Exploring the oxidation and iron binding profile of a cyclodextrin encapsulated quercetin complex unveiled a controlled complex dissociation through a chemical stimulus

Background

Flavonoids possess a rich polypharmacological profile and their biological role is linked to their oxidation state protecting DNA from oxidative stress damage. However, their bioavailability is hampered due to their poor aqueous solubility. This can be surpassed through encapsulation to supramolecular carriers as cyclodextrin (CD). A quercetin- 2HP-β-CD complex has been formerly reported by us. However, once the flavonoid is in its 2HP-β-CD encapsulated state its oxidation potential, its decomplexation mechanism, its potential to protect DNA damage from oxidative stress remained elusive. To unveil this, an array of biophysical techniques was used.

环糊精葡萄糖基转移酶的性质、应用与固定化研究进展

本文总结了环糊精葡萄糖基转移酶的性质、应用与固定化研究的进展情况,引用文献４７篇。     

Biomolecular interaction study of hydralazine with bovine serum albumin and effect of β‐cyclodextrin on binding by fluorescence, 3D,synchronous, CD,and Raman spectroscopic methods

Spectrofluoremetric technique was employed to study the binding behavior of hydralazine with bovine serum albumin (BSA) at different temperatures. Binding study of bovine serum albumin with hydralazine has been studied by ultraviolet–visible spectroscopy, fluorescence spectroscopy and confirmed by three‐dimensional, synchronous, circular dichroism, and Raman spectroscopic methods. Effect of β‐cyclodextrin on binding was studied. The experimental results showed a static quenching mechanism in the interaction of hydralazine with bovine serum albumin. The binding constant and the number of binding sites are calculated according to Stern–Volmer equation. The thermodynamic parameters ?H^o, ?G^o, ?S^o at different temperatures were calculated. These indicated that the hydrogen bonding and weak van der Waals forces played an important role in the interaction. Based on the Förster's theory of non‐radiation energy transfer, the binding average distance, r, between the donor (BSA) and acceptor (hydralazine) was evaluated and found to be 3.95 nm. Spectral results showed that the binding of hydralazine to BSA induced conformational changes in BSA. The effect of common ions on the binding of hydralazine to BSA was also examined. Copyright © 2016 John Wiley & Sons, Ltd.     

On the synthesis of cyclodextrin–peptide conjugates by the Huisgen reaction

A,D‐substituted cyclodextrin (CDX) substituted on their primary rim side are ideal scaffolds for the macromolecular assembly and formation of templated structures. Their substitution can be achieved through various reactions. However, the use of the well‐known Huisgen reaction in this context is under‐reported. We present here results of the synthesis of model conjugates formed between CDX and representative peptides by click chemistry. Notably, bis‐conjugation of peptides onto a unique scaffold promotes α‐helix formation. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Chiral separation of vinpocetine using cyclodextrin-modified micellar electrokinetic chromatography

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) technique has been developed for enantioseparation of vinpocetine using an inexpensive 2-hydroxypropyl-β-CD (HP-β-CD) as the chiral selector (CS). The best chiral separation was achieved using 40 mM HP-β-CD as the CS in 50 mM phosphate buffer (pH 7.0) consisting of 40 mM sodium dodecyl sulfate (SDS) at a separation temperature and separation voltage of 25°C and 25 kV, respectively. To the author's best knowledge, this is the first CD-MEKC study able to successfully separate the four stereoisomer of vinpocetine in separation time of 9.5 min and resolution of 1.04-3.87.     

DNA compaction into new DNA vectors based on cyclodextrin polymer: surface enhanced Raman spectroscopy characterization

The ability of DNA to bind polycation yielding polyplexes is widely used in nonviral gene delivery. The aim of the present study was to evaluate the DNA compaction with a new DNA vector using Raman spectroscopy. The polyplexes result from an association of a beta-cyclodextrin polymer (polybeta-CD), an amphiphilic cationic connector (DC-Chol or adamantane derivative Ada2), and DNA. The charge of the polymeric vector is effectively controlled by simple addition of cationic connector in the medium. We used surface enhanced Raman spectroscopy (SERS) to characterize this ternary complex, monitoring the accessibility of adenyl residues to silver colloids. The first experiments were performed using model systems based on polyA (polyadenosine monophosphate) well characterized by SERS. This model was then extended to plasmid DNA to study polybeta-CD/Ada2/DNA and polybeta-CD/DC-Chol/DNA polyplexes. The SERS spectra show a decrease of signal intensity when the vector/DNA charge ratio (Z+/-) increases. At the highest ratio (Z+/- = 10) the signal is 6-fold and 3-fold less intense than the DNA reference signal for Ada2 and DC-Chol polyplexes, respectively. Thus adenyl residues have a reduced accessibility as DNA is bound to the vector. Moreover, the SERS intensity variations are in agreement with gel electrophoresis and zeta potential experiments on the same systems. The overall study clearly demonstrates that the cationic charges neutralizing the negative charges of DNA result in the formation of stable polyplexes. In vitro transfection efficiency of those DNA vectors are also presented and compared to the classical DC-Chol lipoplexes (DC-Chol/DNA). The results show an increase of the transfection efficiency 2-fold higher with our vector based on polybeta-CD.     

Unexpected reaction of beta-cyclodextrin tosylate with pyrrolidinones

Substitution reactions of 6I-O-p-tolylsulfonylcyclomaltoheptaose with alkyl- and arylamines in 1-methyl-2-pyrrolidinone and various pyrrolidinones were investigated. An unexpected reaction of the tosyl group with pyrrolidinones was observed resulting in products deriving from nucleophilic attack by the lactam carbonyl oxygen and further opening of the heterocyclic ring. The new compounds have been fully characterized by ESIMS and NMR analyses.