(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.
System
Definition:
(n.) An assemblage of objects arranged in regular subordination, or after some distinct method, usually logical or scientific; a complete whole of objects related by some common law, principle, or end; a complete exhibition of essential principles or facts, arranged in a rational dependence or connection; a regular union of principles or parts forming one entire thing; as, a system of philosophy; a system of government; a system of divinity; a system of botany or chemistry; a military system; the solar system.
(n.) Hence, the whole scheme of created things regarded as forming one complete plan of whole; the universe.
(n.) Regular method or order; formal arrangement; plan; as, to have a system in one's business.
(n.) The collection of staves which form a full score. See Score, n.
(n.) An assemblage of parts or organs, either in animal or plant, essential to the performance of some particular function or functions which as a rule are of greater complexity than those manifested by a single organ; as, the capillary system, the muscular system, the digestive system, etc.; hence, the whole body as a functional unity.
(n.) One of the stellate or irregular clusters of intimately united zooids which are imbedded in, or scattered over, the surface of the common tissue of many compound ascidians.
Example Sentences:
(1) This particular variant of rheumatoid arthritis (RA) is characterized by the presence of subcutaneous rheumatoid nodules, scanty or absent systemic manifestations and a clinically benign course.
(2) These factors might account for the lower systemic bioavailability of these compounds.
(3) The most actively proliferating region of the excurrent duct system is zone 3 of the epididymis, whereas the least active region is the ductuli efferentes.
(4) In 49 cases undergoing systemic lymphadenectomy 32 were found to have glandular involvement, of which both aortic and pelvic nodes were positive in 17 cases (53.1%), aortic nodes positive but pelvic negative in six (18.8%), and pelvic nodes positive but aortic negative in nine (28.1%).
(5) An automated continuous flow sample cleanup system intended for rapid screening of foods for pesticide residues in fresh and processed vegetables has been developed.
(6) Spectral analysis of spontaneous heart rate fluctuations, a powerful noninvasive tool for quantifying autonomic nervous system activity, was assessed in Xenopus Laevis, intact or spinalized, at different temperatures and by use of pharmacological tools.
(7) Herpesviruses such as EBV, HSV, and human herpes virus-6 (HHV-6) have a marked tropism for cells of the immune system and therefore infection by these viruses may result in alterations of immune functions, leading at times to a state of immunosuppression.
(8) It is concluded that during exposure to simulated microgravity early signs of osteoporosis occur in the tibial spongiosa and that changes in the spongy matter of tubular bones and vertebrae are similar and systemic.
(9) The telencephalic proliferative response has been studied in adult newts after lesion on the central nervous system.
(10) In dogs, cibenzoline given i.v., had no effects on the slow response systems, probably because of sympathetic nervous system intervention since the class 4 effects of cibenzoline appeared after beta-adrenoceptor blockade.
(11) The various evocational changes appear to form sets of interconnected systems and this complex network seems to embody some plasticity since it has been possible to suppress experimentally some of the most universal evocational events or alter their temporal order without impairing evocation itself.
(12) The Cavitron Ultrasonic Surgical Aspirator (CUSA) is a dissecting system that removes tissue by vibration, irrigation and suction; fluid and particulate matter from tumors are aspirated and subsquently deposited in a canister.
(13) In cardiac tissue the adenylate system is not a good indicator of the energy state of the mitochondrion, even when the concentrations of AMP and free cytosolic ADP are calculated from the adenylate kinase and creatine kinase equilibria.
(14) These results suggest the presence of a new antigen-antibody system for another human type C retrovirus related antigens(s) and a participation of retrovirus in autoimmune diseases.
(15) The combined analysis of pathogenesis and genetics associated with the salmonella virulence plasmids may identify new systems of bacterial virulence and the genetic basis for this virulence.
(16) We determined whether serological investigations can assist to distinguish between chronic idiopathic autoimmune thrombocytopenia (cAITP) and immune-mediated thrombocytopenia in patients at risk to develop systemic lupus erythematosus (SLE); 82 patients were seen in this institution for the evaluation of immune thrombocytopenia.
(17) The results demonstrated that K2PtCl4 was bound to a greater degree than CDDP in this system with 3-5 and 1-2 platinum atoms respectively, bound per transferrin molecule.
(18) IgE-mediated acute systemic reactions to penicillin continue to be an important clinical problem.
(19) The PSB dioxygenase system displayed a narrow substrate range: none of 18 sulphonated or non-sulphonated analogues of PSB showed significant substrate-dependent O2 uptake.
(20) Although solely nociresponsive neurons are clearly likely to fill a role in the processing and signalling of pain in the conscious central nervous system, the way in which such useful specificity could be conveyed by multireceptive neurons is difficult to appreciate.