(1) However, at a 50-fold higher strand concentration, the single-stranded oligomer is gradually converted into the quadruplex.
(2) We propose a model in which duplex or hairpin forms of G-DNA are folding intermediates in the formation of either 1-, 2-, or 4-stranded quadruplex structures.
(3) There has been much recent interest in the self-association of short deoxyguanosine-rich motifs within single-stranded DNAs to generate monovalent cation modulated four-stranded helical segments called G-quadruplexes stabilized by hydrogen-bonded G-tetrad alignments.
(4) Thus the number of T residues surrounding the dG cluster might control the rigidity of the quadruplex structure.
(5) Equilibrium ultracentrifugation studies confirm that these quadruplexes are composed of two strands of d(G3T4G3).
(6) The only precedent known (to us) for a cation-specific stabilization is that seen in the quadruplex structure formed by poly I.
(7) The quadruplex, [d(TTGGGGTT)]4, is resistant to denaturation in 7 M urea, in which the Watson-Crick type d(TTGGGGTT).d(AACCCCAA) duplex dissociates.
(8) We observe well-resolved proton NMR spectra corresponding to a G-quadruplex monomer conformation predominant at 50 mM K cation concentration and a G-quadruplex dimer conformation predominant at 300 mM K cation concentration.
(9) Our results indicate that specific differences in ionic interactions can result in a switch in telomeric DNAs between intramolecular hairpin-like or quadruplex-containing species and intermolecular quadruplex structures, all of which involve G.G base pairing interactions.
(10) The possible biological function of quadruplexes is discussed.
(11) The DNA oligonucleotide d(CGCG3GCG) can form either a Watson-Crick (WC) hairpin or a parallel-stranded quadruplex structure containing six G-quartet base pair assemblies.
(12) We find that these molecules fold to form a symmetrical bimolecular and an intramolecular quadruplex, respectively.
(13) An increase in ionic strength stabilizes the single-stranded structure, so it seems to inhibit the formation of the quadruplex.
(14) Experiments on ethidium bromide binding to the oligonucleotides have shown that the oligomer anti(A-T) exists, at a low ionic strength, as a four stranded complex ("quadruplex") contains two antiparallel helices, d(A).d(T), which have a parallel orientation and are bound to one another owing to the formation of additional hydrogen bonds between nucleic acid bases.
(15) The quadruplex is stable in the presence of 40 mM K+ at micromolar DNA concentration and can be kinetically trapped as a metastable form when prepared at millimolar DNA concentration and then diluted into buffer containing 40 mM Na+.
(16) Cations stabilize the quadruplex in the order K+ greater than Ca2+ greater than Na+ greater than Mg2+ greater than Li+ and K+ greater than Rb+ greater than Cs+, indicating that K+ has an optimum ionic radius for complex formation and that ionic charge affects the extent of ion-induced stabilization.
(17) Comparison with the corresponding CD spectral characteristics suggests that the electrophoretic intensity enhancement of the intermolecular G-quadruplex band is correlated to the intensity enhancement of of the positive CD maximum at 265 nm.
(18) Similar but less dramatic enhancement of the intermolecular quadruplex band is also observed in T4.
(19) Since K+ and NH4+ are known to stabilize a parallel-stranded quadruplex structure of poly[r(I)4], we infer that the multistranded structure is a quadruplex.
(20) UV thermal denaturation curves show a single concentration-dependent transition and provide data for quantitating the thermodynamics of quadruplex formation.
Telegraphy
Definition:
(n.) The science or art of constructing, or of communicating by means of, telegraphs; as, submarine telegraphy.
Example Sentences:
(1) The compression technique is a variation of the Consultive Committee on International Telephony and Telegraphy Joint Photograph Experts Group compression that suppresses the blocking of the discrete cosine transform except in areas of very high contrast.
(2) The recognition of telegraphy disturbed by noise seems to follow the relations known from experiments with short-tone audiometry.
(3) These facts should be taken into consideration when training telegraphy operators as well as in the construction of radio receivers to permit listening at low frequencies.
(4) He was susceptible to get-rich-quick schemes: the ventures he invested in and promoted – even as he was writing his greatest books – included vineyards, a steam generator, a steam pulley, a watch company, an insurance company, marine telegraphy, a food supplement called Plasmon, a chalk engraving process called Kaolatype, self-adjusting suspenders and the Paige typesetting machine, which bankrupted him at the height of his fame and forced him back on to the lecture circuit to pay his debts, in part, it's been suggested, to protect the value of his "honourable" brand.
(5) The licence fee has funded the BBC since 1923, when the Wireless Telegraphy Act was introduced to cover radio sets.