Employer-sponsored health insurance and labor market outcomes for men in same-sex couples: Evidence from the advent of pre-exposure prophylaxis

In the United States, the cost of providing employer-sponsored health insurance (ESI) varies for employers based on the medical expenditures of their employees, a practice known as “experience rating”. Experience rating increases the cost of employing workers who have greater medical expenditures, one example being men in same-sex couples. To study whether ESI affects labor market outcomes for men in same-sex couples, I use the 2012 advent of Pre-Exposure Prophylaxis (PrEP), a $24,000 per year drug that effectively prevents Human Immunodeficiency Virus (HIV) acquisition. Using American Community Survey data and a difference-in-difference empirical approach – comparing post-PrEP changes in earnings among men who have ESI – I find that annual earnings for men in same-sex couples decline by $2,650 (approximately 3.9%) relative to comparable men after PrEP becomes available. For those who are most likely to be taking Truvada (the brand name for PrEP), such as young men and white men, effects on earnings are considerably larger. I also observe a 3.7 percentage point (4.6%) decline in ESI prevalence and a 0.8 percentage point (10.7%) increase in part-time employment among men in same-sex couples. Event studies provide support for a causal interpretation for my findings. My estimates are also robust to placebo analyses, various specification permutations, and a range of sensitivity checks.     

Qualitative analysis and HPLC isolation and identification of procyanidins from Vicia faba

The soluble proanthocyanidins of the coloured seed coats of Vicia faba L. were isolated and separated by solvent partition. The chemical characteristics of the proanthocyanidins were elucidated by total oxidation and partial degradation in the presence of phloroglucinol followed by HPLC analysis. The native extract of proanthocyanidins contained (+)-gallocatechin, (-)-epigallocatechin, (+)-catechin and (-)-epicatechin units. Oligomeric procyanidins were purified by chromatography on Sephadex LH-20 and the accessible compounds were isolated by RP-HPLC using a Licrospher Li 100 Column. The structures of the purified oligomeric procyanidins were elucidated using a procedure involving TLC, UV spectroscopy, ESI-MS and HPLC analysis of the products from the phloroglucinol reaction. The major condensed tannins of Vicia faba comprise six compounds identified as two A-type procyanidin dimers, the procyanidin dimers B1, B2 and B3, and a procyanidin trimer.     

Characterization of methanotrophic bacteria on the basis of intact phospholipid profiles

The intact phospholipid profiles (IPPs) of seven species of methanotrophs from all three physiological groups, type I, II and X, were determined using liquid chromatography/electrospray ionization/mass spectrometry. In these methanotrophs, two major classes of phospholipids were found, phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) as well as its derivatives phosphatidylmethylethanolamine (PME) and phosphatidyldimethylethanolamine (PDME). Specifically, the type I methanotrophs, Methylomonas methanica, Methylomonas rubra and Methylomicrobium album BG8 were characterized by PE and PG phospholipids with predominantly C16:1 fatty acids. The type II methanotrophs, Methylosinus trichosporium OB3b and CSC1 were characterized by phospholipids of PG, PME and PDME with predominantly C18:1 fatty acids. Methylococcus capsulatus Bath, a representative of type X methanotrophs, contained mostly PE (89% of the total phospholipids). Finally, the IPPs of a recently isolated acidophilic methanotroph, Methylocella palustris, showed it had a preponderance of PME phospholipids with 18:1 fatty acids (94% of total). Principal component analysis showed these methanotrophs could be clearly distinguished based on phospholipid profiles. Results from this study suggest that IPP can be very useful in bacterial chemotaxonomy.     

Absolute quantification of DcR3 and GDF15 from human serum by LC‐ESI MS

Biomarkers are widely used in clinical diagnosis, prognosis and therapy monitoring. Here, we developed a protocol for the efficient and selective enrichment of small and low concentrated biomarkers from human serum, involving a 95% effective depletion of high‐abundant serum proteins by partial denaturation and enrichment of low‐abundant biomarkers by size exclusion chromatography. The recovery of low‐abundance biomarkers was above 97%. Using this protocol, we quantified the tumour markers DcR3 and growth/differentiation factor (GDF)15 from 100 μl human serum by isotope dilution mass spectrometry, using ¹⁵N metabolically labelled and concatamerized fingerprint peptides for the both proteins. Analysis of three different fingerprint peptides for each protein by liquid chromatography electrospray ionization mass spectrometry resulted in comparable concentrations in three healthy human serum samples (DcR3: 27.23 ± 2.49 fmol/ml; GDF15: 98.11 ± 0.49 fmol/ml). In contrast, serum levels were significantly elevated in tumour patients for DcR3 (116.94 ± 57.37 fmol/ml) and GDF15 (164.44 ± 79.31 fmol/ml). Obtained data were in good agreement with ELISA and qPCR measurements, as well as with literature data. In summary, our protocol allows the reliable quantification of biomarkers, shows a higher resolution at low biomarker concentrations than antibody‐based strategies, and offers the possibility of multiplexing. Our proof‐of‐principle studies in patient sera encourage the future analysis of the prognostic value of DcR3 and GDF15 for colon cancer patients in larger patient cohorts.     

Mass spectrometry for the biophysical characterization of therapeutic monoclonal antibodies

Monoclonal antibodies (mAbs) are powerful therapeutics, and their characterization has drawn considerable attention and urgency. Unlike small-molecule drugs (150–600 Da) that have rigid structures, mAbs (∼150 kDa) are engineered proteins that undergo complicated folding and can exist in a number of low-energy structures, posing a challenge for traditional methods in structural biology. Mass spectrometry (MS)-based biophysical characterization approaches can provide structural information, bringing high sensitivity, fast turnaround, and small sample consumption. This review outlines various MS-based strategies for protein biophysical characterization and then reviews how these strategies provide structural information of mAbs at the protein level (intact or top-down approaches), peptide, and residue level (bottom-up approaches), affording information on higher order structure, aggregation, and the nature of antibody complexes.     

Rapid method for simultaneous determination of 20 components in Isodon nervosa by high‐performance liquid chromatography–electrospray ionisation tandem mass spectrometry

Introduction – Isodon nervosa is a commonly used traditional Chinese medicine including diterpenoids, phenolic acids, triterpenoids and volatile oil. Qualitative and quantitative analysis of multi‐components is important for its quality control. Objective – To establish a liquid chromatography–electrospray ionisation–mass spectrometry method for simultaneous analysis of 20 bioactive constituents of Isodon nervosa in different places of China and different parts of this herb. Methodology – The optimal chromatographic conditions were achieved on a C₁₈ column (250 × 4.6 mm, 5 µm) with with linear gradient elution with 0.1% aqueous formic acid : methanol containing 0.1% formic acid at a flow‐rate of 0.7 mL/min in 15 min. The identification and quantification of those analytes were achieved on a hybrid quadrupole linear ion trap mass spectrometer. Multiple‐reaction monitoring scanning was employed for quantification with switching electrospray ion source polarity between positive and negative modes in a single run. Full validation of the method was carried out (linearity, precision, accuracy, limit of detection and limit of quantification). Results – The results indicated that the method was simple, rapid, specific and reliable. The proposed method was successfully applied for the qualitative and quantitative analysis of 20 chemical compositions in Isodon nervosa samples. Conclusion – Twenty chemical compositions in 21 batches of wild and cultivated Isodon nervosa samples from different sources had great variation in the contents. Copyright © 2010 John Wiley & Sons, Ltd.     

Selective separation and enrichment of peptides for MS analysis using the microspheres composed of Fe3O4@nSiO2 core and perpendicularly aligned mesoporous SiO2 shell

In this work, we report the development of a novel enrichment protocol for peptides by using the microspheres composed of Fe₃O₄@nSiO₂ Core and perpendicularly aligned mesoporous SiO₂ shell (designated Fe₃O₄@nSiO₂@mSiO₂). The Fe₃O₄@nSiO₂@mSiO₂ microspheres possess useful magnetic responsivity which makes the process of enrichment fast and convenient. The highly ordered nanoscale pores (2 nm) and high‐surface areas of the microspheres were demonstrated to have good size‐exclusion effect for the adsorption of peptides. An increase of S/N ratio over 100 times could be achieved by using the microspheres to enrich a standard peptide, and the application of the microspheres to enrich universal peptides was performed by using myoglobin tryptic digest solution. The enrichment efficiency of re‐used Fe₃O₄@nSiO₂@mSiO₂ microspheres was also studied. Large‐scale enrichment of endogenous peptides in rat brain extract was achieved by the microspheres. Automated nano‐LC‐ESI‐MS/MS was applied to analyze the sample after enrichment, and 60 unique peptides were identified in total. The facile and low‐cost synthesis as well as the convenient and efficient enrichment process of the novel Fe₃O₄@nSiO₂@mSiO₂ microspheres makes it a promising candidate for selectively isolation and enrichment of endogenous peptides from complex biological samples.     

EZYprep LC‐coupled MALDI‐TOF/TOF MS: An improved matrix spray application for phosphopeptide characterisation

The quality of MALDI‐TOF mass spectrometric analysis is highly dependent on the matrix and its deposition strategy. Although different matrix‐deposition methods have specific advantages, one major problem in the field of proteomics, particularly with respect to quantitation, is reproducibility between users or laboratories. Compounding this is the varying crystal homogeneity of matrices depending on the deposition strategy used. Here, we describe a novel optimised matrix‐deposition strategy for LC‐MALDI‐TOF/TOF MS using an automated instrument that produces a nebulised matrix “mist” under controlled atmospheric conditions. Comparisons of this with previously reported strategies showed the method to be advantageous for the atypical matrix, 2,5‐DHB, and improved phosphopeptide ionisation when compared with deposition strategies for CHCA. This optimised DHB matrix‐deposition strategy with LC‐MALDI‐TOF/TOF MS, termed EZYprep LC, was subsequently optimised for phosphoproteome analysis and compared to LC‐ESI‐IT‐MS and a previously reported approach for phosphotyrosine identification and characterisation. These methods were used to map phosphorylation on epidermal growth factor‐stimulated epidermal growth factor receptor to gauge the sensitivity of the proposed method. EZYprep DHB LC‐MALDI‐TOF/TOF MS was able to identify more phosphopeptides and characterise more phosphorylation sites than the other two proteomic strategies, thus proving to be a sensitive approach for phosphoproteome analysis.