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Journal of the American Chemical Society 145(15), 8285-8290 (2023). doi:10.1021/jacs.3c00581, Published by American Chemical Society Publications, Washington, DC

International audience; Fe/N/C single-atom catalysts containing Fe−N x sites prepared by pyrolysis are promising cathode materials for fuel cells and metal-air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2- or N3-chelating coordination structures with preorganized aromatic rings in a 1,12-diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe−N 4 sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe−N 4 sites without iron aggregates. X-ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3-coordination is more effectively converted to Fe−N 4 sites catalyzing ORR with a TOF value of 0.21 e∙site −1 ∙s −1 at 0.8 V vs RHE. This indicates that the formation of Fe−N 4 sites is controlled by precise tuning of the chemical structure of the iron complex precursor.

Incorporation of a synthetic metal catalyst into a protein scaffold yields a biohybrid catalyst, with a remarkable performance in aqueous media and the broad reaction scope of organometallic catalysts. A major challenge for efficient catalysis is the design of the interface between the protein scaffold and the metal catalyst. Until now, protein scaffolds have primarily been engineered by exchanging individual amino acids to anchor metal catalysts and alter their immediate environment. Here, cavity size engineering of the β-barrel protein nitrobindin was performed by duplicating multiple β-strands to generate an expanded variant. The approach of cavity size engineering enabled covalent incorporation of bulky catalysts at excellent coupling efficiencies and yielded excellent conversions in olefin metathesis, including ring-closing metathesis, ring-opening metathesis polymerization, and cross metathesis (conversions up to 99% and turnover numbers up to 10000).

Horseradish peroxidase apoprotein (apoHRP) was immobilized on a heme-modified polythiophene film, which was electropolymerized on an indium tin oxide surface to yield immobilized and reconstituted HRP. The HRP-immobilized electrode exhibits a 6-fold enhanced electrochemical response toward hydrogen peroxide reduction relative to having the protein randomly immobilized on the polythiophene electrode. This indicates that the insertion of the heme moiety into the heme pocket of HRP leads to an increase in the electrocatalytic current.

A unique π-expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β-barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N-(1-pyrenyl)maleimide (Pyr) to prepare a series of NB-Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB-Pyr indicates that azachalcone (aza), which is a dienophile for a Diels-Alder (DA) reaction, is efficiently incorporated within the pyrene-linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB-Pyr in the presence of CuII ion in high yield and high enantio- and regioselectivity.

A WO3 photoelectrode immobilizing a fibrous gold nanoparticle (AuNP) assembly using an amyloid-β (Aβ) peptide was constructed and its ability for photocurrent generation upon visible light irradiation was investigated. AuNPs attached using Aβ peptide (Aβ-AuNP) assemble with a fibrous structure at pH 4.5, which disperses at pH 11. The modified Aβ-AuNPs are immobilized on the surface of WO3 fabricated on a fluorine-doped tin oxide (FTO) electrode (Aβ-AuNPass@WO3/FTO or Aβ-AuNPdis@WO3/FTO, respectively). The photocurrent generation response of the Aβ-AuNPass@WO3/FTO electrode is clearly increased relative to that of Aβ-AuNPdis@WO3/FTO upon visible light irradiation (λ = 420–750 nm), indicating that the fibrous AuNP assembly enhances the visible light response of the WO3 photoelectrode.

ConspectusIn nature, heme cofactor-containing proteins participate not only in electron transfer and O2 storage and transport but also in biosynthesis and degradation. The simplest and representative cofactor, heme b, is bound within the heme pocket via noncovalent interaction in many hemoproteins, suggesting that the cofactor is removable from the protein, leaving a unique cavity. Since the cavity functions as a coordination sphere for heme, it is of particular interest to investigate replacement of native heme with an artificial metal complex, because the substituted metal complex will be stabilized in the heme pocket while providing alternative chemical properties. Thus, cofactor substitution has great potential for engineering of hemoproteins with alternative functions. For these studies, myoglobin has been a focus of our investigations, because it is a well-known oxygen storage hemoprotein. However, the heme pocket of myoglobin has been only arranged for stabilizing the heme-bound dioxygen, so the st...

Photoinduced charge separation on a hybrid titanium dioxide (TiO2) surface with a gold nanoparticle (AuNP) assembly immobilized via a biotin-streptavidin interaction was visualized by Kelvin force microscopy (KFM). Biotinylated AuNP (Biot-AuNP) with a diameter of ca. 15 nm was assembled using streptavidin (STV) and the AuNP assembly was immobilized on a TiO2 surface modified with 1-(3-aminopropyl)silatrane. KFM reveals that the local contact potential difference (CPD) of dispersed AuNP, which is −17 ± 4.2 mV in the dark, undergoes a negative shift of −46 ± 3.0 mV upon UV-irradiation (λ=240-300 nm). In contrast, the AuNP assembly on the TiO2 surface exhibits a greater negative shift of −58 ± 6.0 mV of the CPD, although the CPD value of −16 ± 5.8 mV in the dark is similar to that of the dispersed AuNP. KFM visualization demonstrates that assembly of the AuNP on the TiO2 surface contributes to efficient storage of the negative charge generated by excited electrons in TiO2 during photoinduced charge separation.

A supramolecular conjugate of myoglobin (Mb) and water-soluble poly(acrylate), (PA5k and PA25k , where 5k and 25k represent the molecular weight of the polymers, respectively), is constructed on the basis of a noncovalent heme-heme pocket interaction. The modified heme with an amino group linked to the terminus of one of the heme-propionates is coupled to the side-chain carboxyl groups of poly(acrylate) activated by N-hydroxysuccinimide. The ratios of the heme-modified monomer unit and the unmodified monomer unit (m:n) in the polymer chains of Heme-PA5k and Heme-PA25k were determined to be 4.5:95.5 and 3.1:96.9, respectively. Subsequent addition of apoMb to the conjugated polymers provides Mb-connected fibrous nanostructures confirmed by atomic force microscopy. A mixture of the heme-modified polymer and dimeric apomyoglobin as a cross-linker forms a microgel in which the reconstituted myoglobin retains its native exogenous ligand binding activity.

A series of Grubbs–Hoveyda type catalyst precursors for olefin metathesis containing a maleimide moiety in the backbone of the NHC ligand was covalently incorporated in the cavity of the β-barrel protein nitrobindin. By using two protein mutants with different cavity sizes and choosing the suitable spacer length, an artificial metalloenzyme for olefin metathesis reactions in water in the absence of any organic cosolvents was obtained. High efficiencies reaching TON > 9000 in the ROMP of a water-soluble 7-oxanorbornene derivative and TON > 100 in ring-closing metathesis (RCM) of 4,4-bis(hydroxymethyl)-1,6-heptadiene in water under relatively mild conditions (pH 6, T = 25–40 °C) were observed.

meso-Monobenzoporphycene (mMBPc) and meso-dibenzoporphycene (mDBPc), in which one or two benzene moieties are fused at ethylene-bridged positions (meso-positions) of porphycene, were prepared in an effort to further delocalize the π-electrons within the porphycene molecule. mMBPc and mDBPc were fully characterized by mass spectrometry, (1)H and (13)C NMR spectroscopy, and X-ray crystallography. The longest-wavelength Q-bands of mMBPc and mDBPc are red-shifted by 92 nm and 418 nm, respectively, compared to that of the unsubstituted porphycene (Pc). Electrochemical measurements indicate that the HOMO is destabilized and the LUMO is stabilized by the fused benzene moieties at the meso positions. Furthermore, both XPS and theoretical studies support the presence of a cis tautomeric form in the ground state of mDBPc, despite the fact that essentially all known porphycene derivatives adopt the trans tautomeric form.

A non-precious metal catalyst (NPMC) promoting a four-electron oxygen reduction reaction (ORR) was synthesized by heat treatment of myoglobin (Mb) containing a heme (iron protoporphyrin IX) as a source of iron, nitrogen, and carbon atoms. Samples of the mixture of Mb and carbon black (Vulcan XC72R: VC) were pyrolyzed at 740, 840, 940, 1040 or 1140°C under N2flow. The microstructures of the carbonized Mb catalysts were characterized by XRD, Raman spectroscopy, XPS, and TEM. Results indicate that the iron-containing active site is embedded within the surface structure in an amorphous domain of the carbon materials. The catalyst ink in a 0.05 wt% Nafion solution in isopropanol was coated onto a glassy carbon electrode and the ORR activity of Mb-based NPMCs was evaluated in a rotating disk electrode experiment in an O2-saturated 0.1 M HClO4solution at 25°C. The catalyst synthesized at 940°C has the highest ORR activity in terms of the onset potential and the current density. In contrast, pyrolytic temperatures above 940°C decrease the activity, suggesting that the active structure of the catalyst apparently decomposes at higher temperatures. The Koutecky–Levich plots indicate that the Mb-based catalyst prepared at 940°C catalyzes four-electron ORR (n = ca. 4). The catalysts prepared at other temperatures have n values of 3.6 at 740°C, 3.7 at 840°C, and 2.9 at 1040°C. The ORR of Mb/VC is diffusion-controlled at potentials lower than 0.3 V (vs. RHE) and the onset potential is 0.84 ± 0.01 V.

Nonprecious metal electrocatalysts are being explored as alternatives to platinum-group metal electrocatalysts for the oxygen reduction reaction (ORR) which is required for cathode materials in fuel cells. Herein, we describe a new method for preparing bimetallic nitrogen-containing carbon catalysts with high ORR activity using π-expanded M(salen) precursors. The M/N/C and bimetallic FeM/N/C ORR catalysts were obtained by pyrolysis of a mixture of a carbon support (Vulcan XC-72R) and the metal complex as a precursor. The bimetallic FeCu catalyst prepared from Fe and Cu complexes with the N,N′-bis(2-hydroxy-1-naphthylidene)-1,2-phenylenediamine ligand (2NAPD) is found to have an onset potential of 0.87 V, which is positively shifted by 50 mV from that of the catalyst prepared from the monometallic Fe(2NAPD) complex. The FeCu/N/C catalyst promotes efficient four-electron reduction in the ORR. High-resolution transmission electron microscopy studies reveal that both Fe and Cu metals together with pyridinic nitrogen species are highly dispersed within the carbonaceous structure in FeCu/2NAPD@VC, suggesting that the N-coordinated Fe and Cu sites promote efficient four-electron reduction of O2. This new methodology facilitates design of nonprecious bimetallic carbon catalysts with excellent ORR activity.

The O2 adduct of an aqueous synthetic heme/copper model system built on a porphyrin/cyclodextrin supramolecular complex has been characterized., In mitochondria, cytochrome c oxidase (CcO) catalyses the reduction of oxygen (O2) to water by using a heme/copper hetero-binuclear active site. Here we report a highly efficient supramolecular approach for the construction of a water-soluble biomimetic model for the active site of CcO. A tridentate copper(ii) complex was fixed onto 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(iii) (FeIIITPPS) through supramolecular complexation between FeIIITPPS and a per-O-methylated β-cyclodextrin dimer linked by a (2,2′:6′,2′′-terpyridyl)copper(ii) complex (CuIITerpyCD2). The reduced FeIITPPS/CuITerpyCD2 complex reacted with O2 in an aqueous solution at pH 7 and 25 °C to form a superoxo-type FeIII–O2–/CuI complex in a manner similar to CcO. The pH-dependent autoxidation of the O2 complex suggests that water molecules gathered at the distal Cu site are possibly involved in the FeIII–O2–/CuI superoxo complex in an aqueous solution. Electrochemical analysis using a rotating disk electrode demonstrated the role of the FeTPPS/CuTerpyCD2 hetero-binuclear structure in the catalytic O2 reduction reaction.

Supramolecular assembly of an engineered hemoprotein with an externally-attached heme moiety via an azobenzene or stilbene linker demonstrates drastic structural transitions between two distinct forms: the thermodynamically stable fiber-type assembly and the kinetically trapped metastable micelle-type assembly induced by transient thermal stimulus.

Heme can be removed from a number of native hemoproteins, thus forming corresponding apoproteins, each of which provides a site for binding of a metal complex. In one example, myoglobin, an O2 storage protein, can be reconstituted with iron porphycene to dramatically enhance the O2 affinity. Although it is known that myoglobin has poor enzymatic activity, the insertion of iron corrole or iron porphycene into apomyoglobin increases its H2O2-dependent peroxidase/peroxygenase activities. Furthermore, reconstitution with manganese porphycene promotes hydroxylation of an inert CH bond. It is also of interest to insert a non-porphyrinoid complex into an apoprotein. A cavity of apocytochrome c has been found to bind a diiron carbonyl complex, serving as a functional model of diiron hydrogenase. Aponitrobindin has a rigid β-barrel structure that provides an excellent cavity for covalently anchoring a metal complex. A rhodium complex embedded in the cavity of genetically modified nitrobindin has been found to promote stereoselective polymerization of phenylacetylene.

The hydrogen-evolving diiron complex, (μ-S)2Fe2(CO)6 with a tethered maleimide moiety was synthesized and covalently embedded within the cavity of a rigid β-barrel protein matrix by coupling a maleimide moiety to a cysteine residue within the β-barrel. The (μ-S)2Fe2(CO)6 core within the cavity was characterized by UV–vis absorption and a characteristic CO vibration determined by IR measurements. The diiron complex embedded within the cavity retains the necessary catalytic activity (TON up to 130 for 6 h) to evolve H2 via a photocatalytic cycle with a Ru photosensitizer in a solution of 100 mM ascorbate and 50 mM Tris/HCl at pH 4.0 and 25 °C.

Two different types of artificial glycosylated haemins (glycohaemins), in which a monosaccharide (galactose) or a disaccharide (lactobionic acid, 4-O-β-galactopyranosyl-d-gluconic acid) was introduced at the terminals of the two haem-propionate side chains, were synthesised to serve as a designed interface on the myoglobin surface. These glycohaemins were successfully inserted into apomyoglobin to yield an artificial glycoprotein by the conventional method. The interprotein interaction between the reconstituted myoglobin and peanut agglutinin lectin (PNA), a β-galactose-recognising protein, was confirmed by two different assay systems, i.e. a fluorometric assay using the fluorescein isothiocyanate-labelled lectin and an ELISA-like assay using the peroxidase-labelled lectin. The results revealed that each myoglobin reconstituted with the glycohaemin makes a complex with PNA, in which the glycoprotein with the disaccharides showed a higher binding affinity with the lectin compared to the glycoprotein with t...

Neutral zinc porphyrin containing flexible alkyl linker, 5-[4-(5-hydroxypentyloxy)phenyl]-10,15,20-tri-p-tolylporphyrinatozinc, was attached to the 5′ ends of 20- and 30-bp oligodeoxynucleotides (O...

Zinc finger fusion proteins, having a Ca-binding site from troponin C, were created to develop Ca-responsive regulation of DNA binding. The typical zinc finger folding of a novel fusion protein with a single finger, F2-Tn, was investigated using UV-vis spectroscopy of the Co-substituted form and CD experiments. Detailed structural analyses of F2-Tn/Zn2+ using NMR experiments and structural calculations clarify that our fusion protein gives a native zinc finger folding with the artificial Ca-binding domain intervening two helices. The Ca-responsive DNA-binding affinity of troponin-fused protein with two fingers (using F1F2-Tn) was investigated by electrophoretic mobility shift assay (EMSA). EMSA analyses of F1F2-Tn were performed under the conditions of various concentrations of the Ca ion. F1F2-Tn has a Kd value of 5.8 nM in the absence of Ca ion and shows a higher Kd value of 13 nM in the presence of 100 equiv of Ca ion. The artificially designed fusion zinc finger protein with a Ca-binding domain has Ca-responsive DNA-binding affinity. It is leading to a better understanding of the construction of zinc finger-based artificial transcriptional factors with a Ca switch.

The formation of the NH···O hydrogen bonds of carboxylic acids, 2,6-(t-BuCONH)2C6H3COOH (1) and 2-t-BuCONH-6-MeC6H3COOH (2), carboxylate, [NEt4][2,6-(t-BuCONH)2C6H3COO] (3), and a mixed complex, [N...

Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin–avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin–biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area., High-energy particles can be used for precise fabrication of nanostructures by inducing cross-linking between structures. Here the authors use a single particle fabrication technique to assemble protein nanowires, giving structures with high aspect ratios retaining biological functions.

The O2-binding carboxylate-bridged diiron site in DcrH-Hr with an engineered His residue in place of Ile119 promotes the oxidation of guaiacol and 1,4-cyclohexadiene upon addition of H2O2., The O2-binding carboxylate-bridged diiron site in DcrH-Hr was engineered in an effort to perform the H2O2-dependent oxidation of external substrates. A His residue was introduced near the diiron site in place of a conserved residue, Ile119. The I119H variant promotes the oxidation of guaiacol and 1,4-cyclohexadiene upon addition of H2O2.

Artificial prosthetic groups tethering a polyamine moiety at the terminal of two peripheral heme–propionate side chains as a molecular interface were inserted into apocytochrome b562 to provide pos...

The title compound, {[Tb(C11H11N2O4)3(H2O)3]·H2O}n, has a Tb ion coordinated by bulky benzoate ligands. The Tb ion coordination sphere is occupied by nine O atoms, five from benzoate groups, three from water mol­ecules and one from an amide carbonyl group of a neighboring ligand. Five amide NH groups of the three ligands are involved in intramolecular N—H⋯O hydrogen bonds.

In the title compound, C46H36N2O3, very bulky tri­phenyl­methyl groups interfere with intermolecular interactions; intramolecular hydrogen bonds N—H⋯O—H⋯O=C between the phenol and two amide groups are observed in the structure.

The title complex, chloro(6,6′′-dimesityl-2,2′:6′,2′′-ter­pyri­dine)palla­dium(II) tetrachloropalladium(II) dichloromethane tetrasolvate, [PdIICl(dmtpy)]2[PdIICl4]·4CH2Cl2 (dmtpy is 6,6′′-dimesityl-2,2′:6′,2′′-ter­pyridine, C33H31N3), was synthesized and the crystal structure of the di­chloro­methane tetra­solvate has been determined. The complex has a distorted square-planar coordination formed by three N atoms and a chloride ion, the distortion caused by the extremely bulky substituted terpyridyl ligand.

A native protein in a biological system spontaneously produces large and elegant assemblies via self-assembly or assembly with various biomolecules which provide non-covalent interactions. In this context, the protein plays a key role in construction of a unique supramolecular structure operating as a functional system. Our group has recently highlighted the structure and function of hemoproteins reconstituted with artificially created heme analogs. The heme molecule is a replaceable cofactor of several hemoproteins. Here, we focus on the successive supramolecular protein assemblies driven by heme–heme pocket interactions to afford various examples of protein fibers, networks and three-dimensional clusters in which an artificial heme moiety is introduced onto the surface of a hemoprotein via covalent linkage and the native heme cofactor is removed from the heme pocket. This strategy is found to be useful for constructing hybrid materials with an electrode or with nanoparticles. The new systems described herein are expected to lead to the generation of various biomaterials with functions and characteristic physicochemical properties similar to those of hemoproteins.

Supramolecular hemoprotein assemblies via heme-heme pocket interaction were prepared by synthetic heme dimers containing a linker with charged amino acids and apohemoprotein disulfide dimers. The mixture of the negatively charged heme dimer and the apomyoglobin dimer provides heterotropic fibrous hemoprotein assemblies, which were characterized by size-exclusion chromatography (SEC) and atomic force microscopy (AFM).

Our group recently prepared a hybrid catalyst containing a rhodium complex, Rh(Cp)(cod), with a maleimide moiety at the peripheral position of the Cp ligand. This compound was then inserted into a β-barrel protein scaffold of a mutant of aponitrobindin (Q96C) via a covalent linkage. The hybrid protein is found to act as a polymerization catalyst and preferentially yields trans-poly(phenylacetylene) (PPA), although the rhodium complex without the protein scaffold normally produces cis PPA.

A myoglobin–cadmium telluride quantum dot conjugate was constructed using an artificial heme modified with a thiol moiety as a linker. Irradiation of the myoglobin–cadmium telluride conjugate generated the photoreduced ferrous myoglobin via an electron transfer from the photoexcited quantum dot, leading to the formation of CO-bound myoglobin under a CO atmosphere.

All connected: a protein-immobilized electrode comprising hierarchical assemblies of photoactive cytochrome b(562) reconstituted with zinc protoporphyrin IX exhibits remarkably enhanced photocurrent generation relative to an electrode bearing a single zinc-substituted hemoprotein layer. The protein oligomers, which bear a covalently linked protoporphyrin group, assemble by a supramolecular heme/heme pocket interaction.

It is shown that an intramolecularly linked cofactor dyad enforces the assocn. of two different proteins according to a predefined program. The present study demonstrates that the heme bis(biotin) conjugate contains the information to produce a stable 2:1 Mb SAv complex. Propagation of this moiety into a polymer results from using a dimericMb building block. The supramol. composite fiber obsd. by AFM techniques is the first example of a chem. programmed heterotropic protein copolymer with alternating alignment. The heme cofactor's dioxygen binding function is maintained upon incorporation within the fiber suggesting that this approach is well suited for the creation of functional nanobiomaterials. Immobilization of the first building block will allow to: (1) study the programmed assembly by quartz microbalance anal. (2) increase the complexity by varying the capping groups on the dyad and/or (3) introduce addnl. protein building blocks to afford protein polymers with a desired sequence and function. Potential applications include multifunctional catalysis artificial photosynthesis and smart nanomaterials for medical applications. [on SciFinder(R)]

The diiron carbonyl cluster is held by a native CXXC motif, which includes Cys14 and Cys17, in the cytochrome c sequence. It is found that the diiron carbonyl complex works well as a catalyst for H(2) evolution. It has a TON of ∼80 over 2 h at pH 4.7 in the presence of a Ru-photosensitizer and ascorbate as a sacrificial reagent in aqueous media.

The title compound, C12H19OP4, with a bulky group, exhibits one-dimensional hydrogen-bonded chains of bifurcated P—OH⋯O=P interactions. This one-dimensional chain structure with double P—OH⋯O=P hydrogen bonds is induced by the bulky iso­propyl groups.

The application of low-flux sunlight begins with the synthesis of effective antenna systems. This requires the development of dye integrates with optimized dye orientation for effective energy transfer. We here report a series of peptide-linked porphyrin arrays, denoted by Boc-(Por(Zn,S))(n)-OBu(t) (n = 2, 4, and 8), that change their dye orientation to increase fluorescence responsively to additive reagents. The B-band absorption (AB) regions of the arrays show blue shifts (dimer, 407.6 nm; tetramer, 408.2 nm; octamer, 407.8 nm) in organic solvents as compared to that of Boc-Por(Zn,S)-OBu(t) (monomer, 422.6 nm) and the fluorescence yield Phi' of the arrays decreases with increasing n, obeying the relationship Phi' = 0.03/n(1.5); however, the arrays are tuned up in fluorescence emission by the addition of 1,2-diaminoethane (en). The addition of a sufficient amount of en increases the fluorescence of the porphyrins in monomer, dimer, tetramer, and octamer by approximately 5, approximately 12, approximately 12, and730 times, respectively, when compared with that observed in the absence of en. This also causes asymptotic red shifts in absorption (AB) bands (B-band lambda(max): 410 to 429-430 nm), as well as changes in circular dichroism (CD) spectra, and makes porphyrins approach new mutual asymmetric orientations. Our results show the potentiality of the tunable dye polymers that are a posteriori optimized in dye orientation and fluorescence emission by additive reagents for the development of effective light-harvesting materials.

Three new polynuclear Ca(II)- and Na(I) phosphate complexes with two strategically oriented bulky amide groups, 2,6-(PhCONH)(2)C(6)H(3)OPO(3)H(2), were synthesized, including one with a zigzag-chain, [Ca(II)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](H(2)O)(4)(EtOH)](n), a cyclic-octanuclear form, [Ca(II)(8)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](8)(O=CHNMe(2))(8)(H(2)O)(12)], and a hexanuclear complex, (NHEt(3))[Na(3)[O(3)POC(6)H(3)-2,6-(NHCOPh)(2)](2)(H(2)O)(MeOH)(7)]. X-ray crystallography revealed that all have an unsymmetric ligand position due to the bulky amide groups. A dynamic transformation of the Ca(II) zigzag-chain structure to the cyclic-octanuclear complex was induced by changing coordination of DMF molecules, which caused a reorganization of the intermolecular/intramolecular hydrogen bond network.

The peptide ligand, Cys-Pro-Leu-Cys, was covalently immobilized on the surface of quartz via (3-aminopropyl) triethoxysilane (APTES) by the general peptide-synthesis method; then, Ni2+ was introduc...

A novel poly(vinyl phosphate) ligand was synthesized as a model of biopolymer ligands containing the OH···O hydrogen bonds and CaHPO4·2H2O (brushite) composites with the polymer ligands were also p...

Poly{1-[(Z)-3-carboxyl-2-propenylaminomethyl]ethylene} binding on the edge of calcite crystals was observed directly by 13C CP/MAS NMR and FE/SEM measurements. Comparing the results taken both befo...

13C CP/MAS NMR and FE/TEM measurements of the aragonite brick of the nacreous layer of Pinctada fucata indicate that it assembles with highly oriented aragonite nanocrystals, which are regulated by biopolymers.

The title compound, [CuI(dmtpy)(NCMe)](PF6) (dmtpy = 6,6′′-dimesityl-2,2′:6′,2′′-ter­pyridine) or [Cu(C2H3N)(C33H31N3)](PF6), displays a distorted square-planar coordination, with four N atoms from dmtpy and aceto­nitrile mol­ecules, as a result of the extremely bulky terpyridyl ligand.

Artificial self-assembling systems comprised of proteins have the potential not only for mimicking naturally occurring protein clusters but also for creating functionalized supramolecular polymers. Here we report a new type of a supramolecular protein polymer which utilizes the original character and reactivity of the monomer protein. Myoglobin, an oxygen storage hemoprotein, was chosen as the monomer unit and was provided with an externally-attached heme on the protein surface which drives the formation of the fibrous supramolecular assembly through successive interprotein interactions between the external heme and the protein matrix. This assembly governed by myoglobin characteristics shows chemically-responsive stability and can be converted into extremely large protein clustersvia cross-linking. Interestingly, the assembly retains the oxygen storage function. Our present system can be used for construction of smart nanobiomaterials using various hemoproteins.

Interaction of apohemoprotein with a covalently immobilized heme moiety onto a gold nanoparticle surface resulted in supramolecular hemoprotein-gold nanoparticle conjugates. The addition of an apohemoprotein dimer further led to a densely-packed hemoprotein-gold nanoparticle assembly, which was visualized by TEM and AFM measurements.

Novel zigzag-chain, cyclic-octanuclear Ca- and hexanuclear Na-phosphate complexes were synthesized using bulky amide aryl dihydrogen phosphate ligands. The metal complexes with bulky amides have a unique unsymmetric ligand position. The zigzag-chain structure transformed into a cyclic-octanuclear one in cooperating with the coordination of DMF molecule and reorganization of the intermolecular/intramolecular hydrogen bond networks. biomineral calcium phosphate complex NH···O hydrogen bonds polynuclear complex structural transformation