Antioxidant effects of live and heat-killed probiotic Lactobacillus plantarum Ln1 isolated from kimchi

The aim of this study was to evaluate the probiotic properties of Lactobacillus plantarum Ln1 isolated from kimchi and the antioxidant activities of live and heat-killed cells. L. plantarum KCTC 3108, which has been used as a commercial probiotic strain, was used as a control. L. plantarum strains (Ln1 and KCTC 3108) can survive under artificial gastric conditions (pH 2.5 in 0.3% pepsin for 3 h and 0.3% oxgall for 24 h), and adhere strongly to HT-29 cells. In addition, L. plantarum Ln1 did not produce carcinogenic β-glucuronidase, whereas it showed a higher β-galactosidase production of 3067.42 mU/mL. The antioxidant activity of L. plantarum Ln1 was assessed using the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, β-carotene and linoleic acid inhibition, and reducing power assays. In all these methods, live L. plantarum Ln1 showed a higher antioxidant activity than the control strain. In heat-killed cells of L. plantarum Ln1, β-carotene bleaching inhibitory activity and reducing power was higher than DPPH and ABTS radical scavenging activity. These results suggested that live or heat-killed L. plantarum Ln1 isolated from kimchi might be useful as an antioxidant probiotic.

Dissecting a known RNA-protein interaction using a yeast three-hybrid system

The yeast three-hybrid system has been applied to known protein-RNA interactions for a variety of purposes. For instance, protein and RNA mutants with altered or relaxed binding specificities can be identified. Mutant RNAs can also be analyzed to better understand RNA-binding specificity of a specific protein. Furthermore, this system complements other biochemical techniques, for example, SELEX, co-immunoprecipitation and cross-linking experiments (see UV crosslinking of interacting RNA and protein in cultured cells and PAR-CLIP (Photoactivatable Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation): a step-by-step protocol to the transcriptome-wide identification of binding sites of RNA-binding proteins).

Identifying proteins that bind a known RNA sequence using the yeast three-hybrid system

The yeast three-hybrid system can be used to identify a protein partner of a known RNA sequence by screening a cDNA library fused to a transcription activation domain, with a hybrid RNA as 'bait.' Most commonly, such screens are performed to identify proteins that interact with a given RNA in vivo.

A simple and sensitive biosensor strain for detecting toxoflavin using β-galactosidase activity

In this study, we developed a simple and sensitive biosensor for the determination of toxoflavin (which is toxic to various plants, fungi, animals, and bacteria) in natural samples based on β-galactosidase activity. The proposed toxoflavin detection method for toxin-producing bacteria or toxin-contaminated foods is simple and cost effective. Burkholderia glumae, a species known to cause rice grain rot and wilt in various field crops, produces toxoflavin under the control of a LysR-type transcriptional regulator ToxR and its ligand toxoflavin. As the expression of toxoflavin biosynthetic genes requires toxoflavin as a co-activator of ToxR, a novel biosensor stain was constructed based on lacZ reporter gene integration into the first gene of the toxoflavin biosynthesis operon, toxABCDE of B. glumae. The biosensor was composed of a sensor strain (COK71), substrates (X-gal or ONPG), and culture medium, without any complex preparation process. We demonstrated that the biosensor strain is highly specific to toxoflavin, and can quantify relative amounts of toxoflavin compared with known concentrations of toxoflavin. The proposed method was reliable and simple; samples containing 50-500 nM of toxoflavin could be analyzed. More importantly, the proposed biosensor strain could identify toxoflavin-producing bacteria in real samples. The excellent performance of this biosensor is useful for diagnostic purposes, such as detecting toxoflavin-contaminated foods and environmental samples.

Determination of Acid β-Galactosidase Activity: Methodology and Perspectives

Early, accurate diagnosis of lysosomal storage disorders is a major challenge, even for trained specialists. Finding innovative, accurate diagnostic methods, and high throughput, cost-effective tools are crucial to medical progress and will contribute to improved quality of life. The goal of this work was to improve currently used protocols to determine activity of acid β-galactosidase, and discuss the possibility analysing lysosomal enzymes with microfluidic systems. A principle of the determination of β-galactosidase activity was fluorometric measurement of a deprotonated form of 4-methylumbelliferone released in the enzymatic reaction. Measurements were performed using Jurkat T cells as a source of the enzyme. We observed the temperature-dependent substrate inhibition effect and determined the substrate (4-MU-β-d-galactopyranoside) concentration which should be used to determine acid β-galactosidase activity at 37 °C (0.8 mM) and at room temperature (0.6 mM). We proved that the sample incubation time may be significantly reduced to only a few minutes. We also showed that the amount of alkaline buffer used to stop the enzymatic reaction may be minimized and even, in some cases, eliminated. The presented results show how the sensitivity of the available methods to diagnose patients suffer from gangliosidosis GM1 or Morquio B disease can be improved. The proposed method may be easily implemented with microfluidic systems, which currently are promising tools for point-of-care applications.