Remote Raman Sensing Using a Single-Grating Monolithic Spatial Heterodyne Raman Spectrometer: A Potential Tool for Planetary Exploration

Advances in Raman instrumentation have led to the implementation of a remote dispersive Raman spectrometer on the Perseverance rover on Mars, which is used for remote sensing. For remote applications, dispersive spectrometers suffer from a few setbacks such as relatively larger sizes, low light throughput, limited spectral ranges, relatively low resolutions for small devices, and high sensitivity to misalignment. A spatial heterodyne Raman spectrometer (SHRS), which is a fixed grating interferometer, helps overcome some of these problems. Most SHRS devices that have been described use two fixed diffraction gratings, but a variance of the SHRS called the one-grating SHRS (1g-SHRS) replaces one of the gratings with a mirror, which makes it more compact. In a recent paper we described monolithic two-gratings SHRS, and in this paper, we investigate a single-grating monolithic SHRS (1g-mSHRS), which combines the 1g-SHRS with a monolithic setup previously tested at the University of South Carolina. This setup integrates the beamsplitter, grating, and mirror into a single monolithic device. This reduces the number of adjustable components, allows for easier alignment, and reduces the footprint of the device (35 × 35 × 25 mm with a weight of 80 g). This instrument provides a high spectral resolution (∼9 cm^-1) and large spectral range (7327 cm^-1) while decreasing the sensitivity to alignment with a field of view of 5.61 mm at 3m. We discuss the characteristics of the 1g-mSHRS by measuring the time-resolved remote Raman spectra of a few inorganic salts, organics, and minerals at 3 m. The 1g-mSHRS makes a good candidate for planetary exploration because of its large spectral range, greater sensitivity, competitively higher spectral resolution, low alignment sensitivity, and high light throughput in a compact easily aligned system with no moving parts.

Orientational Analysis of Monolayers at Low Surface Concentrations Due to an Increased Signal-to-Noise Ratio (S/N) Using Broadband Sum Frequency Generation Vibrational Spectroscopy

Sum frequency generation (SFG) * Equal contributors. spectroscopy was used to deduce the orientation of the terminal methyl (CH₃) group of self-assembled monolayers (SAMs) at the air-solid and air-liquid interfaces at surface concentrations as low as 1% protonated molecules in the presence of 99% deuterated molecules. The SFG spectra of octadecanethiol (ODT) and deuterated octadecanethiol (d₃₇ ODT) SAMs on gold were used for analysis at the air-solid interface. However, the eicosanoic acid (EA) and deuterated EA (d₃₉ EA) SAMs on the water were analyzed at the air-liquid interface. The tilt angle of the terminal CH₃ group was estimated to be ∼39 ° for a SAM of 1% ODT : 99% d₃₇ ODT, whereas the tilt angle of the terminal CH₃ group of the 1% EA : 99% d₃₉ EA monolayer was estimated to be ∼32 °. The reliability of the orientational analysis at low concentrations was validated by testing the sensitivity of the SFG spectroscopy. A signal-to-noise (S/N) ratio of ∼60 and ∼45 was obtained for the CH₃ symmetric stretch (SS) of 1% ODT : 99% d₃₇ ODT and 1% EA : 99% d₃₉ EA, respectively. The estimated increase in S/N ratio values, as a measure of the sensitivity of the SFG spectroscopy, verified the capacity to acquire the SFG spectra at low concentrations of interfacial molecules under ambient conditions. Overall, the orientational analysis of CH₃ SS vibrational mode was feasible at low concentrations of protonated molecules due to increased S/N ratio. In support, the improved S/N ratio on varying incident power density of the visible beam was also experimentally demonstrated.

Concentrations and potential health hazards of organochlorine pesticides in (shallow) groundwater of Taihu Lake region, China

A total of 27 shallow groundwater samples were collected from the Taihu Lake region (TLR), to determine the concentrations of 14 organochlorine pesticide (OCP) species, identify their possible sources, and estimate health risk of drinking the shallow groundwater. All OCP species occurred in the shallow groundwater of TLR with high detection frequency except p, p'-dichlorodiphenyldichlorothane (p, p'-DDD) and p, p'-dichlorodiphenyltrichloroethane (p, p'-DDT). DDTs and hexachlorocyclohexanes (HCHs) were the dominant OCP contaminants in the shallow groundwater of TLR, and they account for 44.2% total OCPs. The low α-HCH/γ-HCH ratio, high β-HCH/(α+γ)-HCH ratio and β-HCH being the dominant HCH isomers for the majority of samples suggest that the HCHs were mainly from the historical use of lindane after a period of degradation. p, p'-DDE being the dominant DDT metabolite for all the samples indicated that the DDTs were mainly from the historical residues. Compositional analysis also suggested that there were fresh input sources of heptachlors, aldrins and endrins in addition to the historical residues. Correlation analysis indicated the hexachlorobenzene (HCB) impurity in the shallow groundwater of TLR was likely from the historical application of lindane and technical HCH (a mixture of HCH isomers that is produced by photochlorination of benzene). Carcinogenic risk values for α-HCH, heptachlor, heptachlor epoxide, aldrins and dieldrin in the shallow groundwater in majority area of TLR were found to be >10(-6), posing a potentially serious cancer risk to those dependant on shallow groundwater for drinking water.

Quantification of four artificial sweeteners in Finnish surface waters with isotope-dilution mass spectrometry

The artificial sweeteners sucralose (SCL), acesulfame (ACS), saccharin (SAC), and cyclamate (CYC) have been detected in environmental waters in Europe and North America. Higher environmental levels are expected in view of the increasing consumption of these food additives. In this study, an isotope-dilution mass spectrometry (IDMS) LC-MS/MS method was developed and validated for quantifying the four artificial sweeteners in boreal lakes (n = 3) and rivers (n = 12). The highest concentrations of ACS, SAC, CYC and SCL were 9,600, 490, 210 and 1000 ng/L, respectively. ACS and SAC were detected in all studied samples, and CYC and SCL in 98% and 56% of the samples. Seasonal trends of ACS and SAC were observed in some rivers. ACS and SCL concentrations in rivers correlated linearly with population equivalents of the wastewater treatment plants in the catchment areas, whereas SAC and CYC concentrations depend more on the source.

Measurement of succinyl-carnitine and methylmalonyl-carnitine on dried blood spot by liquid chromatography-tandem mass spectrometry

Methylmalonic aciduria (MMA) is one of the most frequent organic acidurias, a class of diseases caused by enzymatic defects mainly involved in the catabolism of branched-chain amino acids. Recently, mild MMA and C4-dicarboxylyl-carnitine (C4DC-C) accumulation have been reported in patients carrying mutation in genes encoding the α-subunit (SUCLG1) and the β-subunit (SUCLA2) of the ADP-forming succinyl-CoA synthetase (SCS). We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify in dried blood spot the two isobaric compounds of C4DC-C, succinyl-carnitine and methylmalonyl-carnitine, to allow the differential diagnosis between classical MMA and SCS-related defects. This method, with an easy liquid-phase extraction and derivatization procedure, has been validated to demonstrate the specificity, linearity, recovery, lowest limit of quantification (LLOQ), accuracy and precision for quantitative determination of blood succinyl-carnitine and methylmalonyl-carnitine. The assay was linear over a concentration range of 0.025-10 μmol/L and achieved the LLOQ of 0.025 μmol/L for both metabolites. The average slope, intercept, and coefficient of linear regression (r(2)) were respectively: 0.3389 (95% confidence interval 0.2888-0.3889), 0.0113 (95% confidence interval -0.0157 to 0.0384), 0.9995 (95% confidence interval 0.9990-1.0000) for succinyl-carnitine and 0.5699 (95% confidence interval 0.5263-0.6134), 0.0319 (95% confidence interval -0.0038 to 0.0677), 0.9997 (95% confidence interval 0.9995-1.0000) for methylmalonyl-carnitine. Within-day and between-day coefficients of variation (CV) were 1.94% and 3.19% for succinyl-carnitine and 3.21%, and 2.56 for methylmalonyl-carnitine. This method is accurate and provides a new tool to differentiate patients with classical methylmalonic acidemia from those with SCS-related defects.

HPLC method development, validation and impurity characterization for an antitumor Hsp90 inhibitor-PU-H71 (NSC 750424)

An HPLC method for the assay of the heat shock protein 90 inhibitor, PU-H71 (NSC 750424), has been developed and validated. The stress testing of PU-H71 was carried out in accordance with ICH guidelines Q1A (R2) under aqueous, acidic, alkaline, oxidative, thermolytic and photolytic conditions. The separation of PU-H71 from its impurities and degradation products was achieved within 50min on a Mac-Mod ACE 3 C18 column (150mm×4.6mm i.d., 3μm) with a gradient mobile phase comprising 20-95% acetonitrile in water, with 0.1% trifluroacetic acid in both phases. LC-quadrupole TOF/MS was used to obtain accurate mass data on various components as well as on their fragments for characterization of impurities and degradation products. The proposed HPLC assay method was validated for specificity, linearity (concentration range 0.1-0.3mg/mL, r≥0.9998), accuracy (recovery 99.7-101.1%), precision (intra-lab RSD≤1.39%, inter-lab RSD≤0.91%), sensitivity (LOD 0.08μg/mL), and ruggedness. The developed method was suitable for the assay and stability monitoring of PU-H71 drug substance.

Diagnostic performance of selected commercial HEV IgM and IgG ELISAs for immunocompromised and immunocompetent patients

BACKGROUND

Hepatitis E virus (HEV) genotype 3 is recognised as an emerging pathogen in industrialised countries. The currently commercially available HEV-specific enzyme linked immunosorbent assays (ELISAs) are primarily designed for the detection of antibodies against genotypes 1 (Burma) and 2 (Mexico) and may not sensitively detect HEV genotypes 3 or 4.

OBJECTIVES

This study aimed to evaluate the analytical and clinical performances of eight commercially available HEV serum antibody immunoglobulin M (IgM)- and immunoglobulin G (IgG)-specific ELISAs for genotype 1 and 3 HEV infections in a clinical setting and to study the antibody responses against HEV of immunocompromised versus immunocompetent patient groups.

STUDY DESIGN

Analytical performance and diagnostic sensitivity and specificity were assessed using well-defined reference samples and samples from patients with polymerase chain reaction (PCR)-confirmed HEV infection (n=88) and a specificity panel (n=98).

RESULTS

Limiting dilutions indicated that the highest analytical sensitivity in head-to-head comparison was measured for the Mikrogen_new IgG assay. Taking the serum working dilutions of each assay into account, the Wantai IgG assay was the most sensitive assay. Receiver operator curve (ROC) analysis showed area under the curve (AUC) values of 0.943, 0.964, 0.969, 0.971, 0.974 and 0.994 for the DSI, Mikrogen_old, MP Diagnostics, Mikrogen_new, Wantai and DiaPro anti-HEV IgM assays, respectively. The highest specificity of currently available assays was found for the IgM Wantai assay (>99%). If anti-HEV IgM and IgG results from each supplier were combined, DSI and Wantai assays were able to detect the highest number of (passed) HEV infections.

CONCLUSIONS

Our study showed that current commercial HEV ELISAs could be used to diagnose HEV genotype 3 infection adequately in a clinical setting.

E. coli sabotages the in vivo production of O-linked β-N-acetylglucosamine-modified proteins

The O-linked β-N-acetylglucosamine (O-GlcNAc) post-translational modification is an important, regulatory modification of cytosolic and nuclear enzymes. To date, no 3-dimensional structures of O-GlcNAc-modified proteins exist due to difficulties in producing sufficient quantities with either in vitro or in vivo techniques. Recombinant co-expression of substrate protein and O-GlcNAc transferase in Escherichia coli was used to produce O-GlcNAc-modified domains of human cAMP responsive element-binding protein (CREB1) and Abelson tyrosine-kinase 2 (ABL2). Recombinant expression in E. coli is an advantageous approach, but only small quantities of insoluble O-GlcNAc-modified protein were produced. Adding β-N-acetylglucosaminidase inhibitor, O-(2-acetamido-2-dexoy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), to the culture media provided the first evidence that an E. coli enzyme cleaves O-GlcNAc from proteins in vivo. With the inhibitor present, the yields of O-GlcNAc-modified protein increased. The E. coli β-N-acetylglucosaminidase was isolated and shown to cleave O-GlcNAc from a synthetic O-GlcNAc-peptide in vitro. The identity of the interfering β-N-acetylglucosaminidase was confirmed by testing a nagZ knockout strain. In E. coli, NagZ natively cleaves the GlcNAc-β1,4-N-acetylmuramic acid linkage to recycle peptidoglycan in the cytoplasm and cleaves the GlcNAc-β-O-linkage of foreign O-GlcNAc-modified proteins in vivo, sabotaging the recombinant co-expression system.

LC/ESI-MS/MS analysis of urinary 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its amides: new biomarkers for the detection of Niemann-Pick type C disease

We developed a sensitive, reliable, and accurate LC/ESI-MS/MS method for measurement of 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its glycine and taurine amides in urine. This atypical C24 bile acid has been reported previously to be present in the urine of patients with Niemann-Pick Type C (NPC) disease. In the method, targeted analytes are concentrated at the front edge of a trapping column, Shim-pack MAYI-C8, which permits elimination of contaminating molecules in the urinary matrix. The trapped analytes are then eluted, separated on a YMC-Pack Pro C18, and quantified with MS/MS using selected reaction monitoring. The method could detect (as amount injected) 2pg of nonamidated 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid, 2pg of its glycine-amide, and 0.6pg of its taurine-amide, and is linear up to 300pg. The method was then used to measure the three analytes in the urine of NPC patients (N=2), 3β-hydroxysteroid dehydrogenase deficiency patients (N=2), and healthy volunteers (N=8). Measurable concentrations of all three analytes were present in all subjects. The urinary concentration of the sum of all three analytes was four hundred times greater in the 3month NPC patient and 40times greater in the adult patient than that of healthy volunteers. The markedly elevated urinary concentration of 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its amides in NPC patients suggests that these compounds may be valuable biomarkers for detection of NPC disease.

Global gas chromatography/time-of-flight mass spectrometry (GC/TOFMS)-based metabonomic profiling of lyophilized human feces

Gas chromatography mass spectrometry (GC/MS)-based fecal metabonomics represents a powerful systems biology approach for elucidating metabolic biomarkers of lower gastrointestinal tract (GIT) diseases. Unlike metabolic profiling of fecal water, the profiling of complete fecal material remains under-explored. Here, a gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) method was developed and validated for the global metabonomic profiling of human feces. Fecal and fecal water metabotypes were also profiled and compared. Additionally, the unclear influence of blood in stool on the fecal metabotype was investigated unprecedentedly. Eighty milligram of lyophilized feces was ultrasonicated with 1mL of methanol:water (8:2) for 30min, followed by centrifugation, drying of supernatant, oximation and trimethylsilylation for 45min. Lyophilized feces demonstrated a more comprehensive metabolic coverage than fecal water, based on the number of chromatographic peaks. Principal component analysis (PCA) indicated occult blood (1mgHb/g feces) exerted a negligible effect on the fecal metabotype. Conversely, a unique metabotype related to feces spiked with gross blood (100mgHb/g feces) was revealed (PCA, R(2)X=0.837, Q(2)=0.794), confirming the potential confounding effect of gross GIT bleeding on the fecal metabotype. This pertinent finding highlights the importance of prudent interpretation of fecal metabonomic data, particularly in GIT diseases where bleeding is prevalent.

Neurochemical changes within human early blind occipital cortex

Early blindness results in occipital cortex neurons responding to a wide range of auditory and tactile stimuli. These changes in tuning properties are accompanied by an extensive reorganization of the occipital cortex that includes alterations in anatomical structure, neurochemical and metabolic pathways. Although it has been established in animal models that neurochemical pathways are heavily affected by early visual deprivation, the effects of blindness on these pathways in humans is still not well characterized. Here, using (1)H magnetic resonance spectroscopy in nine early blind and normally sighted subjects, we find that early blindness is associated with higher levels of creatine, choline and myo-Inositol and indications of lower levels of GABA within the occipital cortex. These results suggest that the cross-modal responses associated with early blindness may, at least in part, be driven by changes within occipital biochemical pathways.

Development of a biosensor-based immunogenicity assay capable of blocking soluble drug target interference

As with other protein therapeutics, trebananib (AMG 386), an investigational peptide Fc-fusion protein ("peptibody") that inhibits angiogenesis by neutralizing the interaction of angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) with the Tie2 receptor, has the potential to trigger an immune response in cancer patients treated with the therapeutic. An electrochemiluminescence bridging anti-drug antibody (ADA) assay that was utilized to support early-phase clinical trials in the development of trebananib was found to lack adequate sensitivity and drug tolerance in later-phase clinical studies when higher doses of trebananib were administered. Therefore, we developed a surface plasmon resonance (SPR) immunoassay method utilizing a secondary confirmatory detector antibody (goat anti-human IgG F[ab']2) known to cross-react with human IgG and IgM to better assess the potential impact of immunogenicity on the pharmacokinetics, pharmacodynamics, and toxicity of trebananib. The SPR method was more sensitive than the electrochemiluminescence bridging assay because of signal amplification from the confirmatory binding of the detector antibody; drug tolerance was improved since antibody binding avidity does not affect detection on this platform. Despite the inability of the confirmatory detector antibody to bind angiopoietins in protein-free buffer, false-positive ADA results were generated from patient serum samples containing Ang1 and Ang2 through an apparently specific binding between the angiopoietins and the confirmatory detector antibody, likely mediated by the interaction of the angiopoietins with serum immunoglobulins. Addition to the sample diluent of a human antibody that specifically binds to Ang1 and Ang2 with high affinity resulted in a complete block of angiopoietin interference without affecting ADA detection. This biosensor-based assay provides a reliable method for assessing immunogenicity in phase 3 clinical trials.

Direct tandem mass spectrometric profiling of sulfatides in dry urinary samples for screening of metachromatic leukodystrophy

BACKGROUND

Prediagnostic steps in suspected metachromatic leukodystrophy (MLD) rely on clinical chemical methods other than enzyme assays. We report a new diagnostic method which evaluates changes in the spectrum of molecular types of sulfatides (3-O-sulfogalactosyl ceramides) in MLD urine.

METHODS

The procedure allows isolation of urinary sulfatides by solid-phase extraction on DEAE-cellulose membranes, transportation of a dry membrane followed by elution and tandem mass spectrometry (MS/MS) analysis in the clinical laboratory. Major sulfatide isoforms are normalized to the least variable component of the spectrum, which is the indigenous C18:0 isoform. This procedure does not require the use of specific internal standards and minimizes errors caused by sample preparation and measurement.

RESULTS

Urinary sulfatides were analyzed in a set of 21 samples from patients affected by sulfatidosis. The combined abundance of the five most elevated isoforms, C22:0, C22:0-OH, C24:0, C24:1-OH, and C24:0-OH sulfatides, was found to give the greatest distinction between MLD-affected patients and a control group.

CONCLUSIONS

The method avoids transportation of liquid urine samples and generates stable membrane-bound sulfatide samples that can be stored at ambient temperature. MS/MS sulfatide profiling targeted on the most MLD-representative isoforms is simple with robust results and is suitable for screening.