Polynucleotides triplexes

Figure 11. Molecular hysteresis in polynucleotide—triplex organizations. Cyclic spectrophotometric acid—base titrations. Absorbance (A) as a function of pH c = 1.67 10 M triplex, (o

Figure 46. Effects of preincubotion of mouse L-cells with polynucleotide triplexes and their partial analogues on subsequent interferon induction by NDV and on VSV propagation (78, 143). Assays 10 fxg/ml DEAE-dextran T = 37°C pH 7.2 PBS concentration of the complexes 10 M (sum of bases), (a) Interferon priming ...

Polynucleotides were reported to form triple helices as early as 1957. Triple strands can form by non-Watson-Crick hydrogen bonds between the third strand and purines involved in Watson-Crick hydrogen bonding with the complementary strand of the duplex (for review, see Ref 34). Thus, triple-stranded structures can be formed between a third strand composed of pyrimidines or purines that interact with a homopurine strand in a homopurine-homopyrimidine strand in a duplex DNA. With the demonstration that homopyrimidine oligonucleotides could indeed form triplex structures (35-37), interest in triple-strand approaches to inhibit transcription heightened. 

Fig. 2. Hydrogen-bonding patterns in polynucleotides, including Watson-Crick pairing characteristic of duplex DNA and RNA (top) Hoogsteen pairing formed in triplex structures (bottom left) and wobble pairing often found in RNA (bottom right).

Figure 9 Pressure-area isotherms of nucleobase amphiphUe monolayers (a) mixed monolayers spread on pure water subphase (b) 1 1 mixture spread on various polynucleotide subphases (c) schematic illustration of triplex formation at the air-water interface.

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