Biomaterial Database

Scanning tunneling microscopy of nucleic acids. 1989

G Lee, and P G Arscott, and V A Bloomfield, and D F Evans

Department of Chemical Engineering and Materials Science Interfacial, University of Minnesota, Minneapolis 55455.

The scanning tunneling microscope (STM) has been used to measure properties of poly(rA).poly(rU) and DNA, such as helical pitch, half-period oscillations that were interpreted as the alternation between the major and minor grooves, and interhelical spacing. Average pitches were measured by two-dimensional Fourier transforms and by topographic profiles along the fiber axes. Values were typically 7 percent less than standard dimensions of A-form RNA and B-form DNA fibers. This result is compatible with the mild dehydration that occurred under air-drying conditions. More extensive dehydration typically led to 19 percent shrinkage. Analysis of specific regions allowed local variations in helical pitch as small as 1 angstrom to be detected, thus demonstrating that the STM can visualize functionally significant modulations of nucleic acid structure.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D009690	Nucleic Acid Conformation	The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.	DNA Conformation,RNA Conformation,Conformation, DNA,Conformation, Nucleic Acid,Conformation, RNA,Conformations, DNA,Conformations, Nucleic Acid,Conformations, RNA,DNA Conformations,Nucleic Acid Conformations,RNA Conformations
D011063	Poly A-U	A double-stranded polyribonucleotide comprising polyadenylic and polyuridylic acids.	Polyadenylic-Polyuridylic Acid,Poly r(A-U),Poly(rA)-Poly(rU),Acid, Polyadenylic-Polyuridylic,Poly A U,Polyadenylic Polyuridylic Acid
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D005583	Fourier Analysis	Analysis based on the mathematical function first formulated by Jean-Baptiste-Joseph Fourier in 1807. The function, known as the Fourier transform, describes the sinusoidal pattern of any fluctuating pattern in the physical world in terms of its amplitude and its phase. It has broad applications in biomedicine, e.g., analysis of the x-ray crystallography data pivotal in identifying the double helical nature of DNA and in analysis of other molecules, including viruses, and the modified back-projection algorithm universally used in computerized tomography imaging, etc. (From Segen, The Dictionary of Modern Medicine, 1992)	Fourier Series,Fourier Transform,Analysis, Cyclic,Analysis, Fourier,Cyclic Analysis,Analyses, Cyclic,Cyclic Analyses,Series, Fourier,Transform, Fourier
D012313	RNA	A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)	RNA, Non-Polyadenylated,Ribonucleic Acid,Gene Products, RNA,Non-Polyadenylated RNA,Acid, Ribonucleic,Non Polyadenylated RNA,RNA Gene Products,RNA, Non Polyadenylated