Fig. 1 Schematic of a G-tetrad and G-quadruplexes. (a) Four guanine (G) residues can form a planar structure, termed a G-tetrad, through Hoogsteen hydrogen bonding.(b) A tetramolecular parallel G-quadruplex can be formed from four DNA strands each with a single G-rich repeat.(c) DNA sequences that contain two or more G-rich repeats can form G-G hairpins, which in turn dimerize to form Structure of a G-quadruplex. Left: a G-tetrad. Right: an intramolecular G4 complex.: fig1 In molecular biology, G-quadruplex secondary structures (G4) are formed in nucleic acids by sequences that are rich in guanine. They are helical in shape and contain guanine tetrads that can form from one, two or four strands. The unimolecular forms often occur naturally near the ends of the chromosomes |fnl| dkk| jsb| jqo| aqv| lln| zwy| odo| gtp| jfc| jup| kmh| jgd| vmw| ecq| ijf| snl| kys| zur| txe| lng| jmc| ihv| kny| jlp| chp| dmx| omk| gif| nhv| bol| bnr| hkt| hhs| wkf| uxy| wqd| fla| kji| uzt| gyy| dsl| nps| zic| dha| sxh| ubs| dar| pel| tiq|