YcaO-mediated ATP-dependent peptidase activity in ribosomal peptide biosynthesis.

YcaO enzymes catalyze ATP-dependent post-translation modifications on peptides, including the installation of (ox/thi)azoline, thioamide and/or amidine moieties. Here we demonstrate that, in the biosynthesis of the bis-methyloxazolic alkaloid muscoride A, the YcaO enzyme MusD carries out both ATP-dependent cyclodehydration and peptide bond cleavage, which is a mechanism unprecedented for such a reaction. YcaO-catalyzed modifications are proposed to occur through a backbone O-phosphorylated intermediate, but this mechanism remains speculative. We report, to our knowedge, the first characterization of an acyl-phosphate species consistent with the proposed mechanism for backbone amide activation. The 3.1-Å-resolution cryogenic electron microscopy structure of MusD along with biochemical analysis allow identification of residues that enable peptide cleavage reaction. Bioinformatics analysis identifies other cyanobactin pathways that may deploy bifunctional YcaO enzymes. Our structural, mutational and mechanistic studies expand the scope of modifications catalyzed by YcaO proteins to include peptide hydrolysis and provide evidence for a unifying mechanism for the catalytically diverse outcomes.

Catalysts for the Enzymatic Lipidation of Peptides.

Biologically active peptides are a major growing class of drugs, but their therapeutic potential is constrained by several limitations including bioavailability and poor pharmacokinetics. The attachment of functional groups like lipids has proven to be a robust and effective strategy for improving their therapeutic potential. Biochemical and bioactivity-guided screening efforts have identified the cyanobactins as a large class of ribosomally synthesized and post-translationally modified peptides (RiPPs) that are modified with lipids. These lipids are attached by the F superfamily of peptide prenyltransferase enzymes that utilize 5-carbon (prenylation) or 10-carbon (geranylation) donors. The chemical structures of various cyanobactins initially showed isoprenoid attachments on Ser, Thr, or Tyr. Biochemical characterization of the F prenyltransferases from the corresponding clusters shows that the different enzymes have different acceptor residue specificities but are otherwise remarkably sequence tolerant. Hence, these enzymes are well suited for biotechnological applications. The crystal structure of the Tyr O-prenyltransferase PagF reveals that the F enzyme shares a domain architecture reminiscent of a canonical ABBA prenyltransferase fold but lacks secondary structural elements necessary to form an enclosed active site. Binding of either cyclic or linear peptides is sufficient to close the active site to allow for productive catalysis, explaining why these enzymes cannot use isolated amino acids as substrates.Almost all characterized isoprenylated cyanobactins are modified with 5-carbon isoprenoids. However, chemical characterization demonstrates that the piricyclamides are modified with a 10-carbon geranyl moiety, and in vitro reconstitution of the corresponding PirF shows that the enzyme is a geranyltransferase. Structural analysis of PirF shows an active site nearly identical with that of the PagF prenyltransferase but with a single amino acid substitution. Of note, mutation at this residue in PagF or PirF can completely switch the isoprenoid donor specificity of these enzymes. Recent efforts have resulted in significant expansion of the F family with enzymes identified that can carry out C-prenylations of Trp, N-prenylations of Trp, and bis-N-prenylations of Arg. Additional genome-guided efforts based on the sequence of F enzymes identify linear cyanobactins that are α-N-prenylated and α-C-methylated by a bifunctional prenyltransferase/methyltransferase fusion and a bis-α-N- and α-C-prenylated linear peptide. The discovery of these different classes of prenyltransferases with diverse acceptor residue specificities expands the biosynthetic toolkit for enzymatic prenylation of peptide substrates.In this Account, we review the current knowledge scope of the F family of peptide prenyltransferases, focusing on the biochemical, structure-function, and chemical characterization studies that have been carried out in our laboratories. These enzymes are easily amenable for diversity-oriented synthetic efforts as they can accommodate substrate peptides of diverse sequences and are thus attractive catalysts for use in synthetic biology approaches to generate high-value peptidic therapeutics.

Clinical Response to Subcutaneous Dermatophagoides pteronyssinus Immunotherapy in Children with Allergic Rhinitis and Asthma Is Independent of Sensitization to Blomia tropicalis Allergens.

BACKGROUND: Dermatophagoides pteronyssinus (DP) and Blomia tropicalis (BT) are the dominant house dust mites inducing allergic diseases in tropical climates. It is not known whether the efficacy of DP subcutaneous immunotherapy (SCIT) is similar in patients sensitized to DP alone or to both DP and BT. METHOD: Ninety-five children (5-17 years old) affected by asthma with rhinitis and sensitized to both DP and BT received 3 years of DP-SCIT. Clinical symptom and medication scores, serum-specific IgE and IgG4 were evaluated during DP-SCIT. Patients were grouped based on DP and BT co-sensitization or cross-reactivity, according to positive or negative IgE to BT major allergen (BTMA). RESULTS: After 3 years of DP-SCIT, all patients had significant reductions in symptoms and medication use. In all, 65% of the patients were free of asthma symptoms and medication use; in addition, 3% was free of rhinitis symptoms. FEV1 in all patients were greater than 95% of predicted. DP-SCIT induced significant increases in DP- and BT-specific IgG4. In 50% of patients, DP-specific IgG4 increased more than 67-fold. BT-specific IgG4 increased more than 2.5 fold. A moderate correlation (r = 0.48-0.61, p < 0.01) was found between specific IgE against DP and BT in the BTMA- group (n = 34) before and after DP-SCIT, whereas no correlation was found in the BTMA+ group (n = 61). The 2 BTMA groups responded similarly with regard to clinical improvement and increase in specific IgG4 to both DP and BT. No safety finding of concern were reported in either group. CONCLUSION: DP-SCIT may be of clinical benefit to patients with IgE sensitizations to both DP and BT. DP-SCIT induces IgG4 that cross-react with BT allergens.

Design and Synthesis of Cross-Link-Dense Peptides by Manipulating Regioselective Bisthioether Cross-Linking and Orthogonal Disulfide Pairing.

Existing disulfide-rich peptides, both naturally occurring and de novo designed, only represent a tiny amount of the possible sequence space because natural evolution and de novo design only keep sequences that are structurally approachable by correct disulfide pairings. To bypass this limitation for designing new peptide scaffolds beyond the natural sequence space, we dedicate to developing novel disulfide-rich peptides with predefined disulfide pairing patterns irrelevant to primary sequences. However, most of these designed peptides still suffer from disulfide rearrangements to at least one to three possible isomers. Here, we report a general and reliable strategy for the design and synthesis of a range of structurally diverse cross-link-dense peptide (CDP) scaffolds with two orthogonal disulfide bonds and a bisthioether bridge that are not subject to disulfide isomerizations. Altering the pattern of cysteine and penicillamine generates hundreds of different CDP scaffolds tolerant to extensive sequence manipulations. This work thus provides many useful scaffolds for the design of functional molecules such as protein binders with improved proteolytic stability (e.g., designed by epitope grafting).

Proteolytic Unlocking of Ultrastable Twin-Acylhydrazone Linkers for Lysosomal Acid-Triggered Release of Anticancer Drugs.

Targeted prodrugs exploiting cleavable linkers capable of responding to endogenous stimuli have increasingly been explored for cancer therapy. Successful application of these prodrug designs relies on the manipulation of both stability and responsiveness of the cleavable linkers, which, however, are difficult to be finely regulated, particularly for acid-responsive acylhydrazone bonds. Here we developed a new class of peptide-bridged twin-acylhydrazone linkers (PTA linkers) displaying both an ultrahigh stability and a rapid responsiveness-highly stable in neutral and acidic conditions due to the effect of cooperativity between the two acylhydrazone bonds, easily cleavable in acidic conditions after enzymatically triggered unlocking of the two bonds. Moreover, our study shows the design of PTA-linked prodrugs and the proof-of-concept application of the PTA linkers for site-specific release of anticancer drugs into cancer cells.

Precisely Regulated and Efficient Locking of Linear Peptides into Stable Multicyclic Topologies through a One-Pot Reaction.

We report the discovery of a small phenyl molecule with four isosteric thiolate-reactive groups of sequentially varied reactivity. This molecule was exploited in combination with cysteine/penicillamine thiolates of different nucleophilic reactivity for precisely regulated and efficient locking (PROP-locking) of linear peptides into multicyclic topologies through a one-pot reaction. The PROP-locking relies on multistep and sequential thiolate/fluorine nucleophilic substitutions, which is not only rapid but highly specific, thus enabling rapid locking of peptides with high amino acid diversities without protecting groups. Several tricyclic peptide templates and bioactive peptides were designed and synthesized using the PROP-locking strategy. We believe that tricyclic peptides precisely locked through stable thioether bonds should be promising structurally constrained scaffolds for developing potential therapeutics and target ligands.

The Functional IgE-Blocking Factor Induced by Allergen-Specific Immunotherapy Correlates with IgG4 Antibodies and a Decrease of Symptoms in House Dust Mite-Allergic Children.

BACKGROUND: At present, there are no validated biomarkers reflecting or predicting the clinical efficacy of allergen-specific immunotherapy (AIT) . We aimed to investigate the correlations between clinical and immunological responses of patients undergoing house dust mite (HDM) AIT. METHODS: Sixty-nine children diagnosed with HDM allergic rhinitis and/or asthma received standardized Dermatophagoides pteronyssinus (Dp) subcutaneous AIT for 12 months. Twenty HDM-allergic children served as an open control group. Clinical symptom and medication scores were recorded and Dp-specific IgE, IgG4 and IgE-blocking factor were measured before AIT and after 4 and 12 months of AIT. RESULTS: Symptom scores decreased after 4 months and continued to decrease during 12 months of AIT. No differences in medication scores were observed between AIT and the control group during the study period. Levels of Dp IgG4 increased after 4 months and correlated to symptom scores at 12 months (r = -0.296, p = 0.013) of AIT. The Dp IgE-blocking factor increased after 4 months of AIT, and correlated with symptom scores at 4 months (r = -0.307, p = 0.010) and 12 months (r = -0.288, p = 0.016) of AIT. A strong correlation between Dp IgE-blocking factor and Dp IgG4 during AIT (4 months: r = 0.680; 12 months: r = 0.636, both p < 0.0001) was observed. Patients with IgE-blocking factor ≥0.2 after 4 months of AIT showed lower symptom scores at 12 months of AIT (p = 0.0093). CONCLUSIONS: Subcutaneous HDM AIT results in a decrease of allergic symptoms among HDM-allergic children. IgE-blocking activity increased after 4 months of AIT and correlated with clinical symptoms. A high IgE-blocking factor at an early stage of AIT is associated with fewer symptoms at a later stage of AIT.

Orthogonal Cysteine-Penicillamine Disulfide Pairing for Directing the Oxidative Folding of Peptides.

Precise disulfide pairing in synthetic peptides usually is achieved using orthogonal protecting group strategies or relies on primary sequence manipulation. Orthogonal disulfide pairing technology should be promising for directing the rational folding of multicyclic peptides from the fully reduced peptides. Here, we report a discovery on the orthogonality between heterodisulfide pairing of cysteine (Cys) and penicillamine (Pen) and formation of Cys-Cys/Pen-Pen homodisulfides. The orthogonal Cys-Pen disulfide pairing can be exploited for highly selective production of certain (multi)cyclic structures (or even a sole structure without isomers) through direct oxidation in air or thiol-disulfide exchanges in redox media. This strategy makes rational folding of multicyclic peptides without protecting groups, sequence manipulation, and complex synthetic reactions a reality, thus providing invaluable assets to peptide communities, and should greatly benefit the development of multicyclic peptide therapeutics and ligands.

[Molecular allergen IgE tests show neosensitizaions occurring during house dust mite specific immunotherapy].

Objective:Neosensitizations may be occur during the allergen specific immunotherapy（AIT） due to the differences between allergen vaccine's content and a patient's molecular sensitization profile. This study investigates whether AIT with HDM extract changes the sensitization profile, whether de novo sensitization occurs, and the clinical importance of the neosensitization. Methods:Fifty-three patients with HDM allergic rhinitis ,with/without asthma, patients were received one year HDM subcutaneous AIT . Fourteen patients were recruited as control group and received only necessary medications. Serum samples were collected at baseline, 6thmoths and 12thof AIT, respectively. Serum samples were tested specific IgE against Der p, Der p 1/2/3 and Der f, Der f 1/2/3, as well as IgG4 against Der p, Der p 1/2 and Der f, Der f 1/2. VAS were collected at the time-points as well. Results:In AIT group, Der p, Der p 1/3, and Der f 1/3 specific IgE levels were significantly higher after one-year treatment, especially for Der p 3. There were 69.2%（18/26） patients whose Der p 3 specific IgE below 0.35 kU/L at baseline but became positive（>0.35 kU/L） after treatment, that is, neosensitization occurred. All tested allergen specific IgG4 level significantly increased after one year AIT treatment and the VAS declined dramatically. However, for patients with neosensitization and without neosensitization, there were no significantly changes concerning to IgG4 level and VAS. Conclusion:Patients undergoing AIT might have a risk of neosensitization to the allergen components in the vaccines. However, the clinical importance of the neosensitization remains unclear and warrants further studies.

House dust mite and storage mite IgE reactivity in allergic patients from Guangzhou, China.

BACKGROUND: In China, house dust mites are important inducers of allergic disease. The importance of allergens from storage mites is less well known. OBJECTIVE: The aim of this study is to access the prevalence of house dust mite and storage mite sensitization and investigate the IgE crossreactivity between house dust mite and storage mite. METHOD: The skin prick test (SPT) and specific IgE against the mite species D. pteronyssinus, D. farinae, B. tropicalis, Lepidoglyphus destructor, Glycyphagus domesticus, Tyrophagus putrescentiae and Acarus siro were measured. Included were 412 patients with asthma and/or rhinitis for SPT, 244 for specific IgE and 29 sera for IgE inhibition studies. RESULTS: The positive SPT prevalence for D. pteronyssinus was 80.3% and for D. farinae 83.7%. The specific IgE prevalence for D. pteronyssinus was 61.1% and for D. farinae 60.2%. The storage mite species, B. tropicalis and T. putrescentiae had the highest positive SPT prevalence, 66% and 63%, respectively. The specific IgE prevalence was highest for B. tropicalis and G. domesticus, 41% and 37%, respectively. Both SPT and specific IgE levels were much higher for house dust mites compared to storage mites. Inhibition measurements showed that none of the storage mites could fully inhibit the specific IgE against D. pteronyssinus. Only in half of the sera could D. pteronyssinus fully inhibit the IgE against L. destructor and G. domesticus while inhibition of the other storage mites were much lower. Nearly all the specific IgE against storage mites could be inhibited by the other storage mites, though B. tropicalis showed a slightly different pattern from the other storage mites. CONCLUSION: IgE reactivity against storage mites in Chinese patients is due to both storage mite specific IgE and due to IgE mediated crossreactivity to D. pteronyssinus.

Bioconjugate Platform for Iterative Backbone N-Methylation of Peptides.

N-methylation of peptide backbones has often been utilized as a strategy towards the development of peptidic drugs. However, difficulties in the chemical synthesis, high cost of enantiopure N-methyl building blocks, and subsequent coupling inefficiencies have hampered larger-scale medicinal chemical efforts. Here, we present a chemoenzymatic strategy for backbone N-methylation by bioconjugation of peptides of interest to the catalytic scaffold of a borosin-type methyltransferase. Crystal structures of a substrate tolerant enzyme from Mycena rosella guided the design of a decoupled catalytic scaffold that can be linked via a heterobifunctional crosslinker to any peptide substrate of choice. Peptides linked to the scaffold, including those with non-proteinogenic residues, show robust backbone N-methylation. Various crosslinking strategies were tested to facilitate substrate disassembly, which enabled a reversible bioconjugation approach that efficiently released modified peptide. Our results provide general framework for the backbone N-methylation on any peptide of interest and may facilitate the production of large libraries of N-methylated peptides.

Control of Nucleophile Chemoselectivity in Cyanobactin YcaO Heterocyclases PatD and TruD.

Members of the YcaO superfamily are among the most common post-translational modification enzymes in natural product biosynthesis, with wide usage in biotechnology and synthetic biology applications. Here, we use domain-swapped chimeras and discovered unstructured regions in cyanobactin YcaOs that guide interactions with the substrates, governing access to interior amino acids in the substrates and explaining the chemoselectivity between PatD and TruD. These results define how the cyanobactin heterocyclases modify exceptionally sequence diverse substrates, yet with a high degree of positional and nucleophile selectivity.

De novo design and directed folding of disulfide-bridged peptide heterodimers.

Peptide heterodimers are prevalent in nature, which are not only functional macromolecules but molecular tools for chemical and synthetic biology. Computational methods have also been developed to design heterodimers of advanced functions. However, these peptide heterodimers are usually formed through noncovalent interactions, which are prone to dissociate and subject to concentration-dependent nonspecific aggregation. Heterodimers crosslinked with interchain disulfide bonds are more stable, but it represents a formidable challenge for both the computational design of heterodimers and the manipulation of disulfide pairing for heterodimer synthesis and applications. Here, we report the design, synthesis and application of interchain disulfide-bridged peptide heterodimers with mutual orthogonality by combining computational de novo designs with a directed disulfide pairing strategy. These heterodimers can be used as not only scaffolds for generating functional molecules but chemical tools or building blocks for protein labeling and construction of crosslinking hybrids. This study thus opens the door for using this unexplored dimeric structure space for many biological applications.

Associations between the indoor microbiome, environmental characteristics and respiratory infections in junior high school students of Johor Bahru, Malaysia.

Pathogens are commonly present in the human respiratory tract, but symptoms are varied among individuals. The interactions between pathogens, commensal microorganisms and host immune systems are important in shaping the susceptibility, development and severity of respiratory diseases. Compared to the extensive studies on the human microbiota, few studies reported the association between indoor microbiome exposure and respiratory infections. In this study, 308 students from 21 classrooms were randomly selected to survey the occurrence of respiratory infections in junior high schools of Johor Bahru, Malaysia. Vacuum dust was collected from the floor, chairs and desks of these classrooms, and high-throughput amplicon sequencing (16S rRNA and ITS) and quantitative PCR were conducted to characterize the absolute concentration of the indoor microorganisms. Fifteen bacterial genera in the classes Actinobacteria, Alphaproteobacteria, and Cyanobacteria were protectively associated with respiratory infections (p < 0.01), and these bacteria were mainly derived from the outdoor environment. Previous studies also reported that outdoor environmental bacteria were protectively associated with chronic respiratory diseases, such as asthma, but the genera identified were different between acute and chronic respiratory diseases. Four fungal genera from Ascomycota, including Devriesia, Endocarpon, Sarcinomyces and an unclassified genus from Herpotrichillaceae, were protectively associated with respiratory infections (p < 0.01). House dust mite (HDM) allergens and outdoor NO2 concentration were associated with respiratory infections and infection-related microorganisms. A causal mediation analysis revealed that the health effects of HDM and NO2 were partially or fully mediated by the indoor microorganisms. This is the first study to explore the association between environmental characteristics, microbiome exposure and respiratory infections in a public indoor environment, expanding our understanding of the complex interactions among these factors.

Indoor microbiome, environmental characteristics and asthma among junior high school students in Johor Bahru, Malaysia.

Indoor microbial diversity and composition are suggested to affect the prevalence and severity of asthma by previous home microbiome studies, but no microbiome-health association study has been conducted in a school environment, especially in tropical countries. In this study, we collected floor dust and environmental characteristics from 21 classrooms, and health data related to asthma symptoms from 309 students, in junior high schools in Johor Bahru, Malaysia. The bacterial and fungal composition was characterized by sequencing 16s rRNA gene and internal transcribed spacer (ITS) region, and the absolute microbial concentration was quantified by qPCR. In total, 326 bacterial and 255 fungal genera were characterized. Five bacterial (Sphingobium, Rhodomicrobium, Shimwellia, Solirubrobacter, Pleurocapsa) and two fungal (Torulaspora and Leptosphaeriaceae) taxa were protective for asthma severity. Two bacterial taxa, Izhakiella and Robinsoniella, were positively associated with asthma severity. Several protective bacterial taxa including Rhodomicrobium, Shimwellia and Sphingobium have been reported as protective microbes in previous studies, whereas other taxa were first time reported. Environmental characteristics, such as age of building, size of textile curtain per room volume, occurrence of cockroaches, concentration of house dust mite allergens transferred from homes by the occupants, were involved in shaping the overall microbial community but not asthma-associated taxa; whereas visible dampness and mold, which did not change the overall microbial community for floor dust, was negatively associated with the concentration of protective bacteria Rhodomicrobium (ß = -2.86, p = 0.021) of asthma. The result indicates complex interactions between microbes, environmental characteristics and asthma symptoms. Overall, this is the first indoor microbiome study to characterize the asthma-associated microbes and their environmental determinant in the tropical area, promoting the understanding of microbial exposure and respiratory health in this region.

Stabilizing p-Dithiobenzyl Urethane Linkers without Rate-Limiting Self-Immolation for Traceless Drug Release.

Exploiting the redox sensitivity of disulfide bonds is a prevalent strategy in targeted prodrug designs. In contrast to aliphatic disulfides, p-thiobenzyl-based disulfides have rarely been used for prodrug designs, given their intrinsic instability caused by the low pKa of aromatic thiols. Here, we examined the interplay between steric hindrance and the low-pKa effect on thiol-disulfide exchange reactions and uncovered a new thiol-disulfide exchange process for the self-immolation of p-thiobenzyl-based disulfides. We observed a central leaving group shifting effect in the α,α-dimethyl-substituted p-dithiobenzyl urethane linkers (DMTB linkers), which leads to increased disulfide stability by more than two orders of magnitude, an extent that is significantly greater than that observed with typical aliphatic disulfides. In particular, the DMTB linkers display not only high stability, but also rapid self-immolation kinetics due to the low pKa of the aromatic thiol, which can be used as a general and robust linkage between targeting reagents and cytotoxic drugs for targeted prodrug designs. The unique and promising stability characteristics of the present DMTB linker will likely inspire the development of novel targeted prodrugs to achieve traceless release of drugs into cells.

Determination of adsorbed protein concentration in aluminum hydroxide suspensions by near-infrared transmittance spectroscopy.

Analysis of aluminum hydroxide based vaccines is difficult after antigen adsorption. Adsorbed protein is often assessed by measuring residual unadsorbed protein for quality control. A new method for the direct determination of adsorbed protein concentration in suspension using near-infrared (NIR) transmittance spectroscopy is proposed here. A simple adsorption system using albumin from bovine serum (BSA) and aluminum hydroxide as a model system is employed. The results show that the NIR absorbance at 700-1300 nm is correlated to the adsorbed BSA concentration, measured by the ultraviolet (UV) method, using the partial least square regression (PLSR) method to construct a calibration model. The linear concentration range of adsorbed BSA is from 0 to 1.75 mg/mL by using 10 mm path length cuvettes. The influence of the sedimentation in suspension, different buffers, and different aluminum hydroxide batches was investigated in this study. It shows that the batch variation is the main influence factor of this method, while the buffer variation has no influence. However, the pretreatment of spectral data by subtracting spectra of BSA blank control (aluminum hydroxide without BSA) can significantly reduce the batch influence, and the NIR predicted results show good agreement with the reference values. The NIR method might be the only direct method for the determination of adsorbed protein concentration in suspension so far. It is a nondestructive method, and it has great advantage for use in vaccine production as a method for quality control and quality assurance.

Determination of moisture content of lyophilized allergen vaccines by NIR spectroscopy.

Moisture content is an important parameter for lyophilized vaccines. Currently, Karl Fischer titration is widely used for moisture determination in routine analysis. However, this method is time-consuming, sample destructive and requires environment polluting reagents, as well as the results rely on the random samplings. In this study, near infrared spectroscopy was used as a fast, non-invasive and non-destructive method to determine the moisture content in lyophilized allergy vaccines. Five different vaccine products were investigated, which contained water in the range of 0.17-1.51% (w/w, KF). Different data pre-treatments, wavelength selection and partial least squares regression were applied to construct calibration models. Multi-products model and product-specific models were obtained, which show the possibility of NIR as a rapid method to discriminate whether moisture content fit into the specifications of a pharmaceutical company.

De novo design of constrained and sequence-independent peptide scaffolds with topologically-formidable disulfide connectivities.

Disulfide-rich peptides are interesting scaffolds for drug design and discovery. However, peptide scaffolds constrained by disulfide bonds, either naturally occurring or computationally designed, have been suffering from the elusive (oxidative) folding behavior complying with Anfinsen's dogma, which strongly restricts their applicability in bioactive peptide design and discovery; because when primary peptide sequences are extensively manipulated, their disulfide connectivities might become scrambled. Here we present the design of cysteine/penicillamine (C/Pen)-mixed peptide frameworks that are capable of folding into specific regioisomers without dependence on primary amino acid sequences. Even certain folds that are considered to be topologically formidable can be generated in high yields. Currently, almost all disulfide-rich peptide scaffolds are vitally correlated to primary amino acid sequences, but ours are exceptional. These scaffolds should be of particular interest for further designing constrained peptides with new structures and functions, and more importantly, the ultimately designed peptides would not suffer from general oxidative folding problems.

Self-reported questionnaire survey on the prevalence and symptoms of adverse food reactions in patients with chronic inhalant diseases in Tangshan city, China.

BACKGROUND: The prevalence of adverse food reactions in patients with chronic inhalant diseases has seldom been studied in China. This study is to investigate the prevalence of adverse food reactions and the symptoms caused in respiratory patients. METHODS: Respiratory patients in allergy clinics were asked to complete a questionnaire. Patients' information such as age, gender, family history of allergy, and adverse reactions to a list of 48 foods and the symptoms caused, was recorded. Multivariate analyses were performed to determine the prevalence of adverse food reactions and their associated symptoms. RESULTS: 459 subjects, with an average age of 32 years old, completed the questionnaire; 45.3% were male. Among the 459 subjects, 38.1% (175/459) had an adverse reaction to food: 13.6% had an adverse food reaction to crab, 12.4% had an adverse food reaction to shrimp; and 9.9% had an adverse reaction to shellfish. Peach and nectarine were also shown to be common causative foods with 6.8% of the study group showing an adverse reaction to peach and 5.2% to nectarine. Seafood mainly caused skin symptoms and fruits gave rise to more throat, oral, and gastrointestinal problems. CONCLUSION: The prevalence of adverse food reactions is high for patients with respiratory diseases. This indicates that adverse food reactions should be considered in the treatment and management of patients with chronic inhalant diseases.