Chemistry of Lipid A: At the Heart of Innate Immunity

In many Gram‐negative bacteria, lipopolysaccharide (LPS) and its lipid A moiety are pivotal for bacterial survival. Depending on its structure, lipid A carries the toxic properties of the LPS and acts as a potent elicitor of the host innate immune system via the Toll‐like receptor 4/myeloid differentiation factor 2 (TLR4/MD‐2) receptor complex. It often causes a wide variety of biological effects ranging from a remarkable enhancement of the resistance to the infection to an uncontrolled and massive immune response resulting in sepsis and septic shock. Since the bioactivity of lipid A is strongly influenced by its primary structure, a broad range of chemical syntheses of lipid A derivatives have made an enormous contribution to the characterization of lipid A bioactivity, providing novel pharmacological targets for the development of new biomedical therapies. Here, we describe and discuss the chemical aspects regarding lipid A and its role in innate immunity, from the (bio)synthesis, isolation and characterization to the molecular recognition at the atomic level.     

Strong Convergence Theorems for Mixed Typ e Asymptotically Nonexpansive Mappings

The purpose of this paper is to study a new two-step iterative scheme with mean errors of mixed type for two asymptotically nonexpansive self-mappings and two asymptotically nonexpansive nonself-mappin...     

Development and validation of a reversed‐phase HPLC method for CYP1A2 phenotyping by use of a caffeine metabolite ratio in saliva

CYP1A2 is important for metabolizing various clinically used drugs. Phenotyping of CYP1A2 may prove helpful for drug individualization therapy. Several HPLC methods have been developed for quantification of caffeine metabolites in plasma and urine. Aim of the present study was to develop a valid and simple HPLC method for evaluating CYP1A2 activity during exposure in xenobiotics by the use of human saliva. Caffeine and paraxanthine were isolated from saliva by liquid‐liquid extraction (chlorophorm/isopropanol 85/15v/v). Extracts were analyzed by reversed‐phase HPLC on a C₁₈ column with mobile phase 0.1% acetic acid/methanol/acetonitrile (80/20/2 v/v) and detected at 273nm. Caffeine and paraxanthine elution times were <13min with no interferences from impurities or caffeine metabolites. Detector response was linear (0.10–8.00µg/ml, R²>0.99), recovery was >93% and bias <4.47%. Intra‐ and inter‐day precision was <5.14% (n=6). The limit of quantitation was 0.10µg/ml and the limit of detection was 0.018±0.002µg/mL for paraxanthine and 0.032±0.002µg/ml for caffeine. Paraxanthine/caffeine ratio of 34 healthy volunteers was significantly higher in smokers (p<0.001). Saliva paraxanthine/caffeine ratios and urine metabolite ratios were highly correlated (r=0.85, p<0.001). The method can be used for the monitoring of CYP1A2 activity in clinical practice and in studies relevant to exposure to environmental and pharmacological xenobiotics. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly efficient water‐soluble visible light photoinitiators

The monoacylphosphineoxide (MAPO) salts Na‐TPO and Li‐TPO and the bisacylphosphineoxide (BAPO) salts BAPO‐ONa and BAPO‐OLi define an important and in the latter case a new class of water‐soluble photoinitiators (PIs) for radical polymerization. These compounds showed excellent water‐solubility of at least 29 g/L for Na‐TPO and up to 60 g/L for BAPO‐ONa in deionized water, thus exceeding the solubility of the state of the art PI for water‐based systems Irgacure 2959 ( I2959 ) 6‐ to 12‐fold. However, biocompatibility, storage stability, and reactivity were equally important to replace the state of the art compounds. Concerning these properties, the MAPO and BAPO salts were at least in the same range (biocompatibility, stability) or showed even better results (reactivity) and had the additional advantage of visible light initiation. Na‐TPO and Li‐TPO achieved double bond conversions of an aqueous solution of N‐acryloylmorpholine over 97% with broad band irradiation (320–500 nm), Li‐TPO showed additionally very good biocompatibility (LC₅₀ = 3.1 mmol/L) and BAPO‐OLi showed highest reactivity with visible light irradiation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 473–479     

Universal power law behavior of the AC conductivity versus frequency of agglomerate morphologies in conductive carbon nanotube‐reinforced epoxy networks

The Jonscher universal power law for ac conductivity versus frequency (f = ω/2π) in the dispersion region was tested for a multiwall carbon nanotube/epoxy nanocomposite. The effect of changes in agglomerate morphology on the fitting parameters A and n in the equation σ_{ac =} Aωⁿ was investigated. Changing nanotube agglomerate morphology was tracked by optical microscopy through curing. Evolving morphology was compared alongside ac conductivity obtained via a broadband dielectric spectrometer to elucidate possible physical meaning of the universal power law in the context of this system. The ?logA/n was unaffected by changes in agglomerate morphology affected during cure, yet connected with each other in their dependence on temperature. For this system, the relationship between the fitting parameters in the universal dynamic response equation remains empirical at this stage with regard to biphasic “texture” or morphology within such a network. Electrical conductivity σ versus frequency ω for a composite consisting of agglomerated multiwalled carbon nanotubes dispersed throughout a cured epoxy matrix was discovered to follow the empirical universal dynamic response equation of Jonscher. The frequency behavior of the exponent n is discussed in terms of underlying morphology throughout which charge carriers migrate. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1918–1923     

Effect of matrices and additives on phosphorylated and ketodeoxyoctonic acid lipids A analysis by matrix‐assisted laser desorption ionization‐mass spectrometry

Lipid A is a major compound of the outer membrane of gram‐negative bacteria and is a key factor of bacterial virulence. As lipid A's structure differs among bacterial species and varies between strains of the same species, knowing its modifications is essential to understand its implications in the infectious process. To analyze these lipids, matrix‐assisted laser desorption ionization‐mass spectrometry (MALDI‐MS) is a well‐suited method that is fast and efficient. However, there are limitations with the matrix and additives used, such as the suppression of signal or prompt fragmentations that could give a false overview of lipid A composition in biological samples. For a comprehensive analysis of the entire lipid A species present in a sample, we tested 16 matrices and 11 additives on two commercial lipids A. The first commercial one contains single phosphorylation group, and the second contains two phosphorylation and two ketodeoxyoctonic acid (KDO) groups. The lipid A containing KDO groups was essentially detected by the 3‐hydroxypicolinic acid (3‐HPA) matrix, whereas the monophosphorylated lipid A could be detected by 13 matrices out of the 16. We also demonstrated that the signal of diphosphorylated lipid A can be enhanced with the use of additives in the matrix. Our study indicated that the best conditions to obtain a clear signal of both lipids A without prompt fragmentation was the use of 3‐HPA with 10mM trifluoroacetic acid (TFA).     

Mass spectrometry combined with affinity probes for the identification of CP4 EPSPS in genetically modified soybeans

Sample preparation methods used for genetically modified organisms (GMOs) analysis are often time consuming, require extensive manual manipulation, and result in limited amounts of purified protein, which may complicate the detection of low‐abundance GM protein. A robust sample pretreatment method prior to mass spectrometry (MS) detection of the transgenic protein (5‐enolpyruvylshikimate‐3‐phosphate synthase [CP4 EPSPS]) present in Roundup Ready soya is investigated. Liquid chromatography‐multiple reaction monitoring tandem MS (nano LC‐MS/MS‐MRM) was used for the detection and quantification of CP4 EPSPS. Gold nanoparticles (AuNPs) and concanavalin A (Con A)‐immobilized Sepharose 4B were used as selective probes for the separation of the major storage proteins in soybeans. AuNPs that enable the capture of cysteine‐containing proteins were used to reduce the complexity of the crude extract of GM soya. Con A‐sepharose was used for the affinity capture of β‐conglycinin and other glycoproteins of soya prior to enzymatic digestion. The methods enabled the detection of unique peptides of CP4 EPSPS at a level as low as 0.5% of GM soya in MRM mode. Stable‐isotope dimethyl labeling was further applied to the quantification of GM soya. Both probes exhibited high selectivity and efficiency for the affinity capture of storage proteins, leading to the quantitative detection at 0.5% GM soya, which is a level below the current European Union's threshold for food labeling. The square correlation coefficients were greater than 0.99. The approach for sample preparation is very simple without the need for time‐consuming protein prefractionation or separation procedures and thus presents a significant improvement over existing methods for the analysis of the GM soya protein.     

On the metabolites produced by Colletotrichum gloeosporioides a fungus proposed for the Ambrosia artemisiifolia biocontrol; spectroscopic data and absolute configuration assignment of colletochlorin A

Ambrosia artemisiifolia L. is responsible for serious allergies induced on humans. Different approaches for its control were proposed during the COST Action FA1203 “Sustainable management of Ambrosia artemisiifolia in Europe” (SMARTER). Fungal secondary metabolites often show potential herbicidal activity. Three phytotoxins were purified from the fungal culture filtrates of Colletotrichum gloeosporioides, isolated from infected leaves of A. artemisiifolia. They were identified by spectroscopic and chemical methods as colletochlorin A, orcinol and tyrosol (1, 2 and 3). The absolute configuration 6’R to colletochlorin A was assigned for the first time applying the advanced Mosher’s method. When assayed by leaf-puncture on A. artemisiifolia only 1 caused the appearance of large necrosis. The same symptoms were also induced by 1 on ambrosia plantlets associated with plant wilting. On Lemna minor, colletochlorin A caused a clear fronds browning, with a total reduction in chlorophyll content.