Hydrodynamic Characteristics and Adsorption Particularity of Nanobiological Feedstock Along the Bed Height in a Novel Chromatography Column

Expanded bed adsorption (EBA) is a practical method for the separation of nanoparticulates. In order to analysis the local hydrodynamic and adsorption behavior of nanoparticle (NP)-based biological feedstock, a modified Nano Biotechnology Group EBA column with a 26-mm inner diameter was used to withdraw liquid from different axial positions of the column. Fabricated egg albumin (EA) NPs with an average size of 70 nm were employed as a model system and viral size/charge mimic to assess the relationship between hydrodynamic and adsorption performance of NPs at the different column regions. The effects of influential factors, including flow velocity and initial concentration of NPs, on NP hydrodynamic behavior and adsorption kinetics along the bed height were investigated. NP hydrodynamic studies confirmed that non-uniform behavior dominated the system and a decreasing trend of liquid mixing/dispersion with increase of bed height was observed in this column. The results demonstrated an increase in the mixing/dispersion at certain bed heights with the increase in both the velocity and feed initial concentration. Breakthrough curves were measured at various column points to determine the adsorption performance [dynamic binding capacity (DBC) and yield] in different bed positions/zones. Yield and DBC of NPs were improved along the bed height, whereas liquid velocity had the opposite effect. Increasing the initial concentration of NPs enhanced only the DBC. Separation of EA NPs under optimal conditions was 87 %, which is an excellent result for a one-pass frontal chromatography method.

     

Density Functional Theory Studies on the Oxidation of 5'-dGMP and 5'-dAMP by a Platinum(IV) Complex

Density functional theory has been used to investigate the oxidation of a guanine nucleotide by platinum(IV), a process that can be important in the degradation of DNA. For the first time, we have provided a comprehensive mechanism for all of the steps in this process. A number of intermediates are predicted to occur but with short lifetimes that would make them difficult to observe experimentally. A key step in the mechanism is electron transfer from guanine to platinum(IV), and we show that this is driven by the loss of a chloride ligand from the platinum complex after nucleophilic attack of 5'-phosphate to C8 of guanine. We have investigated several different initial platinum(IV) guanine adducts and shown that the adduct formed from replacement of an axial chlorine ligand in the platinum(IV) complex undergoes oxidation more easily. We have studied adenine versus guanine adducts, and our results show that oxidation of the former is more difficult because of disruption of the aromatic π system that occurs during the process. Finally, our results show that the acidic hydrolysis step to form the final oxidized product occurs readily via an initial protonation of N7 of the guanine.     

Spectrofluorimetric and spectrophotometric stability-indicating methods for determination of some oxicams using 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl)

Two sensitive and selective spectrofluorimetric and spectrophotometric stability-indicating methods have been developed for the determination of some non-steroidal anti-inflammatory oxicam derivatives namely lornoxicam (Lx), tenoxicam (Tx) and meloxicam (Mx) after their complete alkaline hydrolysis. The methods are based on derivatization of alkaline hydrolytic products with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl). The products showed an absorption maximum at 460 nm for the three studied drugs and fluorescence emission peak at 535 nm in methanol. The color was stable for at least 48 h. The optimum conditions of the reaction were investigated and it was found that the reaction proceeds quantitatively at pH 8, after heating in a boiling water bath for 30 min. The methods were found to be linear in the ranges of 1-10 microg ml(-1) for Lx and Tx and 0.5-4.0 microg ml(-1) for Mx for spectrophotometric method, while 0.05-1.0 microg ml(-1) for Lx and Tx and 0.025-0.4 microg ml(-1) for Mx for the spectrofluorimetric method. The validity of the methods was assessed according to USP guidelines. Statistical analysis of the results revealed high accuracy and good precision. The suggested procedures could be used for the determination of the above mentioned drugs in pure and dosage forms as well as in the presence of their degradation products.     

Synthesis and characterization of nanostructured-segmented block copolyetheramide based on nylon6 and poly(ethylene oxide)

<正>Segmented block copolymer based on nylon6(N6) and polyethylene oxide(PEO) with stochiometric ratio was synthesized via a two-step process.The first step represents end capping of N6 in the presence of adipic acid leading to carboxy terminated N6,and the second one is polycondensation of the latter product with PEO in the presence of catalyst and thermostabilizer to form a high molecular weight multi-block copolymer.Several methods were applied to characterize the synthesized copolymer such as Fourier transform infrared spectroscopy,proton nuclear magnetic resonance spectroscopy,differential thermal analysis,differential scanning calorimetry,X-ray diffraction and atomic force microscopy. The obtained results confirmed the multi-block structure for copolymer with a very high degree of micro-phase separation. Atomic force microscopy micrographs indicated that the morphology was the dispersion of high stiffness nanostructured polyamide(PA) domains in the amorphous region of PEO matrix,which can be very important in their performance for membrane processes.     

A sensitive opto-fluidic biosensor based on plasmonic-graphene/black phosphorous configuration for detection of hemoglobin concentrations

Optical Review - In this paper, a sensitive Opto-fluidic biosensor for detection of Hemoglobin concentrations in blood samples is proposed and considered. The proposed system is based on the...     

Site-Specific Ubiquitination of Tau Amyloids Promoted by the E3 Ligase CHIP

Post-translational modifications of Tau are emerging as key players in determining the onset and progression of different tauopathies such as Alzheimer's disease, and are recognized to mediate the structural diversity of the disease-specific Tau amyloids. Here we show that the E3 ligase CHIP catalyzes the site-specific ubiquitination of Tau filaments both in vitro and in cellular models, proving that also Tau amyloid aggregates are direct substrate of PTMs. Transmission electron microscopy and mass spectrometry analysis on ubiquitin-modified Tau amyloids revealed that the conformation of the filaments restricts CHIP-mediated ubiquitination to specific positions of the repeat domain, while only minor alterations in the structure of the fibril core were inferred using seeding experiments in vitro and in a cell-based tauopathy model. Overexpression of CHIP significantly increased the ubiquitination of exogenous PHF, proving that the ligase can interact and modify Tau aggregates also in a complex cellular environment.     

Functionally substituted alkylbenzotriazoles: Reactivity of alkylbenzotriazoles toward electrophilic and nucleophilic reagents

The reactivity of benzotriazolylacetone toward a variety of carbon and nitrogen electrophiles is reported. Several novel azolylbenzotriazoles as well as benzotriazolyl‐cinnolines have been synthesized. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:141–145, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10009