Coordination chemistry of natural polyphenols and transition metals allows rapid self-assembly of conformal coatings on diverse substrates. Herein, we report that this coordination-driven self-assembly process applies to simple phenolic molecules with monotopic or ditopic chelating sites (as opposed to macromolecular, multitopic polyphenols), leading to surface-confined amorphous films upon metal coordination. Films fabricated from gallic acid, pyrogallol, and pyrocatechol, which are the major monomeric building blocks of polyphenols, have been studied in detail. Pyrocatechol, with one vicinal diol group (i.e., bidentate), has been observed to be the limiting case for such assembly. This study expands the toolbox of available phenolic ligands for the formation of surface-confined amorphous films, which may find application in catalysis, energy, optoelectronics, and the biomedical sciences. ■ INTRODUCTIONModular control over the rational design of supramolecular architectures has been achieved in the last two decades by smart engineering of coordination-driven self-assembly processes. 1 Early prediction of the inherent preferences for directionality and binding affinity within the complementary building blocks of coordination complexes has paved the way for fabricating structures with extended networks of metal clusters bridged by compatible organic ligands. 2,3 Porous coordination polymers or metal−organic frameworks (MOFs) with distinct spatial and geometrical arrangements of the interconnecting motifs are examples of such organic−inorganic hybrid materials. 4−7 These crystalline materials with structurally encoded nano-and microporosities have potential application for gas storage, separations, and sensing. 8−13 On the other hand, surface-bound or freestanding amorphous thin films/coatings are another class of network materials of importance in several branches of science, 14−16 where polymeric compounds are commonly used structural components. Research has also focused on exploring novel strategies to incorporate inorganic moieties in polymeric films to obtain functional hybrid materials that exploit the synergistic effects of the organic and inorganic constituents. 17,18 In this context, processes utilizing self-assembly of coordination complexes are a promising strategy toward facile engineering of thin films with defined properties.Recently, we reported a facile assembly approach that exploits metal−polyphenol interactions, specifically between tannic acid (TA) and iron(III) (Fe III ) ions, to form thin films. 19 Our interest in these metal−polyphenol systems arises from the facile and versatile nature of the assembly process, which produces tunable, dynamic materials. Using TA as a ligand, we demonstrated the formation of capsules with engineered pHresponsive degradation, luminescence, and positron emission, by judicious choice of the incorporated metal, 20 as well as pHresponsive drug delivery vectors 21 and cytoprotective coatings. 22 Furthermore, we reported the assembly of Fe IIIpolyphenol capsules fro...

The synthesis of hybrid functional materials using the coordination-driven assembly of metal-phenolic networks (MPNs) is of interest in diverse areas of materials science. To date, MPN assembly has been explored as monoligand systems (i.e., containing a single type of phenolic ligand) where the phenolic components are primarily obtained from natural sources via extraction, isolation, and purification processes. Herein, we demonstrate the fabrication of MPNs from a readily available, crude phenolic source-green tea (GT) infusions. We employ our recently introduced rust-mediated continuous assembly strategy to prepare these GT MPN systems. The resulting hollow MPN capsules contain multiple phenolic ligands and have a shell thickness that can be controlled through the reaction time. These multiligand MPN systems have different properties compared to the analogous MPN systems reported previously. For example, the Young's modulus (as determined using colloidal-probe atomic force microscopy) of the GT MPN system presented herein is less than half that of MPN systems prepared using tannic acid and iron salt solutions, and the disassembly kinetics are faster (∼50%) than other, comparable MPN systems under identical disassembly conditions. Additionally, the use of rust-mediated assembly enables the formation of stable capsules under conditions where the conventional approach (i.e., using iron salt solutions) results in colloidally unstable dispersions. These differences highlight how the choice of phenolic ligand and its source, as well as the assembly protocol (e.g., using solution-based or solid-state iron sources), can be used to tune the properties of MPNs. The strategy presented herein expands the toolbox of MPN assembly while also providing new insights into the nature and robustness of metal-phenolic interfacial assembly when using solution-based or solid-state metal sources.

Background Diagnostic tests for fish allergy are hampered by the large number of under‐investigated fish species. Four salmon allergens are well‐characterized and registered with the WHO/IUIS while no catfish allergens have been described so far. In 2008, freshwater‐cultured catfish production surpassed that of salmon, the globally most‐cultured marine species. We aimed to identify, quantify, and compare all IgE‐binding proteins in salmon and catfish. Methods Seventy‐seven pediatric patients with clinically confirmed fish allergy underwent skin prick tests to salmon and catfish. The allergen repertoire of raw and heated protein extracts was evaluated by immunoblotting using five allergen‐specific antibodies and patients' serum followed by mass spectrometric analyses. Results Raw and heated extracts from catfish displayed a higher frequency of IgE‐binding compared to those from salmon (77% vs 70% and 64% vs 53%, respectively). The major fish allergen parvalbumin demonstrated the highest IgE‐binding capacity (10%‐49%), followed by triosephosphate isomerase (TPI; 19%‐34%) in raw and tropomyosin (6%‐32%) in heated extracts. Six previously unidentified fish allergens, including TPI, were registered with the WHO/IUIS. Creatine kinase from salmon and catfish was detected by IgE from 14% and 10% of patients, respectively. Catfish L‐lactate dehydrogenase, glyceraldehyde‐3‐phosphate dehydrogenase, pyruvate kinase, and glucose‐6‐phosphate isomerase showed IgE‐binding for 6%‐13% of patients. In salmon, these proteins could not be separated successfully. Conclusions We detail the allergen repertoire of two highly farmed fish species. IgE‐binding to fish tropomyosins and TPIs was demonstrated for the first time in a large patient cohort. Tropomyosins, in addition to parvalbumins, should be considered for urgently needed improved fish allergy diagnostics.

The basicity of highly protonated cytochrome c (cyt c) and myoglobin (myo) ions were investigated using tandem mass spectrometry,i on-molecule reactions (IMRs), and theoretical calculations as af unction of charge state. Surprisingly,h ighly charged protein ions (HCPI) can readily protonate non-polar molecules and inert gases,i ncluding Ar, O 2 ,a nd N 2 in thermal IMRs.T he most HCPIs that can be observed are over 130 kJ mol À1 less basic than the least basic neutral organic molecules known( tetrafluoromethane and methane). Based on theoretical calculations,itispredicted that protonated cyt ca nd myo ions should spontaneously lose ap roton to vacuum for charge states in which every third residue is protonated. In this study,H CPIs are formed where every fourth residue on average is protonated. These results indicate that protein ions in higher charge states can be formed using al ow-pressure ion source to reduce proton-transfer reactions between protein ions and gases from the atmosphere.Electrospray ionization (ESI) is renowned for its ability to form intact, gaseous,m ultiply charged protein ions for rapid and sensitive detection by mass spectrometry.[1] However,the mechanism by which protein ions are formed in ESI is controversial and continues to be actively debated. Thet wo primary competing models to explain ion formation are known as the charge residue model (CRM) [2] and the ion evaporation model (IEM).[3] In both models,a sn eutral molecules evaporate from ac harged droplet, the electric field at the surface of the droplet increases,w hich initiates fission.[4] Such droplet fission events result in the emission of afine stream of smaller droplets that remove less than 1% of the mass but more than 30 %o ft he charge of the precursor droplet. [4,5] In the CRM, sequential droplet evaporation and Coulombic fission events yield acharged droplet that contains asingle analyte ion, which evaporates to dryness via the loss of neutral solvent molecules.Inthe IEM, the electric field on the surface of ah ighly charged droplet near the moment of ion formation is sufficient to result in the ejection of an analyte ion from the surface of the ionic droplet. Themajority of current evidence indicates that fully desolvated protein ions formed from buffered aqueous solutions are formed by the CRM. Charge carriers such as solvated hydronium ions can be lost via ion evaporation during the ESI process. [6] Recently,the chain-ejection model (CEM), [7] which is related to the IEM, was proposed to explain the formation of protein ions from denaturing solutions based on results from molecular dynamics simulations. [7] In the CEM, ad enatured, disordered protein chain is ejected from ah ighly charged, nanometer-sized ionic droplet. As the protein ion protrudes and is ejected from the droplet, proton transfer to the protein ion can occur. However,t he mechanism by which highly charged protein ions (HCPIs) are formed from denaturing solutions is less well established with evidence supporting both the CRM [8] and CEM/IEM h...

Porphyromonas gingivalis and Tannerella forsythia use the type IX secretion system to secrete cargo proteins to the cell surface where they are anchored via glycolipids. In P. gingivalis, the glycolipid is anionic lipopolysaccharide (A-LPS), of partially known structure. Modified cargo proteins were deglycosylated using trifluoromethanesulfonic acid and digested with trypsin or proteinase K. The residual modifications were then extensively analyzed by tandem mass spectrometry. The C terminus of each cargo protein was amide-bonded to a linking sugar whose structure was deduced to be 2-N-seryl, 3-N-acetylglucuronamide in P. gingivalis and 2-N-glycyl, 3-N-acetylmannuronic acid in T. forsythia. The structures indicated the involvement of the Wbp pathway to produce 2,3-di-N-acetylglucuronic acid and a WbpS amidotransferase to produce the uronamide form of this sugar in P. gingivalis. The wbpS gene was identified as PGN_1234 as its deletion resulted in the inability to produce the uronamide. In addition, the P. gingivalis vimA mutant which lacks A-LPS was successfully complemented by the T. forsythia vimA gene; however, the linking sugar was altered to include glycine rather than serine. After removal of the acetyl group at C-2 by the putative deacetylase, VimE, VimA presumably transfers the amino acid to complete the biosynthesis. The data explain all the enzyme activities required for the biosynthesis of the linking sugar accounting for six A-LPS-specific genes. The linking sugar is therefore the key compound that enables the attachment of cargo proteins in P. gingivalis and T. forsythia. We propose to designate this novel linking sugar biosynthetic pathway the Wbp/Vim pathway. IMPORTANCE Porphyromonas gingivalis and Tannerella forsythia, two pathogens associated with severe gum disease, use the type IX secretion system (T9SS) to secrete and attach toxic arrays of virulence factor proteins to their cell surfaces. The proteins are tethered to the outer membrane via glycolipid anchors that have remained unidentified for more than 2 decades. In this study, the first sugar molecules (linking sugars) in these anchors are identified and found to be novel compounds. The novel biosynthetic pathway of these linking sugars is also elucidated. A diverse range of bacteria that do not have the T9SS were found to have the genes for this pathway, suggesting that they may synthesize similar linking sugars for utilization in different systems. Since the cell surface attachment of virulence factors is essential for virulence, these findings reveal new targets for the development of novel therapies.