Development of sensitive and specific multiplex PCR method for the detection of microcystin producing cyanobacteria in spirulina food supplements

Food Science and Biotechnology - Spirulina has emerged as the next-generation dietary supplement owing to its health benefits. Despite the advantages, there have been reports of contamination by...     

Domains of DnaA protein involved in interaction with DnaB protein, and in unwinding the Escherichia coli chromosomal origin

DnaA protein of Escherichia coli is a sequence-specific DNA-binding protein required for the initiation of DNA replication from the chromosomal origin, oriC. It is also required for replication of several plasmids including pSC101, F, P-1, and R6K. A collection of monoclonal antibodies to DnaA protein has been produced and the primary epitopes recognized by them have been determined. These antibodies have also been examined for the ability to inhibit activities of DNA binding, ATP binding, unwinding of oriC, and replication of both an oriC plasmid, and an M13 single-stranded DNA with a proposed hairpin structure containing a DnaA protein-binding site. Replication of the latter DNA is dependent on DnaA protein by a mechanism termed ABC priming. These studies suggest regions of DnaA protein involved in interaction with DnaB protein, and in unwinding of oriC, or low-affinity binding of ATP.     

Dysfunctional cGMP Signaling Leads to Age-Related Retinal Vascular Alterations and Astrocyte Remodeling in Mice

The nitric oxide–guanylyl cyclase-1–cyclic guanylate monophosphate (NO–GC-1–cGMP) pathway is integral to the control of vascular tone and morphology. Mice lacking the alpha catalytic domain of guanylate cyclase (GC1^−/−) develop retinal ganglion cell (RGC) degeneration with age, with only modest fluctuations in intraocular pressure (IOP). Increasing the bioavailability of cGMP in GC1^−/− mice prevents neurodegeneration independently of IOP, suggesting alternative mechanisms of retinal neurodegeneration. In continuation to these studies, we explored the hypothesis that dysfunctional cGMP signaling leads to changes in the neurovascular unit that may contribute to RGC degeneration. We assessed retinal vasculature and astrocyte morphology in young and aged GC1^−/− and wild type mice. GC1^−/− mice exhibit increased peripheral retinal vessel dilation and shorter retinal vessel branching with increasing age compared to Wt mice. Astrocyte cell morphology is aberrant, and glial fibrillary acidic protein (GFAP) density is increased in young and aged GC1^−/− mice, with areas of dense astrocyte matting around blood vessels. Our results suggest that proper cGMP signaling is essential to retinal vessel morphology with increasing age. Vascular changed are preceded by alterations in astrocyte morphology which may together contribute to retinal neurodegeneration and loss of visual acuity observed in GC1^−/− mice.     

Preferred exocyclic-amino coordination of W(CO)5 on 2-aminopyrimidine and 4-aminopyrimidine vs. heterocyclic N-1 coordination for 2-aminopyridine

2-Aminopyrimidine (2-ampym) and 4-aminopyrimidine (4-ampym) coordinate to W(CO)₅ predominantly via the exocyclic amino group (>91% in 10 min photolysis) rather than to the endocyclic N-1 position as found for 2-aminopyridine (2-ampy). Photolysis of W(CO)₆ in acetone in the presence of these ligands forms amino-bound [W(CO)₅(2-ampym)] and [W(CO)₅(4-ampym)] complexes. Secondary photolysis generates 18% (1.0 h photolysis) [W(CO)₄(2-ampym)] or [W(CO)₄(4-ampym)], chelated via the exocyclic amine and the adjacent endocyclic position (N-1 and N-3, respectively). Only ca. 10% of the more unhindered N-1-bound W(CO)₅(4-ampym) was detected compared to virtually complete coordination via the exocyclic amino group for [W(CO)₅(2-ampym)]. M 94 calculations show that the W(CO)₅ coordination to the exocyclic donor is favored by 98.8 and 95.6 kcal/mol over the adjacent endocyclic position in the 2-ampym and 4-ampym complexes, respectively. Calculated W–N bond lengths by the M 94 methods gave exo-amine W–N bond distances of 2.24 and 2.26 Å and theoretical adjacent endocyclic W–N bond distances of 2.37 and 2.35 Å (isomers not observed from photolysis) for the 2-ampym and 4-ampym complexes, respectively. A W–(N-1) bond of 2.28 Å for this isomer of [W(CO)₅(4-ampym)] was calculated. All W–N bonds are near the 2.18–2.33 Å range (mean of 2.27±0.06) for [W(CO)₅L] (L=pyridine, piperidine, glycine, 1-(2-py)-1,2,4-triazole, [W(CO)₅CN]⁻, 5-MeU⁻).     

Thioether‐Functionalized Corn Oil Biosorbents for the Removal of Mercury and Silver Ions from Aqueous Solutions

Heavy‐metal contamination is one of the most important environmental problems faced in the world, particularly in developing countries. Metals such as silver and mercury from drinking water, food, and air sources can accumulate in living organisms and present significant health concerns. Meanwhile, the demand for these metals in many industries continues to increase. In the present study, thioether‐functionalized corn oil (TFCO) from a photoinitiated thiol‐ene synthesis was utilized to remove Ag⁺ and Hg²⁺ ions from an aqueous solution. An aqueous solution containing AgNO₃ and Hg[NO₃]₂ was prepared and contacted directly with TFCO. After vortex mixing for 60 s, the experiment ran for 351 min with the aqueous phase being periodically sampled for the analysis of metal ions (M ⁿ⁺). Results showed that 88.9% of Ag⁺ and 99.6% of Hg²⁺ ions were removed from the aqueous phase by the TFCO. Mass balances indicated that the total M ⁿ⁺ concentration in the oil phase was 13.890 g kg^?1 under the conditions studied. TFCO exhibited higher selectivity for removing Hg²⁺ than for Ag⁺ ions. Analysis of the adsorption kinetics showed that a pseudosecond‐order model may be used to determine the rate of Ag⁺ ion sorption by the oil phase. The presence of the Hg²⁺ ions interfered with the adsorption of Ag⁺ ions from the aqueous solution.     

Short-Time Oxidation Behavior of Low-Carbon, Low-Silicon Steel in Air at 850–1180 °C: II. Linear to Parabolic Transition Determined Using Existing Gas-Phase Transport and Solid-Phase Diffusion Theories

Existing gas-phase transport and solid-phase diffusion theories are used to calculate the oxidation kinetics of low carbon and low silicon steel in flowing air at 850–1180 °C. The linear-to-parabolic transition scale thickness derived is proportional to the parabolic rate constant and inversely proportional to the linear rate constant. Calculated parabolic rate constants are consistent with experimental results, whereas calculated linear rate constants are 40% smaller and calculated linear-to-parabolic transition scale thicknesses are 20–40% greater than the experimental results. Introduction of a correction factor cannot simultaneously resolve the discrepancies. Various sources causing the discrepancies are discussed. One important issue identified is that the conditions for deriving the equation for calculating the linear rate constant are different from those in laboratory furnaces. The linear-to-parabolic transition scale thickness derived is also a function of gas composition, gas velocity and sample length. An intrinsic gas-phase mass-transfer factor, independent of gas velocity and sample size, is recommended to express the gas-phase mass-transfer coefficient for calculating the linear rate constant.     

Relative effects of cultivar, heat-treatment and sucrose content on the sensory properties of blackcurrant juice

The effects of processing treatments (heat, sucrose addition) on the sensory quality of blackcurrant juices prepared from two genetically diverse cultivars (Ben Lomond and Ben Alder) were examined using sensory profiling. Sucrose level had the largest effect on the sensory profile, with heating and cultivar having smaller but still significant effects. Some interaction between sucrose level and heating of the juices was observed in the sensory profile. The results indicate that selection of preferred genotypes remains an important breeding objective in blackcurrant improvement programmes, since the sensory attributes associated with genotype persist, despite processing effects, in the extracted juice.     

Faecal recovery and diurnal variation in excretion of dietary chromium by mature swine

Diurnal variation in faecal excretion of dietary chromium (Cr) was studied in this experiment in mature swine. Five gestating sows weighing between 225 and 250 kg were fed a corn/soya bean meal diet containing 14% crude protein, NRC recommended amounts of vitamins and minerals with a Ca: P ratio of 1.3:1. Chromic oxide was added (0.1% w/w) to the test diet, and ferric oxide was added (0.5% w/w) to the pre-test and post-test diets as dietary markers. Sows received 0.9 kg of the diet twice daily for 8 days. Total faeces from the test diet were collected and a sample of approximately 150 g of morning samples for days 6 to 9 of the experiment was separated. Faecal recovery of dietary Cr was calculated from the total collection and the samples of the 4-day period. It was found that faecal concentration of the Cr varied between days (P < 0.05) and between times of the day (P < 0.05); true equilibrium of Cr excretion was never reached. Diurnal variation in faecal excretion of dietary Cr was shown to exist; Cr concentration was higher in the late morning samples than in the morning samples (P < 0.05). Total faecal recovery of dietary Cr was 93.27%, whereas a greater (P < 0.05) value was obtained by morning sampling (118.76%). A portion of the dietary Cr (6.73%) was retained in the gastrointestinal tract even after 2 days of Cr withdrawal from the diet.