Phosphate Clusters Research Articles

Self-Assembly of a Tris(Urea) Receptor as Tetrahedral Cage for the Encapsulation of a Discrete Tetrameric Mixed Phosphate Cluster (H2PO4–•HPO42–)2

A tris(2-aminoethyl)amine-based tris(urea) receptor L, in the presence of excess TBA(H2PO4) self-assembled into a tetrahedral molecular cage by encapsulation of a tetrameric tetrahedral mixed phosphate cluster (H2PO4–•HPO42–)2 via 24 −NH hydrogen bonds [complex (n-TBA)6{4L(H2PO4–•HPO42–)2}] (1). Further, in the presence of orthophosphoric acid the receptor L has been observed to be self-assembled with side-cleft bonded tetrameric anion-acid cluster (H2PO4–•H3PO4)2 [complex {(LH)+(H2PO4–•H3PO4)DMSO•H 2O}] (2). In a proof of concept experiment, transformation of salt complex 2 into neutral phosphate encapsulated complex has been demonstrated in solution state by quantitative 1H NMR titration with (TBA)OH in DMSO-d6 (298 K). Extensive studies with receptor L have also been carried out with other halides in the solid state. Crystal structure elucidation revealed the formation of a pseudodimeric (2 + 2) capsular self-assembly with 1:1 host:guest ratio in fluoride encapsulated complex, (TEA)[L(F)] (3). 2D-NOESY NMR (DMSO-d6) experiments were carried out on the phosphate complexes (complexes 1 and 2) to study the binding discrepancies of phosphate anion with the neutral and charged host.

Is Single-4-Ring the Most Basic but Elusive Secondary Building Unit That Transforms to Larger Structures in Zinc Phosphate Chemistry?

Haloaryl phosphates (X-dippH2, X = Cl, Br, I) react with zinc acetate in the presence of collidine or 2-aminopyridine (2-apy) to yield zinc phosphate clusters [Zn(X-dipp)(collidine)]4 (X = Cl (1), Br (2), I (3)) and [Zn(X-dipp)(2-apy)]4·2MeOH (X = Cl (4), Br (5), I (6)), respectively. Single-crystal X-ray diffraction studies reveal that collidine and 2-apy capped zinc phosphates 1-6 exist as discrete tetrameric zinc phosphate molecules, exhibiting a cubane-shaped D4R core. In contrast, when the same reaction has been carried out in the presence of 4-cyanopyridine (4-CNpy), polymeric zinc phosphates {[Zn4(X-dipp)4(4-CNpy)2(MeOH)2]·2H2O}n (X = Cl (7), Br (8), I (9)) have been isolated. Compounds 7-9 are square-wave-shaped, one-dimensional polymers composed of fused S4R repeating units. The common structural motif found both in D4R cubanes 1-6 and polymers 7-9 is the S4R building block, which presumably undergoes further fusion because of the coordinative unsaturation at zinc and the simultaneous presence of free P═O. The closed shell cubanes 1-6 are obviously formed by a face-to-face dimerization involving two S4R units in which the two P═O groups are in cis-configuration. On the other hand, the one-dimensional (1-D) square-wave polymers 7-9 are formed from a face-to-face association of S4R building units in which the two P═O groups are in a trans-configuration. In order to stabilize these elusive S4R zinc phosphates, the reaction between Cl-dippH2 and zinc acetate was carried out in the presence of excess imidazole as an ancillary ligand (1:1:4), although only an imidazole decorated cubane cluster [Zn(Cl-dipp)(imz)]4.2MeOH (10) was isolated. The chelating N,N'-donor 1,10-phenanthroline ligand was used to eventually isolate cyclic S4R phosphate [Zn(μ2-Cl-dipp)(1,10-phen)(OH2)]2·MeOH·H2O (11). The change of Zn(2+) source to zinc nitrate and the phosphate source to 2,6-dimethylphenyl phosphate (dmppH2) led to the isolation of another polymeric phosphate [Zn(dmpp)(MeOH)]n (12), with a zigzag backbone, formed through an edge-to-edge to polymerization of S4R building units with P═O groups in trans-configuration. The isolation of four different structural types of zinc phosphates A-D in the present study can be rationalized in terms of fusion of S4R rings in a variety of ways to either produce discrete clusters or 1-D polymers.

In Situ Detection of Calcium Phosphate Clusters in Solution and Wet Amorphous Phase by Synchrotron X-ray Absorption Near-Edge Spectroscopy at Calcium K-Edge

Calcium phosphate clusters are present in both aqueous solutions and an amorphous phase during crystallization. It is a challenging task to acquire the structural information on such clusters, owing to their small size, chemical lability, and inaccessibility to most detection techniques. Here, we demonstrate the feasibility of detecting such clusters in situ by synchrotron X-ray absorption near-edge spectroscopy at calcium K-edge, a technique that is sensitive to the short-range order in calcium coordination sphere. At the initial stage of crystallization, the most abundant clusters are detected to be Ca(η2-PO43–)2L2 (L = H2O or η1-PO43–) in solution. More reactive clusters engage in the development of an amorphous phase via growing and fusing. The amorphous phase exhibits a dual character in its short-range order: Some of its clusters are similar to hydrated calcium ions, and some others to those in crystalline hydroxyapatite. When the amorphous dissolves, the detected unit is mainly Ca(η2-PO43–)(H2O)4 i...

Microhydrated dihydrogen phosphate clusters probed by gas phase vibrational spectroscopy and first principles calculations.

We report infrared multiple photon dissociation (IRMPD) spectra of cryogenically-cooled H2PO4(-)(H2O)n anions (n = 2-12) in the spectral range of the stretching and bending modes of the solute anion (600-1800 cm(-1)). The spectra cannot be fully understood using the standard technique of comparison to harmonic spectra of minimum-energy structures; a satisfactory assignment requires considering anharmonic effects as well as entropy-driven hydrogen bond network fluctuations. Aided by finite temperature ab initio molecular dynamics simulations, the observed changes in the position, width and intensity of the IRMPD bands with cluster size are related to the sequence of microsolvation. Due to stronger hydrogen bonding to the two terminal P[double bond, length as m-dash]O groups, these are hydrated before the two P-OH groups. By n = 6, all four end groups are involved in the hydrogen bond network and by n = 12, the cluster spectra show similarities to the condensed phase spectrum of H2PO4(-)(aq). Our results reveal some of the microscopic details concerning the formation of the aqueous solvation environment around H2PO4(-), provide ample testing grounds for the design of model solvation potentials for this biologically relevant anion, and support a new paradigm for the interpretation of IRMPD spectra of microhydrated ions.

The structure of casein micelles: a review of small-angle scattering data

Casein micelles are association colloids found in mammalian milk. Small-angle scattering data on casein micelles have been collected and are reviewed, including contrast variation. The scattering spectra are quite consistent at medium and high scattering wavevectors [Q= 4πnsin(θ/2)/λ, wherenis the refractive index, λ is the wavelength and θ is the scattering angle]. Differences are noted, especially at lowQ, which may be attributed to sample preparation, particularly the presence of residual fat globules. Scattering spectra are calculated using a generalized scattering function and a composite particle model, and it is possible to give a self-consistent calculation of the spectra using one set of parameters for all contrasts in both small-angle X-ray scattering and small-angle neutron scattering. The data and calculations show that a casein micelle is a homogeneous particle. The polydispersity in size is about 35% and therefore experimental data on particle size depend very much on the method used. A `reference set' of numbers is proposed for casein micelles from pooled cows' milk, which may be given as follows: β = 0.35,R10= 60 nm,Rg= 110 nm,Rhydr= 96 nm (at 90° scattering). Often, use is made of dynamic light scattering (DLS), which gives anRhydr= 〈R6〉/〈R5〉 of 80–100 nm at 90° scattering. Values will be considerably higher at low(er) angles, and lower at backscattering angles, which are currently used in many DLS setups. Larger values are probably due to clusters of casein micelles or residual fat. The structure of a casein micelle can best be described as a protein matrix in which calcium phosphate clusters (2 nm radius) are dispersed. The protein matrix has density variations on a similar length scale. The casein micelle–submicelle model and models with large voids and channels are highly improbable.

Assessing the phosphate distribution in bioactive phosphosilicate glasses by 31P solid-state NMR and molecular dynamics simulations.

Melt-derived bioactive phosphosilicate glasses are widely utilized as bone-grafting materials for various surgical applications. However, the insight into their structural features over a medium-range scale up to ∼ 1 nm remains limited. We present a comprehensive assessment of the spatial distribution of phosphate groups across the structures of 11 Na2O-CaO-SiO2-P2O5 glasses that encompass both bioactive and nonbioactive compositions, with the P contents and silicate network connectivities varied independently. Both parameters are known to strongly influence the bioactivity of the glass in vitro. The phosphate distribution was investigated by double-quantum (31)P nuclear magnetic resonance (NMR) experiments under magic-angle spinning (MAS) conditions and by molecular dynamics (MD) simulations. The details of the phosphate-ion dispersion were probed by evaluating the MD-derived glass models against various scenarios of randomly distributed, as well as clustered, phosphate groups. From comparisons of the P-P interatomic-distance spreads and the statistics of small phosphate clusters assessed for variable cutoff radii, we conclude that the spatial arrangement of the P atoms in phosphosilicate glasses is well-approximated by a statistical distribution, particularly across a short-range scale of ≤ 450 pm. The primary distinction is reflected in slightly closer P-P interatomic contacts in the MD-derived structures over the distance span of 450-600 pm relative to that of randomly distributed phosphate groups. The nature of the phosphate-ion dispersion remains independent of the silicate network polymerization and nearly independent of the P content of the glass throughout our explored parameter space of 1-6 mol % P2O5 and silicate network connectivities up to 2.9.

Potentiometric and semi-empirical quantum chemical studies on liquid–liquid micro-extraction of 4-tert-butylphenol with trioctyl phosphate clusters

In the present paper, the liquid–liquid micro extraction of 4-tert-butylphenol from aqueous solution to trioctyl phosphate organic phase in carbon paste electrode was studied by potentiometry and semi-empirical quantum chemistry with MOPAC2009. The extraction dynamic process was monitored by open circuit potential method, which follows an exponential association function with the apparent first extraction kinetic rate constant of 0.01685s−1. The Nernstian plot of potential difference of the open circuit potentials against logarithm of 4-tert-butylphenol concentration at 500s extraction time gives a slope of 0.01382, and indicates that 3 or 4 of 4-tert-butylphenol molecules can be extracted by one cluster of trioctyl phosphate dimer. This equation can also serve as working curve for the determination of 4-tert-butylphenol in the concentration range of 1.0×10−4–5.0×10−7M with detection limit of 5.0×10−7M (n=3, ratio of signal/noise=3). The semi-empirical quantum chemical calculation offers a thermodynamic evidence for the molecular mechanism of the liquid–liquid micro extraction of 4-tert-butylphenol from aqueous solution to trioctyl phosphate cluster.

Toward continuous LC-MS analysis: surface modification of magnetic microparticles with TiO2 for phosphate adsorption.

Continuous liquid chromatography-mass spectrometry (LC-MS) analysis was successfully demonstrated by using magnetic TiO2/Fe3O4 microparticles at the desalination interface. The particles could be prepared easily even on a practical scale at sufficient quality for efficient phosphate adsorption. Not only phosphate but several biomolecules were adsorbed onto the particles in a non-specific manner. Such samples could still be detected effectively in MS because the removal of phosphate derived from the LC eluent enhanced sample ionization and resulted in a significant reduction of phosphate cluster ions.

Mineralization of DNA into nanoparticles of hydroxyapatite

Encapsulation of DNA into hydroxyapatite (HAp) has been investigated using a rational approach that involves computer simulation and experimental techniques. The temporal evolution of the radial distribution functions derived from atomistic molecular dynamics simulations of Ca(2+), PO4(3-) and OH(-)-containing aqueous solutions in the presence and absence of B-DNA has been used to conclude that the backbone of the double helix acts as a template for HAp growth. More specifically, results reveal the formation of calcium phosphate clusters at the first stages of the simulations, which subsequently re-organize to nucleate HAp. This effect is produced in the absence and, especially, presence, of DNA indicating that the biomolecules do not inhibit but even promote mineral growth. Furthermore, computer simulations suggest that the diffusion of the OH(-) anions through the inorganic solution is the limiting step for the nucleation of the biomineral. Nanocapsules and crystalline nanorods of HAp containing DNA molecules inside have been prepared by mixing solutions containing Ca(2+) and PO4(3-) ions with fish sperm DNA at high pH. The dimensions and morphology of such nanostructures have been examined by transmission electron microscopy, while the characterization of the biomineral has been focused on the identification of DNA inside HAp using infrared, X-ray photoelectron and UV-vis spectroscopies, as well as gel electrophoresis. The biominerals reported in this work are important for biomedical applications requiring the protection of DNA from aggressive environmental conditions.

Water-soluble multi-cage super tetrahedral uranyl peroxide phosphate clusters

Combination of uranyl, peroxide, phosphate, and counter ions under ambient conditions in aqueous solution over the pH range 5.5–6.5 results in the self-assembly of a large super tetrahedral cluster containing 124 uranyl hexagonal bipyramids and 32 phosphate tetrahedra designated U124P32. With a diameter of 4 nm, U124P32 consists of four symmetrically identical cage clusters, each built from 23 uranyl hexagonal bipyramids and eight phosphate tetrahedra, as well as a central cage defined by 52 uranyl hexagonal bipyramids and 32 phosphate tetrahedra. It is the first uranyl-based cluster that contains multiple cages and it also has the highest number of uranyl ions. U124P32 contains 152 peroxide groups that are bidentate bridges between uranyl ions. Crystals of U124P32 provided structural details, and were dissolved for subsequent small-angle X-ray scattering and electrospray ionization mass spectrometry characterization that indicated U124P32 remains intact upon dissolution in water. Whereas uranyl phosphates are generally insoluble in water, prompting interest in their applications in remediating contaminated water, U124P32 is highly soluble, reflecting the impact of the nanoscale structure on solubility.

Growth of Crystalline Hydroxyapatite Thin Films at Room Temperature by Tuning the Energy of the RF-Magnetron Sputtering Plasma

Right angle radio frequency magnetron sputtering technique (RAMS) was redesigned to favor the production of high-quality hydroxyapatite (HA) thin coatings for biomedical applications. Stoichiometric HA films with controlled crystallinity, thickness varying from 254 to 540 nm, crystallite mean size of 73 nm, and RMS roughness of 1.7 ± 0.9 nm, were obtained at room temperature by tuning the thermodynamic properties of the plasma sheath energy. The plasma energies were adjusted by using a suitable high magnetic field confinement of 143 mT (1430 G) and a substrate floating potential of 2 V at the substrate-to-magnetron distance of Z = 10 mm and by varying the sputtering geometry, substrate-to-magnetron distance from Z = 5 mm to Z = 18 mm, forwarded RF power and reactive gas pressure. Measurements that were taken with a Langmuir probe showed that the adjusted RAMS geometry generated a plasma with an adequate effective temperature of Teff ≈ 11.8 eV and electron density of 2.0 × 10(15) m(-3) to nucleate nanoclusters and to further crystallize the nanodomains of stoichiometric HA. The deposition mechanism in the RAMS geometry was described by the formation of building units of amorphous calcium phosphate clusters (ACP), the conversion into HA nanodomains and the crystallization of the grain domains with a preferential orientation along the HA [002] direction.

Landscape-scale geographic variations in microbial biomass and enzyme-labile phosphorus in manure-amended Hapludults

Long-term nutrient management practices have lasting effects on the geographic distribution of soil microorganisms, loci of enhanced activity, and non-mobile nutrients such as phosphorus (P) to ultimately influence nutrient use efficiency by crops and edge-of-field losses. We determined the distribution of soil microbial biomass, phosphomonoesterases' activity, and P forms in a 10-ha no-till field that received annual additions of dairy manure at 0, 15, and 30 kg P ha−1 at the field scale for 16 consecutive years. The spatial structure of soil microbial indices and extractable P fractions were characterized based on their semivariance distributions for each manure treatment. The buildup in soil P occurred, although replacement was done at a crop removal rate. Manure additions resulted in overall mean increases in total labile P of 73 % and 156 % and alterations in the soil microbial ecosystem that depended on manure inorganic-to-enzyme-labile P composition in soils treated with 15 and 30 kg P ha−1, respectively. Distinct clusters of phosphate- and enzyme-labile organic P were observed within manure treatments, where accumulation of the latter forms was associated with high soil microbial biomass C and reduced acid phosphomonoesterase activity. The geographic variability highlighted the critical need for improving methods of field-scale application of manure and non-mobile nutrients. In addition, current soil testing methods that depend upon composite representative samples for estimating microbiological parameters linked to nutrient turnover and P requirements for optimal crop production should be modified to include site-specificity in sampling and interpretation approaches.

Direct Probing of the Phosphate-Ion Distribution in Bioactive Silicate Glasses by Solid-State NMR: Evidence for Transitions between Random/Clustered Scenarios

By employing 31P multiple-quantum coherence-based solid-state nuclear magnetic resonance spectroscopy, we present the first comprehensive experimental assessment of the nature of the orthophosphate-ion distributions in silicate-based bioactive glasses (BGs). Results are provided both from melt-prepared BG and evaporation-induced self-assembly-derived mesoporous bioactive glass (MBG) structures of distinct compositions. The phosphate species are randomly dispersed in melt-derived BGs (comprising 44–55 mol % SiO2) of the Na2O–CaO–SiO2–P2O5 system, whereas a Si-rich (86 mol % SiO2) and Ca-poor ordered MBG structure exhibits nanometer-sized amorphous calcium phosphate clusters, conservatively estimated to comprise at least nine orthophosphate groups. A Ca-richer MBG (58 mol % SiO2) reveals a less pronounced phosphate clustering. We rationalize the variable structural role of P in these amorphous biomaterials.

Modeling biominerals formed by apatites and DNA.

Different aspects of biominerals formed by apatite and DNA have been investigated using computer modeling tools. Firstly, the structure and stability of biominerals in which DNA molecules are embedded into hydroxyapatite and fluoroapatite nanopores have been examined by combining different molecular mechanics methods. After this, the early processes in the nucleation of hydroxyapatite at a DNA template have been investigated using molecular dynamics simulations. Results indicate that duplexes of DNA adopting a B double helix can be encapsulated inside nanopores of hydroxyapatite without undergoing significant distortions in the inter-strand hydrogen bonds and the intra-strand stacking. This ability of hydroxyapatite is practically independent of the DNA sequence, which has been attributed to the stabilizing role of the interactions between the calcium atoms of the mineral and the phosphate groups of the biomolecule. In contrast, the fluorine atoms of fluoroapatite induce pronounced structural distortions in the double helix when embedded in a pore of the same dimensions, resulting in the loss of its most relevant characteristics. On the other hand, molecular dynamics simulations have allowed us to observe the formation of calcium phosphate clusters at the surface of the B-DNA template. Electrostatic interactions between the phosphate groups of DNA and Ca2+ have been found to essential for the formation of stable ion complexes, which were the starting point of calcium phosphate clusters by incorporating from the solution.Electronic supplementary materialThe online version of this article (doi:10.1186/1559-4106-8-10) contains supplementary material, which is available to authorized users.

Evidence of Nanometric-Sized Phosphate Clusters in Bioactive Glasses As Revealed by Solid-State 31P NMR

Bioactive glasses are able to form strong bonds to bone. This property, crucial for medical applications, depends on the glass composition and structure. Dissolution of phosphates in melt-quenched silicate glasses raises the question of chemical homogeneity and possible formation of clusters. A detailed structural characterization of the bioactive glasses is thus highly desirable. In this work, the nature of the distribution of phosphate units in a melt-quenched bioactive glass is elucidated for the first time using 31P spin-counting solid-state NMR experiments. The structure of a dense bioactive calcium silicate glass with 2.6 mol % of phosphorus oxide is shown to exhibit nanometric-sized chemical and structural heterogeneities. Clear experimental evidence of the presence of phosphate clusters of five and six PO4 tetrahedral units embedded in the disordered polymeric silicate network is given.

Cationic D4R zinc phosphate–anionic polyoxometalate hybrids: synthesis, spectra, structure and catalytic studies

A facile synthetic strategy for the generation of a new class of inorganic-organic-inorganic hybrids is reported. Replacement of labile DMSO ligands from the preformed Double-Four-Ring (D4R) zinc phosphate cluster [Zn(dipp){(CH3)2SO}]4 by the addition of 4-aminopyridine (4-ampyr) results in the isolation of another discrete D4R cluster [Zn(dipp)(4-ampyr)]4 (1), which forms a hydrogen-bonded framework in solid-state. If 1-methyl-4,4'-bipyridinium salts are employed instead, tetra-cationic D4R cluster [Zn(dipp)(L)]4[PF6]4 (2) and [Zn(dipp)(L)]4[ClO4]4 (3) (L = 1-methyl-4,4'-bipyridinium, dipp = 2,6-di-iso-propylphenylphosphate) are isolated. Compound 2 was reacted with three different polyoxometalates, [TBA]4[Mo8O26] (POM-1), [TBA]4[PMo11VO40] (POM-2), and [TBA]4[SiMo12O40] (POM-3) to obtain amorphous hybrids, [Zn(dipp)(L)]4[Mo8O26] (4), [Zn(dipp)(L)]4[PMo11VO40] (5), and [Zn(dipp)(L)]4[SiMo12O40] (6), respectively. All the hybrid materials have been characterized by analytical and spectroscopic studies. The molecular structure of 1 has also been determined by single-crystal XRD measurements. N2 gas sorption analyses show moderate BET surface area and also establish the mesoporous nature of the hybrids 4-6. The catalytic potential of hybrids 4, 5 and 6 has been explored towards epoxidation of cyclohexene.

Calcium Phosphopeptides — Mechanisms of Action and Evidence for Clinical Efficacy

Phosphoproteins/phosphopeptides with clusters of acidic residues are found throughout nature, where they aid in the prevention of unwanted precipitation of solid calcium phosphates. The acidic residues, particularly phosphoserine, interact with calcium and stabilize clusters of calcium and phosphate. Saliva and milk are two examples of biological fluids that contain such phosphoprotein/phosphopeptide-stabilized calcium phosphates, and both share a similar evolutionary pathway. Saliva has been shown to have remineralization potential and is of critical importance in maintaining the mineral content of teeth in the oral environment. Milk can be enzymatically modified to release casein phosphopeptides that contain the clusters of residues that allow milk to stabilize high concentrations of calcium and phosphate. These casein phosphopeptide-stabilized amorphous calcium phosphate nanocomplexes (CPP-ACP) can stabilize even higher concentrations of calcium and phosphate than milk and can be considered a salivary biomimetic, since they share many similarities to statherin. The mechanisms of action and the growing body of scientific evidence that supports the use of CPP-ACP to augment fluoride in inhibiting demineralization and enhancing the remineralization of white-spot lesions are reviewed.

Molecular Dynamics Simulation of the Early Stages of Nucleation of Hydroxyapatite at a Collagen Template

We have used molecular dynamics simulations to investigate the early processes in the nucleation of hydroxyapatite at a collagen template, by immersing a triple-helical collagen molecule in a stoichiometric solution of Ca2+, PO43–, and OH– ions, where we have observed the formation of calcium phosphate clusters at the collagen template. Electrostatic attractions were prevalent between calcium ions and oxygen atoms of the glycine and hydroxyproline residues, which were the starting point for the formation of the calcium phosphate clusters. Some phosphate ions form hydrogen-bonds with the hydroxy groups of hydroxyproline residues, whereas most of the hydroxy ions stay in solution, although some become attached to calcium phosphate clusters. The observed nucleation and clustering is too early in the hydroxyapatite formation process to show differentiation between distinct hydroxyapatite surfaces. However, calculations of the interaction of a collagen peptide with the (0001) and (0110) surfaces of hydroxyapa...

Posner's cluster revisited: direct imaging of nucleation and growth of nanoscale calcium phosphate clusters at the calcite-water interface

Although many in vitro studies have looked at calcium phosphate (Ca–P) mineralization, they have not emphasized the earliest events and the pathway of crystallization from solvated ions to the final apatitic mineral phase. Only recently has it become possible to unravel experimentally the processes of Ca–P formation through a cluster-growth model. Here we use mineral replacement reactions by the interaction of phosphate-bearing solutions with calcite surfaces in a fluid cell of an atomic force microscope (AFM) and reveal that the mineral surface-induced formation of an apatitic phase proceeds through the nucleation and aggregation of nanosized clusters with dimensions similar to those of Posner's clusters, which subsequently form stable amorphous calcium phosphate (ACP) plates prior to the transformation to the final crystalline phase. Our direct AFM observations provide evidence for the existence of stable Posner's clusters even though no organic template is applied.

Engineering of a phosphorylatable tag for specific protein binding on zirconium phosphonate based microarrays

A phosphorylatable tag was designed and fused at the C-terminal end of proteins, which allowed efficient and oriented immobilization of capture proteins on glass substrates coated with a zirconium phosphonate monolayer. The concept is demonstrated using Nanofitin directed against lysozyme. This peptide tag (DSDSSSEDE) contains four serines in an acidic environment, which favored its in vitro phosphorylation by casein kinase II. The resulting phosphate cluster at the C-terminal end of the protein provided a specific, irreversible, and multipoint attachment to the zirconium surface. In a microarray format, the high surface coverage led to high fluorescence signal after incubation with Alexa Fluor 647 labeled lysozyme. The detection sensitivity of the microarray for the labeled target was below 50 pM, owing to the exceptionally low background staining, which resulted in high fluorescence signal to noise ratios. The performance of this new anchoring strategy using a zirconium phosphonate modified surface compares favorably with that of other types of microarray substrates, such as nitrocellulose-based or epoxide slides, which bind proteins in a nonoriented way.