Single-strand, defined

The reference standards are used to quantitate the standards that are employed in the kits to generate the standard curves. The kit standards are recombinant single-stranded DNA molecules that are added to either negative serum or plasma at known concentrations. Because the standard curve is not constructed with reference standards, Chiron initially chose to use the term equivalent to describe the units of nucleic acid quantitation in clinical samples. An equivalent was defined as the amount of nucleic acid in a clinical sample that gave a signal equal to one molecule of the reference standard nucleic acid. The term copy rather than equivalent is used to describe the units of nucleic acid quantitation in the HIV-1 bDNA assay. The terms are now used interchangeably. 

Although the hybridization of single-stranded DNA to its complement results in detectable changes in electrochemical properties, particularly in support of non-Faradaic current, the DNA bases may also demonstrate redox behavior that gives rise to Faradaic currents. The electrochemical behavior of DNA has been studied over the past few decades. Differential pulse voltammograms show clearly defined peaks for the reduction of cytosine and adenosine. Electrochemical characterization of guanine by cyclic voltammetry has shown... 

The number of DNA molecules doubles in each cycle of the process, so that after 30 cycles, say, we have molecules (approximately 10 copies). However, there is another, less obvious feature that makes the PCR even more useful. In the second cycle, two of the newly synthesized single-stranded chains will be of defined length. They will consist of the target area plus two primers the 5 -ends of the... 

Fig. 3 Thermal denaturation transition of a DNA helix, (a) UV absorbance increases with temperature, following the unstacking of bases, following a sigmoidal shape. AD and Au are lower and upper baselines, also slightly dependent on temperature, (b) Fraction of single strands 6 extracted from data in (a), which defines the melting temperature corresponding to 9 = 0.5. Adapted with permission from [7]...

Double helical structures may be constructed from complementary single-stranded polynucleotide chains sharing a common helical axis according to the procedure outlined below. The two strands of the complex are assumed to be regular helices defined by a common set of backbone and glycosyl torsion angles. The data presented here are limited to model poly(dA) poly(dT) double helices stabilized by Watson-Crick base pairs between anti parallel strands. 

The flexible helix modeled here is best described by the entire array of conformations it can assume. A comprehensive picture of this array is provided by the three-dimensional spatial probability density function Wn(r) of all possible end-to-end vectors (25, 35). This function is equal to the probability per unit volume in space that the flexible chain terminates at vector position relative to the chain origin 0,as reference. An approximate picture of this distribution function is provided by the three flexible single-stranded B-DNA chains of 128 residues in Figure 5(a). The conformations of these molecules are chosen at random by Monte Carlo methods (35, 36) from the conformations accessible to the duplex model. The three molecules are drawn in a common coordinate system defined by the initial virtual bond of each strand. For clarity, the sugar and base moieties are omitted and the segments are represented by the virtual bonds connecting successive phosphorus atoms. 

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