title: 6-methylpyridyl for pyridyl substitution tunes the properties of fluorescent zinc sensors of the Zinpyr family.
abstract: To prepare fluorescent zinc sensors with binding affinities lower than that of the parent 9-(o-carboxyphenyl)-2,7-dichloro-4,5-bis(bis(2-pyridylmethyl)methylaminomethyl)-6-hydroxy-3-xanthenone (ZP1), dimethylated and tetramethylated derivatives were synthesized having either two or four of the pyridyl subunits methylated at the 6-position. Like the parent ZP1, both Me(2)ZP1 and Me(4)ZP1 exhibit increased fluorescence in the presence of Zn(2+). The integrated emission of Me(2)ZP1 increases 4-fold in the presence of excess zinc, whereas Me(4)ZP1 displays 2.5-fold enhanced fluorescence for Zn(2+). Methylating the 6-positions of the pyridyl rings raises the dissociation constant of the sensors and lowers the pK(a) values associated with the tertiary amine ligands in a systematic manner. The properties of the dimethylated Me(2)ZP1 dye resemble those of ZP1, but the tetramethylated Me(4)ZP1 differs greatly from ZP1 in terms of its brightness, affinity toward Zn(2+), exchange kinetics, and metal sensitivity. Both Me(2)ZP1 and Me(4)ZP1 can enter HeLa cells and signal the presence of Zn(2+). Staining caused by both dyes is punctate, with localization patterns resembling that observed for ZP1.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Christian R
authors.initials: CR
authors.lastname: Goldsmith
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lippard
mesh_terms: D002463:Cell Membrane Permeability / Q000502:physiology; D005452:Fluoresceins / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000138:chemical synthesis* / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics; D011725:Pyridines / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000737:chemistry*
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D015032:Zinc; C501987:zinpyr-1