Tyrosine Units Research Articles

Photonics of Hydrothermally Treated β‐Lactoglobulin Amyloids

Increased temperature and high pressure are applied to β‐lactoglobulin fibrils in the autoclave, resulting in the acquisition of a composite material comprised of partially disassembled amyloid fibrils and carbon dots. Confirmation of the preservation of the β‐sheet motif attributed to amyloids in the hydrothermally treated fibrils is obtained through wide‐angle X‐ray scattering and ThT assay. Z‐scan analysis reveals a two‐photon absorption (2PA) enhancement in the low‐lying transition band (La) of tyrosine, while quantum chemical calculations demonstrate a correlation between the yield of 2PA and the interspace distance between aromatic residues. Overall, the intrinsic optical properties of amyloid fibrils treated in a subcritical water environment are found to be linked with the π‐conjugation of tyrosine units and their through‐space coupling. The resulting composite material is employed as a coating for a commercial ultraviolet light‐emitting diode lamp, showcasing the potential utility of sustainable biomaterials with improved optical properties for photonics applications.

Does thermotropic liquid crystalline self-assembly control biological activity in amphiphilic amino acids? - tyrosine ILCs as a case study.

Amphiphilic amino acids represent promising scaffolds for biologically active soft matter. In order to understand the bulk self-assembly of amphiphilic amino acids into thermotropic liquid crystalline phases and their biological properties a series of tyrosine ionic liquid crystals (ILCs) was synthesized, carrying a benzoate unit with 0-3 alkoxy chains at the tyrosine unit and a cationic guanidinium head group. Investigation of the mesomorphic properties by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (WAXS, SAXS) revealed smectic A bilayers (SmAd) for ILCs with 4-alkoxy- and 3,4-dialkoxybenzoates, whereas ILCs with 3,4,5-trisalkoxybenzoates showed hexagonal columnar mesophases (Colh), while different counterions had only a minor influence. Dielectric measurements revealed a slightly higher dipole moment of non-mesomorphic tyrosine-benzoates as compared to their mesomorphic counterparts. The absence of lipophilic side chains on the benzoate unit was important for the biological activity. Thus, non-mesomorphic tyrosine benzoates and crown ether benzoates devoid of additional side chains at the benzoate unit displayed the highest cytotoxicities (against L929 mouse fibroblast cell line) and antimicrobial activity (against Escherichia coli ΔTolC and Staphylococcus aureus) and promising selectivity ratio in favour of antimicrobial activity.

Hydrophilic tyrosine-based phenolic resin with micro-ripples morphology for marine antifouling application

Since biofouling challenges negatively influence the marine and transportation industries, developing effective antifouling materials have attracted extensive concern. A tyrosine-based antifouling phenolic resin (TPP resin) was synthesized using tyrosine as a natural phenol source. TPP exhibited shell-like surface morphology with micro-ripples and excellent anti-adhesion properties against bacteria and diatom. The micro-ripples surface might be caused by the strong hydrogen bonding or ionic interaction among tyrosine units resulting in microphase separation during the curing process. Tyrosine content in TPP resin has a great influence on the surface properties, morphology and antifouling characteristics. The higher the tyrosine content, the higher is the surface hydrophilicity, the denser and more regular is the micro-ripples morphology, and the stronger is the antifouling performance. TPP-60 % exhibited the best antifouling performance. Combination of the surface hydrophilicity and regular micro-ripples surface morphology afford TPP excellent antifouling performance. TPP resins offer a broad prospect for developing phenolic resin in the antifouling field.

Effect of supplementing papaya (Carica papaya) latex on performance, carcass traits and nutrient digestibility in broiler chicken fed recommended and sub-optimal levels of dietary protein

Three experiments were conducted to study the effects of supplementing papaya (Carica papaya) latex (papain) (PL) on performance, carcass variables and apparent ileal digestibility of nitrogen and energy in broiler male chickens (Vencobb 430) fed diets containing varying levels of protein. The PL (4000 TU g−1) was supplemented to maize-soybean meal based control diet (CD) to provide four concentrations of papain (0, 600, 800 and 1000 TU kg−1 diet) in experiment 1. In experiment 2, the CD (100% protein) and a low-protein basal diet (95% less protein i.e. about 1% of diet and proportionate limiting amino acids concentration) were fed with and without PL (0 and 1000 tyrosine units - TU kg−1 diet) in a 2 × 2 factorial design. Three graded levels of dietary protein (88%, 94% and 100% of the recommended level) with three concentrations of PL (0, 1000 and 2000 TU kg−1) were fed in experiment 3 to find the possibility of reducing dietary protein with higher concentrations of papain in the diet. Each diet was fed ad libitum to 10 replicates of 25 broiler chicks in each replicate (6.5 ×4 feet floor pen) from d 1–35. In experiment 1, supplementation of papain at 1000 TU kg−1 to the CD significantly improved the feed efficiency (FE) compared to the control group (1–35d). In experiment 2, by reducing the dietary protein by 1%, the body weight gain (BWG) and FE reduced (1–35 d). However, supplementation of 1000 TU papain significantly improved the BWG and FE, which were similar to the control. The interaction between dietary protein and PL did not influence the performance variables in experiment 3, except the FE during 1–21 d. At 88% protein, PL supplementation significantly improved the FE and such improvement was not observed at 94% and 100% protein during d 1–21. Supplementation of 2000 TU papain / kg improved FE similar to those fed the CD, which implies the possibility of reducing the dietary protein with papain supplementation. BWG and FE improved significantly with papain at 2000 TU kg−1 diet compared to the CD. An increase in dietary protein progressively reduced the relative weights of abdominal fat and liver. Papain supplementation reduced the ready to cook yield and breast weight. Papain supplementation significantly increased the digestibility of energy and nitrogen compared to the control group. Based on the results, it is concluded that papain supplementation (1000–2000 TU kg−1) in the form of papaya latex could able to reduce the requirement of protein (about 95% of the recommendation) in corn soybean meal based diets without affecting the performance. Increased digestibility of energy and protein with papain might be responsible for the reduced requirement of protein as observed in the current study.

GOx/Hb Cascade Oxidized Crosslinking of Silk Fibroin for Tissue-Responsive Wound Repair.

Promising wound dressings can achieve rapid soft-tissue filling while refactoring the biochemical and biophysical microenvironment to recruit endogenous cells, facilitating tissue healing, integration, and regeneration. In this study, a tissue biomolecule-responsive hydrogel matrix, employing natural silk fibroin (SF) as a functional biopolymer and haemoglobin (Hb) as a peroxidase-like biocatalyst, was fabricated through cascade enzymatic crosslinking. The hydrogels possessed mechanical tunability and displayed adjustable gelation times. A tyrosine unit on SF stabilised the structure of Hb during the cascade oxidation process; thus, the immobilized Hb in SF hydrogels exhibited higher biocatalytic efficiency than the free enzyme system, which provided a continuously antioxidative system. The regulation of the dual enzyme ratio endowed the hydrogels with favourable biocompatibility, biodegradability, and adhesion strength. These multifunctional hydrogels provided a three-dimensional porous extracellular matrix-like microenvironment for promoting cell adhesion and proliferation. A rat model with a full-thickness skin defect revealed accelerated wound regeneration via collagen deposition, re-epithelialisation and revascularisation. Enzyme-loaded hydrogels are an attractive and high-safety biofilling material with the potential for wound healing, tissue regeneration, and haemostasis.

Hierarchical Vitalization of Oligotyrosine in Mitigating Islet Amyloid Polypeptide Amyloidogenesis through Multivalent Macromolecules with Conformation-Restrained Nanobody Ligands.

The development of inhibitors that can effectively mitigate the amyloidogenesis of human islet amyloid polypeptide (hIAPP), which is linked to type II diabetes, remains a great challenge. Oligotyrosines are intriguing candidates in that they can block the hIAPP aggregation through multiplex phenol-hIAPP interactions. However, oligotyrosines containing too many tyrosine units (larger than three) may fail to inhibit amyloidogenesis due to their increased hydrophobicity and strong self-aggregation propensity. In this work, we developed a strategy to hierarchically vitalize oligotyrosines in mitigating hIAPP amyloidogenesis. Tetratyrosine YYYY (4Y) was grafted into the third complementary-determining region (CDR3) of a parent nanobody to construct a sequence-programmed nanobody N4Y, in which the conformation of the grafted 4Y fragment was constrained for a significantly enhanced binding affinity with hIAPP. We next conjugated N4Y to a polymer to approach a secondary vitalization of 4Y through a multivalent effect. The in vitro and in vivo experiments validated that the resulting PDN4Y could completely inhibit the hIAPP amyloidogenesis at low stoichiometric concentrations and effectively suppress the generation of toxic reactive oxygen species and alleviate amyloidogenesis-mediated damage to INS-1 cells and zebrafish (Danio rerio) embryos. The hierarchical vitalization of 4Y via a synergistic conformation restraint and multivalent effect represents a strategic prototype of boosting the efficacy of peptide-based amyloidogenesis inhibitors, especially those with a high hydrophobicity and strong aggregation tendency, which holds great promise for future translational studies.

Laccase-catalyzed cross-linking of BSA mediated by tyrosine

Tyrosine was explored as a cross-linking agent to form cross-linked bovine serum albumin (BSA) using laccase as a catalyst. Liquid chromatography-mass spectrometry (LC-MS) and fluorescence spectra indicated that tyrosine can be mainly oxidized to be dityrosine. Spectra analysis and molecular weight were used to characterize the BSA treated with tyrosine and laccase. Both SDS-PAGE and size exclusion chromatography confirmed the formation of cross-linked BSA, while most of the protein products existed as BSA–tyrosine conjugates. The MALDI-TOF analysis revealed that five tyrosine units were grafted on one BSA monomer, however one cross-linked BSA consists of two BSA monomers and 18 tyrosine. Furthermore, the content of the amino acid of BSA was identified using amino acid analysis, among those the percentage of lysine presented a visible decline from 12.36% to 11.43%, corresponding to 4–5 lysine residues. The pure and modified BSA were hydrolyzed by trypsin and the corresponding peptides were obtained. Different mass of five peptides from LC-MS spectra after hydrolysis indicated that tyrosine could react with Lys-136, Lys-204, Lys-224, Lys-322 and Lys-537 in BSA, promoting the formation of BSA–tyrosine conjugates and cross-linked BSA.

Photochemistry of bioinspired dityrosine crosslinking

The dityrosine crosslink plays a vital role in improving mechanical property and stability of polymers, which has been found in most insects. It has also been exploited in new synthetic materials. Therein, the photochemical method provides a path for the formation of dityrosine bonding and shows its unique superiority. Here, we review different photo-innitiation approaches that generate the dityrosine link. This review may offer new strategies for photo-activated tyrosine unit manipulation.

Two Biosynthetic Pathways in Jahnella thaxteri for Thaxteramides, Distinct Types of Lipopeptides.

The structures of five linear lipopeptides, thaxteramides A1, A2, B1, B2, and C isolated from the myxobacterium Jahnella thaxteri, were elucidated. They have a C-terminal common tetrapeptidic Tyr-Gly-β-Ala-Tyr core but differ in the stereochemistry of the tyrosine units, methylations, the remaining amino acids, and the N-terminal polyketide. In silico analysis of the genome sequence complemented with feeding experiments revealed two distinct hybrid PKS/NRPS gene clusters. Three semisynthesized cyclic analogues were found to inhibit the growth of Gram-positive bacteria.

Oligotyrosines Inhibit Amyloid Formation of Human Islet Amyloid Polypeptide in a Tyrosine-Number-Dependent Manner.

Misfolding and amyloid formation of human islet amyloid polypeptide (IAPP) are believed to be critical in the pathogenesis of type 2 diabetes. Inhibitors that can effectively prevent protein aggregation and fibrillation are considered as potential therapeutics for the prevention and treatment of type 2 diabetes. Here, we report that oligotyrosines manipulate IAPP amyloid formation in vitro and modulate IAPP-induced cytotoxicity in a manner that is related to the number of tyrosine units. Tyr2 and Tyr3 can effectively inhibit the aggregation of IAPP, either in bulk solution or in the presence of lipid membranes, and alleviate IAPP-mediated cytotoxicity. On the contrary, Tyr, Tyr4, and Tyr6 do not show significant inhibitory effects on the IAPP aggregation at the same conditions. To the best of our knowledge, this is the first report of a residue-number-dependent inhibition of IAPP aggregation by oligotyrosines, and Tyr2 and Tyr3 are proved to be potent inhibitors of IAPP amyloid formation. The interactions between oligotyrosines and IAPP were simulated through molecular docking, which provides us a new insight about the inhibition mechanism of IAPP amyloid formation that will be helpful for developing antidiabetic drug candidates.

Tyrosine-Rich Peptides as a Platform for Assembly and Material Synthesis.

The self‐assembly of biomolecules can provide a new approach for the design of functional systems with a diverse range of hierarchical nanoarchitectures and atomically defined structures. In this regard, peptides, particularly short peptides, are attractive building blocks because of their ease of establishing structure–property relationships, their productive synthesis, and the possibility of their hybridization with other motifs. Several assembling peptides, such as ionic‐complementary peptides, cyclic peptides, peptide amphiphiles, the Fmoc‐peptide, and aromatic dipeptides, are widely studied. Recently, studies on material synthesis and the application of tyrosine‐rich short peptide‐based systems have demonstrated that tyrosine units serve as not only excellent assembly motifs but also multifunctional templates. Tyrosine has a phenolic functional group that contributes to π–π interactions for conformation control and efficient charge transport by proton‐coupled electron‐transfer reactions in natural systems. Here, the critical roles of the tyrosine motif with respect to its electrochemical, chemical, and structural properties are discussed and recent discoveries and advances made in tyrosine‐rich short peptide systems from self‐assembled structures to peptide/inorganic hybrid materials are highlighted. A brief account of the opportunities in design optimization and the applications of tyrosine peptide‐based biomimetic materials is included.

Exploring Tyrosine-Triazolinedione (TAD) Reactions for the Selective Conjugation and Cross-Linking of N-Carboxyanhydride (NCA) Derived Synthetic Copolypeptides.

Highly efficient functionalization and cross-linking of polypeptides is achieved via tyrosine-triazolinedione (TAD) conjugation chemistry. The feasibility of the reaction is demonstrated by the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) with tyrosine containing block copolymer poly(ethylene glycol)-Tyr4 as well as a statistical copolymer of tyrosine and lysine (poly(Lys40 -st-Tyr10 )) prepared form N-carboxyanhydride polymerization. Selective reaction of PTAD with the tyrosine units is obtained and verified by size exclusion chromatography and NMR spectroscopy. Moreover, two monofunctional and two difunctional TAD molecules are synthesized. It is found that their stability in the aqueous reaction media significantly varied. Under optimized reaction conditions selective functionalization and cross-linking, yielding polypeptide hydrogels, can be achieved. TAD-mediated conjugation can offer an interesting addition in the toolbox of selective (click-like) polypeptide conjugation methodologies as it does not require functional non-natural amino acids.

Poly(colloid)s: "Polymerization" of Poly(l-tyrosine)-silica Composite Particles through the Photoinduced Cross-Linking of Unmodified Proteins Method.

Photoinduced cross-linking of unmodified proteins, PICUP, was extended to core-shell silica-polypeptide composite particles to produce poly(colloid)s. Silica particles coated with poly(l-tyrosine), PTYR-SiO2, served as the monomer units. The PICUP reaction accomplished the formation of dityrosil linkages between the tyrosine units by illumination of photo-oxidizing ruthenium(II) bipyridyl catalyst under physiological conditions. The PICUP method was compared with an enzymatic route intermediated by horseradish peroxidase as catalyst. The PTYR-SiO2 particles feature high PTYR content in the shell, which facilitated the formation of heavily cross-linked but unstructured aggregates. After magnetic alignment of superparamagnetic PTYR-SiO2-cobalt composite particles, only the PICUP approach enabled the preparation of isolated chain-like poly(colloid)s. The cross-linking products were confirmed by FTIR. The native secondary structure of poly(l-tyrosine) is preserved in these poly(colloid)s. Because the PICUP reaction does not require the modification of the polypeptide structure, the cross-linked PTYR will retain its characteristic functions as a poly(amino acid). The PICUP method opens the door to a variety of PTYR-based poly(colloid) architectures.

Photo-assisted generation of phospholipid polymer substrates for regiospecific protein conjugation and control of cell adhesion

Novel photo-reactive phospholipid polymers were synthesized for use in the preparation of nonfouling surfaces with protein conjugation capacity. Poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-ran-N-methacryloyl-(l)-tyrosinemethylester (MAT)] (P(MPC/MAT)) was synthesized by conventional radical polymerization, with the MAT units capable of being oxidized by 254nm UV irradiation. Because of this photo-oxidation, active species such as catechol and quinone were alternately generated in the copolymer. A silicon wafer was subjected to surface modification through spin coating of P(MPC/MAT) from an aqueous solution for use as a model substrate. The surface was then irradiated several times with UV light. The thickness of the polymer layers formed on the Si wafers was influenced by various parameters such as polymer concentration, UV irradiation time, and composition of the MAT units in P(MPC/MAT). Oxidized MAT units were advantageous not only for polymer adhesion to a solid surface but also for protein conjugation with the adhered polymers. The amount of protein immobilized on UV-irradiated P(MPC/MAT) was dependent on the composition of the MAT units in the polymer. Furthermore, it was confirmed that protein immobilization on the polymer occurred through the oxidized MAT units because the protein adsorption was significantly reduced upon blocking these units through pretreatment with glycine. Conjugation of regiospecific protein could also be achieved through the use of a photomask. In addition, nonspecific protein adsorption was reduced on the non-irradiated regions whose surface was covered with physisorbed P(MPC/MAT). Therefore, P(MPC/MAT) can be used in the preparation of nonfouling substrates, which enable micrometer-sized manipulation of proteins through photo-irradiation. Function of proteins immobilized on MPC copolymers was also confirmed by cell adhesion test. As such, photo-reactive MPC copolymers are suitable for performing controlled protein conjugation and preparing polymer–protein hybrid platforms for use in biomedical and diagnostic devices. Statement of SignificanceNovel photo-reactive phospholipid polymers have been synthesized for immobilization on solid surfaces and regiospecific protein conjugation. Tyrosine residues embedded in 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymers could be photo-oxidized, resulting in polymers able to form layers on a solid surface and conjugate with proteins. Moreover, nonspecific biofouling on the surface significantly reduced when the oxidized tyrosine units in the polymer layers were blocked. Upon UV irradiation through a photomask, the UV-exposed tyrosine units were selectively oxidized, forming the only specific regions in which protein conjugation could occur.

Controlled photo-immobilization of proteins on phospholipid polymer surfaces

Event Abstract Back to Event Controlled photo-immobilization of proteins on phospholipid polymer surfaces Masako Tanaka1* and Yasuhiko Iwasaki2, 3* 1 Kansai university, Graduate School of Science and Engineering, Japan 2 Kansai university, Faculty of Chemistry, Materials and Bioengineering, Japan 3 Kansai university, ORDIST, Japan Introduction: Control of protein adsorption on synthetic materials is still important issue for creation of biomedical materials. It is well known that 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers can reduce nonspecific protein adsorption. By adding ligands to MPC polymer surfaces, specific molecular interaction between the surface and proteins or cells could be regulated [1]. In the present study, the photo-reactive MPC polymers bearing tyrosine residues have been newly synthesized. The coating layer of MPC copolymers having tyrosine residues was formed on the solid substrates via UV-irradiation through the binding between oxidized tyrosine residues [2] and the substrate. The nonfouling property on the substrates was improved by the surface modification. Moreover, the protein immobilization through oxidized tyrosine [3] on the MPC copolymers having high composition of tyrosine residues have been performed. Material and Method: Poly(MPC) (PMPC) and MPC copolymers with N-methacryloyl-(L)-tyrosine methylestr(MAT) (P(MPC/MAT)) were synthesized by conventional radical polymerization. The aqueous solution containing 1wt% P(MPC/MAT) was coated on the silicon wafers using a spin coater. The specimens were irradiated UV light (254 nm) for several periods and rinsed with methanol and water. Surface analysis for P(MPC/MAT)-immobilized surfaces was performed using X-ray photoelectron spectroscope (XPS) and ellipsometer. P(MPC/MAT)-immobilized specimens were exposed to 0.45 g/dL fluorescein isothiocyanate (FITC)-labeled bovine albumin in PBS for 30 min, and rinsed with PBS and water. The sample was dried in an argon stream and observed using a fluorescent microscope. Results: The molar fraction of MPC of P(MPC/MAT) was coincident with that in copolymers. Oxidation of tyrosine units via UV light irradiation was monitored using UV-visible spectrophotometer. Fig. 1 shows the thickness of polymer layers immobilized on Si wafers. When the UV irradiation time was adjusted at 60 min, the thickness of P(MPC/MAT) coated on Si wafers was increased with an increase in the concentration of the polymer solution and the molar fraction of MAT. Fig. 2 shows a fluorescence micrograph for protein microarray generated on P(MPC/MAT)70/30. UV light was irradiated on P(MPC/MAT)70/30 coated surface was through a mesh for transmission electron microscopy. The proteins attached on the specific regions whose surface were exposed to UV light. Discussion: Considering from the layer thickness and phosphorus composition of surface analysis, MAT of P(MPC/MAT) is dominant unit to regulate the feature of polymer layers. Oxidized MAT units showed an advantage not only for the polymer adhesion to a solid surface but also protein conjugation with the adherent polymer. The amount of proteins immobilized on oxidized P(MPC/MAT)70/30 increased with an increase in the thickness of the polymer layer. It has been also clarified that conjugation of proteins on P(MPC/MAT) was selectively occurred through the oxidized MAT units. Conclusion: The photo-reactive MPC polymers have been newly designed to generate biofunctional interface. Tyrosine residues incorporated MPC copolymers could be photooxidized and resulted polymers showed functions to bind on solid surfaces and conjugate with proteins. The activity of site-specifically immobilized proteins on MPC polymer surface was well preserved. Moreover, nonspecific biofouling on the surface well reduced. The photo-reactive MPC polymers will be useful for surface preparation of biomedical and diagnostic devices. A part of this work was supported by AMED Strategic Promotion of Innovative Research and Development

Connecting Tyrosine and Tryptophan Units of Diazonamide A and Azonazine by a Diastereodivergent Arylative Dearomatization.

We report the Friedel-Crafts coupling of a tyrosine unit with tryptophan-derived pyrrolindolenium ions which are configurationally stable. The reaction allowed the stereoselective and divergent access to the required quaternary stereocenters found in diazonamide A and azonazine at the junction of the tyrosine and tryptophan units.

Effect of papaya ringspot virus on growth, yield and quality of papaya (Carica papaya) cultivars

The field experiment was conducted during 2008 – 2010 to study the effect of papaya ringspot virus – type P on growth, yield, and quality of papaya (Carica papaya L.) varieties under PRSV infected conditions at Tamil Nadu Agricultural University, Coimbatore. Significant variation was observed for disease score, DAS-ELISA, tree growth, fruit parameters, yield, and quality characters among the varieties evaluated. The results revealed that all the papaya varieties tested were ELISA positive and PRSV adversely affected the growth, yield and quality of papaya varieties. Among the cultivars evaluated, CP 50 performed better even under PRSV infected conditions and recorded the lowest disease score (1.9), ELISA value (0.198), highest plant height (255.60 cm), stem girth (41.76 cm), number of leaves (41.78), maximum yield (29.26 fruits/plant), dry papain production (8.3 g dry papain/fruit) and tyrosine unit (139.2).

Additive Effect of Pronase on the Eradication Rate of First-Line Therapy for Helicobacter pylori Infection.

Background/AimsHelicobacter pylori colonizes on the apical surface of gastric surface mucosal cells and the surface mucous gel layer. Pronase is a premedication enzyme for endoscopy that can disrupt the gastric mucus layer. We evaluated the additive effects of pronase combined with standard triple therapy for H. pylori eradication.MethodsThis prospective, single-blinded, randomized, controlled study was conducted between June and October 2012. A total of 116 patients with H. pylori infection were enrolled in the study (n=112 patients, excluding four patients who failed to meet the inclusion criteria) and were assigned to receive either the standard triple therapy, which consists of a proton pump inhibitor with amoxicillin and clarithromycin twice a day for 7 days (PAC), or pronase (20,000 tyrosine units) combined with the standard triple therapy twice a day for 7 days (PACE).ResultsIn the intention-to-treat analysis, the eradication rates of PAC versus PACE were 76.4% versus 56.1% (p=0.029). In the per-protocol analysis, the eradication rates were 87.5% versus 68.1% (p=0.027). There were no significant differences concerning adverse reactions between the two groups.ConclusionsAccording to the interim analysis of the trial, pronase does not have an additive effect on the eradication of H. pylori infection (ClinicalTrial.gov: NCT01645761).

Tyrosine-mediated two-dimensional peptide assembly and its role as a bio-inspired catalytic scaffold.

In two-dimensional interfacial assemblies, there is an interplay between molecular ordering and interface geometry, which determines the final morphology and order of entire systems. Here we present the interfacial phenomenon of spontaneous facet formation in a water droplet driven by designed peptide assembly. The identified peptides can flatten the rounded top of a hemispherical droplet into a plane by forming a macroscopic two-dimensional crystal structure. Such ordering is driven by the folding geometry of the peptide, interactions of tyrosine and crosslinked stabilization by cysteine. We discover the key sequence motifs and folding structures and study their sequence-specific assembly. The well-ordered, densely packed, redox-active tyrosine units in the YYACAYY (H-Tyr-Tyr-Ala-Cys-Ala-Tyr-Tyr-OH) film can trigger or enhance chemical/electrochemical reactions, and can potentially serve as a platform to fabricate a molecularly tunable, self-repairable, flat peptide or hybrid film.

Energy interactions in amyloid-like fibrils from NNQQNY

We use large-scale MP2 calculations to analyze the interactions appearing in amyloid fibers, which are difficult to determine experimentally. To this end, dimers and trimers of the hexapeptide NNQQNY from the yeast prion-like protein Sup35 were considered as model systems. We studied the energy interactions present in the three levels of organization in which the formation of amyloid fibrils is structured. The structural changes in the hydrogen bonds were studied too. It was found that the most energetic process is the formation of the β-sheet, which is equally due to both hydrogen bonds and van der Waals interactions. The aromatic rings help stabilize these aggregates through stacking of the aromatic rings of tyrosine, the stability produced by the aromatics residues increasing with their aromaticity. The formation of the basic unit of the assembled proto-fiber, the steric zipper, is less energetic and is associated to both dispersion forces and hydrogen bonds. The interactions between pair of β-sheets across the peptide-to-peptide contact through the tyrosine rings are cooperative and due to dispersion effects. Moreover, the strength of this interaction can rationalize the variation of mobility of the aromatic ring in the tyrosine units found in solid NMR experiments.