Stability of a Dinuclear Cu(II)–β-Cyclodextrin Complex

Pattern-based recognition of proteins by an array of fluorescent carbon-nanodot receptors

Protein types and concentrations in human body fluid environment have a direct correlation to health conditions, and can be used for primary screening and diagnostics of a great variety of diseases. Herein, we synthesized a series of fluorescent carbon nanodots (CDs) with various ratios of β-cyclodextrin doping, which can recognize proteins and adjust self-emission by combining both the cavity recognition effect of cyclodextrin and noncovalent bonding effect of carboxyl, amino and hydroxyl groups. The difference in β-cyclodextrin contents of various CDs will result in a differential response to various proteins, based on which a sensor array by four CDs was constructed to detect and discriminate six proteins with various subunit numbers. In order to improve the discriminative effect of the sensor array, CD-sensitive metal ions (Cu²⁺ and Fe³⁺) were introduced as sensing media to increase the action sites between the CDs and proteins, and these proteins were well discriminated by the CD@metal ion sensor array with a detection limit of 50 μM. The sensor array could work in physiological conditions (such as urine and serum) and realize multiple proteins detection. Combining with the good repeatable detection results and higher sensitivity, the sensor array based on the CDs and metal ions provides an efficient and accurate method to detect proteins, which is important for disease diagnosis through assessing protein levels.

Synthesis of a New Copper-Based Supramolecular Catalyst and Its Catalytic Performance for Biodiesel Production

A new copper-based supramolecular (β-cyclodextrins, β-CD) catalyst was synthesized and used for transesterification of Xanthium sibiricum Patr oil to biodiesel. This catalyst exhibited high activity (88.63% FAME yield) in transesterification under the ratio of methanol-oil: 40 : 1; catalyst dosage: 8 wt.%; reaction temperature: 120°C; and reaction time: 9 h. The XRD, SEM, TEM, XPS, and BET characterization results showed that Cu-β-CD catalyst was amorphous and had clear mesoporous structure (17.2 nm) as compared with the native β-CD. This phenomenon is attributed to the coordination of Cu and β-CD.

Cu(II) complex formation with xylitol in alkaline solutions

The formation of four Cu(II)-xylitol complexes was observed in aqueous alkaline solutions (11.0< or =pH< or =14.0, I=1.0, 20 degrees C) by means of direct current polarography and VIS spectrophotometry. Mononuclear hydroxy complexes, CuXyl(OH)- (log beta=17.7 +/- 0.5), CuXyl(OH)2(2-) (log beta=20.2 +/- 0.3) and CuXyl2(OH)2(4-) (log beta=22.4 +/- 0.3), are formed at high ligand-to-metal ratios (L:M> or =10), whereas dinuclear complex Cu2Xyl (log beta=29.2 +/- 0.3) is the predominant species at low ligand-to-metal ratio (L:M=0.5). Diffusion coefficients and molar absorptivities of the complex species were determined. pH variable 13C NMR suggested that pKa values of xylitol are rather similar and equal to 13.8 +/- 0.2, 13.9 +/- 0.1 and 13.9 +/- 0.2 for OH-groups adjacent to (C-1,C-5), (C-3) and (C-2,C-4) carbon atoms, respectively.