Biological Sex Is an Effect Modifier of Allergen-Mediated Alteration of the Lung Proteome.

Asthma exhibits a distinct sex bias in the disease prevalence, severity, and response to therapy. However, sex-related differences in alterations of the lung proteome mediated by aeroallergens critical in asthma, such as house dust mites (HDM), remain unknown. In this study, we define sex-related differences in the lung proteome using an HDM-challenged mouse model by 1D LC-MS/MS. Sex-disaggregated data analysis showed that 406 proteins were uniquely altered in females, 273 proteins were uniquely altered in males, and 414 proteins were altered in both females and males in response to HDM. In a linear mixed model analysis, sex modified the HDM exposure effect for 163 proteins, i.e., a significant sex:exposure interaction was identified in 84 proteins in females and 35 proteins in males. Of these, 12 proteins showed a significant sex effect in both female and male lungs. We further selected 3 proteins Tjp1, Lamtor1, and G3BP2 for independent confirmation studies. Our findings detail the sex-specific lung proteome in response to an aeroallergen critical in asthma and demonstrate that sex is a significant effect modifier of HDM response. These results will serve as a valuable resource for delineating sex-specific mechanisms in aeroallergen-driven responses in asthma research.

Accelerating Proteomics Using Broad Specificity Proteases.

Trypsin is the gold-standard protease in bottom-up proteomics, but many sequence stretches of the proteome are inaccessible to trypsin and standard LC-MS approaches. Thus, multienzyme strategies are used to maximize sequence coverage in post-translational modification profiling. We present fast and robust SP3- and STRAP-based protocols for the broad-specificity proteases subtilisin, proteinase K, and thermolysin. All three enzymes are remarkably fast, producing near-complete digests in 1-5 min, and cost 200-1000× less than proteomics-grade trypsin. Using FragPipe resolved a major challenge by drastically reducing the duration of the required "unspecific" searches. In-depth analyses of proteinase K, subtilisin, and thermolysin Jurkat digests identified 7374, 8178, and 8753 unique proteins with average sequence coverages of 21, 29, and 37%, including 10,000s of amino acids not reported in PeptideAtlas' >2400 experiments. While we could not identify distinct cleavage patterns, machine learning could distinguish true protease products from random cleavages, potentially enabling the prediction of cleavage products. Finally, proteinase K, subtilisin, and thermolysin enabled label-free quantitation of 3111, 3659, and 4196 unique Jurkat proteins, which in our hands is comparable to trypsin. Our data demonstrate that broad-specificity proteases enable quantitative proteomics of uncharted areas of the proteome. Their fast kinetics may allow "on-the-fly" digestion of samples in the future.

Improved Coverage of the N-Terminome by Combining ChaFRADIC with Alternative Proteases.

Many proteolytic cleavage events cannot be covered with conventional trypsin-based N-terminomics workflows. These typically involve the derivatization of protein N-termini and Lys residues as an initial step, such that trypsin will cleave C-terminal of arginine but not lysine residues (ArgC-like cleavage). From 20,422 reviewed human protein sequences in Uniprot, 3597 have known N-terminal signal peptides. An in silico ArgC-like digestion of the corresponding 3597 mature protein sequences reveals that-even for these well-known and well-studied proteolytic events-trypsin-based N-terminomics workflows may miss up to 50% of signaling cleavage events as the corresponding neo-N-terminal peptides will have an unfavorable length of <7 (875 peptides) or >30 (911 peptides) amino acids. In this chapter, we provide a protocol that can be applied to all kinds of samples to improve access to this "inaccessible" N-terminome, by making use of the alternative, broad-specificity protease subtilisin for fast and reproducible digestion of proteins.

Temporal proteomic analyses of human lung cells distinguish high pathogenicity influenza viruses and coronaviruses from low pathogenicity viruses.

Newly re-emerging viruses are of significant global concern. In late 2019, a new coronavirus, SARS-CoV-2, emerged in China and soon spread worldwide, causing the COVID-19 pandemic, which to date has caused >6 M deaths. There has been a wealth of studies on this new virus since its emergence. The coronaviruses consist of many animal and human pathogens, with some of the human coronavirus, such as strain OC43, normally causing only mild cold-like symptoms. Viruses usurp host cellular processes to successfully replicate. We used tandem mass tag mass spectrometry-based proteomic analyses of human lung MRC-5 cells infected with OC43 for various periods of time to delineate virus-induced host cell alterations. Numerous proteins involved in lipid metabolism, molecular transport, small molecule biochemistry, cell death and survival, humoral immune response, and inflammatory response were dysregulated. Comparison of our findings to previous studies that examined a range of differentially pathogenic influenza A viruses (IAV), and to SARS-CoV-2 data, revealed that proteins involved in the cell cycle, cytokine signaling, DNA replication, and anti-inflammatory responses were generally similarly affected by virtually all tested IAV and CoV. However, proteins involved in necrosis, protein metabolism, ECM regulation, and signal transduction were generally different. In addition, the more pathogenic CoV and IAV activated Rb-dependent repression of E2F-mediated transcription, whereas less pathogenic influenza and coronaviruses either inhibited or had no effect on this pathway.

Myelin-associated glycoprotein alters the neuronal secretome and stimulates the release of TGFß and proteins that affect neural plasticity.

Myelin-associated glycoprotein (MAG) and Nogo inhibit neurite outgrowth by binding to receptors such as NgR1, PirB and LRP1, and they have also been shown to induce phosphorylation of Smad2, a key intermediate in the transforming growth factor ß (TGFß) signalling pathway. In this study, we determined that MAG and Nogo do not transactivate the TGFß receptor through their canonical receptors or discoidin domain receptor 1, which we identified as a novel receptor for MAG and Nogo. Instead, MAG and Nogo promoted Smad2 phosphorylation by stimulating secretion of TGFß. Proteomic analysis of the neuronal secretome revealed that MAG also regulated the secretion of proteins that affect central nervous system plasticity-inducing the secretion of S100A6, septin-7 and neurofascin 186, while inhibiting the secretion of frataxin, MAP6, syntenin-1 and GAP-43. This represents a novel function for MAG that has broad implications for the treatment for spinal cord injury.

Rodent Lung Tissue Sample Preparation and Processing for Shotgun Proteomics.

Mass spectrometry (MS) is a routinely used approach to characterize global protein profile in various biological samples. Here we describe rodent lung tissue homogenization, sample preparation, and liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for shotgun proteomics.

Zika Virus Infection of Sertoli Cells Alters Protein Expression Involved in Activated Immune and Antiviral Response Pathways, Carbohydrate Metabolism and Cardiovascular Disease.

Zika virus (ZIKV), a re-emerging virus, causes congenital brain abnormalities and Guillain-Barré syndrome. It is mainly transmitted by Aedes mosquitoes, but infections are also linked to sexual transmissions. Infectious ZIKV has been isolated, and viral RNA has been detected in semen over a year after the onset of initial symptoms, but the mode of long-term persistence is not yet understood. ZIKV can proliferate in human Sertoli cells (HSerC) for several weeks in vitro, suggesting that it might be a reservoir for persistent ZIKV infection. This study determined proteomic changes in HSerC during ZIKV infections by TMT-mass spectrometry analysis. Levels of 4416 unique Sertoli cell proteins were significantly altered at 3, 5, and 7 days after ZIKV infection. The significantly altered proteins include enzymes, transcription regulators, transporters, kinases, peptidases, transmembrane receptors, cytokines, ion channels, and growth factors. Many of these proteins are involved in pathways associated with antiviral response, antigen presentation, and immune cell activation. Several immune response pathway proteins were significantly activated during infection, e.g., interferon signaling, T cell receptor signaling, IL-8 signaling, and Th1 signaling. The altered protein levels were linked to predicted activation of immune response in HSerC, which was predicted to suppress ZIKV infection. ZIKV infection also affected the levels of critical regulators of gluconeogenesis and glycolysis pathways such as phosphoglycerate mutase, phosphoglycerate kinase, and enolase. Interestingly, many significantly altered proteins were associated with cardiac hypertrophy, which may induce heart failure in infected patients. In summary, our research contributes to a better understanding of ZIKV replication dynamics and infection in Sertoli cells.

HLA-A, HSPA5, IGFBP5 and PSMA2 Are Restriction Factors for Zika Virus Growth in Astrocytic Cells.

(1) Background: Zika virus (ZIKV), an arbo-flavivirus, is transmitted via Aeges aegyptii mosquitoes Following its major outbreaks in 2013, 2014 and 2016, WHO declared it a Public Health Emergency of International Concern. Symptoms of ZIKV infection include acute fever, conjunctivitis, headache, muscle & joint pain and malaise. Cases of its transmission also have been reported via perinatal, sexual and transfusion transmission. ZIKV pathologies include meningo-encephalitis and myelitis in the central nervous system (CNS) and Guillain-Barré syndrome and acute transient polyneuritis in the peripheral nervous system (PNS). Drugs like azithromycin have been tested as inhibitors of ZIKV infection but no vaccines or treatments are currently available. Astrocytes are the most abundant cells in the CNS and among the first cells in CNS infected by ZIKV; (2) Methods: We previously used SOMAScan proteomics to study ZIKV-infected astrocytic cells. Here, we use mass spectrometric analyses to further explain dysregulations in the cellular expression profile of glioblastoma astrocytoma U251 cells. We also knocked down (KD) some of the U251 cellular proteins using siRNAs and observed the impact on ZIKV replication and infectivity; (3) Results & Conclusions: The top ZIKV dysregulated cellular networks were antimicrobial response, cell death, and energy production while top dysregulated functions were antigen presentation, viral replication and cytopathic impact. Th1 and interferon signaling pathways were among the top dysregulated canonical pathways. siRNA-mediated KD of HLA-A, IGFBP5, PSMA2 and HSPA5 increased ZIKV titers and protein synthesis, indicating they are ZIKV restriction factors. ZIKV infection also restored HLA-A expression in HLA-A KD cells by 48 h post-infection, suggesting interactions between this gene product and ZIKV.

The Small RNAs PA2952.1 and PrrH as Regulators of Virulence, Motility, and Iron Metabolism in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that undergoes swarming motility in response to semisolid conditions with amino acids as a nitrogen source. With a genome encoding hundreds of potential intergenic small RNAs (sRNAs), P. aeruginosa can easily adapt to different conditions and stresses. We previously identified 20 sRNAs that were differentially expressed (DE) under swarming conditions. Here, these sRNAs were overexpressed in strain PAO1 and were subjected to an array of phenotypic screens. Overexpression of the PrrH sRNA resulted in decreased swimming motility, whereas a ΔprrH mutant had decreased cytotoxicity and increased pyoverdine production. Overexpression of the previously uncharacterized PA2952.1 sRNA resulted in decreased swarming and swimming motilities, increased gentamicin and tobramycin resistance under swarming conditions, and increased trimethoprim susceptibility. Transcriptome sequencing (RNA-Seq) and proteomic analysis were performed on the wild type (WT) overexpressing PA2952.1 compared to the empty vector control under swarming conditions, and these revealed the differential expression (absolute fold change [FC] ≥ 1.5) of 784 genes and the differential abundance (absolute FC ≥ 1.25) of 59 proteins. Among these were found 73 transcriptional regulators, two-component systems, and sigma and anti-sigma factors. Downstream effectors included downregulated pilus and flagellar genes, the upregulated efflux pump MexGHI-OpmD, and the upregulated arn operon. Genes involved in iron and zinc uptake were generally upregulated, and certain pyoverdine genes were upregulated. Overall, the sRNAs PA2952.1 and PrrH appeared to be involved in regulating virulence-related programs in P. aeruginosa, including iron acquisition and motility.IMPORTANCE Due to the rising incidence of multidrug-resistant (MDR) strains and the difficulty of eliminating P. aeruginosa infections, it is important to understand the regulatory mechanisms that allow this bacterium to adapt to and thrive under a variety of conditions. Small RNAs (sRNAs) are one regulatory mechanism that allows bacteria to change the amount of protein synthesized. In this study, we overexpressed 20 different sRNAs in order to investigate how this might affect different bacterial behaviors. We found that one of the sRNAs, PrrH, played a role in swimming motility and virulence phenotypes, indicating a potentially important role in clinical infections. Another sRNA, PA2952.1, affected other clinically relevant phenotypes, including motility and antibiotic resistance. RNA-Seq and proteomics of the strain overexpressing PA2952.1 revealed the differential expression of 784 genes and 59 proteins, with a total of 73 regulatory factors. This substantial dysregulation indicates an important role for the sRNA PA2952.1.

Zika Infection Disrupts Proteins Involved in the Neurosensory System.

Newly re-emerging viruses are of great global concern, especially when there are no therapeutic interventions available during the time of an outbreak. There are still no therapeutic interventions for the prevention of Zika virus (ZIKV) infections despite its resurgence more than a decade ago. Newborns infected with ZIKV suffer from microcephaly and delayed neurodevelopment, but the underlying causes are largely unknown. All viruses hijack the host cellular machinery to undergo successful replication. Our tandem mass tag mass spectrometry-based proteomic monitoring of cells infected with ZIKV revealed that among the thousands of host proteins dysregulated over time, many protein candidates were linked to neurodevelopmental processes, including the development of the auditory and visual/retinal system. The role of these dysregulated neurodevelopmental-associated host proteins for ZIKV propagation in eukaryotic cells remains elusive. For the first time, we present temporal neurodevelopmental proteomic responses in cells undergoing ZIKV infection. The future goal is to identify host proteins whose dysregulation results in neurosensory alterations reported in children born to ZIKV-infected mothers.

Activity-based protein profiling guided identification of urine proteinase 3 activity in subclinical rejection after renal transplantation.

BACKGROUND: The pathophysiology of subclinical versus clinical rejection remains incompletely understood given their equivalent histological severity but discordant graft function. The goal was to evaluate serine hydrolase enzyme activities to explore if there were any underlying differences in activities during subclinical versus clinical rejection. METHODS: Serine hydrolase activity-based protein profiling (ABPP) was performed on the urines of a case control cohort of patients with biopsy confirmed subclinical or clinical transplant rejection. In-gel analysis and affinity purification with mass spectrometry were used to demonstrate and identify active serine hydrolase activity. An assay for proteinase 3 (PR3/PRTN3) was adapted for the quantitation of activity in urine. RESULTS: In-gel ABPP profiles suggested increased intensity and diversity of serine hydrolase activities in urine from patients undergoing subclinical versus clinical rejection. Serine hydrolases (n = 30) were identified by mass spectrometry in subclinical and clinical rejection patients with 4 non-overlapping candidates between the two groups (i.e. ABHD14B, LTF, PR3/PRTN3 and PRSS12). Western blot and the use of a specific inhibitor confirmed the presence of active PR3/PRTN3 in samples from patients undergoing subclinical rejection. Analysis of samples from normal donors or from several serial post-transplant urines indicated that although PR3/PRTN3 activity may be highly associated with low-grade subclinical inflammation, the enzyme activity was not restricted to this patient group. CONCLUSIONS: There appear to be limited qualitative and quantitative differences in serine hydrolase activity in patients with subclinical versus clinical renal transplant rejection. The majority of enzymes identified were present in samples from both groups implying that in-gel quantitative differences may largely relate to the activity status of shared enzymes. However qualitative compositional differences were also observed indicating differential activities. The PR3/PRTN3 analyses indicate that the activity status of urine in transplant patients is dynamic possibly reflecting changes in the underlying processes in the transplant. These data suggest that differential serine hydrolase pathways may be active in subclinical versus clinical rejection which requires further exploration in larger patient cohorts. Although this study focused on PR3/PRTN3, this does not preclude the possibility that other enzymes may play critical roles in the rejection process.

Overexpression of the Small RNA PA0805.1 in Pseudomonas aeruginosa Modulates the Expression of a Large Set of Genes and Proteins, Resulting in Altered Motility, Cytotoxicity, and Tobramycin Resistance.

Pseudomonas aeruginosa is a motile species that initiates swarming motility in response to specific environmental cues, i.e., a semisolid surface with amino acids as a nitrogen source (relevant to the human lung). Swarming is an intricately regulated process, but to date posttranscriptional regulation has not been extensively investigated. Small noncoding RNAs (sRNAs) are hypothesized to play posttranscriptional regulatory roles, largely through suppression of translation, and we previously demonstrated 20 sRNA species that were dysregulated under swarming conditions. One of these, sRNA PA0805.1 (which was 5-fold upregulated under swarming conditions), when cloned, transformed into wild-type (WT) PAO1, and overexpressed, led to broad phenotypic changes, including reduced swarming, swimming, and twitching motilities, as well as increased adherence, cytotoxicity, and tobramycin resistance. A ΔPA0805.1 deletion mutant was more susceptible to tobramycin than the WT under swarming conditions. The strain overexpressing PA0805.1 was compared to the empty-vector strain by transcriptome sequencing (RNA-Seq) and proteomics under swarming conditions to determine sRNA targets. Broad transcriptional and proteomic profiles showed 1,121 differentially expressed genes and 258 proteins with significantly different abundance. Importantly, these included 106 transcriptional regulators, two-component regulatory systems, and sigma and anti-sigma factors. Downstream of these regulators were found downregulated type IV pilus genes, many upregulated adherence and virulence factors, and two multidrug efflux systems, mexXY and mexGHI-opmD Therefore, the sRNA PA0805.1 appears to be a global regulator that influences diverse bacterial lifestyles, most likely through a regulatory cascade.IMPORTANCE P. aeruginosa is an opportunistic pathogen of humans. With roughly 10% of its genes encoding transcriptional regulators, and hundreds of small noncoding RNAs (sRNAs) interspersed throughout the genome, P. aeruginosa is able to fine-tune its response to adapt and survive in the host and resist antimicrobial agents. Understanding mechanisms of genetic regulation is therefore crucial to combat pathogenesis. The previously uncharacterized sRNA PA0805.1 was overexpressed in P. aeruginosa strain PAO1, resulting in decreased motility, increased adherence, cytotoxicity, and tobramycin resistance. In contrast, a ΔPA0805.1 deletion mutant had increased susceptibility to tobramycin under swarming conditions. Omic approaches uncovered 1,121 transcriptomic and 258 proteomic changes in the overexpression strain compared with the empty-vector strain, which included 106 regulatory factors. Downstream of these regulators were upregulated adherence factors, multidrug efflux systems, and virulence factors in both transcriptomics and proteomics. This study provides insights into the role of the sRNA PA0805.1 in modulating bacterial adaptations.

Separation Orthogonality in Liquid Chromatography-Mass Spectrometry for Proteomic Applications: Comparison of 16 Different Two-Dimensional Combinations.

Peptide separation orthogonality for 16 different 2D LC-ESI MS systems has been evaluated. To compare and contrast the behavior of the first dimension columns, a large proteomic retention data set of ∼30 000 tryptic peptides was collected for each 2D pairing. The selection of the first dimension system was made to cover the most popular peptide separation modes applied in proteomics: reversed-phase (RP) separations with different pH, hydrophilic interaction liquid chromatography (HILIC), strong cation and anion exchange (SCX, SAX), and mixed-mode separations. The separation orthogonality generally increases in the order RP < SCX < HILIC < SAX, with the exception of high pH RP-low pH RP system, which showed the second best orthogonality value (68%), just behind PolySAX LP column (74%). The identification output of the 2D LC-MS/MS system is driven by both separation orthogonality and efficiency, making high pH RP the best choice for the first dimension separation. Its performance in combination with a standard C18 at acidic pH can be increased further through the application of pairwise fraction concatenation. The effect of the latter has been evaluated using in silico fraction concatenation, which has been proven to show improvement only for RP separations in the first dimension. Concatenation of two, three, and four-five fractions into one is shown to be the most effective for high pH RP and HFBA- and TFA-based C18 separations, respectively. We also suggest simple guidelines for the unbiased determination of dissimilarity for two separation dimensions and evaluate separation orthogonality in 3D LC-LC-MS separation space for all systems under investigation.

Tandem mass tag-based quantitative proteomic analysis reveal the inhibition mechanism of thyme essential oil against flagellum of Listeria monocytogenes.

In this study, the antimicrobial mechanism of thyme essential oil (EO) against Listeria monocytogenes (LM) was investigated at the protein level using tandem mass tag-based quantitative proteomic analysis. The proteomic profiles of LM with 2 log CFU/ml reduction after thyme EO treatment (0.28 µl/ml, Treatment-1) were compared with those of 4 log CFU/ml reduction (0.31 µl/ml, Treatment-2) to identify key proteins involved in microbial inhibition. The results show that 100 and 745 differentially expressed proteins in LM subjected to Treatment-1 vs control and Treatment-2 vs control, respectively. The differentially expressed proteins were functionally categorized using gene ontology enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and STRING analyses. The differentially expressed proteins of LM in Treatment-1 vs control were involved in 45 biological processes, 18 cellular components, 48 molecular functions and 31 KEGG pathways. That of LM in Treatment-2 vs control were involved in 246 biological processes, 45 cellular components, 309 molecular functions and 86 KEGG pathways. It demonstrated that thyme EO treatment induced the cellular processes, environmental information processing, genetic information processing, human diseases, metabolism, organismal systems in LM according to the differently expression protein. Based on the known protein components of flagellar assembly and bacterial chemotaxis, the results suggest that treatment with thyme EO might inhibit flagellar synthesis, block the flagellar motility, and induce partial structural collapse in LM. The structure of flagella filament was damaged by thyme EO treatment. In addition, treatment with thyme EO might affect motility related to chemotaxis and adaptation in LM. This research contributes to the understanding of the molecular mechanisms underlying the inhibiting effects of thyme EO against foodborne pathogens and provide novel insights for further development of EO antimicrobial agents.

Activity-based Protein Profiling Approaches for Transplantation.

Enzyme activity may be more pathophysiologically relevant than enzyme quantity and is regulated by changes in conformational status that are undetectable by traditional proteomic approaches. Further, enzyme activity may provide insights into rapid physiological responses to inflammation/injury that are not dependent on de novo protein transcription. Activity-based protein profiling (ABPP) is a chemical proteomic approach designed to characterize and identify active enzymes within complex biological samples. Activity probes have been developed to interrogate multiple enzyme families with broad applicability, including but not limited to serine hydrolases, cysteine proteases, matrix metalloproteases, nitrilases, caspases, and histone deacetylases. The goal of this overview is to describe the overall rationale, approach, methods, challenges, and potential applications of ABPP to transplantation research. To do so, we present a case example of urine serine hydrolase ABPP in kidney transplant rejection to illustrate the utility and workflow of this analytical approach. Ultimately, developing novel transplant therapeutics is critically dependent on understanding the pathophysiological processes that result in loss of transplant function. ABPP offers a new dimension for characterizing dynamic changes in clinical samples. The capacity to identify and measure relevant enzyme activities provides fresh opportunities for understanding these processes and may help identify markers of disease activity for the development of novel diagnostics and real-time monitoring of patients. Finally, these insights into enzyme activity may also help to identify new transplant therapeutics, such as enzyme-specific inhibitors.

An in situ-Synthesized Gene Chip for the Detection of Food-Borne Pathogens on Fresh-Cut Cantaloupe and Lettuce.

Fresh foods are vulnerable to foodborne pathogens which cause foodborne illness and endanger people's life and safety. The rapid detection of foodborne pathogens is crucial for food safety surveillance. An in situ-synthesized gene chip for the detection of foodborne pathogens on fresh-cut fruits and vegetables was developed. The target genes were identified and screened by comparing the specific sequences of Salmonella Typhimurium, Vibrio parahemolyticus, Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli O157:H7 from the National Center for Biotechnology Information database. Tiling array probes were designed to target selected genes in an optimized hybridization system. A total of 141 specific probes were selected from 3,227 hybridization probes, comprising 26 L. monocytogenes, 24 S. aureus, 25 E. coli O157:H7, 20 Salmonella Typhimurium, and 46 V. parahemolyticus probes that are unique to this study. The optimized assay had strong amplification signals and high accuracy. The detection limit for the five target pathogens on fresh-cut cantaloupe and lettuce was approximately 3 log cfu/g without culturing and with a detection time of 24 h. The detection technology established in this study can rapidly detect and monitor the foodborne pathogens on fresh-cut fruits and vegetables throughout the logistical distribution chain, i.e., processing, cleaning, fresh-cutting, packaging, storage, transport, and sale, and represents a valuable technology that support the safety of fresh agricultural products.

Chromatographic behavior of peptides containing oxidized methionine residues in proteomic LC-MS experiments: Complex tale of a simple modification.

On average, the oxidation of a single Met residue to Mso (methionine S-oxide, methionine sulfoxide) and Msn (methionine S,S-dioxide, methionine sulfone) decreases peptide retention in RP HPLC by 2.37 and 1.95 Hydrophobicity Index units (% acetonitrile), respectively. At the same time, the magnitude of the retention shift varies greatly (-9.1 to +0.4% acetonitrile for Mso) depending on peptide sequence. The latter effects are mostly associated with the stabilization of secondary structures upon peptide interaction with the hydrophobic stationary phase: when an oxidized residue is located in the hydrophobic face of an amphipathic helix, the decrease in retention is profound. The same amino acid positioning leads to complete or partial resolution of pairs of peptides containing diastereomeric Mso residues. Contrary to all previously reported observations, and the nature of this modification, we also demonstrate for the first time that methionine oxidation may increase peptide hydrophobicity. This behavior is characteristic for Met residues in the N3 position of an N-capping box stabilization motif prior to the amphipathic helix. All these findings indicate that the prediction of peptide secondary structures upon interaction with hydrophobic surfaces must become an integral part of peptide retention modeling in proteomic applications going forward.

N-capping motifs promote interaction of amphipathic helical peptides with hydrophobic surfaces and drastically alter hydrophobicity values of individual amino acids.

Capping rules, which govern interactions of helical peptides with hydrophobic surfaces, were never established before due to lack of methods for the direct measurement of polypeptide structure on the interphase boundary. We employed proteomic techniques and peptide retention modeling in reversed-phase chromatography to generate a data set sufficient for amino acid population analysis at helix ends. We found that interactions of amphipathic helical peptides with a hydrophobic C18 phase are induced by a unique motif featuring hydrophobic residues in the N1 and N2 positions adjacent to the N-cap (Asn, Asp, Ser, Thr, Gly), followed by Glu, Gln, or Asp in position N3 to complete a capping box. A favorable N-capping arrangement prior to amphipathic helix may result in the highest hydrophobicity (retention on C18 columns) of Asp/Asn (or Glu/Gln) peptide analogues among all naturally occurring amino acids when placed in N-cap or N3 position, respectively. These results contradict all previously reported hydrophobicity scales and provide new insights into our understanding of the phenomenon of hydrophobic interactions.

Characterization and complete separation of major cyclolinopeptides in flaxseed oil by reversed-phase chromatography.

Organoleptic properties of flaxseed oil deteriorate during storage due to methionine oxidation in its major cyclolinopeptides. Cyclolinopeptide E was previously identified as being responsible for the manifestation of bitter taste with flaxseed oil ageing. We developed a chromatographic procedure to monitor the oxidation of major cyclic peptides in flaxseed oil. We also used liquid chromatography with mass spectrometry and high-efficiency core-shell reversed-phase sorbents to study the separation of cyclolinopeptides in detail. The Kinetex(TM) family of stationary phases (C8, C18, phenyl-hexyl) was tested, along with the standard porous Luna(TM) C18(2) media. We found that only the phenyl-hexyl stationary phase allows for complete resolution of major cyclolinopeptides, thus permitting direct UV monitoring of degree of conversion for cyclolinopeptide B into C and L into E. We also report, for the first time, a significant effect of peak splitting for some methionine S-oxide (Mso) containing cyclolinopeptides, which most likely appear due to diastereomerization. This results in poor separation efficiency for cyclolinopeptides F, G, and E, and gives baseline resolution of diastereomeric pairs for cyclolinopeptides I and P. Thus, a single oxidation of cyclolinopeptide N yields three distinct chromatographic peaks corresponding to cyclolinopeptide T (cyclo-MsoLMPFFWV, reported for the first time) and pair of cyclolinopeptide I (cyclo-MLMsoPFFWV) diastereomers.

Traditional Chinese medicine versus western medicine as used in China in the management of rheumatoid arthritis: a randomized, single-blind, 24-week study.

This study is designed to compare the efficacy and safety of traditional Chinese medicine (TCM) with western medicine (WM) in the management of rheumatoid arthritis (RA). This is a 24-week, randomized, multicenter, single-blind study comparing TCM with WM (as used in China) carried out between June 2002 and December 2004 in nine research centers in China, involving 489 patients. Patients were randomized to receive TCM (n = 247), MTX and SSZ (n = 242). MTX was started at a dose of 5 mg to a final dose of 7.5-15 mg weekly. The maintenance dose was 2.5-7.5 mg weekly. The starting dose of SSZ was 0.25 g bid, increasing by 0.25 g a day once a week to a final dose of 0.5-1 g qid. The maintenance dose was 0.5 g tid to qid. Primary end point was the proportion of patients with response according to the American College of Rheumatology 20 % improvement criteria (ACR20) at weeks 24. At 24 weeks, ACR20 responses were 53.0 % in TCM group and 66.5 % in WM group, (P < 0.001) at 24 weeks. ACR 50 responses were 31.6 % of TCM group and 42.6 % in WM group, (P = 0.01). ACR70 responses were 12.6 % in TCM group and 17.4 % in WM group, (P = 0.14). Side effects were observed more frequently in WM group. In this study, ACR20, ACR50 responses at 24 weeks were significantly better in the WM treated group, by intention to treat (ITT) and per protocol analysis. The ACR 70 response showed no significant difference between the two groups. TCM, while effective in treating RA, appears to be less effective than WM in controlling symptoms, but TCM is associated with fewer side effects.