Effects of naturally occurring S47F/A mutations on the structure and function of human cytochrome c.

The sequence and structure of human cytochrome c (hCyt c) exhibit evolutionary conservations, with only a limited number of naturally occurring mutations in humans. Herein, we investigated the effects of the naturally occurring S47F/A mutations on the structure and function of hCyt c in the oxidized form. Although the naturally occurring S47F/A mutations did not largely alter the protein structure, the S47F and S47A variants exhibited a small fraction of high-spin species. Kinetic studies showed that the peroxidase activity of the variants was enhanced by ∼2.5-fold under neutral pH conditions, as well as for the rate in reaction with H2O2, when compared to those of wild-type hCyt c. In addition, we evaluated the interaction between hCyt c and human neuroglobin (hNgb) by isothermal titration calorimetry (ITC) studies, which revealed that the binding constant was reduced by ∼8-fold as result of the mutation of the hydrophilic Ser to the hydrophobic Phe/Ala. These findings provide valuable insights into the role of Ser47 in Ω-loop C in sustaining the structure and function of hCyt c.

Phosphine-Catalyzed Atroposelective Formal [3 + 2] Cycloaddition Desymmetrization of N-Arylmaleimides.

Herein, a new strategy for the enantioselective synthesis of axially chiral N-aryl succinimides was devised by [3 + 2] annulation of MBH carbonates and N-aryl maleimides under chiral phosphine. This desymmetrization process allows for quick construction of both two stereogenic carbon centers and a remote CAr-N atropisomeric chirality. A series of structurally diverse N-aryl succinimides were obtained with good to excellent yields, diastereoselectivities, and enantioselectivities. The process is mild, efficient, and scalable and features a broad substrate scope.

Revisiting imidazolium receptors for the recognition of anions: highlighted research during 2010-2019.

Imidazolium based receptors selectively recognize anions, and have received more and more attention. In 2006 and 2010, we reviewed the mechanism and progress of imidazolium salt recognition of anions, respectively. In the past ten years, new developments have emerged in this area, including some new imidazolium motifs and the identification of a wider variety of biological anions. In this review, we discuss the progress of imidazolium receptors for the recognition of anions in the period of 2010-2019 and highlight the trends in this area. We first classify receptors based on motifs, including some newly emerging receptors, as well as new advances in existing receptor types at this stage. Then we discuss separately according to the types of anions, including ATP, GTP, DNA and RNA.

Self-assembling nanoprobes that display two-dimensional fluorescent signals for identification of surfactants and bacteria.

The imidazolium-pyrene self-assembling nanoprobes can rapidly discriminate four types of surfactants. The surfactants disassembled the probes to turn on significant fluorescence and transform between a pyrene monomer and an excimer, generating a two-dimensional analysis map. The probes were further used to identify different bacterial species.

Rapid Identification of Bacteria by Membrane-Responsive Aggregation of a Pyrene Derivative.

An imidazolium-derived pyrene aggregation was developed to rapidly identify and quantify different bacteria species. When the nonemissive aggregates bound to the anionic bacteria surface, the sensor disassembled to turn on significant fluorescence. At the same time, ratiometric signals between pyrene monomer and excimer emission were controlled by different interactions with various bacteria surfaces. The resulted different fluorescent emission profiles then were obtained as fingerprints for various bacterial species. By converting emission profiles directly into output signals of two channels, fluorescence increase and ratiometric change, a two-dimensional analysis map was generated for bacteria identification. We demonstrated that our sensor rapidly identified 10 species of bacteria and 14 clinical isolated multidrug-resistant bacteria, and we determined their staining properties (Gram-positive or Gram-negative).

The environmental-sensitivity of a fluorescent ZTRS-Cd(ii) complex was applied to discriminate different types of surfactants and determine their CMC values.

We have, for the first time, reported a fluorescent probe (ZTRS-C18-Cd(ii) complex) which discriminated four types of surfactants. This recognition was realized depending on the transformation of ZTRS-Cd2+ binding patterns in different microenvironments formed in various types of surfactants.