Research and Application of Highly Selective Molecular Imprinting Technology in Chiral Separation Analysis

Since residual chiral pollutants in the environment and toxic or ineffective chiral components in drugs can threat human health, there is an urgent need for methods to separation and analyze chiral molecules. Molecular imprinting technology (MIT) is a biomimetic technique for specific recognition of analytes with high potential for application in the field of chiral separation and analysis. However, since MIT has some disadvantages when used for chiral recognition, such as poor rigidity of imprinted materials, a single type of recognition site, and poor stereoselectivity, reducing the interference of conformationally and structurally similar substances to increase the efficiency of chiral recognition is difficult. Therefore, improving the rigidity of imprinted materials, increasing the types of imprinted cavity recognition sites, and constructing an imprinted microenvironment for highly selective chiral recognition are necessary for the accurate identification of chiral substances. In this article, the principle of chiral imprinting recognition is introduced, and various strategies that improve the selectivity of chiral imprinting, using derivative functional monomers, supramolecular compounds, chiral assembly materials, and biomolecules, are reviewed in the past 10 years.

A comparative study on the nickel binding ability of peptides containing separate cysteinyl residues

Nickel(ii) complexes of peptides CSSACS-NH2, ACSSACS-NH2, SSCSSACS-NH2 and GACAAH-NH2 have been studied by potentiometric and various spectroscopic (UV-vis, CD, NMR, and ESI-MS) techniques. All peptides have high nickel(ii) binding ability in the form of square planar complexes and the stability order of the peptides is: CSSACS-NH2 > ACSSACS-NH2 > SSCSSACS-NH2 ∼ GACAAH-NH2. The different metal binding affinities of these peptides are related to the differences in the speciation and in the binding modes of the major species. An almost exclusive formation of bis(ligand) complexes via an (NH2,S-) 5-membered chelate from the amino terminus is characteristic of CSSACS-NH2. The (NH2,N-,S-) tridentate chelate is the major coordination mode of ACSSACS-NH2 but the distant cysteine can also contribute to metal binding. The higher nickel(ii) binding ability of AC[combining low line]SSAC[combining low line]S-NH2 relative to the peptides containing an N-terminal XY-Cys motif may have important biological consequences. For example, the occurrence of the (NH2,N-,S-,S-) donor set is a common feature of both the ACSSACS-NH2 ligand and the nickel(ii) binding loop of the NiSOD enzyme (HC[combining low line]DLPC[combining low line]G…..,). In the case of SSCSSACS-NH2 and GACAAH-NH2 the amino terminus of one peptide can completely saturate the coordination sphere of the nickel(ii) ion via the formation of the (NH2,N-,N-,S-) binding mode. This rules out the formation of bis(ligand) complexes and any contribution of the distant cysteine or histidine to nickel(ii) binding in the 1 : 1 complexes. On the other hand the distant cysteine of SSCSSACS-NH2 and histidine of GACAAH-NH2 can behave as independent metal binding sites for the formation of dinuclear complexes in the presence of excess metal ions.

The ability of the NiSOD binding loop to chelate zinc(ii): the role of the terminal amino group in the enzymatic functions

Equilibrium and detailed spectroscopic characterization of zinc(ii) complexes with NiSOD binding loop and their related model fragments are reported in the whole investigated pH-range. The zinc(ii) complexes of L1 (HCDLPCGVY-NH2), L2 (Ac-HCDLPCGVY-NH2) and L3 (HCDLACGVY-NH2) and the nickel(ii) and zinc(ii) complexes of L4 (HCDLPCG-NH2) were studied by pH-potentiometric and several spectroscopic methods. The results indicated that the macrochelate coordinated zinc(ii) complexes are dominant in a whole pH-range and the side chain donors of the peptides are involved in the metal binding. Therefore, the deprotonation and coordination of the peptide backbone occur only in a strongly alkaline solution. The acetylation of the peptide amino terminus (L2) significantly enhances the zinc(ii) binding ability compared to the corresponding nickel(ii) complexes. L2 complexes of zinc(ii) are 2 or 3 orders of magnitude more stable than the corresponding nickel(ii) complexes. This effect clearly shows the crucial role of the terminal amino group in the nickel binding for the NiSOD enzyme.

Half-sandwich type rhodium(iii)–aminohydroxamate complexes: the role of the position of the amino group in metal ion binding

Relative order of the pH-dependent conditional stability of the hydroxamate type (O,O) and (N_amino,N_hydroxamato) chelates determines the coordination modes in the various mono- and dinuclear complexes of [(η⁵-Cp*)Rh^III(H₂O)₃]²⁺ with α-, β- and γ-aminohydroxamic acids.