Relationship between Individual and Competitive Adsorption Isotherms on Molecularly Imprinted Polymers

Molecularly imprinted polymers (MIP) are a new generation of selective adsorbents. In practical applications of MIPs simultaneous adsorption of at least two compounds occurs. Simultaneous (typically competitive) adsorption on MIPs has not yet been quantitatively analyzed. This paper shows that with a typical type of MIP the individual isotherms of two compounds coincide with their competitive isotherms in the logD-logq isotherm plot, where D is the distribution coefficient and q is the adsorbed concentration. Based on this observation the usual competitive isotherm, i.e., the (c1,c2 ) to (q1,q2 ) mapping can be established from the two individual isotherms. (The c-s are the respective solution phase equilibrium concentrations.) Batch separation experiments can be easily designed and the selectivity of the MIPs is also easily determined without the tedious measurement of the full competitive isotherm.

Analytical Approaches for the Quantitation of Redox-active Pyridine Dinucleotides in Biological Matrices

Some of the main electron carriers in the metabolism are mono- or dinucleotides and they play crucial roles in maintaining a balanced redox homeostasis of cells, and in coupling many anabolic and catabolic reactions. Altered cellular redox status can be an indicator of various metabolic disorders such as obesity, the metabolic syndrome, or type 2 diabetes and of other pathological conditions, which involve oxidative stress, such as cardiovascular diseases. Adequate NAD+/NADH and NADP+/NADPH ratios are fundamental for normal cellular functions, thus accurate measurement of these pyridine dinucleotides is essential in biochemical research. Liquid chromatography coupled to tandem mass spectrometry has become the leading analytical technology in (targeted) state-of-the-art metabolic profiling. Main difficulties that hamper quantification of metabolites are chemical similarities, high polarity, and chemical and biological instability of the molecules to be measured. In this review, some critical steps of studying cellular redox status are described, in particular, different techniques of sample preparation and challenges in chromatographic separation

Relationship between Commonly Used Adsorption Isotherm Equations Impedes Isotherm Selection

If the measured isotherm data of an adsorption system are well described by the Freundlich equation, then they can similarly well be described by the bi-Langmuir or tri-Langmuir model in most practical cases. This is proved by Monte Carlo simulation and by comparison of the mathematical functions of the respective isotherm models

Identification of lipophilic bioproduct portfolio from bioreactor samples of extreme halophilic archaea with HPLC-MS/MS

Extreme halophilic archaea are a yet unexploited source of natural carotenoids. At elevated salinities, however, material corrosivity issues occur and the performance of analytical methods is strongly affected. The goal of this study was to develop a method for identification and downstream processing of potentially valuable bioproducts produced by archaea. To circumvent extreme salinities during analysis, a direct sample preparation method was established to selectively extract both the polar and the nonpolar lipid contents of extreme halophiles with hexane, acetone and the mixture of MeOH/MTBE/water, respectively. Halogenated solvents, as used in conventional extraction methods, were omitted because of environmental considerations and potential process scale-up. The HPLC-MS/MS method using atmospheric pressure chemical ionization was developed and tuned with three commercially available C-40 carotenoid standards, covering the wide polarity range of natural carotenoids, containing different number of OH-groups. The chromatographic separation was achieved on a C-30 RP-HPLC column with a MeOH/MTBE/water gradient. Polar lipids, the geometric isomers of the C-50 carotenoid bacterioruberin, and vitamin MK-8 were the most valuable products found in bioreactor samples. In contrast to literature on shake flask cultivations, no anhydrous analogues of bacterioruberin, as by-products of the carotenoid biosynthesis, were detected in bioreactor samples. This study demonstrates the importance of sample preparation and the applicability of HPLC-MS/MS methods on real samples from extreme halophilic strains. Furthermore, from a biotechnological point-of-view, this study would like to reveal the relevance of using controlled and defined bioreactor cultivations instead of shake flask cultures in the early stage of potential bioproduct profiling

Two-dimensional percolation at the free water surface and its relation with the surface tension anomaly of water

The percolation temperature of the lateral hydrogen bonding network of the molecules at the free water surface is determined by means of molecular dynamics computer simulation and identification of the truly interfacial molecules analysis for six different water models, including three, four, and five site ones. The results reveal that the lateral percolation temperature coincides with the point where the temperature derivative of the surface tension has a minimum. Hence, the anomalous temperature dependence of the water surface tension is explained by this percolation transition. It is also found that the hydrogen bonding structure of the water surface is largely model-independent at the percolation threshold; the molecules have, on average, 1.90 +/- 0.07 hydrogen bonded surface neighbors. The distribution of the molecules according to the number of their hydrogen bonded neighbors at the percolation threshold also agrees very well for all the water models considered. Hydrogen bonding at the water surface can be well described in terms of the random bond percolation model, namely, by the assumptions that (i) every surface water molecule can form up to 3 hydrogen bonds with its lateral neighbors and (ii) the formation of these hydrogen bonds occurs independently from each other. (C) 2014 AIP Publishing LLC

A novel method of molecular imprinting applied to the template cholesterol

A novel method is successfully tested for non-covalent imprinting. Conditions are used which practically exclude the formation of prepolymerization complexes. The template is cholesterol, and no so-called functional monomer is used. The polymers contain only an acrylic diester crosslinker. The porogen isopropanol prevents even hydrogen bonding between the template and the monomer in the prepolymerization solution. Despite of these apparently very disadvantageous conditions, appreciable imprinting factors for cholesterol and imprinted selectivity against some other steroids are observed, similar to other cholesterol MIPs with proven analytical usefulness

Supplementary data for article: Dorkó, Z.; Szakolczai, A.; Verbic, T.; Horvai, G. Binding Capacity of Molecularly Imprinted Polymers and Their Nonimprinted Analogs. Journal of Separation Science 2015, 38 (24), 4240–4247. https://doi.org/10.1002/jssc.201500874

Supporting information for: [https://doi.org/10.1002/jssc.201500874]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1720

Cdkn2a (Arf) loss drives NF1-associated atypical neurofibroma and malignant transformation

Plexiform neurofibroma (PN) tumors are a hallmark manifestation of neurofibromatosis type 1 (NF1) that arise in the Schwann cell (SC) lineage. NF1 is a common heritable cancer predisposition syndrome caused by germline mutations in the NF1 tumor suppressor, which encodes a GTPase-activating protein called neurofibromin that negatively regulates Ras proteins. Whereas most PN are clinically indolent, a subset progress to atypical neurofibromatous neoplasms of uncertain biologic potential (ANNUBP) and/or to malignant peripheral nerve sheath tumors (MPNSTs). In small clinical series, loss of 9p21.3, which includes the CDKN2A locus, has been associated with the genesis of ANNUBP. Here we show that the Cdkn2a alternate reading frame (Arf) serves as a gatekeeper tumor suppressor in mice that prevents PN progression by inducing senescence-mediated growth arrest in aberrantly proliferating Nf1−/− SC. Conditional ablation of Nf1 and Arf in the neural crest-derived SC lineage allows escape from senescence, resulting in tumors that accurately phenocopy human ANNUBP and progress to MPNST with high penetrance. This animal model will serve as a platform to study the clonal development of ANNUBP and MPNST and to identify new therapies to treat existing tumors and to prevent disease progression