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We report here on a new class of siderophores isolated from Rhodococcus erythropolis IGTS8, the first structurally characterized from any species of Rhodococcus and for which we suggest the name heterobactins. These siderophores consist of a tripeptide of sequence (N-OH)-L-Orn-Gly-D-Orn-(δ-N-dihydroyxbenzoate). The alpha amino group of the D-Orn is derivatized either as a 2-hydroxybenzoxazolate in heterobactin A or remains free in heterobactin B. The structures were determined by a combination of amino acid analysis, mass spectrometry and NMR methods. The two new compounds are true siderophores in that they relieve iron limited growth in the producing strain. The heterobactins are also transported by other non-producing bacteria. Growth promotion tests using various transport mutants revealed that in E. coli heterobactin A is only recognized by the catecholate receptor Cir while heterobactin B is taken up in both E. coli and A. flavescens JG9 via a hydroxamate transport system.

The hydrogen-bond accepting ligand K[TpCO2Et,Me] was prepared and its complexes with divalent Ni, Co, Mn and Cu reveal a stabilization of penta- or hexa-coordinate metal aquo complexes of the general form [TpCO2Et,MeM(H2O)x] (x = 2 or 3) which are unprecedented for the alkyl substituted Tp analogs. These complexes make good structural models for many of the enzymes of the vicinal oxygen chelate superfamily.

The Zn(II)CH3 complexes of the heteroscorpionate ligands (3-tert-butyl-2-hydroxy(or thio)-5-methylphenyl)bis(3,5-dimethylpyrazolyl)methane, L1OH or L2SH react with pentafluorothiophenol (HSPhF5). For [(L1O)ZnCH3], this resulted in the formation of the pseudo-tetrahedral Zn(II) complexes [(L1O)ZnSPhF5] (1) or [(L1OH)Zn(SPhF5)2] depending on the ratio of pentafluorothiophenol used. However, when [(L2S)ZnCH3] was reacted with 1 or 2 equiv. of HSPhF5, in addition to the expected [(L1S)ZnSPhF5] (2) or [(L1SH)Zn(SPhF5)2] (3), one additional product, [(L2S)Zn(L2S)Zn(SPhF5)2] (4) was observed. The structures of four of the complexes, i.e. [(L1O)ZnSPhF5] (1), [(L2S)ZnSPhF5] (2), [(L2SH)Zn(SPhF5)2] (3), and [(L2S)Zn(L2S)Zn(SPhF5)2] (4) have been determined by X-ray crystallography.

A series of pseudotetrahedral and octahedral zinc(II) complexes of the heteroscorpionate ligand bis(3,5-dimethylpyrazolyl)(1-methyl-1-sulfanylethyl)methane (L3SH) have been synthesized and most characterized by X-ray crystallography. Pseudotetrahedral complexes isolated include [Zn(L3S)(CH3)], [Zn(L3S)(Cl)], [Zn(L3S)(OAc)], [Zn(L3S)(SPhF5)], [Zn(L3S)(SBz)] (Bz = CH2Ph), [Zn(L3S)(OPhp-NO2)], and [Zn(L3S)2]. In addition, the octahedral complex [Zn2{(L3S)2Zn}{O2P(OPh)2}4] was also synthesized. Comparisons between these complexes and those of the corresponding tris(pyrazolyl)borate, Tp−, or aromatic phenol or benzenethiolate ligands (L1O)− and (L2S)− reveal significant differences. Among these is a change in binding of acetate from pure unidentate to anisobidentate as the ligand donor is changed from S to N to O. Trends such as these may aid in understanding how the donor set affects the structure and reactivity at pseudotetrahedral zinc centers in metalloproteins.

Nine new pseudotetrahedral Zn(II) complexes of the heteroscorpionate ligands (3-tert-butyl-2-hydroxy(or thio)-5-methylphenyl)bis(3,5-dimethylpyrazolyl)methane, L1OH or L2SH, have been prepared and characterized (in most cases crystallographically). Complexes isolated include [(L1O)ZnCl], [(L1O)ZnI], [(L1OH)ZnI(2)], [(L1O)ZnCH(3)], [(L1O)ZnOAc], [(L1O)ZnSPh], [(L1O)ZnSBz], [(L2S)ZnCH(3)], [(L2S)ZnSPh], and [(L2S)(2)Zn]. In conjunction with the widely studied tris(pyrazolyl)borates this new series of heteroscorpionates provides a set of isolobal and isoelectronic ligands differing in donor set, i.e. N(3), N(2)O, and N(2)S. Preliminary reactivity studies with HX species, MeI, or trimethyl phosphate suggest differences between the three sets of ligands.

The synthesis and characterization of the Fe(III) and Co(II/III) complexes of tridentate heteroscorpionate ligands, (2-hydroxyphenyl) bis(pyrazolyl)methane, L1, and its derivatives, L2 and L3 are reported. Complexes prepared include [Fe(L)2][ClO4] where L=1–3, [Co(L3)2], [Co(L3)2][BPh4], and [Co(L)2]2Ag(MeCN)[BF4]3 where L=1 and 2. X-ray crystallographic analysis of several of the complexes have been completed. Electrochemical and other methods show that there is an oxidation state and ligand dependant cis/trans isomerization in these complexes.

The synthesis of a trinuclear thiolate bridged NiII system, [Ni3(L5S)4]2+ [L5SH = (2-sulfanylphenyl)bis(pyrazolyl)methane] which contains a linear NiS2NiS2Ni moiety, is reported. Two octahedrally coordinated (L5S)2Ni complexes, in which the thiol sulfurs are mutually cis, constitute the two terminal positions while the central position contains a distorted tetrahedral, four-coordinate, Ni(II) ion. In the presence of alkyl- or aryl-nitriles, such as MeCN, the [Ni3(L5S)4]2+ cation undergoes cleavage and rearrangement reactions to give thiolate bridged dinuclear dications, either [Ni2(L5S)2(MeCN)4]2+ or [Ni2(L5S)2(MeCN)2(H2O)2]2+, in which MeCN ligand N-donors (and/or H2O O-donors) occupy the vacant coordination sites of each Ni2+ atom. An analogous Co(II) dimer is also reported. The trimer → dimer reaction can be reversed by desolvation of [Ni2(L5S)2(MeCN)4]2+ or [Ni2(L5S)2(MeCN)2(H2O)2]2+ by an appropriate non-nitrile solvent, such as MeNO2 resulting in reformation of the [Ni3(L5S)4]2+ cation. Variable temperature magnetic data indicate that the Ni atoms in the trimer are weakly antiferromagnetically coupled while they are weakly ferromagnetically coupled in the dimer.

From the tridentate, mixed functionality ligands, bis(pyrazol-1-yl)methane(phen-2′-ol) (L1OH), bis(3,5-dimethylpyrazol-1-yl)methane(phen-2′-ol) (L2OH), and bis(3-isopropylpyrazol-1-yl)methane(phen-2′-ol) (L3OH), the following Cu(II) complexes have been synthesized, Cu(L1OH)2(solvent)BF42·H2O (1·H2O), Cu(L2OH)(L2O)BF4·H2O (2·H2O), Cu(L2O)2·MeCN·H2O (3·MeCN·H2O), and Cu2(μ-L3O)(L3OH)(μ-OH)(H2O)BF42·0.5CH2Cl2 (4·0.5CH2Cl2). 1, 2 and 4 have been characterized by X-ray crystallography, giving the following structural parameters: 1(MeCN)·MeCN, C30H28N10B2Cu1F8O2, monoclinic, a = 16.581(3); b = 12.041(2); c = 18.111(3) A; β = 103.102(8)°, V = 3521.0(10) A3, space group P21/c, Z=4.2·H2O, C34H39N8B1Cu1F4O3, monoclinic, a=9.513(2); b=26.808(3); c=14.148(5) A; β=90.39(2)°, V=3608.1(12) A3, space group P21/c, Z=4. 4·2(CH3)2CO, C45H49N8B2Cu2F8O5, monoclinic, a = 10.934(3); b = 21.701(5); c = 22.646(6) A; β = 96.77(3)°, V = 5336.0(20) A3, space group P21/c, Z=4.

The synthesis and characterization of the tridentate “heteroscorpionate” mixed functionality ligand, (2-thiophenyl)bis(pyrazolyl)methane, L1, is reported. This ligand was used to synthesize the complexes, [Fe(L1)2][ClO4], [Co(L1)2][BPh4], and [V(L1)2][BPh4]. X-ray crystallographic analysis of the latter two complexes gave the following structural parameters: [V(L1)2][BPh4]·MeCN·iPr2O, C58H57N9B1O1S2V1, monoclinic, a = 16.197(2) A, b = 19.281(2) A, c = 17.985(2) A, β = 102.343(9)°, space group P21/c; [Co(L1)2][BPh4]·CH2Cl2, C51H42N8B1Cl2Co1S2, triclinic, a = 12.751(1) A, b = 12.830(1) A, c = 14.740(1) A, α = 98.351(7)°, β = 98.122(6)°, γ = 97.023(8)°, space group P1. An example of the use of this new class of “heteroscorpionate” ligands for systematic comparisons of electronic properties of metal complexes with identical topology that vary only in the nature of one of the donor atoms is given.

The mixed functionality pyrazole/phenol ligand (2-hydroxyphenyl)bis(pyrazolyl)methane, L1OH, has been used to prepare a series of linear trimetallic systems with the general structural motif [M3(L1...

1H NMR spectra on the paramagnetic CoII and NiII, ML2 “sandwich” complexes of the “heteroscorpionate” ligands (2-hydroxyphenyl)bis (pyrazolyl)methane and its derivatives revealed the presence of isomeric, cis ↔ trans equilibria of these complexes in solution. The presence of some of the cis isomer in solution at equilibrium has been exploited to synthesize new heterometallic trinuclear species of the type [M1(L1O)2M2(L1O)2M1][BF4], where M1 (octahedral) and M2 (tetrahedral) are Zn2+, Cu2+, Ni2+, and Co2+. Rearrangements during the synthesis of some of these heterometallic species provided an interesting experimental confirmation of the site preferences (octahedral vs tetrahedral) for the first-row transition metals as predicted on the basis of crystal field stabilization energies. X-ray crystallographic characterization of many of the complexes reported in this study gives the following structural parameters: [Co2(L2O)2Cl2]·MeCN, C36H41N9Cl2Co2O2, monoclinic, a = 10.742(1) A, b = 21.387(2) A, c = 16.890(...

The heterobimetallic complex 1, [LV(mgr;-O)(mgr;-OAc)(2)MnL] (where L = hydridotris(pyrazolyl)borate), has been synthesized and characterized. X-ray crystal structural analysis of 1 gave the following parameters: C(24)H(29)B(2)N(13)O(5)VMn, Cmc2(1), a = 13.364(2) Å, b = 17.383(3) Å, c = 14.132(3) Å, Z = 4, V = 3289.9(16) Å(3). An analysis of the structure, optical and resonance Raman spectroscopies, and magnetic measurements indicates that a V(IV)=O.Mn(II) valence formulation is the best description of the oxo-bridged core in 1, although other resonance forms must also contribute.

The preparation of a new class of mixed functionality biomimetic ligand, (2-hydroxyphenyl)bis(pyrazolyl)methane, L1, (2-hydroxyphenyl)bis(3,5-dimethylpyrazolyl)methane, L2, and (2-hydroxyphenyl)bis(3-isopropylpyrazolyl)methane, L3, is described. These ligands were used to synthesize the nickel(II) complexes, [Ni(L1)2], 1·MeCN; [Ni(L2)2], 2·0.5MeOH and 2·2H2O; [Ni(μ-L2)2NiCl2], 3·2H2O and 3·2CH2Cl2; [Ni3(μ3-Cl)2(μ-L3)2(L3)(MeOH)]Cl, 4·MeOH·4H2O and 4·MeOH·1.42iPr2O; and [Ni3(μ3-OH)2(μ-L3)3][BF4], 5 and 5·2Me2CO. X-ray crystal analysis of 1−5 gave the following structural parameters: 1·MeCN, C28H25N9NiO2, triclinic, a = 10.600(3) A, b = 11.371(3) A, c = 12.194(3) A, α = 71.17(2)°, β = 94.69(2)°, γ = 83.04(2)°, space group P1, Z = 2; 2·2H2O, C34H42N8NiO4, monoclinic, a = 9.037(2) A, b = 19.272(3) A, c = 19.643(3) A, β = 94.69(2)°, space group C2/c, Z = 4; 3·2CH2Cl2, C36H42N8Cl6Ni2O2, monoclinic, a = 13.891(4) A, b = 18.188(7) A, c = 15.012(4) A, β = 92.70(2)°, space group C2/c, Z = 4; 4·MeOH·1.42iPr2O, C67...

The syntheses of a new class of potentially biomimetic, tripodal, mixed functionality ligands, (2-hydroxyphenyl)bis(pyrazolyl)methane (L1), (2-hydroxyphenyl)bis(3,5-dimethylpyrazolyl)methane (L2), and (2-hydroxyphenyl)bis(3-isopropylpyrazolyl)methane (L3), are described. These ligands have been used to prepare the cobalt(II) complexes [Co(L1)2]·2.5MeOH·1.5H2O, 1·2.5MeOH·1.5H2O; [Co(L2)2]·0.5H2O, 2·0.5H2O; [Co(L3)Cl2], 3; and [Co3(μ3-OH)2(μ-L3)2(L3)(H2O)]BF4, 4. X-ray structural analysis of 1−4 gave the following structural parameters: 1, C30H34N8CoO6, triclinic, a = 8.286(2) A, b = 10.053(3) A, c = 10.562(2) A, α = 109.66(2)°, β = 96.57(1)°, γ = 91.11(3)°, space group P1, Z = 1; 2, C38H38N8CoO6, triclinic, a = 8.746(5) A, b = 10.900(5) A, c = 11.399(8) A, α = 70.82(4)°, β = 75.13(5)°, γ = 81.46(4)°, space group P1, Z = 1; 3, C20H26N4Cl4CoO, monoclinic, a = 10.934(2) A, b = 12.404(2) A, c = 19.267(3) A, β = 98.33(1)°, space group P21/n, Z = 4; 4, C58H70N12BCo3F4O9, monoclinic, a = 14.798(5) A, b = 23.65...

Boron in the ocean is generally considered a nonbiological element due to its relatively high concentration (0.4 mM) and depth independent concentration profile. Here we report an unexpected role for boron in the iron transport system of the marine bacterium Marinobacter algicola. Proteome analysis under varying boron concentrations revealed that the periplasmic ferric binding protein (Mb-FbpA) was among the proteins whose expression was most affected, strongly implicating the involvement of boron in iron utilization. Here we show that boron facilitates Fe(3+) sequestration by Mb-FbpA at pH 8 (oceanic pH) by acting as a synergistic anion (B(OH)4(1-)). Fe(3+) sequestration does not occur at pH 6.5 where boric acid (B(OH)3; pK(a) = 8.55) is the predominant species. Borate anion is also shown to bind to apo-Mb-FbpA with mM affinity at pH 8, consistent with the biological relevance implied from boron's oceanic concentration (0.4 mM). Borate is among those synergistic anions tested which support the strongest Fe(3+) binding to Mb-FbpA, where the range of anion dependent affinity constants is log K'(eff) = 21-22. Since the pKa of boric acid (8.55) lies near the pH of ocean water, changes in oceanic pH, as a consequence of fluctuations in atmospheric CO2, may perturb iron uptake in many marine heterotrophic bacteria due to a decrease in oceanic borate anion concentration.

While there has been extensive interest in the use of boron isotope ratios as a surrogate of pH in paleoclimate studies in the context of climate change-related questions, the high (0.4 mM) concentration and the depth-independent (conservative or non-nutrient-like) concentration profile of this element have led to boron being neglected as a potentially biologically relevant element in the modern ocean. Here we report that boron affects the expression of a number of protein and genes in the “algal-associated” Gram-negative marine bacterium Marinobacter algicola DG893. Most intriguingly, a number of these proteins and genes are related to iron uptake. In a recent separate publication we have shown that boron regulates one such iron transport related protein, i.e. the periplasmic iron binding protein FbpA via a direct interaction of the metalloid with this protein. Here we show that a number of other iron uptake related genes are also affected by boron but in the opposite way i.e. they are up-regulated. We propose that the differential effect of boron on FbpA expression relative to other iron transport related genes is a result of an interaction between boron and the global iron regulatory protein Fur.

Iron is an essential element for oceanic microbial life but its low bioavailability limits microorganisms in large areas of the oceans. To acquire this metal many marine bacteria produce organic chelates that bind and transport iron (siderophores). While it has been hypothesized that the global production of siderophores by heterotrophic bacteria and some cyanobacteria constitutes the bulk of organic ligands binding iron in the ocean because stability constants of siderophores and these organic ligands are similar, and because ligand concentrations rise sharply in response to iron fertilization events, direct evidence for this proposal is lacking. This lack is due to the difficulty in characterizing these ligands due both to their extremely low concentrations and their highly heterogeneous nature. The situation for characterizing photoactive siderophores in situ is more problematic because of their expected short lifetimes in the photic zone. An alternative approach is to make use of high sensitivity molecular technology (qPCR) to search for siderophore biosynthesis genes related to the production of photoactive siderophores. In this way one can access their "biochemical potential" and utilize this information as a proxy for the presence of these siderophores in the marine environment. Here we show, using qPCR primers designed to detect biosynthetic genes for the siderophores vibrioferrin, petrobactin and aerobactin that such genes are widespread and based on their abundance, the "biochemical potential" for photoactive siderophore production is significant. Concurrently we also briefly examine the microbial biodiversity responsible for such production as a function of depth and location across a North Atlantic transect.

The syntheses of five mixed ligand vanadium(III) phosphate/phosphonate complexes are described: dinuclear I, [LVCl{μ-(PhO)2PO2}]2; II, [LVCl{μ-Ph2PO2}]2; and III, [LVCl{μ-PhP(H)O2}]2; along with mononuclear IV, [LV{(PhO)2POS}2DMF]; and V, [LV{(PhO)2PO2}]2·H2O where L = hydrotris(pyrazolyl)borate. X-ray crystal structure analysis of I, II, IV, and V gave the following parameters: I, C12H40B2Cl2N12O8P2V2, P1, a = 9.949(4)A, b = 11.732(4) A, c = 12.729(3) A, α = 110.37(1)°, β = 106.78(1)°, γ = 104.36(1)°, Z = 1, V = 1228.8(7) A3; II, C46H98B2Cl10N12O4P2V2, P1, a = 11.801(2) A, b = 12.086(1) A, c = 12.955(2) A, α = 81.99(1)°, β = 65.51(1)°, γ = 62.60(1)°, Z = 1, V = 1491.1(5) A3; IV, C36H37BN7O7P2S2V, P1, a = 11.003(2) A, b = 11.816(2) A, c = 17.167(5) A, α = 98.68(2)°, β = 101.81(2)°, γ = 102.59(2)°, Z = 2, V = 2087.0(6) A3; V, C69.5H65B2N15O8P4V2, C2/c, a = 12.360(2) A, b = 26.362(4) A, c = 23.254(2) A, β = 91.24(8)°, Z = 4, V = 7575(2) A3. Magnetic measurements indicate little or no interaction betwee...

The synthesis and characterization of two linear trinuclear V(III) complexes are described: 1, [LV(μ-(PhO)2PO2)3-V-(μ-(PhO)2PO2)3VL]PF6, and 2, LV(μ-(PhO)2PO2)2(μ-OH)V(μ-(PhO)2PO2)2(μ-OH)VL]ClO4, ...

Culture of the oil-degrading marine bacterium Marinobacter hydrocarbonoclasticus gave the known siderophore petrobactin (1) and the new metabolite petrobactin sulfonate (2), the first marine siderophore containing a sulfonated 3,4-dihydroxy aromatic ring. The structure of petrobactin sulfonate was elucidated from spectral data, resulting in a revision of the NMR assignments of petrobactin.

The reaction of (iPr2N)2PN3 (1) with Fe2(CO)9 in toluene solution at 25°C produces the complex (iPr2N)2P(N3)-Fe(CO)4 (3) with a high yield. The cophotolysis of 1 and Cr(CO)6 in tetrahydrofuran solution results in the formation of (iPr2N)2P(N3)-Cr(CO) 5 (4). Complexes 3 and 4 were found to be stable to UV irradiation (254 nm). The chromium complex 4 and the free phosphine azide (c-Hex2N)2PN3 (2) have been characterized by single-crystal X-ray diffraction.

Correction for 'Surface binding, localization and storage of iron in the giant kelp Macrocystis pyrifera' by Eric P. Miller et al., Metallomics, 2016, 8, 403-411.

Iron is an essential element for all living organisms due to its ubiquitous role in redox and other enzymes, especially in the context of respiration and photosynthesis. The iron uptake and storage systems of terrestrial/higher plants are now reasonably well understood with two basic strategies for iron uptake being distinguished: strategy I plants use a mechanism involving soil acidification and induction of Fe(III)-chelate reductase (ferrireductase) and Fe(II) transporter proteins while strategy II plants have evolved sophisticated systems based on high-affinity, iron specific, binding compounds called phytosiderophores. In contrast, there is little knowledge about the corresponding systems in marine plant-like lineages. Herein we report a study of the iron uptake and storage mechanisms in the coccolithophore Emiliania huxleyi. Short term radio-iron uptake studies indicate that iron is taken up by Emiliania in a time and concentration dependent manner consistent with an active transport process. Based on inhibitor studies it appears that iron is taken up directly as Fe(iii). However if a reductive step is involved the Fe(II) must not be accessible to the external environment. Upon long term exposure to (57)Fe we have been able, using a combination of Mössbauer and XAS spectroscopies, to identify a single metabolite which displays spectral features similar to the phosphorus-rich mineral core of bacterial and plant ferritins.

Iron is an essential element for all living organisms due to its ubiquitous role in redox and other enzymes, especially in the context of respiration and photosynthesis. The iron uptake and storage systems of terrestrial/higher plants are now reasonably well understood, with two basic strategies for iron uptake being distinguished: strategy I plants use a mechanism involving induction of Fe(III)-chelate reductase (ferrireductase) and Fe(II) transporter proteins, while strategy II plants utilize high-affinity, iron-specific, binding compounds called phytosiderophores. In contrast, little is known about the corresponding systems in marine, plant-like lineages, particularly those of multicellular algae (seaweeds). Herein the first study of the iron uptake and storage mechanisms in the brown alga Ectocarpus siliculosus is reported. Genomic data suggest that Ectocarpus may use a strategy I approach. Short-term radio-iron uptake studies verified that iron is taken up by Ectocarpus in a time- and concentration-dependent manner consistent with an active transport process. Upon long-term exposure to (57)Fe, two metabolites have been identified using a combination of Mössbauer and X-ray absorption spectroscopies. These include an iron-sulphur cluster accounting for ~26% of the total intracellular iron pool and a second component with spectra typical of a polymeric (Fe(3+)O(6)) system with parameters similar to the amorphous phosphorus-rich mineral core of bacterial and plant ferritins. This iron metabolite accounts for ~74% of the cellular iron pool and suggests that Ectocarpus contains a non-ferritin but mineral-based iron storage pool.

Vanadium(III) and -(V) alkolo complexes of the ligands hydridotripyrazolylborate, L, and hydridotris(3,5-dimethylpyrazolyl)borate, L * , have been prepared and characterized by X-ray diffraction, 1 H, 13 C, and 51 V NMR, electrochemistry, optical spectroscopy, and EXAFS. Two general classes of V(V) complexes have been synthesized with the general formulas LVO(OR) 2 and LVO(OR)Cl. The latter complexes contain the shortest V-OR bonds yet reported (1.706-1.754 A) and show that a vanadium-alkoxide bond could account for the short vanadium «light atom» interaction seen in the EXAFS of the enzyme, bromoperoxidase

Iron is an essential element for oceanic microbial life but its low bioavailability limits microorganisms in large areas of the oceans. To acquire this metal many marine bacteria produce organic chelates that bind and transport iron (siderophores). We have previously shown that algal-associated heterotrophic bacteria belonging to the γ-proteobacterial Marinobacter genus release the siderophore vibrioferrin (VF). The iron-VF complex was shown to be both far more photolabile than all previously examined photolabile siderophores and to generate a photoproduct incapable of re-chelating the released iron. Thus, the photo-generated iron was shown to be highly bioavailable both to the producing bacterium and its algal partner. In exchange, we proposed that algal cells produced dissolved organic matter that helped support bacterial growth and ultimately fueled the biosynthesis of VF through a light-dependent “carbon for iron mutualism”. While our knowledge of the importance of light to phototrophs is vast, there are almost no studies that examine the effects of light on microbial heterotrophs. Here, we characterize iron uptake mechanisms in “algal-associated” VF-producers. Fe uptake by a VF knock-out mutant mimics the wild-type strain and demonstrates the versatility of iron uptake mechanisms in Marinobacter VF-producers. We also show that VF-producers selectively regulate a subset of their siderophore-dependent iron uptake genes in response to light exposure. The regulation of iron uptake and transport genes by light is consistent with the light driven algal–bacterial “carbon for iron mutualism” hypothesis in the marine environment.

Marinobacter belong to the class of Gammaproteobacteria and these motile, halophilic or halotolerent bacteria are widely distributed throughout the world’s oceans having been isolated from a wide variety of marine environments. They have also been identified as members of the bacterial flora associated with other marine organisms. Here, using a combination of natural products chemistry and genomic analysis, we assess the nature of the siderophores produced by this genus and their potential relationship to phylogeny and lifestyle/ecological niche of this diverse group of organisms. Our analysis shows a wide level of diversity in siderophore based iron uptake systems among this genus with three general strategies: (1) production and utilization of native siderophores in addition to utilization of a variety of exogenous ones, (2) production and utilization of native siderophores only, (3) lack of siderophore production but utilization of exogenous ones. They all share the presence of at least one siderophore-independent iron uptake ABC transport systems of the FbpABC iron metal type and lack the ability for direct transport of ferrous iron. Siderophore production and utilization can be correlated with phylogeny and thus it forms a type of chemotaxonomic marker for this genus.

The reaction of the V(V) complex of sulfonated 1,5,10-tris(2,3-dihydroxybenzoyl)-1,5,10-triazadecane (3,4 LICAMS) with H 2 S has been studied as a model for the Stretford process. Oxidation of the hydrogen sulfide is found to occur in two steps. The first involves the pH dependent formation of a V(V) LICAMS-H 2 S intermediate while the second is a pH independent electron transfer to produce elemental sulfur and V(IV) LICAMS. Rate constants have been measured and the significance of these data to the design of new catalysts is discussed.

The reaction of Cy 2 GaCl with LiNHR in diethylether at −78°C produces the dinuclear primary amido bridged complexes [Cy 2 GaNHR] 2 (R  Interestingly, compounds 1 – 3 feature short Ga⋯HN distances, which are 2.113 A, 2.33 A and 2.28(9) A for 1 , 2 and

This article reviews published archaeological research that explores the potential of combined chemical and petrographic analyses to distinguish manufacturing methods of ceramics made From Nile river silt. The methodology was initially applied to distinguish the production methods of Egyptian and Nubian- style vessels found in New Kingdom and Napatan Period Egyptian colonial centers in Upper Nubia. Conducted in the context of ongoing excavations and surveys at the third cataract, ceramic characterization can be used to explore the dynamic role pottery production may have played in Egyptian efforts to integrate with or alter native Nubian culture. Results reveal that, despite overall similar geochemistry, x-ray fluorescence (XRF), instrumental neutron activation analysis (INAA), and petrography can distinguish Egyptian and Nubian-style ceramic traditions based on the relative degree of compositional homogeneity and subtle differences in paste recipes. This in turn indicates that cultural differences in craft production were sustained over time within the ethnically mixed communities of Upper Nubia. Based on these positive results, the methodology shows potential for addressing additional research questions in the Nile Valley, and a current research plan by the authors applies these same techniques to an evaluation of the role of ceramic craft centralization in the rise of the native Nubian Kerma state.

F. Organisms that accumulate vanadium ......... (i) Amanita muscaria (ii) Tunicates G. Vanadium-protein interactions (i) Vanadium transferrin (ii) Vanadoenzymes (a) Vanadium bromoperoxidase (b) Vanadium nitrogenase H. Other systems (i) Vanadyl-substituted bleomycin (ii) Vanadyl-substituted dopamine /J-monooxygenase (iii) Vanadocene interaction with nucleic acids .... I. Summary and a look to the future Acknowledgements References

Tris(2,3,4,5-tetramethylphospholyl)phosphine (1) has been prepared via the reaction of Li(PC4Me4) with PCl3. The structure of 1 was determined by single-crystal X-ray diffraction: triclinic, space group P with a = 8.795(2), b = 11.489(2), c = 14.557(3) A, α = 72.89(3), β = 88.92(3), γ = 67.69(3)°, V = 1293.4(7) A3 and Z = 2.

Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related. These seaweeds are the dominant species in rocky coastal ecosystems and they exhibit many interesting adaptations to these, often harsh, environments. Brown algae are also one of only a small number of eukaryotic lineages that have evolved complex multicellularity (Fig. 1). We report the 214 million base pair (Mbp) genome sequence of the filamentous seaweed Ectocarpus siliculosus (Dillwyn) Lyngbye, a model organism for brown algae, closely related to the kelps (Fig. 1). Genome features such as the presence of an extended set of light-harvesting and pigment biosynthesis genes and new metabolic processes such as halide metabolism help explain the ability of this organism to cope with the highly variable tidal environment. The evolution of multicellularity in this lineage is correlated with the presence of a rich array of signal transduction genes. Of particular interest is the presence of a family of receptor kinases, as the independent evolution of related molecules has been linked with the emergence of multicellularity in both the animal and green plant lineages. The Ectocarpus genome sequence represents an important step towards developing this organism as a model species, providing the possibility to combine genomic and genetic approaches to explore these and other aspects of brown algal biology further. © 2010 Macmillan Publishers Limited. All rights reserved.

Vanadium(V) complexes of catechol and several polydentate analogs have been prepared and characterized in solution by optical and [sup 51]V NMR spectroscopies as well by solution thermodynamic measurements. The vanadium(V) catecholate species displayed relatively sharp [sup 51]V NMR signals in the range [minus]164 to [minus]268 ppm but in general were susceptible to decomposition by internal redox reactions yielding V(IV) and quinone, particularly in aqueous solution. The complexes of 1,5,10-tris(2,3-dihydroxybenzoyl)-1,5,10-triazadecane, and its sulfonated analog (3,4-LICAM and LICAMS) are an exception to this generalization and were quite stable. The sulfonated V(V)-LICAMS complex undergoes reversible protonations in aqueous solutions similar to those seen in the analogous Fe[sup 3+] complexes. The proton dependent formation constant for the reaction, K[sup *] = [V[sup V]LICAMS]/[VO[sub 2][sup +]][LICAMS][H[sup +]] has been measured, yielding a log K[sub ML] of 24.2 (1) at 0.5 M in KNO[sub 3] at 25[degrees]C and pH 5.50.

A series of vanadium(III) and -(IV) complexes of the type [L 2 V]BPh 4 , [LVCl 2 DMF], [LVOCIDMF], and [LVO(acac)] where L is either the anion of hydridotris(pyrazolyl)borate, HB(pz) 3 , or hydridotris(3,5-dimethylpyrazolyl)borate, HB(Me 2 pz) 3 , have been synthesized and characterized by elemental analysis, molar conductance, electrochemistry, magnetic, UV-vis, IR, and ESR techniques. In all cases, the metal ion is in a distorted octahedral environment

The photoreactivep-azidobenzoyl analog of ferrioxamine B was used to show that ferrioxamine-B-mediated iron transport is separate and distinct from coprogen-mediated iron transport inEscherichia coli. Photolysis of this analog inhibited uptake of [59Fe]ferrioxamine B but not [59Fe]coprogen or [59Fe]ferrichrome. Conversely, photolysis of thep-azidobenzoyl analog of coprogen B inhibited uptake of [59Fe]coprogen but not [59Fe]ferrioxamine B or [59Fe]ferrichrome. Photolabeling of outer membranes withp-azidobenzoyl-[59Fe]ferrioxamine B resulted in the labeling of two iron-regulated peptides with molecular masses of about 66 and 26 kDa. Expression of these peptides was increased when ferrioxamine B was the sole iron source. Both peptides were present in outer membrane preparations of thefhuF mutant H1717, but the 66 kDa peptide was not inducible. These results are evidence for an outer membrane receptor inE. coli unique for linear ferrioxamines.

Vibrioferrin (VF) is a member of the carboxylate class of siderophores originally isolated from Vibrio parahaemolyticus, an enteropathogenic estuarine bacterium often associated with seafood-borne gastroenteritis. Recently we have also isolated this siderophore from several species of Marinobacter, which are closely associated or "symbiotic" with toxic, bloom-forming dinoflagellates such as Gymnodinium catenatum. We have measured the overall metal-ligand binding constant for iron-vibrioferrin (FeVF) as 10(24.02(5)) making vibrioferrin one of the weakest iron chelators of any known marine siderophore. FeVF is also shown to be considerably more sensitive to photolysis under relatively low illumination conditions than other photoactive siderophores leading primarily to a monodecarboxylated photoproduct that has no significant affinity for Fe(III). The consequences that these features have on bacterial-algal interactions with potential importance to understanding the origin and sustenance of harmful algal blooms are discussed.

The new ditopic heteroscorpionate ligand, (3-methoxy-4-hydroxyphenyl)bis(3,5-dimethylpyrazolyl)methane (L5v), and four coordination polymers of silver Ag(I) derived therefrom, have been synthesized and characterized by X-ray diffraction, ESI-MS, IR spectroscopy and elemental analysis. The presence of different anions (i.e. BF4−, CF3SO3−, NO3−, or SbF6−) lead to different crystal packing schemes due to different H-bonding patterns that depend on the relative charge delocalization and/or shape of the anion.

Marine microalgae support world fisheries production and influence climate through various mechanisms. They are also responsible for harmful blooms that adversely impact coastal ecosystems and economies. Optimal growth and survival of many bloom-forming microalgae, including climatically important dinoflagellates and coccolithophores, requires the close association of specific bacterial species, but the reasons for these associations are unknown. Here, we report that several clades of Marinobacter ubiquitously found in close association with dinoflagellates and coccolithophores produce an unusual lower-affinity dicitrate siderophore, vibrioferrin (VF). Fe-VF chelates undergo photolysis at rates that are 10–20 times higher than siderophores produced by free-living marine bacteria, and unlike the latter, the VF photoproduct has no measurable affinity for iron. While both an algal-associated bacterium and a representative dinoflagellate partner, Scrippsiella trochoidea , used iron from Fe-VF chelates in the dark, in situ photolysis of the chelates in the presence of attenuated sunlight increased bacterial iron uptake by 70% and algal uptake by >20-fold. These results suggest that the bacteria promote algal assimilation of iron by facilitating photochemical redox cycling of this critical nutrient. Also, binary culture experiments and genomic evidence suggest that the algal cells release organic molecules that are used by the bacteria for growth. Such mutualistic sharing of iron and fixed carbon has important implications toward our understanding of the close beneficial interactions between marine bacteria and phytoplankton, and the effect of these interactions on algal blooms and climate.

F. Organisms that accumulate vanadium ......... (i) Amanita muscaria (ii) Tunicates G. Vanadium-protein interactions (i) Vanadium transferrin (ii) Vanadoenzymes (a) Vanadium bromoperoxidase (b) Vanadium nitrogenase H. Other systems (i) Vanadyl-substituted bleomycin (ii) Vanadyl-substituted dopamine /J-monooxygenase (iii) Vanadocene interaction with nucleic acids .... I. Summary and a look to the future Acknowledgements References

Vanadium (3,5-dimethylpyrazolyl) borate complexes with a series of phenolate ligands have been prepared and characterized. The single-crystal X-ray structure of the p-bromophenol derivative tris[(3,5-dimethylpyrazolylborato]bis(p-bromophenoxy)oxovanadium(V) has been determined by standard methods and refined to an unweighted R factor of 0.052. The dark green triclinic crystals belong to space group P1

Two isomeric tunichrome model compounds have been prepared from spermidine and trihydroxybenzoic acid. The coordination chemistry of these ligands with V(III), (IV), and (V) are reported. Vanadium(V) is found to undergo rapid reduction to V(IV) in the presence of these ligands, Vanadium(IV) complexes were characterized by optical and EPR spectroscopy as well as elemental analysis and magnetic measurements. Vanadium(III) also reacts rapidly with these ligands, producing what is thought to be a VOV dimer in acidic solution. The biological implications of the coordination chemistry reported herein with respect to vanadium metabolism in ascidians is discussed.

On the occasion of the 200th anniversary of the discovery of boron, we review the oceanic biogeochemistry of boron as well as suitable analytical techniques for its determination. This overview includes aspects of biogeochemistry including geochemical stable isotope variations, uptake, transport, storage, nutritional value, toxicity, and distribution within biological materials, providing a framework for discussion of the role of boron in marine organisms, which remains largely enigmatic.

A series of ferric phenolate complexes with Schiff base or methylamine substitutents ortho to the phenolic oxygen have been investigated. These include complexes with N,N'-ethylenebis((o-hydroxyphenyl)glycine), N-[2-(o-salicylideneamino)ethyl](o-hydroxyphenyl)glycine, and N 1 ,N 4 -disalicylidenetriethylenetetramine