Supramolecular self-assembly of nucleotide–metal coordination complexes: From simple molecules to nanomaterials

CdSe/ZnS quantum dots coated with carboxy-PEG and modified with the terbium(III) complex of guanosine 5'-monophosphate as a fluorescent nanoprobe for ratiometric determination of arsenate via its inhibition of acid phosphatase activity

A ratiometric fluorometric method is described for the determination of arsenate via its inhibitory effect on the activity of the enzyme acid phosphatase. A nanoprobe was designed that consists of CdSe/ZnS quantum dots (QDs) coated with the terbium(III) complex of guanosine monophosphate (Tb-GMP). The nanoprobe was synthesized from carboxylated QDs, Tb(III) and GMP via binding of Tb(III) by both the carboxy and the phosphate groups. The nanoprobe, under single-wavelength excitation (at 280 nm), displays dual (red and green) emission, with peaks at around 652 nm from the QDs, and at 547 nm from the Tb-GMP coordination polymers. It is shown to be a viable nanoprobe for fluorometric determination of As(V) detection through it inhibitory action on the activity of acid phosphatase (ACP). The enzyme destroys the Tb-GMP structure via hydrolysis of GMP, and hence the fluorescence of the Tb-GMP complex is quenched. In contrast, the fluorescence of the CdSe/ZnS QDs remains inert to ACP. It therefore can serve as an internal reference signal. In the presence of arsenate (an analog of phosphate), the activity of ACP is inhibited due to competitive binding. Thus, hydrolysis of GMP is prevented. These findings were used to design a ratiometric fluorometric method for the quantification of As(V). The ratio of fluorescences at 547 and 652 nm increases linearly in the 0.5 to 200 ppb As(V) concentation range, and the limit of detection is 0.39 ppb. Under a UV lamp, the probe shows distinguishable color from green to red on increasing the concentration of As(V). Graphical abstract Schematic illustration of CdSe/ZnS quantum dot coated with carboxy-PEG and modified with the terbium(III)-GMP complex as a fluorescent nanoprobe for ratiometric determination of arsenate via its inhibition of ACP activity.

Continuously Tunable Nucleotide/Lanthanide Coordination Nanoparticles for DNA Adsorption and Sensing

Metal-organic coordination polymers (CPs) have attracted great research interest because they are easy to prepare, porous, flexible in composition, and designable in structure. Their applications in biosensor development, drug delivery, and catalysis have been explored. Lanthanides and nucleotides can form interesting CPs, although most previous works have focused on a single type of metal ligand. In this work, we explored mixed nucleotides and studied their DNA adsorption properties using fluorescently labeled oligonucleotides. Adenosine monophosphate (AMP) and guanosine monophosphate (GMP) formed negatively charged CP nanoparticles with most lanthanides, and thus a salt was required to adsorb negatively charged DNA. DNA adsorption was faster and reached a higher capacity with lighter lanthanides. Desorption of pre-adsorbed DNA by inorganic phosphates, urea, proteins, surfactants, and competing DNA was successively carried out. The results suggested the importance of the DNA phosphate backbone, although hydrogen bonding and DNA bases also contributed to adsorption. The AMP CPs adsorbed DNA more strongly than the GMP ones, and using mixtures of AMP and GMP, continuous tuning of DNA adsorption affinity was achieved. Such CPs were also used as a sensor for DNA detection based on the different affinities of single- and double-stranded DNA, and a detection limit of 0.9 nM target DNA was achieved. Instead of tuning DNA adsorption by varying the length and sequence of DNA, the composition of CPs can also be controlled to achieve this goal.

Robust Hydrogels from Lanthanide Nucleotide Coordination with Evolving Nanostructures for a Highly Stable Protein Encapsulation

Metal coordination with organic ligands often produce crystalline metal-organic frameworks and sometimes amorphous nanoparticles. In this work, we explore a different type of material from the same chemistry: hydrogels. Lanthanides are chosen as the metal component because of their important technological applications and continuously tunable properties. Adenosine monophosphate (AMP) and lanthanides form two types of coordination materials: the lighter lanthanides from La³⁺ to Tb³⁺ form nanoparticles, whereas the rest heavier ones initially form nanoparticles but later spontaneously transform to hydrogels. This slow sol-to-gel transition is accompanied by heat release, as indicated by isothermal titration calorimetry. The transition is also accompanied by a morphology change from nanoparticles to nanofibers, as indicated by transmission electron microscopy. These gels are insensitive to ionic strength or temperature with excellent stability. Gelation is unique to AMP because other nucleotides or other adenine derivatives only yield nanoparticles or soluble products. Entrapment of guest molecules such as glucose oxidase is also explored, where the hydrogels allow a better enzyme activity and stability compared to nanoparticles. Further applications of lanthanide coordinated hydrogels might include biosensors, imaging agents, and drug delivery.

A Novel Manganese Complex with Mixed Ligands: Preparation, Structure, Photoluminescent and Semiconductive Properties

A manganese complex with mixed ligands, [Mn(2,2′-biim)2(4,4′-bipy)] n[Mn(2,2′-biim)3]2 n6 n(ClO4)•8 nH2O (2,2′-biim = 2,2′-biimidazole; 4,4′-bipy = 4,4′-bipyridine), has been obtained by a hydrothermal procedure and its structure determined by single-crystal X-ray crystallography. A two-dimensional (2-D) supramolecular layer is established through hydrogen-bonding interactions. Solid-state photoluminescence measurement reveals that this complex shows a blue light emission. Solid-state diffuse reflectance determination uncovers the presence of a narrow optical band gap of 2.18 eV in this complex.

Spatially controlled clustering of nucleotide-stabilized vesicles

A two-step hierarchical self-assembly process is presented relying on the GMP-induced formation of vesicles, which then cluster into large aggregates upon the addition of Ag⁺-ions.

Spectroelectrochemical study of the AMP-Ag+and ATP-Ag+complexes using silver mesh electrodes

In this study, electrochemical reaction mechanism of adenosine monophosphate (AMP) and adenosine triphosphate (ATP) on a silver mesh was investigated in acetate buffer using spectroelectrochemical technique.

Crystal structures of N6-modified-aminoacid/peptide nucleobase analogs: hybrid adenine–glycine and adenine–glycylglycine molecules

Anion–π interactions in crystal structures of N⁶-modified-aminoacid and dipeptide adenine analogs are investigated using X-ray crystallography and DFT calculations.

Double layer zinc–UDP coordination polymers: structure and properties

Double layer Zn–UDP coordination polymers with potentially open sites can be used for heterogeneous fluorescent sensors of amino acids.

Nucleobases, nucleosides, and nucleotides: versatile biomolecules for generating functional nanomaterials

The incorporation of biomolecules into nanomaterials generates functional nanosystems with novel and advanced properties, presenting great potential for applications in various fields. Nucleobases, nucleosides and nucleotides, as building blocks of nucleic acids and biological coenzymes, constitute necessary components of the foundation of life. In recent years, as versatile biomolecules for the construction or regulation of functional nanomaterials, they have stimulated interest in researchers, due to their unique properties such as structural diversity, multiplex binding sites, self-assembly ability, stability, biocompatibility, and chirality. In this review, strategies for the synthesis of nanomaterials and the regulation of their morphologies and functions using nucleobases, nucleosides, and nucleotides as building blocks, templates or modulators are summarized alongside selected applications. The diverse applications range from sensing, bioimaging, and drug delivery to mimicking light-harvesting antenna, the construction of logic gates, and beyond. Furthermore, some perspectives and challenges in this emerging field are proposed. This review is directed toward the broader scientific community interested in biomolecule-based functional nanomaterials.

Hydrogels Based on Ag+ -Modulated Assembly of 5'-Adenosine Monophosphate for Enriching Biomolecules

Supramolecular hydrogels obtained by combining 5'-adenosine monophosphate (AMP) with Ag⁺ were fabricated in this work. Their gelation capability was enhanced by increasing the concentration of Ag⁺ or decreasing the pH. The gels are very sensitive to light, which endows them with potential applications as visible-light photosensitive materials. Coordination between the nucleobase of AMP and Ag⁺ , as well as π-π stacking of nucleobases, are considered to be the main driving forces for self-assembly. The hydrogels successfully achieved the encapsulation and enrichment of biomolecules. Hydrogen bonding between the amino group of guest molecules and silver nanoparticles along the nanofibers drives the enrichment and is considered to be a crucial interaction.

Directed adenine functionalization for creating complex architectures for material and biological applications

In this feature article, targeted design strategies are outlined for modified adenine nucleobase derivatives in order to construct metal-mediated discrete complexes, ring-expanded purine skeletons, linear and catenated coordination polymers, shape-selective MOFs, and purine-capped nanoparticles, with a wide range of applications from gas and solvent adsorption to bioimaging agents and anticancer metallodrugs. The success of such design strategies could be ascribed to the rich chemistry of purine and pyrimidine derivatives, versatile coordination behavior, ability to bind a host of metal ions, which could be further tuned by the introduction of additional functionalities, and their inherent propensity to hydrogen bond and exhibit π-π interactions. These noncovalent interactions produce stable frameworks and network solids that are useful as advanced materials, and the biocompatibility of these ligand complexes provides an impetus for assessing novel biological applications.

Cytosine-Cytosine Base-Pair Mismatch and Chirality in Nucleotide Supramolecular Coordination Complexes

The base-pair sequences are the foundation for the biological processes of DNA or RNA, and base-pair mismatch is very important to reveal genetic diseases and DNA rearrangements. However, the lack of well-defined structural information about base-pair mismatch is obstructing the investigation of this issue. The challenge is to crystallize the materials containing the base-pair mismatch. Engineering the small-molecule mimics or model is an effective strategy to solve this issue. Here, six cytidine-5'-monophosphate (CMP) and 2'-deoxycytidine-5'-monophosphate (dCMP) coordination polymers were reported containing cytosine-cytosine base-pair mismatch (i-motif), and their single-crystal structures and chiralities were studied. The precise control over the formation of the i-motif was demonstrated, in which the regulating of supramolecular interactions was achieved based on molecular design. In addition, the chiralities of these coordination polymers were investigated according to their crystal structures and solution- and solid-state circular dichroism spectroscopy.

Multicopper Laccase Mimicking Nanozymes with Nucleotides as Ligands

Using nanomaterials to achieve functional enzyme mimics (nanozymes) is attractive for both applied and fundamental research. Laccases are multicopper oxidases highly important for biotechnology and environmental remediation. In this work, we report an exceptionally simple yet functional laccase mimic based on guanosine monophosphate (GMP) coordinated copper. It forms an amorphous metal-organic framework (MOF) material. The ratio of copper and GMP is 3:4 as determined by isothermal titration calorimetry. It has excellent laccase-like activity and converts a diverse range of phenol containing substrates such as hydroquinone, naphthol, catechol and epinephrine. Comparative work shows that the activity is originated from guanosine coordination instead of phosphate binding in GMP. Cu²⁺ is required and cannot be substituted by other metal ions. At the same mass concentration, the Cu/GMP nanozyme has a higher V_max and similar K_m compared to the protein laccase. To achieve the same catalytic efficiency, the cost of the Gu/GMP is ∼2400-fold lower than that of laccase. The Cu/GMP is much more stable at extreme pH, high salt, high temperature and for long-term storage. This is one of the first laccase-mimicking nanozymes, which will find important applications in analytical chemistry, environmental protection, and biotechnology.

Unusual crystal structure and chirality of uridine 5′-monophosphate coordination polymer

The auxiliary ligand effect in the structure and charility of uridine 5′-monophosphate coordination polymer was investigated.

Kinetic trapping - a strategy for directing the self-assembly of unique functional nanostructures

Supramolecular self-assembly into various nano- or microscopic structures based on non-covalent interactions between molecules has been recognized as a very efficient approach that leads to functional materials. Since most non-covalent interactions are relatively weak and form and break without significant activation barriers, the thermodynamic equilibrium of many supramolecular systems can be easily influenced by processing pathways that allow the system to stay in a kinetically trapped state. Thus far, kinetic traps have been found to be very important in producing more elaborate structural and functional diversity of self-assembled systems. In this review, we try to summarize the approaches that can produce kinetically trapped self-assemblies based on examples made by us. We focus on the following subjects: (1) supramolecular pathway dependent self-assembly, including kinetically trapped self-assemblies facilitated by host-guest chemistry, coordination chemistry, and electrostatic interactions; (2) physical processing pathway dependent self-assembly, including solvent quality controlled self-assembly, evaporation induced self-assembly and crystallization induced self-assembly.

Lamellar supramolecular materials based on a chelated metal complex for organic dye adsorption

The industrial poisonous waste chelated copper complex can be made into recyclable lamellar supramolecular materials which display excellent adsorption ability towards organic dyes.

Non-covalent marriage of β-cyclodextrin-polyethylene glycol and functional polyacrylamide via host–guest interaction: construction, characterization and performances

This paper reports the non-covalent marriage of bridged β-cyclodextrin and functional acrylamide polymers via host–guest interactions.

Structure advantage and peroxidase activity enhancement of deuterohemin-peptide–inorganic hybrid flowers

Hybridizing deuterohemin-peptide (DhHP-6) with copper phosphate to form hybrid flowers was prepared for preventing DhHP-6 aggregation.

Controllable synthesis of nucleotide complex based on pH control: a small-molecule fluorescent probe as an auxiliary ligand to indicate the pre-organization of the nucleotide complex in solution

Different CMP-bpe-M(ii) (CMP = cytidine monophosphate, bpe = bis(4-pyridyl)ethylene, M(ii) = Mn(2+) and Co(2+)) complexes are synthesized controllably based on pH control and well studied by X-ray single-crystal diffraction analysis. Interestingly, the suitable pH conditions are explored by considering the pre-organization modes of CMP, bpe, and M(2+) in aqueous solution by fluorescence spectroscopy based on acid/basic titration. The organic base bpe serves as a small-molecule fluorescent probe to indicate the changes of pre-organization modes along with the changes of the solution acidity. Furthermore, a perfect self-complementary sugar-base hydrogen bond is first reported based on the crystal structure analysis in this work, and different chiralities and SHG activities of CMP-bpe-Mn(ii) complexes obtained at different pH values are studied.