Pt(II) ion; the other two, Pt2 [potassium dichloro-{(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoate (O,S)} platinum(II)] and Pt3 [potassium dichloro-{(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoate (O,N)} platinum(II)], were isomers bearing one TioxAla unit, and two chlorides as Pt-ligands. Pt coordination involved preferentially the amino, carboxylic and thione functions of TioxAla. By preliminary antiproliferative assays, a moderate cytotoxic activity on cancer cells was observed only for Pt2 and Pt3, while no anticancer activity was found for both the chloride-free complex (Pt1) and TioxAla. This cytotoxicity, however lower than that of cisplatin, well correlated with the marked ability, here found only for Pt2 and Pt3 complexes, to bind DNA sequences either in random coil or in structured forms (duplex and G-quadruplex), as verified by spectroscopic and spectrometric analysis.

Rigorous sampling of docking poses unveils binding hypothesis for the halogenated ligands of L-type Amino acid Transporter 1 (LAT1)

L-type Amino acid Transporter 1 (LAT1) plays a significant role in the growth and propagation of cancer cells by facilitating the cross-membrane transport of essential nutrients, and is an attractive drug target. Several halogen-containing L-phenylalanine-based ligands display high affinity and high selectivity for LAT1; nonetheless, their molecular mechanism of binding remains unclear. In this study, a combined in silico strategy consisting of homology modeling, molecular docking, and Quantum Mechanics-Molecular Mechanics (QM-MM) simulation was applied to elucidate the molecular basis of ligand binding in LAT1. First, a homology model of LAT1 based on the atomic structure of a prokaryotic homolog was constructed. Docking studies using a set of halogenated ligands allowed for deriving a binding hypothesis. Selected docking poses were subjected to QM-MM calculations to investigate the halogen interactions. Collectively, the results highlight the dual nature of the ligand-protein binding mode characterized by backbone hydrogen bond interactions of the amino acid moiety of the ligands and residues I63, S66, G67, F252, G255, as well as hydrophobic interactions of the ligand’s side chains with residues I139, I140, F252, G255, F402, W405. QM-MM optimizations indicated that the electrostatic interactions involving halogens contribute to the binding free energy. Importantly, our results are in good agreement with the recently unraveled cryo-Electron Microscopy structures of LAT1.

Synthesis and In Vitro Neuroprotective Activity of Analogs with Various Spacer Lengths of a Dimeric Dipeptide Mimetic (GK-2) of Nerve Growth Factor

Dimeric dipeptide mimetic GK-2 or hexamethylenediamide bis-(N-monosuccinyl-L-glutamyl-L-lysine), which activated TrkA receptors and exhibited neuroprotective activity in vitro (10–5 – 10–9 M) and in vivo (0.05 – 5 mg/kg i.p.), was designed by us earlier based on the beta-turn of the nerve growth factor (NGF) fourth loop. The effect of dimerizing spacer length on the manifestation of neuroprotective activity was studied by synthesizing GK-2 (11 σ-bonds) analogs tetramethylenediamide bis-(N-monosuccinyl-L-glutamyl-Llysine) (GK-2c); pentamethylenediamide bis-(N-monosuccinyl-L-glutamyl-L-lysine) (GK-2b); and trimethylenediamide bis-(N-monosuccinyl-L-glutamyl-L-lysyl-6-aminohexanoic acid) (GK-2a) containing 9, 10, and 22 σ-bonds, respectively, between the lysine Cα-atoms of the dipeptide fragments. Neuroprotective activity was investigated in vitro using HT-22 mouse hippocampal neuronal cell culture under H2O2-induced oxidative stress and showed that the neuroprotective activity as measured by the minimum effective concentration was 104 times less if the distance between the dipeptide fragments increased from 11 to 22 σ-bonds. The neuroprotective activity decreased insignificantly if this distance was decreased from 11 to 10 σ bonds (GK-2b) and disappeared with 9 σ -bonds (GK-2c). Therefore, the hexamethylene spacer was optimal although the distance between the corresponding amino-acid moieties of natural NGF from an x-ray structure analysis was considerably greater at 33 σ-bonds. This contradiction could have arisen because two ionically bound mimetic molecules interacted with TrkA receptors. Another possible explanation was that TrkA molecules could approach closer in the presence of bis-dipeptide GK-2 than NGF.

Amino acid secretion influences the size and composition of copper carbonate nanoparticles synthesized by ureolytic fungi

The ureolytic activity of Neurospora crassa results in an alkaline carbonate-rich culture medium which can precipitate soluble metals as insoluble carbonates. Such carbonates are smaller, often of nanoscale dimensions, than metal carbonates synthesized abiotically which infers that fungal excreted products can markedly affect particle size. In this work, it was found that amino acid excretion was a significant factor in affecting the particle size of copper carbonate. Eleven different amino acids were found to be secreted by Neurospora crassa, and l-glutamic acid, l-aspartic acid and l-cysteine were chosen to examine the impact of amino acids on the morphology and chemical composition of copper carbonate minerals. X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the obtained copper carbonate samples. Copper carbonate nanoparticles with a diameter of 100–200 nm were produced with l-glutamic acid, and the presence of l-glutamic acid was found to stabilize these particles in the early phase of crystal growth and prevent them from aggregation. FTIR and TG analysis revealed that the amino acid moieties were intimately associated with the copper mineral particles. Component analysis of the final products of TG analysis of the copper minerals synthesized under various conditions showed the ultimate formation of Cu, Cu2O and Cu2S, suggesting a novel synthesis method for producing these useful Cu-containing materials.

Surfaces based on amino acid functionalized polyelectrolyte films towards active surfaces for enzyme immobilization.

Surface based on polyelectrolytes functionalized with amino acids onto amino-terminated solid surfaces of silicon wafers was prepared, with the purpose of evaluate the chemical functionality of the polyelectrolyte films in adsorption and catalytic activity of an enzyme. In this work, the adsorption of the enzyme glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides (LmG6PD) was studied as model. The polyelectrolytes were obtained from poly (maleic anhydride-alt-vinylpyrrolidone) [poly(MA-alt-VP)] and functionalized with amino acids of different hydropathy index: glutamine (Gln), tyrosine (Tyr) and methionine (Met). The polyelectrolytes were adsorbed onto the amino-terminated silicon wafer at pH 3.5 and 4.5 and at low and high ionic strength. At low ionic strength and pH 3.5, the largest quantity of adsorbed polyelectrolyte was on the films containing glutamine moiety as the most hydrophilic amino acid in the side chain of polymer chain (5.88 mg/m2), whereas at high ionic strength and pH 4.5, the lowest quantity was in films containing tyrosine moiety in the side chain (1.88 mg/m2). The films were characterized by ellipsometry, contact angle measurements and atomic force microscopy (AFM). The polyelectrolyte films showed a moderate degree of hydrophobicity, the methionine derivative being the most hydrophobic film. With the aim of evaluate the effect of the amino acid moieties on the ability of the surface to adsorb enzymes, we study the activity of the enzyme on these surfaces. We observed that the polarity of the side chain of the amino acid in the polyelectrolyte affected the quantity of LmG6PD adsorbed, as well as its specific activity, showing that films prepared from poly(MA-alt-VP) functionalized with Met provide the best enzymatic performance. The results obtained demonstrated that the surfaces prepared from polyelectrolytes functionalized with amino acids could be an attractive and simple platform for the immobilization of enzymes, which could be of interest for biocatalysis applications.

Molecular and supramolecular helicity induction in trityl group-containing compounds: The case of chiral 3,3,3-triphenylpropionic acid derivatives

The process of dynamic chirality transmission from permanent chirality element to stereodynamic triphenylmethyl group placed in the distance of 4 bonds, has been studied for series of optically active 3,3,3-triphenylpropionic acid derivatives. Structural analysis, carried out with the use of complementary methods and supported by theoretical calculations, enabled us to determine the mechanism of chirality transmission. The observed chirality transfer phenomenon, demonstrated unequivocally as raising of non-zero Cotton effects in the region of UV absorption of trityl group, is a cascade process driven by weak intramolecular interactions. Despite the much larger inductor-effector distance, the sensitivity in chirogenesis is comparable to other stereodynamic probes reported so far. In the crystalline phase, the combination of trityl group with amino acid moiety results in the formation of helical superstructures, where individual molecules are held together by hydrogen bonding cascades. The proper combination of functionalities in the molecule skeleton allows, to some extent, the control over the association process and authorizes determination of the trityl group as the supramolecular synthon.

Investigation by DFT Methods of the Damage of Human Serum Albumin Including Amino Acid Derivative Schiff Base Zn(II) Complexes by IR-FEL Irradiation

An infrared free electron laser (IR-FEL) can decompose aggregated proteins by excitation of vibrational bands. In this study, we prepared hybrid materials of protein (human serum albumin; HSA) including several new Schiff base Zn(II) complexes incorporating amino acid (alanine and valine) or dipeptide (gly-gly) derivative moieties, which were synthesized and characterized with UV-vis, circular dichroism (CD), and IR spectra. Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations were also performed to investigate vibrational modes of the Zn(II) complexes. An IR-FEL was used to irradiate HSA as well as hybrid materials of HSA-Zn(II) complexes at wavelengths corresponding to imine C=N, amide I, and amide II bands. Analysis of secondary structures suggested that including a Zn(II) complex into HSA led to the structural change of HSA, resulting in a more fragile structure than the original HSA. The result was one of the characteristic features of vibrational excitation of IR-FEL in contrast to electronic excitation by UV or visible light.

Stimuli-responsive poly(phenyl acetylene) microparticles with tunable chirality

Chiral polymeric microparticles combine the characteristics of chirality and spherical morphology in one matter, which may provide confined microenvironments to switch chirality and to promote conformation transition. Here we report on fabrication of chiral polymeric microparticles (CMPs) from dendronized copolymers, and investigation of their tunable chirality upon external stimuli, such as temperature, pH, metal ion complexation and solvents. These polymeric microparticles were constructed via one-pot approach through precipitation copolymerization of phenylacetylene derivatives. The monomers contain dendritic oligoethylene glycol (OEG) to afford copolymers thermoresponsiveness and alkynyl groups for polymerization and crosslinking. Chirality of the polymeric microparticles was afforded by intrinsic chirality from the amino acid moieties. Furthermore, thermoresponsiveness of these microparticles paves a novel route to switch their chirality and mediate their responsive behavior to metal ion coordination.

Application of probe electrospray ionization-tandem mass spectrometry to ultra-rapid determination of glufosinate and glyphosate in human serum

Glufosinate and glyphosate, which are non-selective herbicides that include an amino acid moiety in their structures, are frequently used worldwide to control unwanted vegetation. Unfortunately, these readily available herbicides are also used by people to commit suicide, and thus represent important chemicals of interest in the fields of clinical medicine and forensics. Because of the high water solubility of these herbicides, most analytical methods for their detection require a derivatization step, which results in longer analysis times. Therefore, derivatization-based methods do not currently contribute to judgements on treatment decisions in emergency medicine. In this study, we addressed this limiting factor by developing an ultra-rapid and simple analytical technique using a combination of probe electrospray ionization (PESI) and tandem mass spectrometry (MS/MS), which gives quantitative results within 0.3 min. Herbicide standards were added to human serum that was then subjected to analysis (N = 5 per concentration). The analysis was repeated daily over eight consecutive days. The limit of detection (LOD) was 0.59 μg/mL for glufosinate and 0.20 μg/mL for glyphosate. The limit of quantitation (LOQ), i.e., the lowest point on the calibration curves, was 1.56 μg/mL for both the herbicides. The matrix effects were observed at three different concentrations (between 95.7%–104% for glufosinate, and between 90.7%–95.7% for glyphosate). When applied to samples taken from actual poisoning cases (six samples for each herbicide), the present method gave almost the same quantitative values as those obtained by conventional high-performance liquid chromatography with fluorescence detection. Thus, we believe that PESI-MS/MS could emerge as a rapid diagnosis method in the clinical emergency field.