Protein-encapsulated gold nanoclusters have shown many advantages over other gold nanocluster systems, including green synthesis, biocompatibility, high water solubility, and the ease of further conjugation. In this article, we systematically investigated the effects of the protein size and amino acid content on the formation and fluorescent properties of gold nanoclusters using four model proteins (bovine serum albumin, lysozyme, trypsin, and pepsin). We discovered that the balance of amine and tyrosine/tryptophan containing residues was critical for the nanocluster formation. Protein templates with low cysteine contents caused blue shifts in the fluorescent emissions and difference in fluorescent lifetimes of the gold nanoclusters. Furthermore, the protein size was found to be a critical factor for the photostability and long-term stability of gold nanoclusters. The size of the protein also affected the Au nanocluster behaviour after immobilization.

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Host-guest chemistry is governed by the principle of size and shape complementarity: given a particular guest, a concave host must be designed whose cavity presents geometrical features complementary to those of the guest.[1] Moreover, the cavity must offer groups capable of establishing strong yet reversible interactions with the guest. A classical example is provided by octamine cages such as 1 and 2, in which two tren subunits (tren = tris(2-aminoethyl)amine) are linked by either aliphatic (-CH 2 CH 2 -, 1) or aromatic (1,3-xylyl, 2) spacers. In aqueous acidic solution, the six secondary amine[*] Dr.

The organophosphate class of compounds includes common herbicides as well as highly toxic nerve gases whose detection is important from an environmental and a public safety perspective. We describe here a fluorescence turn-on sensor array for the rapid detection and quantitation of relevant organophosphates in neutral water. The array elements self-assemble from commercially available dyes and PAMAM dendrimers, and sensing is based on an indicator displacement assay. Data interpretation through pattern recognition methods (PCA, LDA) showed excellent cluster separation and sample classification. In addition, we were also able to use this system for simultaneous differentiation and quantitative analysis of methylphosphonate (a nerve gas byproduct), glyphosate (a ubiquitous herbicide), and inorganic phosphate over a wide range of concentrations (10 μM to 2 mM).

Ruthenium complexes bearing protic diimine ligands are cytotoxic to certain cancer cells upon irradiation with blue light. Previously reported complexes of the type [(N,N)2Ru­(6,6′-dhbp)]­Cl2 with 6,6′-dhbp = 6,6′-dihydroxybipyridine and N,N = 2,2′-bipyridine (bipy) (1 A ), 1,10-phenanthroline (phen) (2 A ), and 2,3-dihydro-[1,4]­dioxino­[2,3-f]­[1,10]­phenanthroline (dop) (3 A ) show EC50 values as low as 4 μM (for 3 A ) vs breast cancer cells upon blue light irradiation (Inorg. Chem.20177519). Herein, subscript A denotes the acidic form of the complex bearing OH groups, and B denotes the basic form bearing O– groups. This photocytotoxicity was originally attributed to photodissociation, but recent results suggest that singlet oxygen formation is a more plausible cause of photocytotoxicity. In particular, bulky methoxy substituents enhance photodissociation but these complexes are nontoxic (Dalton Trans201815685). Cellular studies are presented herein that show the formation of reactive oxygen species (ROS) and apoptosis indicators upon treatment of cells with complex 3 A and blue light. Singlet oxygen sensor green (SOSG) shows the formation of 1O2 in cell culture for cells treated with 3 A and blue light. At physiological pH, complexes 1 A -3 A are deprotonated to form 1 B -3 B in situ. Quantum yields for 1O2 (ϕΔ) are 0.87 and 0.48 for 2 B and 3 B , respectively, and these are an order of magnitude higher than the quantum yields for 2 A and 3 A . The values for ϕΔ show an increase with 6,6′-dhbp derived substituents as follows: OMe < OH < O–. TD-DFT studies show that the presence of a low lying triplet metal-centered (3MC) state favors photodissociation and disfavors 1O2 formation for 2 A and 3 A (OH groups). However, upon deprotonation (O– groups), the 3MLCT state is accessible and can readily lead to 1O2 formation, but the dissociative 3MC state is energetically inaccessible. The changes to the energy of the 3MLCT state upon deprotonation have been confirmed by steady state luminescence experiments on 1 A -3 A and their basic analogs, 1 B -3 B . This energy landscape favors 1O2 formation for 2 B and 3 B and leads to enhanced toxicity for these complexes under physiological conditions. The ability to convert readily from OH to O– groups allowed us to investigate an electronic change that is not accompanied by steric changes in this fundamental study.