Oligonucleotide

About: Oligonucleotide is a research topic. Over the lifetime, 23747 publications have been published within this topic receiving 1055723 citations. The topic is also known as: oligonucleotides.

Rapid and efficient site-specific mutagenesis without phenotypic selection.

Abstract: Several single-base substitution mutations have been introduced into the lacZ alpha gene in cloning vector M13mp2, at 40-60% efficiency, in a rapid procedure requiring only transfection of the unfractionated products of standard in vitro mutagenesis reactions. Two simple additional treatments of the DNA, before transfection, produce a site-specific mutation frequency approaching 100%. The approach is applicable to phenotypically silent mutations in addition to those that can be selected. The high efficiency, approximately equal to 10-fold greater than that observed using current methods without enrichment procedures, is obtained by using a DNA template containing several uracil residues in place of thymine. This template has normal coding potential for the in vitro reactions typical of site-directed mutagenesis protocols but is not biologically active upon transfection into a wild-type (i.e., ung+) Escherichia coli host cell. Expression of the desired change, present in the newly synthesized non-uracil-containing covalently closed circular complementary strand, is thus strongly favored. The procedure has been applied to mutations introduced via both oligonucleotides and error-prone polymerization. In addition to its utility in changing DNA sequences, this approach can potentially be used to examine the biological consequences of specific lesions placed at defined positions within a gene.

A versatile vector for gene and oligonucleotide transfer into cells in culture and in vivo: polyethylenimine

Abstract: Several polycations possessing substantial buffering capacity below physiological pH, such as lipopolyamines and polyamidoamine polymers, are efficient transfection agents per se--i.e., without the addition of cell targeting or membrane-disruption agents. This observation led us to test the cationic polymer polyethylenimine (PEI) for its gene-delivery potential. Indeed, every third atom of PEI is a protonable amino nitrogen atom, which makes the polymeric network an effective "proton sponge" at virtually any pH. Luciferase reporter gene transfer with this polycation into a variety of cell lines and primary cells gave results comparable to, or even better than, lipopolyamines. Cytotoxicity was low and seen only at concentrations well above those required for optimal transfection. Delivery of oligonucleotides into embryonic neurons was followed by using a fluorescent probe. Virtually all neurons showed nuclear labeling, with no toxic effects. The optimal PEI cation/anion balance for in vitro transfection is only slightly on the cationic side, which is advantageous for in vivo delivery. Indeed, intracerebral luciferase gene transfer into newborn mice gave results comparable (for a given amount of DNA) to the in vitro transfection of primary rat brain endothelial cells or chicken embryonic neurons. Together, these properties make PEI a promising vector for gene therapy and an outstanding core for the design of more sophisticated devices. Our hypothesis is that its efficiency relies on extensive lysosome buffering that protects DNA from nuclease degradation, and consequent lysosomal swelling and rupture that provide an escape mechanism for the PEI/DNA particles.

Specific synthesis of DNA in vitro via a polymerase-catalyzed chain reaction.

Abstract: Publisher Summary This chapter discusses the specific synthesis of deoxyribonucleic acid (DNA) in vitro through the medium of a polymerase-catalyzed chain reaction. A method whereby a nucleic acid sequence can be exponentially amplified in vitro is described in the chapter. The same method can be used to alter the amplified sequence or to append new sequence information to it. It is necessary that the ends of the sequence be known in sufficient detail that oligonucleotides can be synthesized, which will hybridize to them and that a small amount of the sequence be available to initiate the reaction. The oligonucleotides are complementary to different strands of the desired sequence and at relative positions along the sequence such that the DNA polymerase extension product of the one, when denatured, can serve as a template for the other and vice versa. Oligonucleotides were synthesized using an automated DNA synthesis machine (Biosearch, Inc., San Rafael, California) using phosphoramidite chemistry. “Mispriming"” can be usefully employed to make intentional in vitro mutations or to add sequence information to one or both ends of a given sequence. The chapter explores the possibility of utilizing a heat-stable DNA polymerase so as to avoid the need for addition of new enzyme after each cycle of thermal denaturation

Process for amplifying, detecting, and/or-cloning nucleic acid sequences

Abstract: The present invention is directed to a process for amplifying and detecting any target nucleic acid sequence contained in a nucleic acid or mixture thereof. The process comprises treating separate complementary strands of the nucleic acid with a molar excess of two oligonucleotide primers, extending the primers to form complementary primer extension products which act as templates for synthesizing the desired nucleic acid sequence, and detecting the sequence so amplified. The steps of the reaction may be carried out stepwise or simultaneously and can be repeated as often as desired. In addition, a specific nucleic acid sequence may be cloned into a vector by using primers to amplify the sequence, which contain restriction sites on their non-complementary ends, and a nucleic acid fragment may be prepared from an existing shorter fragment using the amplification process.