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The feasibility of using pyrene as a fluorescent probe in complexes cyclodextrin-pyrene-analyte in aqueous solutions was studied for several analytes (A) of different polarity. Bands that prove the formation of the complex PyβCD were found for the first time in the UV-VIS spectrum of an aqueous solution of pyrene in the presence of β-cyclodextrin. A characteristic of a fluorescent probe is the ratio I/ I in the fluorescence spectrum, where I is the intensity of the third vibronic line at ∼800 cm, and I is the intensity of the 0-0 transition. The value of I/ I for PyβCD is highly sensitive to the addition of an analyte with a concentration of several μM/L to the aqueous solution. Dependences of ( I/ I)/ C on the function of the dielectric constant ɛ of the analyte fɛ= (ɛ − 1)/(2ɛ + 1) are divided into two straight lines with different slopes for nonpolar and polar solvents. Energies of insertion of analytes into PyβCD were calculated by the quantumchemical PM3 method. An increase in ( I/ I)/ C corresponds to the more thermodynamically stable complex 2APyβCD. [ABSTRACT FROM AUTHOR]

Abstract: A novel approach for highly sensitive and selective genotyping of single-nucleotide polymorphism (SNP) has been developed based on ligation-rolling circle amplification (L-RCA) and stemless molecular beacon. In this approach, two tailored DNA probes were involved. The stemless molecular beacon, formed through the inclusion interactions of γ-cyclodextrin (γ-CD) and bis-pyrene labeled DNA fragment, was served as signal probe. In the absence of mutant target, the two pyrene molecules were bound in the γ-CD cavity to form an excimer and showed a strong fluorescence at 475nm. It was here named γ-CD-P-MB. The padlock DNA probe was designed as recognition probe. Upon the recognition of a point mutation DNA targets, the padlock probe was ligated to generate a circular template. An RCA amplification was then initiated using the circular template in the presence of Phi29 polymerase and dNTPs. The L-RCA products, containing repetitive sequence units, subsequently hybridized with the γ-CD-P-MB. This made pyrene molecules away from γ-CD cavity and caused a decrease of excimer fluorescence. As a proof-of-concept, SNP typing of β-thalassemia gene at position −28 was investigated using this approach. The detection limit of mutated target was determined to be 40fM. In addition, DNA ligase offered high fidelity in distinguishing the mismatched bases at the ligation site, resulting in positive detection of mutant target even when the ratio of the wildtype to the mutant is 999:1. Given these attractive characteristics, the developed approach might provide a great genotyping platform for pathogenic diagnosis and genetic analysis. [Copyright &y& Elsevier]

β-Cyclodextrin-modified chitosan 1 was synthesized via the Schiff base reaction between 6-O-(4-formylphenyl)-β-cyclodextrin and chitosan (CHIT), and then the supramolecular dyad assemblies 2 and 3 were respectively fabricated from the subunit 1 through the inclusion of adamantane-modified pyrene into the β-cyclodextrin cavity and the wrapping of a CHIT chain on multiwalled carbon nanotubes (MWCNTs). The water-soluble dyad 3 further interacted with adamantane-modified pyrene, forming a stable triad assembly 4. They were extensively characterized by NMR, thermogravimetric analysis, UV-vis, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy (AFM). Furthermore, the DNA condensation abilities of 1-4 were validated by AFM and dynamic light scattering, which indicates that the DNA-condensing capability of CHIT can be pronouncedly improved by either the pyrene grafts or the MWCNT medium. The cooperation between cationic and aromatic groups as well as the dispersion of CHIT agglomerates by MWCNTs are the key factors to enhance DNA condensation of cationic polymers. [ABSTRACT FROM AUTHOR]