Fluorescence quenching of triazatruxene-based glycocluster induced by peanut agglutinin lectin

A novel triazatruxene-based fluorescent glycocluster was synthesized and its selective binding interactions with PNA lectin were investigated by fluorescence spectroscopy,CD spectroscopy,and a turbidity assay.The glycocluster exhibited a strong binding affinity for PNA lectin with a Stern-Volmer quenching constant of 5.8×10⁵ mol^-1L     

Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces

It was originally shown [10] that urease retains its enzymatic activity when adsorbed at bare mercury and solid amalgam surfaces. However the opinion later prevailed that, when adsorbed at bare metal electrodes, proteins are irreversibly denatured. Here we confirm that urease is enzymatically active at a bare solid amalgam surface as found by Santhanam et al., and we show that this enzyme is equally active at a thiol-modified amalgam surface. We also show that it is the reduced form of urease, which is enzymatically active at Hg surfaces. Oxidation of the protein, resulting in formation of disulfide bonds, strongly decreases the enzyme activity. Using constant current chronopotentiometric stripping (CPS) we show that the exposure of surface-attached urease to negative potentials results in the protein unfolding. The extent of the unfolding depends upon the amount of time for which the protein is exposed to negative potentials, and at very short times this unfolding can be avoided. At thiol-modified Hg surfaces the protein is less vulnerable to the effects of the electric field. We conclude that the loss of enzymatic activity, resulting from a 10 min exposure of the protein to −0.58 V, is not due to reduction of the disulfide bonds as suggested by Santhanam et al. This loss is probably a result of protein reorientation, due to reduction of the Hg-S bonds (formed by accessible cysteines), followed by prolonged electric field effect on the surface-attached protein.     

Surface plasmon resonance sensing of nucleic acids: A review

Biosensors based on surface plasmon resonance (SPR) have become a central tool for the investigation and quantification of biomolecules and their interactions. Nucleic acids (NAs) play a vital role in numerous biological processes and therefore have been one of the major groups of biomolecules targeted by the SPR biosensors. This paper discusses the advances of NA SPR biosensor technology and reviews its applications both in the research of molecular interactions involving NAs (NA–NA, NA–protein, NA–small molecule), as well as for the field of bioanalytics in the areas of food safety, medical diagnosis and environmental monitoring.     

In Vitro Antimicrobial Activity of Lavender,Mint, and Rosemary Essential Oils and the Effect of Their Vapours on Growth of Penicillium spp. in a Bread Model System

The chemical composition, antioxidant activity, and antimicrobial properties of three commercially available essential oils: rosemary (REO), lavender (LEO), and mint (MEO), were determined in the current study. Our data revealed that the major components of REO, MEO, and LEO were 1,8-cineole (40.4%), menthol (40.1%), and linalool acetate (35.0%), respectively. The highest DPPH radical-scavenging activity was identified in MEO (36.85 ± 0.49%) among the investigated EOs. Regarding antimicrobial activities, we found that LEO had the strongest inhibitory efficiencies against the growth of Pseudomonas aeruginosa and Candida (C.) tropicalis, MEO against Salmonella (S.) enterica, and REO against Staphylococcus (S.) aureus. The strongest antifungal activity was displayed by mint EO, which totally inhibited the growth of Penicillium (P.) expansum and P. crustosum in all concentrations; the growth of P. citrinum was completely suppressed only by the lowest MEO concentration. The lowest minimal inhibitory concentrations (MICs) against S. enterica, S. aureus, and C. krusei were assessed for MEO. In situ analysis on the bread model showed that 125 µL/L of REO exhibited the lowest mycelial growth inhibition (MGI) of P. citrinum, and 500 µL/L of MEO caused the highest MGI of P. crustosum. Our results allow us to make conclusion that the analysed EOs have promising potential for use as innovative agents in the storage of bakery products in order to extend their shelf-life.     

Design, synthesis and stimuli responsive gelation of novel stigmasterol-amino acid conjugates

An efficient synthesis of three novel stigmasterol-amino acid (glycine, L-leucine and L-phenylalanine) conjugates as stimuli responsive gelators is reported. The gelation properties of the prepared compounds were investigated in a variety of organic as well as aqueous solvents. The most striking finding of our investigation was that the hydrochloride salts of the prepared conjugates acted as gelators, whereas the neutral conjugates were either non-gelators or formed only a weak gel in anisole. The hydrochloride salts of stigmasteryl glycinate and L-leucinate form gels in n-alcohols (n=4-10) and in ethane-1,2-diol, and that of stigmasteryl L-phenylalaninate forms gels in aromatic solvents and in tetrachloromethane. These unique properties of the gelators were explored to prepare stimuli responsive, "acid-base" triggered reversible sol-gel transitions. The gelators and their gels were characterized by liquid and solid-state NMR as well as FT-IR. The morphology of their corresponding xerogels was investigated by SEM.     

Sequential injection determination of orthophosphate as ion associate of 12-molybdophosphate with Astra Phloxine

A simple and fast reaction between 12-molybdophosphate heteropoly anion and the polymethine dye Astra Phloxine was used for the development of a new SIA method for the determination of orthophosphate. The suggested method has higher sensitivity and a broader calibration range than existing SIA methods. It can be used to detect phosphate in the range from 0.2 to 10 μmol L⁻¹ with a detection limit of 0.1 μmol L⁻¹ and an acceptable throughput of 20 samples h⁻¹. The comparably low molybdate (5.6 mmol L⁻¹) and dye (0.1 mmol L⁻¹) concentrations led to an improvement in the stability of the base line. Inter-day reproducibility was better than 5%, while the intra-day RSD was in the range 0.8-3.5%. The method was used for the analysis of natural water samples and phosphorus-containing chemicals having a low content of orthophosphate.