A dual surface plasmon resonance assay for the determination of ribonuclease H activity

An end-point method based on graphene oxide for RNase H analysis and inhibitors screening

As a highly conserved damage repair protein, RNase H can hydrolysis DNA-RNA heteroduplex endonucleolytically and cleave RNA-DNA junctions as well. In this study, we have developed an accurate and sensitive RNase H assay based on fluorophore-labeled chimeric substrate hydrolysis and the differential affinity of graphene oxide on RNA strand with different length. This end-point measurement method can detect RNase H in a range of 0.01 to 1 units /mL with a detection limit of 5.0×10^-3 units/ mL under optimal conditions. We demonstrate the utility of the assay by screening antibiotics, resulting in the identification of gentamycin, streptomycin and kanamycin as inhibitors with IC₅₀ of 60±5µM, 70±8µM and 300±20µM, respectively. Furthermore, the assay was reliably used to detect RNase H in complicated biosamples and found that RNase H activity in tumor cells was inhibited by gentamycin and streptomycin sulfate in a concentration-dependent manner. The average level of RNase H in serums of HBV infection group was similar to that of control group. In summary, the assay provides an alternative tool for biochemical analysis for this enzyme and indicates the feasibility of high throughput screening inhibitors of RNase H in vitro and in vivo.

A hybrid chimeric system for versatile and ultra-sensitive RNase detection

We developed a new versatile strategy that allows the detection of several classes of RNases (i.e., targeting ss- or ds-RNA, DNA/RNA hetero-hybrid or junctions) with higher sensitivity than existing assays. Our two-step approach consists of a DNA-RNA-DNA chimeric Hairpin Probe (cHP) conjugated to magnetic microparticles and containing a DNAzyme sequence in its terminal region, and molecular beacons for fluorescence signal generation. In the first step, the digestion of the RNA portion of the cHP sequences in presence of RNases leads to the release of multiple copies of the DNAzyme in solution. Then, after magnetic washing, each DNAzyme molecule elicits the catalytic cleavage of numerous molecular beacons, providing a strong amplification of the overall sensitivity of the assay. We successfully applied our approach to detect very low concentrations of RNase A, E. coli RNase I, and RNase H. Furthermore, we analyzed the effect of two antibiotics (penicillin and streptomycin) on RNase H activity, demonstrating the applicability of our strategy for the screening of inhibitors. Finally, we exploited our system to detect RNase activity directly in crude biological samples (i.e., blood and saliva) and in cell culture medium, highlighting its suitability as cheap and sensitive tool for the detection of RNase levels.

5'-O-Methylphosphonate nucleic acids--new modified DNAs that increase the Escherichia coli RNase H cleavage rate of hybrid duplexes

Several oligothymidylates containing various ratios of phosphodiester and isopolar 5'-hydroxyphosphonate, 5'-O-methylphosphonate and 3'-O-methylphosphonate internucleotide linkages were examined with respect to their hybridization properties with oligoriboadenylates and their ability to induce RNA cleavage by ribonuclease H (RNase H). The results demonstrated that the increasing number of 5'-hydroxyphosphonate or 5'-O-methylphosphonate units in antisense oligonucleotides (AOs) significantly stabilizes the heteroduplexes, whereas 3'-O-methylphosphonate AOs cause strong destabilization of the heteroduplexes. Only the heteroduplexes with 5'-O-methylphosphonate units in the antisense strand exhibited a significant increase in Escherichia coli RNase H cleavage activity by up to 3-fold (depending on the ratio of phosphodiester and phosphonate linkages) in comparison with the natural heteroduplex. A similar increase in RNase H cleavage activity was also observed for heteroduplexes composed of miRNA191 and complementary AOs containing 5'-O-methylphosphonate units. We propose for this type of AOs, working via the RNase H mechanism, the abbreviation MEPNA (MEthylPhosphonate Nucleic Acid).

A gold nanoparticles enhanced surface plasmon resonance immunosensor for highly sensitive detection of ischemia-modified albumin

In this study a novel sensitive nanogold particle sensor enhancement based on mixed self-assembled monolayers was explored and used to construct a Surface Plasmon Resonance (SPR) immunosensor to detect Ischemia Modified Albumin (IMA). Compared with a direct binding SPR assay at a limit of detection (LOD) of 100 ng/L, gold nanoparticles (AuNPs) of 10 nm dramatically improved the LOD of IMA to 10 ng/L. Meanwhile, no interfering substance that may lead to false positive results was identified. These results suggested that the SPR biosensor presented superior properties, and provided a simple label-free strategy to increase assay sensitivity for further acute coronary syndrome (ACS) diagnosis.

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.

Real-Time Analysis of Specific Protein-DNA Interactions with Surface Plasmon Resonance

Several proteins, like transcription factors, bind to certain DNA sequences, thereby regulating biochemical pathways that determine the fate of the corresponding cell. Due to these key positions, it is indispensable to analyze protein-DNA interactions and to identify their mode of action. Surface plasmon resonance is a label-free method that facilitates the elucidation of real-time kinetics of biomolecular interactions. In this article, we focus on this biosensor-based method and provide a detailed guide how SPR can be utilized to study binding of proteins to oligonucleotides. After a description of the physical phenomenon and the instrumental realization including fiber-optic-based SPR and SPR imaging, we will continue with a survey of immobilization methods. Subsequently, we will focus on the optimization of the experiment, expose pitfalls, and introduce how data should be analyzed and published. Finally, we summarize several interesting publications of the last decades dealing with protein-DNA and RNA interaction analysis by SPR.