Search

Deamidated amyloid proteins have been shown to accelerate fibril formation. Herein, the results show the inhibition performance and the interaction site between site-specific inhibitor and amyloid protein are significantly influenced by deamidation; while the inhibition mechanism of non-site specific inhibitor shows no significant disruption caused by amyloid protein deamidation. [ABSTRACT FROM AUTHOR]

Strongly luminescent iridium(III) complexes, [Ir(C,N)2( S, S)]+ ( 1) and [Ir(C,N)2(O,O)] ( 2), containing C,N (phenylquinoline), O,O (diketonate), or S,S (dithione) chelating ligands, have been characterized by X-ray crystallography and DFT calculations. Their long phosphorescence lifetimes in living cancer cells give rise to high quantum yields for the generation of 1O2, with large 2-photon absorption cross-sections. 2 is nontoxic to cells, but potently cytotoxic to cancer cells upon brief irradiation with low doses of visible light, and potent at sub-micromolar doses towards 3D multicellular tumor spheroids with 2-photon red light. Photoactivation causes oxidative damage to specific histidine residues in the key proteins in aldose reductase and heat-shock protein-70 within living cancer cells. The oxidative stress induced by iridium photosensitizers during photoactivation can increase the levels of enzymes involved in the glycolytic pathway. [ABSTRACT FROM AUTHOR]

Strongly luminescent iridium(III) complexes, [Ir(C,N)2( S, S)]+ ( 1) and [Ir(C,N)2(O,O)] ( 2), containing C,N (phenylquinoline), O,O (diketonate), or S,S (dithione) chelating ligands, have been characterized by X-ray crystallography and DFT calculations. Their long phosphorescence lifetimes in living cancer cells give rise to high quantum yields for the generation of 1O2, with large 2-photon absorption cross-sections. 2 is nontoxic to cells, but potently cytotoxic to cancer cells upon brief irradiation with low doses of visible light, and potent at sub-micromolar doses towards 3D multicellular tumor spheroids with 2-photon red light. Photoactivation causes oxidative damage to specific histidine residues in the key proteins in aldose reductase and heat-shock protein-70 within living cancer cells. The oxidative stress induced by iridium photosensitizers during photoactivation can increase the levels of enzymes involved in the glycolytic pathway. [ABSTRACT FROM AUTHOR]

Single-domain antibodies, including variable domains of the heavy chains of heavy chain-only antibodies (VHHs) from camelids and variable domains of immunoglobulin new antigen receptors (VNARs) from cartilaginous fish, show the therapeutic potential of targeting antigens in a cytosol reducing environment. A large proportion of single-domain antibodies contain non-canonical cysteines and corresponding non-canonical disulfide bonds situated on the protein surface, rendering them vulnerable to environmental factors. Research on non-canonical disulfide bonds has been limited, with a focus solely on VHHs and utilizing only cysteine mutations rather than the reducing agent treatment. In this study, we examined an anti-lysozyme VNAR and an anti-BC2-tag VHH, including their non-canonical disulfide bond reduced counterparts and non-canonical cysteine mutants. Both the affinity and stability of the VNARs and VHHs decreased in the non-canonical cysteine mutants, whereas the reduced-state samples exhibited decreased thermal stability, with their affinity remaining almost unchanged regardless of the presence of reducing agents. Molecular dynamics simulations suggested that the decrease in affinity of the mutants resulted from increased flexibility of the CDRs, the disappearance of non-canonical cysteine–antigen interactions, and the perturbation of other antigen-interacting residues caused by mutations. These findings highlight the significance of non-canonical cysteines for the affinity of single-domain antibodies and demonstrate that the mutation of non-canonical cysteines is not equivalent to the disruption of non-canonical disulfide bonds with a reducing agent when assessing the function of non-canonical disulfide bonds. [ABSTRACT FROM AUTHOR]

The metallation of nucleic acids is key to wide‐ranging applications, from anticancer medicine to nanomaterials, yet there is a lack of understanding of the molecular‐level effects of metallation. Here, we apply single‐molecule fluorescence methods to study the reaction of an organo‐osmium anticancer complex and DNA. Individual metallated DNA hairpins are characterised using Förster resonance energy transfer (FRET). Although ensemble measurements suggest a simple two‐state system, single‐molecule experiments reveal an underlying heterogeneity in the oligonucleotide dynamics, attributable to different degrees of metallation of the GC‐rich hairpin stem. Metallated hairpins display fast two‐state transitions with a two‐fold increase in the opening rate to ≈2 s−1, relative to the unmodified hairpin, and relatively static conformations with long‐lived open (and closed) states of 5 to ≥50 s. These studies show that a single‐molecule approach can provide new insight into metallation‐induced changes in DNA structure and dynamics. [ABSTRACT FROM AUTHOR]

Photodynamische Therapien bieten neue Möglichkeiten, um Krebszellen unschädlich zu machen und Resistenzen zu überwinden. In ihrer Zuschrift auf S. 15094 berichten P. B. O'Connor, H. Chao, P. J. Sadler et al. über lumineszierende Organoiridiumkomplexe mit langlebigen angeregten Zuständen, die Krebszellen nach Zwei ‐ Photonen ‐ Aktivierung mit rotem Licht selektiv schädigen. Die Komplexe erzeugen Sauerstoff, der wichtige zelluläre Proteine angreift. (Bildgestaltung: Juanjuan Huang) [ABSTRACT FROM AUTHOR]

Photodynamic therapy can be used to introduce novel mechanisms of killing cancer cells that overcome resistance. In their Communication on page 14898 ff., P. B. O'Connor, H. Chao, P. J. Sadler et al. describe luminescent organoiridium complexes, with long‐lived excited states, which selectively damage cancer cells upon activation by two‐photon red light, thus producing oxygen which attacks key cellular proteins (cover art by Juanjuan Huang). [ABSTRACT FROM AUTHOR]

Keywords: DNA; FRET; metallodrugs; organo-osmium complexes; single-molecule studies EN DNA FRET metallodrugs organo-osmium complexes single-molecule studies 4882 4882 1 04/20/20 20200416 NES 200416 B The metallation of a DNA hairpin b by an organo-osmium anticancer complex was studied using single-molecule Förster resonance energy transfer (FRET) microscopy. Ensemble measurements suggested simple, two-state opening and closing of the hairpin, while single-molecule experiments revealed complex DNA dynamics which are attributed to different degrees of metallation of the GC-rich hairpin stem. DNA, FRET, metallodrugs, organo-osmium complexes, single-molecule studies. [Extracted from the article]

The most widely used anticancer drugs are platinum complexes, but complexes of other transition metals also show promise and may widen the spectrum of activity, reduce side-effects, and overcome resistance. The latter include organo-iridium(iii) ‘piano-stool’ complexes. To understand their mechanism of action, it is important to discover how they bind to biomolecules and how binding is affected by functionalisation of the ligands bound to iridium. We have characterised, by MS and MS/MS techniques, unusual adducts from reactions between 3 novel iridium(iii) anti-cancer complexes each possessing reactive sites both at the metal (coordination by substitution of a labile chlorido ligand) and on the ligand (covalent bond formation involving imine formation by one or two aldehyde functions). Peptide modification by the metal complex had a drastic effect on both Collisonally Activated Dissociation (CAD) and Electron Capture Dissociation (ECD) MS/MS behaviour, tuning requirements, and fragmentation channels. CAD MS/MS was effective only when studying the covalent condensation products. ECD MS/MS, although hindered by electron-quenching at the Iridium complex site, was suitable for studying many of the species observed, locating the modification sites, and often identifying them to within a single amino acid residue. [ABSTRACT FROM AUTHOR]

Mass spectrometry has been applied to determine the deamidation sites and the aggregation region of the deamidated human islet amyloid polypeptide (hIAPP). Mutant hIAPP with iso-aspartic residue mutations at possible deamidation sites showed very different fibril formation behaviour, which correlates with the observed deamidation-induced acceleration of hIAPP aggregation. [ABSTRACT FROM AUTHOR]