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In this work, bovine serum albumin (BSA) and Aspergillus sp. laccase (LC) were encapsulated in situ within two lanthanide-based MOFs (TbBTC and GdBTC) through a green one-pot synthesis (almost neutral aqueous solution, T = 25 °C, and atmospheric pressure) in about 1 h. Pristine MOFs and protein-encapsulated MOFs were characterized through wide angle X-ray scattering, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared and Raman spectroscopies. The location of immobilized BSA molecules, used as a model protein, was investigated through small angle X-ray scattering. BSA occurs both on the inner and on the outer surface of the MOFs. LC@TbBTC, and LC@GdBTC samples were also characterized in terms of specific activity, kinetic parameters, and storage stability both in water and acetate buffer. The specific activity of LC@TbBTC was almost twice that of LC@GdBTC (10.8 μmol min-1 mg-1vs. 6.6 μmol min-1 mg-1). Both biocatalysts showed similar storage stabilities retaining -60% of their initial activity after 7 days and -20% after 21 days. LC@TbBTC dispersed in acetate buffer exhibited a higher storage stability than LC@GdBTC. Additionally, terbium-based MOFs showed interesting luminescent properties. Together, these findings suggest that TbBTC and GdBTC are promising supports for the in situ immobilization of proteins and enzymes. [ABSTRACT FROM AUTHOR]

To tackle the obstacles related to tumor targeting and overcome the limitations of single treatment models, we have developed a nanoplatform that is both tumor-targeted and enzyme-responsive. This nanoplatform integrates photothermal gold nanorods (AuNRs) and protein drugs into a single system. This nanosystem, known as AuNRs@HA-mPEG-Deta-LA, was fabricated by modifying gold nanorods (AuNRs) with a polymeric ligand called hyaluronic acid-grafted-(mPEG/diethylenetriamine-conjugated-lipoic acid). The purpose of this fabrication was to load cytochrome c (CC) and utilize it for the synergetic protein–photothermal therapy of cancer. The resulting nanoplatform exhibited a high efficiency in loading proteins and demonstrated excellent stability in different biological environments. Additionally, CC-loaded AuNRs@HA-mPEG-Deta-LA not only enabled localized hyperthermia for photothermal therapy (PTT) with laser irradiation but also facilitated the release of CC under the action of hyaluronidase, an enzyme known to be overexpressed in tumor cells. The confocal imaging results demonstrated that the presence of a specific polymeric ligand on this nanoparticle enhances the internalization of CD44-positive cancer cells, accelerates endo/lysosomal escape, and facilitates the controlled release of CC within the cells. Furthermore, the results of the MTT assay also showed that AuNRs@HA-mPEG-Deta-LA as a protein nanocarrier demonstrated excellent biocompatibility. Importantly, this synergistic therapeutic strategy effectively induced apoptosis in A549 cancer cells by increasing the intracellular concentration of CC and utilizing the photothermal conversion of AuNRs, which was observed to be more effective compared to using only protein therapy or PTT. Therefore, this study showcased a nanoplatform based on AuNRs that has great potential for tumor-targeted protein delivery in combination with PTT in cancer treatment. [ABSTRACT FROM AUTHOR]

The preceding paper (Dalton Trans., 2008, DOI: 10.1039/b806100a) describes the logical development of a chemical mechanism for the catalysis of hydrogenation of N2to 2NH3that occurs at the Fe7MoS9Nc(homocitrate) cofactor (FeMo-co) of the enzyme nitrogenase. The mechanism uses a single replenishable path for serial supply of protons which become H atoms on FeMo-co, migrating to become S–H and Fe–H donors to N2and to the intermediates that follow. This chemical catalysis at FeMo-co is distinctly intramolecular: transition states and reaction profiles for the preferred 21 step pathway were presented. This paper describes a number of alternative intermediates and pathways that were considered in developing the mechanism. These results reveal further relevant principles of the reactivity of hydrogenated FeMo-co, and the reasons why these pathways are less likely to be part of the mechanism. The intramolecular character of the mechanism, and the relatively small distances over which H atoms transfer, lead to expectations of extensive quantum mechanical hydrogen tunneling as part of the catalytic rate enhancement. This possibility is supported by comparisons of reaction profiles with those for enzyme reactions for which tunneling is established. [ABSTRACT FROM AUTHOR]

In this work, three iridium(III) tetrazolato complexes have been designed and successfully synthesized. Beside photophysical properties, their performances in protein staining have been comprehensively investigated in this work for the first time. Notably, these iridium(III) tetrazolato complexes with high quantum efficiency exhibited much better protein staining properties than the commercial agent Coomassie Brilliant Blue (CBB) under the same experimental conditions, which may pave the way to explore new efficient iridium-based protein staining agents both for commercial markets and academic research in the future. [ABSTRACT FROM AUTHOR]

A novel and highly efficient dual-targeting PtII system was designed to improve the drug delivery capacity and selectivity in cancer treatment. The dual-targeting monofunctional PtII complexes (1–8) having glycosylated pendants as tridentated ligand were achieved by introducing glycosylation modification in the thioaminocarbazone compounds with potential lysosomal targeting ability. The structures and stability of 1–8 were further established by various techniques. Molecular docking studies showed that 2 was efficiently docked into glucose transporters protein 1 (GLUT1) and P-glycoprotein (Pgp) proteins with the optimal CDocker-interaction-energy of −64.84 and −48.85 kcal mol−1. Complex 2 with higher protein binding capacity demonstrated significant and broad-spectrum antitumor efficacy in vitro, even exhibiting a half maximal inhibitory concentration (IC50) value (∼10 μM) than cisplatin (∼17 μM) against human lung adenocarcinoma cells (A549). The inhibitor experiment revealed GLUT-mediated uptake of 2, and the subcellular localization experiment in A549 also proved that 2 could be localized in the lysosome, thereby causing cell apoptosis. Moreover, cellular thermal shift assay (CETSA) confirmed the binding of 2 with the target proteins of GLUT1 and Pgp. The above results indicated that 2 represents a potential anticancer candidate with dual-targeting functions. [ABSTRACT FROM AUTHOR]

Carbon-supported bimetallic NiCo nanoparticles (NPs) have emerged as attractive catalysts and adsorbents for the reduction of 4-nitrophenol (4-NP) and separation of histidine-rich (His-rich) protein recently due to their low cost, high catalytic activity and good affinity for His-rich protein. In this study, new strongly coupled nickel–cobalt alloy/N,P,S co-doped carbon (NPSC) nanocages are rationally designed via chemical etching of the ZIF-67 dodecahedron with Ni2+ under sonication at room temperature, followed by poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) coating and subsequent carbonization treatment in a nitrogen atmosphere. When evaluated as a catalyst for 4-NP or an adsorbent for His-rich protein, the as-prepared NiCo@NPSC nanocages obtained at 700 °C show better performance than those obtained at other temperatures (500 and 900 °C). This improved catalytic effect is attributed to the controllable size and fine distribution of the NiCo NPs together with the effective contact between the catalysts and the N,P,S co-doped carbon matrix, leading to a superior catalytic effect on the reduction of 4-NP and the adsorption of His-rich protein. This catalyst design principle can be easily extended to other catalysis research fields. [ABSTRACT FROM AUTHOR]

Dirhodium complexes of general formula [Rh2(O2CR)4]L2 are a well-known class of bimetallic compounds that are used as efficient catalysts for a variety of reactions and have been shown to be potent antibacterial and anticancer agents. The catalytic and biological properties of these complexes largely depend on the nature of the bridging carboxylate ligands. Trifluoroacetate (tfa)-containing dirhodium compounds have been used to build artificial metalloenzymes upon reaction with peptides and have been shown to be more cytotoxic than dirhodium tetraacetate. However, there is no structural information on the interaction between these compounds and proteins. Here, cis-Rh2(μ-O2CCH3)2(μ-O2CCF3)2 ([cis-Rh2(OAc)2(tfa)2]) has been synthesized and its reaction with bovine pancreatic ribonuclease (RNase A) and hen egg white lysozyme (HEWL) was analyzed using a combination of different techniques, including Fluorine-19 nuclear magnetic resonance spectroscopy and macromolecular X-ray crystallography, with the aim to unveil the differences in the reactivity of tfa-containing dihrodium complexes with proteins when compared to [Rh2(OAc)4]. [cis-Rh2(OAc)2(tfa)2] and [Rh2(OAc)4] bind the N atoms of His side chains of RNase A at the axial position; however the fluorine-containing compound rapidly loses its tfa ligands, while [Rh2(OAc)4] can retain the acetate ligands upon protein binding. The reactivity of [cis-Rh2(OAc)2(tfa)2] with HEWL is slightly distinct when compared to that of [Rh2(OAc)4] under the same experimental conditions; however, both [cis-Rh2(OAc)2(tfa)2] and [Rh2(OAc)4] degrade when soaked within HEWL crystals. These results provide a structural-based guide for the design of new heterogenous chiral dirhodium/peptide and dirhodium/protein adducts with application in the fields of organic synthesis and asymmetric catalysis. [ABSTRACT FROM AUTHOR]

The clinically established gold drug Auranofin was reacted individually with a group of representative proteins, namely ubiquitin, ribonuclease A, carbonic anhydrase, haemoglobin and superoxide dismutase, and adduct formation was monitored in the various cases by ESI-MS analysis. We found that the reaction is highly selective for solvent exposed free cysteines that are modified through coordination of the AuPEt3+ fragment. Indeed, ESI-Q-TOF MS spectra carried out on protein samples incubated with a three fold molar excess of Auranofin allowed direct detection of the native proteins bearing bound AuPEt3+ fragments in the cases of carbonic anhydrase and haemoglobin. At variance, the two proteins that do not possess any free cysteine residue, i.e. ubiquitin and ribonuclease A, were unable to bind the gold fragment. In the case of superoxide dismutase, adduct formation is hindered by the scarce solvent accessibility of the free cysteine residue. These findings were further confirmed by a series of competition binding experiments with ebselen, a potent and selective cysteine-modifying reagent; we observed that pre-treatment with ebselen prevents the binding of the AuPEt3+ fragment to both carbonic anhydrase and haemoglobin. [ABSTRACT FROM AUTHOR]

Organometallic complexes have important application in the field of protein staining, with potential for use in proteomic analysis. The rational synthesis of a trinuclear luminescent organometallic complex with two platinum(II) centres appended to the cyclometalated ligand of the iridium(III) centre is reported here. Two di-2-picolylamine groups bonded to the cyclometalated phenyl pyridine moiety provide three coordinating sites to each platinum centre. The replacement of chloride in the fourth coordination site of two square planar platinum metal centres with the imidazole nitrogen or sulphur atom of histidine/cysteine is evident from the change in luminescence intensity upon binding these amino acids. The increase in luminescence emission intensity upon binding of histidine to the organometallic complex allowed it to be used as a protein staining agent. Reversibility of staining upon washing with imidazole enhances the possibility of its application in mass spectrometric analysis. [ABSTRACT FROM AUTHOR]

Biotinylated pharmaceuticals are of great interest due to the strong interactions between biotinyl-functionality and streptavidin/avidin, which opens up avenues for efficient targeting and localisation. Three new carbon monoxide-releasing molecules (CO-RMs) have been synthesised and characterised using chemical and biological analysis. An alkyne-containing CO-RM 2 was found to be toxic to RAW 264.7 murine macrophages; and thus therapeutically viable CO-RM 1 was employed as the alkyne precursor for [3 + 2] cycloaddition chemistry enabling a new acid-containing CO-RM 4 and biotin-bioconugate-CO-RM (BiotinCORM 5) to be prepared. CO-RM 4 showed significantly improved solubility and BiotinCORM 5 acts as a photo-CO-RM. We have found that an avidin–CORM adduct of 5 is a CO-releasing protein, releasing CO on irradiation with light (400 nm). The avidin–biotinCORM adduct of 5 was found to have a binding energy of 10 kcal mol−1. [ABSTRACT FROM AUTHOR]

The [FeFe] hydrogenase enzyme interconverts protons and molecular hydrogen with remarkable efficiency. The reaction is catalysed by a unique metallo-cofactor denoted as the H-cluster containing an organometallic dinuclear Fe component, the [2Fe] subsite. The HydF protein delivers a precursor of the [2Fe] subsite to the apo-[FeFe] hydrogenase, thus completing the H-cluster and activating the enzyme. Herein we generate a semi-synthetic form of HydF by loading it with a synthetic low valent dinuclear Fe complex. We show that this semi-synthetic protein is practically indistinguishable from the native protein, and utilize this form of HydF to explore the mechanism of H-cluster assembly. More specifically, we show that transfer of the precatalyst from HydF to the hydrogenase enzyme results in the release of CO, underscoring that the pre-catalyst is a four CO species when bound to HydF. Moreover, we propose that an electron transfer reaction occurs during H-cluster assembly, resulting in an oxidation of the [2Fe] subsite with concomitant reduction of the [4Fe4S] cluster present on the HydF protein. [ABSTRACT FROM AUTHOR]

We report a detailed investigation of the formation and self-decomposition of Cu(ii)–hydroperoxo intermediates under the influence of second-coordination-sphere features provided by a cryptand. In solution, an equilibrium between two copper complexes with square-planar and square-pyramidal geometries was identified. Upon addition of H2O2/Et3N, two copper(ii)–hydroperoxo intermediates formed at different rates. Their decomposition via self-oxidation was probed by deuterating select positions on the cryptand. This led to a small kinetic isotope effect of 1.5. Mass spectrometry analysis of the demetallated organic products is consistent with a direct oxygen-atom transfer to a tertiary amine on the cryptand, forming an N-oxide, unlike other models of copper mononuclear monooxygenase enzymes. [ABSTRACT FROM AUTHOR]

Chemotherapeutics for the treatment of tumorigenic conditions that feature novel modes of action are highly sought after to overcome the limitations of current chemotherapies. Herein, we report the conjugation of the alkylating agent chlorambucil to the RAPTA scaffold, a well-established pharmacophore. While chlorambucil is known to alkylate DNA, the RAPTA complexes are known to coordinate to amino acid side chains of proteins. Therefore, such a molecule combines DNA and protein targeting properties in a single molecule. Several chlorambucil-tethered RAPTA derivatives were prepared and tested for their cytotoxicity, stability in water and reactivity to protein and DNA substrates. The anticancer activity of the complexes is widely driven by the cytotoxicity of the chlorambucil moiety. However, especially in the cisplatin-resistant A2780R cells, the chlorambucil-functionalized RAPTA derivatives are in general more cytotoxic than chlorambucil and also a mixture of chlorambucil and the parent organoruthenium RAPTA compound. In a proof-of-principle experiment, the cross-linking of DNA and protein fragments by a chlorambucil–RAPTA derivative was observed. [ABSTRACT FROM AUTHOR]

Correction for 'Novel insights into the metal binding ability of ZinT periplasmic protein from Escherichia coli and Salmonella enterica' by Denise Bellotti et al., Dalton Trans., 2020, 49, 9393–9403, DOI: 10.1039/D0DT01626H. [ABSTRACT FROM AUTHOR]

Cadmium is a highly toxic group XII metal, similar to zinc and mercury. Unlike zinc, which is one of the most common metal cofactors in biology, cadmium is highly toxic. Many Zn2+-binding proteins can bind Cd2+-ions without significantly affecting their structures. Here, the protein data bank is analysed with regard to protein-cadmium interactions, which shows that cadmium can bind to a variety of ion binding sites in proteins. Statistical analysis of Cd2+-side chain interactions is compared with a similar analysis of other ions. This analysis reveals that with regard to amino acid side-chain preference, Cd2+ is more similar to Mn2+ than to Zn2+ or Hg2+. Finally, the interaction energies of three native metal binding proteins are calculated where Cd2+ binds instead of Zn2+, Ca2+ or Cu2+. The interaction energies are decomposed into individual components whose contributions are discussed. [ABSTRACT FROM AUTHOR]

Taking advantage of the facile and versatile synthetic properties of 'click' 1,2,3-triazolylidene N-heterocyclic carbenes (tzNHC's), a range of new organometallic Ru(II) and Os(II) arene complexes containing functionalised tzNHC ligands, [M(η6-p-cymene)(tzNHC)Cl2] [M = Ru(II), Os(II)], have been synthesised and fully characterised, including the X-ray crystal structure of one of the Os(II) complexes. The tzNHC ligands remain coordinated to the metal centres under relevant physiological conditions, and following binding to the model protein, ubiquitin. The in vitro cytotoxicity of the compounds towards human ovarian cancer cells is dependent on the substituent on the tzNHC ligand but is generally <50 μM and in some cases <1 μM, whilst still retaining a high degree of selectivity towards cancer cells over healthy cells (1.85 μM in A2780 ovarian cancer cells versus 435 μM in human embryonic kidney cells in one case). [ABSTRACT FROM AUTHOR]

The non-specific interaction between the surface of gold nanorods (GNRs) and biomolecules is a significant problem in hyperthermia applications. In this work, a novel surface modification strategy was performed using zwitterionic oxidized glutathione (GSSG) to modify the GNRs through robust Au–S bond formation. The GSSG-GNRs were stable in aqueous solution over a broad range of pH and high ionic strength values. Importantly, the glutathione coating greatly reduced non-specific protein adsorption on GNRs due to zwitterions. In order to target tumor sites, folic acid (FA) and Rhodamine B (RBITC) dye were conjugated to GSSG modified GNRs through the reaction between the activated carboxyl group and the amino group. The targeting of RBITC-FA-GSSG-GNRs in human cervical carcinoma cells (HeLa cells) with high-level folate receptor expression was confirmed using confocal laser scanning microscopy (CLSM) to excite Rhodamine B dye at 488 nm. The targeting photothermal therapy efficacy was monitored in real time with the multi-channel function of a confocal laser scanning microscope coupled with an 808 nm laser. The results indicate that the FA-GSSG-GNR hybrids demonstrate efficient photothermal conversion and excellent targeting hyperthermia, and are therefore suitable for biomedical applications. [ABSTRACT FROM AUTHOR]

Reflecting the increasing interest in combinatorial approaches, peptide phage display has seen an unprecedented expansion in a wide range of research areas. Its application to the discovery and analysis of metal binding peptides has opened up new research directions and largely contributed to the nanotechnology field. The rationale behind the need to identify such peptides varies depending on the final aim of the research and its application. Therefore, the possibility to modify the selection technique according to the different requirements would allow for a more systematic approach to be adopted and would ultimately provide substantial benefits. Although the standard panning method can be virtually applied to any target, its use for the identification of metal binding peptides does not provide the characteristics and the flexibility required for an efficient and tailored selection. Here we report on the development of a new panning method that can contribute to a faster, versatile and more informative analysis. Through the use of rolling-circle amplification, polymerase reaction and wild type phage, we have converted the standard selection technique into a more dynamic process in which adjustments can be evaluated and made consistently with the need of the experiment. The successfulness of the improved method is demonstrated in a number of panning experiments with different inorganic targets. The modifications applied to each selection are described and comparisons between the results obtained are made in order to extensively assess and evaluate the impact of the new process. The importance of tailoring the screening method to the specific objectives of a study is also considered. New binder sequences for the materials included in the investigation are identified; their sequences and distinctive characteristics are reported and their ability to act as templates for the nucleation of inorganic material is demonstrated and discussed. [ABSTRACT FROM AUTHOR]

Atomically dispersed Fe species embedded in the nitrogen-containing carbon supports (Fe1/NC) are successfully synthesized using a ball milling approach, with commercial protein powder as the nitrogen source. The catalyst exhibits outstanding performance in the oxidation of aromatic compounds containing saturated C–H bonds into corresponding ketones under ambient conditions, which is superior to those of a nanoparticle catalyst (Fen/NC) and a metal-free catalyst (NC). [ABSTRACT FROM AUTHOR]

Lectins, which exhibit viral-interaction abilities, have garnered attention in the current pandemic era as potential neutralizing agents and vaccine candidates. Viral invasion through envelope proteins is modulated by N-linked glycosylation in the spike (S) protein. This study demonstrates the biophysical aspects between lectins and high-mannose and -galactose N-glycans to provide insights into binding events. [ABSTRACT FROM AUTHOR]

Metallic nickel- or cobalt-based composites with hollow nanostructures such as nanocages can serve as both advanced catalysts and protein adsorbents owing to their high surface area and increased active sites; hence, they have aroused great interest. Herein, we report a facile route to synthesize hollow carbon spheres (HCS) embedded with bimetallic NiCo nanoparticles (NPs) with hollow structures by using NiCo hydroxide layered nanosheet functionalized carboxyl polystyrene spheres (CPS) as a template and polydopamine (PDA) as both the carbon precursor and reductant. This unique hierarchical architecture, including meso- and macro-pores, provides a large specific surface area (244 m2 g−1) and efficient channels for the diffusion of small molecules and biomacromolecules (protein). These features greatly facilitate the excellent performances of C@CoNi for the reduction of 4-nitrophenol and His-rich protein adsorption. Moreover, the size of the surficial CoNi NPs can be facilely modulated by changing the calcination temperature, which can effectively control the catalytic and adsorption performances of the as-prepared nanocomposites. The as-prepared C@CoNi is employed as a catalyst to investigate its catalytic performance in the reduction of 4-nitrophenol (4-NP). Furthermore, the nickel nanoparticles decorated on the hollow microspheres display a strong affinity to His-rich proteins (BHb and BSA) via specific metal affinity forces between the polyhistidine groups and nickel nanoparticles. [ABSTRACT FROM AUTHOR]

One of the most attractive areas in inorganic chemistry is the synthesis of polyoxometalates (POMs) exhibiting new properties and applications. Since the impact of POMs in biochemistry and related fields of research has increased in the last few years, there has been a special interest in this topic. Significant progress in biological applications has been made where the interaction of POMs with amino acids, peptides and proteins is relevant. Versatile POMs play a series of different roles in the interaction with these biomolecules as described in this review. Various types of interactions are established, depending on the POM shape and charge, the amino acid side chain, peptide sequence or protein structure. Experimental conditions such as temperature, acidity, solvent, etc. are also important factors that influence the binding/reactivity of POM with biomolecules, as described herein. This understanding allows the adequate design of the POM-biomolecule couple for tailoring and controlling mechanisms of action such as catalysis, inhibition, and aggregation, or the crystallising agent. [ABSTRACT FROM AUTHOR]

This perspective outlines strategies towards the development of MR imaging probes that our lab has explored over the last 15 years. Namely, we discuss methods to enhance the signal generating capacity of MR probes and how to achieve tissue specificity through protein targeting or probe activation within the tissue microenvironment. [ABSTRACT FROM AUTHOR]

A crystallographic study of the adduct formed between hen egg white lysozyme (HEWL) and NAMI-A, an established ruthenium(III) anticancer agent in clinical trials, is presented here. The X-ray structure reveals that NAMI-A coordinates the protein, as a naked ruthenium ion, at two distinct sites (namely Asp101 or Asp119) after releasing all its original ligands (DMSO, imidazole and Cl-). Structural data of the HEWL/ NAMI-A adduct are compared with those previously obtained for the HEWL adduct of AziRu, a NAMI-A analogue bearing a pyridine in place of imidazole. The present results further support the view that NAMI-A exerts its biological effects acting as a classical "prodrug" first undergoing activation and then causing extensive metalation of relevant protein targets. It is also proposed that the original Ru-ligands, although absent in the final adduct, play a major role in directing the ruthenium center to its ultimate anchoring site on the protein surface. [ABSTRACT FROM AUTHOR]

The antitumour activity of the organometallic ruthenium(ii)–arene mixed phosphine complexes, [Ru(η6-p-cymene)Cl(PTA)(PPh3)]BF41b and [Ru(η6-C6H5CH2CH2OH)Cl(PTA)(PPh3)]BF42b (PTA = 1,3,5-triaza-7-phosphaadamantane), have been evaluated in vitro and compared to their RAPTA analogues, [Ru(η6-p-cymene)Cl2(PTA)] 1a and [Ru(η6-C6H5CH2CH2OH)Cl2(PTA)] 2a. The results show that the addition of the PPh3 ligand to 2a increases the cytotoxicity towards the TS/A adenocarcinoma cancer cells, which correlates with increased uptake, but also increases cytotoxicity to non-tumourigenic HBL-100 cells, thus decreasing selectivity. The decrease in selectivity has been correlated to increased DNA interactions relative to proteins, demonstrated by reactivity of the compounds with a 14-mer oligonucleotide and the model proteins ubiquitin and cytochrome-c. [ABSTRACT FROM AUTHOR]