Leave it to Lefamulin: A Pleuromutilin Treatment Option in Community-Acquired Bacterial Pneumonia.

Lefamulin (BC-3781) is the first systemic pleuromutilin antibiotic found to be safe and effective in the treatment of community-acquired bacterial pneumonia (CABP) in humans. This novel antibiotic was developed to combat the increasing incidence of bacterial resistance to current therapies. As the first semisynthetic pleuromutilin for systemic use in humans, lefamulin has demonstrated efficacy against the most common bacteria responsible for CABP, including strains exhibiting resistance to macrolides, fluoroquinolones, tetracyclines, vancomycin, and beta-lactams. In vitro studies have demonstrated efficacy against Staphylococcus aureus, beta-hemolytic and viridans group streptococci, coagulase-negative staphylococci, Enterococcus faecium, Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophilia, and Moraxella catarrhalis at MIC values lower than those of currently available therapies. Two phase III trials (LEAP-1 and LEAP-2) have demonstrated similar findings, meeting non-inferiority criteria for CABP with a minimal side-effect profile. Pharmacokinetic and pharmacodynamic evaluations have shown sufficient drug levels in plasma, subcutaneous adipose tissue, skeletal muscle, and epithelial lining fluid, warranting further investigation for other clinical uses. Lefamulin was approved by the United States Food and Drug Administration (FDA) on 19 August 2019 for the treatment of CABP.

Thiyl Radical-Based Charge Tagging Enables Sterol Quantitation via Mass Spectrometry.

Inspired by the high reactivity and specificity of thiyl radicals toward alkenes, we have developed a new charge derivatization method to enable fast and quantitative analysis of sterols via electrospray ionization-mass spectrometry (ESI-MS). Thioglycolic acid (TGA), a commercially available compound, has been established as a highly efficient tagging reagent. Initiated from photochemical reactions, the thiyl radical derived from TGA abstracts an allylic hydrogen in the B ring of sterols, forming a radical intermediate which rapidly recombines with a second thiyl radical to produce the final tagged product. Because of the incorporation of a carboxylic acid group, TGA tagging not only improves the limit of detection (sub-nM) for sterols but also facilitates their quantitation via characteristic 44 Da neutral loss scan. This radical based derivatization is fast (1 min) and efficient (>90% yield) when conducted in a flow microreactor. The analytical utility of thiyl radical charge tagging method has been demonstrated by quantifying sterols from human plasma and vegetable oil.

In vitro cytotoxicity and phototoxicity of surface-modified gold nanoparticles associated with neutral red as a potential drug delivery system in phototherapy.

The surface of gold nanoparticles (AuNP) was modified, improving their interaction with neutral red (NR), by using sodium thioglycolate (TGA) as a covering agent. The resulting NR-AuNPTGA system was evaluated as a potential drug delivery system for photodynamic therapy (PDT). The associations of NR with the gold nanoparticles were evaluated using UV-vis spectrometry and measurement of their zeta potential and size distribution. The toxicity and phototoxicity of NR, AuNPTGA and NR-AuNPTGA were evaluated in NIH-3T3 fibroblast and 4T1 tumor cell lines. The compounds NR and NR-AuNPTGA induced toxicity in 4T1 tumor cells and NIH-3T3 fibroblasts under visible light irradiation. Modification of the surface of AuNP with TGA prevented nanoparticle aggregation and allowed greater association with NR molecules than for naked AuNP. The photosensitizer (PS) characteristics were not affected by its association with the modified surface of the gold nanoparticles, leading to a reduction of cell viability in both cell lines assayed. This NR-AuNPTGA system is a promising drug delivery system for photodynamic cancer therapy.

Facile Preparation of Bright-Fluorescent Soft Materials from Small Organic Molecules.

Highly fluorescent and biocompatible soft materials are desirable for many potential applications, but their synthetic processes are somehow complicated. Herein, we have explored the feasibility of synthesis of unconventional fluorescence soft materials from small organic molecules under mild conditions. A new blue-fluorescent soft material with high quantum yield (89.6 %) and eutectic feature prepared by simple heat treatment of citric acid (CA) and cysteine (Cys) aqueous mixtures below 100 °C in air was reported. The as-prepared fluorescent material has the features of facile preparation, low cost, scalable production and easy to process, making it suitable for applications like fluorescent labeling and light-emitting devices. This new finding opens a new venue for the preparation of fluorescent soft materials.

Employment of electrochemically synthesized TGA-CdSe quantum dots for Cr(3+) determination in vitamin supplements.

The fluorescence quenching of TGA-CdSe quantum dots (QDs) was used for Cr(3+) quantification in vitamin supplements. The QD was electrochemically synthesized, demonstrating high reproducibility with control of particle size, thus making it a clean method, without the presence of reducing agents. Under ideal conditions, with the fluorescence band at 551 nm (excitation 365 nm), the maximum fluorescence quenching was observed at pH 4.0, with a time of 200 s for each data acquisition. Under optimum experimental conditions, linear quenching was observed for Cr(3+) in the range of 25.0-325.0 ng L(-1) (R=0.9996, n=6), a limit of detection of 5.67 ng L(-1), and relative standard deviation of 4.43% (n=10). The recovery test for Cr(3+) quantification in vitamin supplements presented results from 82% to 98%. These Cr(3+) determination results were compared to the same vitamin supplement sample using flame atomic absortion spectrometry (FAAS) method, and no significant differences were observed at 95% confidence level.

AG-690/11026014, a novel PARP-1 inhibitor, protects cardiomyocytes from AngII-induced hypertrophy.

Poly(ADP-ribose) polymerase-1 (PARP-1) enzyme, as a sensor of DNA damage, could convert nicotinamide adenine dinucleotide (NAD) into long poly(ADP-ribose) chains and regulate many cellular processes, including DNA repair, gene transcription, cell survival and chromatin remodeling. However, excessive activation of PARP-1 depletes its substrate NAD and leads to cell death. Mounting evidences have shown that PARP-1 overactivation plays a pivotal role in the pathogenesis of cardiac hypertrophy and heart failure. In present study, a novel PARP-1 inhibitor AG-690/11026014 (6014) was identified based on virtual screening and validated by bioassay. Our results further showed that 6014 prevented the cardiomyocytes from AngII-induced hypertrophy, accompanying attenuation of the mRNA and protein expressions of atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP), and reduce in the cell surface area. Additionally, 6014 reversed the depletion ofcellular NAD and SIRT6 deacetylase activity induced by AngII in cardiomyocytes. These observations suggest that anti-hypertrophic effect of 6014 might be partially attributed to the rescue of NAD depletion and subsequent restoring of SIRT6 activity by inhibition of PARP-1. Moreover, 6014 attenuated the generation of oxidative stress via suppression of NADPH oxidase 2 and 4, which might probably contribute to the inhibition of PARP-1.

Mechanism of a decrease in potency for the recombinant influenza A virus hemagglutinin H3 antigen during storage.

The recombinant hemagglutinin (rHA)-based influenza vaccine Flublok® has recently been approved in the United States as an alternative to the traditional egg-derived flu vaccines. Flublok is a purified vaccine with a hemagglutinin content that is threefold higher than standard inactivated influenza vaccines. When rHA derived from an H3N2 influenza virus was expressed, purified, and stored for 1 month, a rapid loss of in vitro potency (∼50%) was observed as measured by the single radial immunodiffusion (SRID) assay. A comprehensive characterization of the rHA protein antigen was pursued to identify the potential causes and mechanisms of this potency loss. In addition, the biophysical and chemical stability of the rHA in different formulations and storage conditions was evaluated over time. Results demonstrate that the potency loss over time did not correlate with trends in changes to the higher order structure or hydrodynamic size of the rHA. The most likely mechanism for the early loss of potency was disulfide-mediated cross-linking of rHA, as the formation of non-native disulfide-linked multimers over time correlated well with the observed potency loss. Furthermore, a loss of free thiol content, particularly in specific cysteine residues in the antigen's C-terminus, was correlated with potency loss measured by SRID.

Multiplexed living cells stained with quantum dot bioprobes for multiplexed detection of single-cell array.

The results of quantum dot (QD) probe preparation for multiplexed single-cell array staining and analysis are reported. By controlling the reaction temperature, time, and ratio of Cd to Se, multicolor CdSe QDs emitting fluorescence ranging from purple to red in a safer, simpler, and more convenient way than traditional methods is obtained. To detect cells using these oil-soluble QDs, they are first coated with water-soluble thioglycolic aid (TGA) so that biocompatible multiwavelength bioprobes can be obtained. QDs' surface is somewhat damaged when binding TGA to QDs is found, which results in a reduction of QDs' emission wavelength and a slight blue shift of QDs' emission wavelength after water-soluble modification with TGA. Comparison of the emission spectrum showed that it is negligible, and the fluorescent properties of QDs capped by TGA are still satisfactory. Living cells are then stained with multiplexed probes by conjugating TGA-QDs with antibodies specific to these cell antigens. Changes in fluorescence intensity can indicate change in the relative quantity of antigens expressed in the same cell caused by external stimulus, offering effective methods to multiplexed optical analysis of single cells.

In vitro antioxidant and antimicrobial activities of Merremia emarginata using thio glycolic acid-capped cadmium telluride quantum dots.

This study was undertaken to evaluate the antioxidant potential of an aqueous extract from Merremia emarginata leaves because this plant has a very high flavonoid and phenol content. The in vitro antioxidant activity was measured by diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid (ABTS), superoxide anion scavenging assay and lipid peroxidation activity; the total reducing capability of the plant extract indicates that this plant is a source for natural antioxidants. Furthermore, we investigated thio glycolic acid-capped cadmium telluride quantum dots (TGA-CdTe QDs) as fluorescent probes to study the antioxidant activity of the M. emarginata extract through fluorescence quenching. The antimicrobial activity was also investigated using a disc diffusion method and fluorescence microscopy. The TGA-CdTe QDs and M. emarginata complex could provide antimicrobial activity through a reactive oxygen species pathway and/or microbial endocytosis through an electrostatic attraction. Based on our findings, we suggest that the QDs act as potential probes for the in vitro antioxidant and antimicrobial activities. In addition, their cooperative effect with the plant extract indicates that QDs could be used as nanocarriers to enhance the antimicrobial capability. Further in vivo studies on the photolabelling of antioxidants with QDs will provide insights into the mechanistic pathways of secondary metabolites against various degenerative diseases.

Thiomers: influence of molar mass on in situ gelling properties.

The aim of this study was to investigate the influence of molar mass of thiolated polymers (thiomers) on their in situ gelling properties. Chitosan-thioglycolic acid (chitosan-TGA) and pectin-cysteine (pectin-Cys) of increasing molar mass were chosen to produce in situ gels in combination with carbamide peroxide. Low molar mass chitosan (~2 kDa) was prepared by oxidative degradation with NaNO(2), whereas pectin was depolymerized by heat treatment. Thiomers, displaying 1271-1616 µmol (chitosan-TGA) and 305-403 µmol (pectin-Cys) free thiol groups per gram polymer, were synthesized via amide bond formation mediated by a carbodiimide. The results showed that a reduction of molar mass combined with increased concentrations of both cationic chitosan-TGA and anionic pectin-Cys leads to higher final viscosities and to a higher relative increase in viscosity within 60 min and 180 min, respectively. Using this method, the dynamic viscosity of a very low molar mass chitosan-TGA (~2 kDa) could be increased 100,000-fold within 60 min and 390,000-fold within 180 min. In view of these in situ gelling properties carbohydrate thiomers might be useful for various pharmaceutical applications such as vehicle for drug delivery or as wound dressing material.

Synthesis of CdSe quantum dots using selenium dioxide as selenium source and its interaction with pepsin.

A novel method has been developed for the synthesis of thioglycolic acid (TGA)-capped CdSe quantum dots (QDs) in an aqueous medium when selenium dioxide worked as a selenium source and sodium borohydride acted as a reductant. The interaction between CdSe QDs and pepsin was investigated by fluorescence spectroscopy. It was proved that the fluorescence quenching of pepsin by CdSe QDs was mainly a result of the formation of CdSe-pepsin complex. Based on the fluorescence quenching results, the Stern-Volmer quenching constant (Ksv), binding constant (KA) and binding sites (n) were calculated. According to the Foster's non-radiative energy transfer theory, the binding distance (r) between pepsin and CdSe QDs was obtained. The influence of CdSe QDs on the conformation of pepsin has been analyzed by synchronous fluorescence spectra, which provided that the secondary structure of pepsin has been changed by the interaction of CdSe QDs with pepsin.

Transformation of thiodiglycol by resting cells of Alcaligenes xylosoxydans PGH10.

A new strain of Alcaligenes xylosoxydans able to aerobically cometabolize thiodiglycol, the primary hydrolysis product of sulfur mustard, was isolated and tested in a laboratory scale stirred tank reactor. The strain, named PGH10, cannot use TDG as sole carbon and energy source for growth, but resting cells previously grown on either rich broth or defined mineral media efficiently metabolize this compound through [(2-hydroxyethyl)thio]acetic acid and thiodiacetic acid as intermediates. Degradation of TDG by PGH10 is shown to take place at late exponential and stationary phase but is not triggered by carbon exhaustion. Cultures pregrown to saturation for 48 h in the absence of TDG can be stored and used for degradation of TDG, reducing significantly the time required to achieve the reduction of the compound concentration to undetectable levels. Degradation can take place in buffered media with no carbon source added, although best results were obtained in mineral media supplemented with citrate or fructose. Oxidation to [(2-hydroxyethyl)thio]acetic acid and thiodiacetic acid was proposed to be catalyzed by a butanol-dehydrogenase activity. Inhibition of TDG transformation in the presence of several alcohols is also shown.

Oxyluciferin, a luminescence product of firefly luciferase, is enzymatically regenerated into luciferin.

The activity regenerating luciferin from the luminescent product oxyluciferin was found in the protein fraction of a lantern extract from Photinus pyralis. The protein, luciferin-regenerating enzyme (LRE), was purified to homogeneity by ammonium sulfate precipitation followed by successive column chromatography on Ultrogel AcA34, S-Sepharose FF, Q-Sepharose FF, TSKgel super Q 5pw and TSKgel G3000 SW(XL). This enzyme was a single polypeptide with a molecular mass of 38 kDa. LRE converted oxyluciferin to 2-cyano-6-hydroxybenzothiazole and thioglycolic acid. In the presence of d-cysteine, 2-cyano-6-hydroxybenzothiazole was turned over into luciferin. The same activities were detected in the extracts from two Japanese fireflies, Luciola cruciata and Luciola lateralis. We have cloned a cDNA encoding LRE from poly(A)+ RNA of the lantern of P. pyralis using reverse transcription-polymerase chain reaction, 5'-RACE (rapid amplification of cDNA ends) and 3'-RACE. The primary structure of LRE from P. pyralis deduced from the nucleotide sequence was shown to consist of 308 amino acids with a molecular weight of 33,619. The cDNA was successfully expressed under the control of the tac promoter in Escherichia coli.

Addition of methyl thioglycolate and benzylamine to (Z)-ligustilide, a bioactive unsaturated lactone constituent of several herbal medicines. An improved synthesis of (Z)-ligustilide.

(Z)-Ligustilide [1] is a dihydrophthalide purported to be the active ingredient of Ligusticum plant species widely used as herbal medicines in the Orient and in Native American and Hispanic cultures. It readily underwent 1,6-conjugate addition with methyl thioglycolate in the presence of triethylamine. The methyl thioglycolate reaction also yielded a product from addition to the C-6-C-7 double bond and a diadduct from both 1,6-addition and addition to the C-6-C-7 bond. Reaction of 1 with benzylamine did not afford a 1,6-adduct, but yielded instead an N-benzyllactam, presumably formed by rearrangement from initial 1,2-addition to the carbonyl. An improved total synthesis of 1 was developed. (Z)-Ligustilide had weak antiviral properties and weak antimicrobial activity against Gram-positive, Gram-negative, and yeast microorganisms. The broad biological activity of 1 and its electrophilic reactivity are consistent with the use of Ligusticum species in folk medicine.

Inhibitory effect of diet related sulphydryl compounds on the formation of carcinogenic nitrosamines.

N-Nitroso compounds (NOCs) are known to be strong carcinogens in various animals including primates (Preussman and Stewart, (1984) N-Nitroso Compounds). Human exposure to these compounds can be by ingestion or inhalation of preformed NOCs or by endogenous nitrosation from naturally occurring precursors (Bartsch and Montesano, Carcinogenesis, 5 (1984) 1381-1393; Tannebaum (1979) Naturally Occuring Carcinogens, Mutagens and Modulators of Carcinogenesis; Shephard et al., Food Chem. Toxicol., 25 (1987) 91-108). Several factors present in the diet can modify levels of endogenously formed nitrosamines by acting as catalysts or inhibitors. Compounds in the human diet that alter nitrosamine formation would thus play an important role in carcinogenesis study. Earlier researchers have reported the nitrite scavenging nature of sulphydryl compounds (Williams, Chem. Soc. Rev., 15 (1983) 171-196). We therefore studied the modifying effect of sulphydryl compounds viz., cysteine (CE), cystine (CI), glutathione (GU), cysteamine (CEA), cystamine (CEI), cysteic acid (CIA) and thioglycolic acid (TGA) on the nitrosation of model amines viz., pyrrolidine (PYR), piperidine (NPIP) and morpholine (NMOR). Many of these compounds are present in the food we consume. The present work also describes the inhibitory effect of onion and garlic juices on the nitrosation reactions. Both onion and garlic are known to contain sulphur compounds (Block, Sci. Am., 252 (1985) 114-119). Most of these compounds behave as antinitrosating agents and their inhibitory activity towards formation of carcinogenic nitrosamines, under different conditions is described.