Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pyrimidine oligonucleotides recognize extended purine sequences in the major groove of double-helical DNA by triple-helix formation. The resulting local triple helices are relatively stable and can block DNA recognition by sequence-specific DNA binding proteins such as restriction endonucleases. Association and dissociation kinetics for the oligodeoxyribonucleotide 5'-CTCTTTCCTCTCTTTTTCCCC (bold C's indicate 5-methylcytosine residues) are now measured with a restriction endonuclease protection assay. When oligonucleotides are present in greater than 10-fold excess over the DNA target site, the binding reaction kinetics are pseudo first order in oligonucleotide concentration. Under our standard conditions (37 degrees C, 25 mM Tris-acetate, pH 6.8, 70 mM sodium chloride, 20 mM magnesium chloride, 0.4 mM spermine tetrahydrochloride, 10 mM beta-mercaptoethanol, 0.1 mg/mL bovine serum albumin) the value of the observed pseudo-first-order association rate constant, k2obs, is 1.8 x 10(3) +/- 1.9 x 10(2) L.(mol of oligomer-1.s-1. Measurement of the dissociation rate constant yields an equilibrium dissociation constant of approximately 10 nM. Increasing sodium ion concentration slightly decreased the association rate, substantially increased the dissociation rate, and thereby reduced the equilibrium binding constant. This effect was reversible by increasing multivalent cation concentration, confirming the significant role of multivalent cations in oligonucleotide-directed triple-helix formation under these conditions. Finally, a small reduction in association rate, a large increase in dissociation rate, and a resulting reduction in the equilibrium binding constant were observed upon increasing the pH between 6.8 and 7.2.
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PMID:Kinetic analysis of oligodeoxyribonucleotide-directed triple-helix formation on DNA. 227 58

A self-complementary decadeoxyribonucleotide d-CpCpApApGpCpTpTpGpG was chemically synthesized by a procedure based on the phosphotriester approach. This procedure was carefully monitored and appropriately modified to ensure the purity of oligomer components at each step of the synthetic scheme. Extensive use was made of both analytical and preparative high-pressure liquid chromatography to purify and characterize the decamer and its constituent oligonucleotides. The final product (1318 A257 units or 16.5 mumol) was obtained in high purity and sufficient quantity for extensive physical studies by UV, CD, and NMR spectroscopy. Our preliminary results show that at a strand concentration of 1.3 X 10(-5) M and in 0.10 M sodium chloride and 0.01 M sodium phosphate buffer, pH 7.0, the decamer duplex has a Tm at 47 degrees C. The CD spectrum of this decamer duplex is similar to that of B-form DNA. All the resonances of the nonexchangeable base protons of the decamer are well resolved in the 1H NMR spectrum, when the single-stranded form was examined by using a 360-MHz spectrometer and when the duplex form was examined by using a 600-MHz spectrometer. These base proton resonances have been tentatively assigned by using the incremental assignment technique. Although the decamer duplex serves as a substrate for AluI restriction endonuclease, it is not cleaved by HindIII endonuclease.
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PMID:Preparation of a decadeoxyribonucleotide helix for studies by nuclear magnetic resonance. 625 55

Low molecular weight homogeneous peptides were used to form peptide/DNA condensates. A peptide possessing 18 lysines was found to protect plasmid DNA from serum endonuclease and sonicative-induced degradation whereas a shorter peptide possessing 8 lysines dissociated in 0.1 M sodium chloride and failed to protect DNA from enzymatic degradation. Peptide-condensed DNA showed no change in the ratio of supercoiled to circular DNA following 100 W sonication for up to 60 s and was able to transfect HepG2 cells with equivalent efficiency as untreated condensed plasmid DNA. Alternatively, uncondensed plasmid DNA was rapidly fragmented by sonication and serum endonucleases and resulted in negligible gene expression following condensation with peptide. Cationic lipid/DNA complexes were only partially effective at stabilizing DNA in serum compared to the complete stabilization afforded by peptide/DNA condensation. These results indicate that the stabilization afforded by condensation with a peptide protects DNA during formulation and preserves its structure in serum. These functions are important to achieve optimal gene expression from a nonviral gene delivery system.
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PMID:Stability of peptide-condensed plasmid DNA formulations. 960 43

The effects of sodium chloride on photoreactivation of Escherichia coli were examined, assuming the discharge of ultraviolet (UV)-treated wastewater to water environment at different salinities. Suspensions of E. coli were first exposed to a low-pressure UV lamp in phosphate buffer to achieve 3 log inactivation, followed by an exposure to fluorescent light in NaCl solutions at the concentration of 1.0, 1.4, 1.9, 2.4 and 2.9 weight/volume %. When photoreactivation was completed in 3 h, survival ratio was recovered about 2 log in 1.0, 1.4, and 1.9% NaCl solutions, which was equivalent to the recovery observed in phosphate-buffered solution. Meanwhile, the recovery was suppressed to 0.8 log and -0.2 log in 2.4 and 2.9% NaCl solutions, respectively, which was significantly less than the recovery in phosphate buffer according to the t-test (p < 0.05). An endonuclease sensitive site assay demonstrated that the suppressed photoreactivation in 2.9% NaCl solution was due to the failure at repairing UV-induced pyrimidine dimers in the genome. In conclusion, photoreactivation of E. coli was significantly suppressed in NaCl solution at 2.4% or higher but not affected in NaCl solution at 1.9% or lower. This implies that photoreactivation of E. coli may potentially occur in brackish and coastal areas where salinity is rather low.
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PMID:Effects of salinity on photoreactivation of Escherichia coli after UV disinfection. 2398 74