Self-assembly of fluorescent inclusion complexes in competitive media including the interior of living cells.
Anthracene-containing tetralactam macrocycles are prepared and found to have an extremely high affinity for squaraine dyes in chloroform (log Ka = 5.2). Simply mixing the two components produces highly fluorescent, near-infrared inclusion complexes in quantitative yield. An X-ray crystal structure shows the expected hydrogen bonding between the squaraine oxygens and the macrocycle amide NH residues, and a high degree of cofacial aromatic stacking. The kinetics and thermodynamics of the assembly process are very sensitive to small structural changes in the binding partners. For example, a macrocycle containing two isophthalamide units associates with the squaraine dye in chloroform 400,000 times faster than an analogous macrocycle containing two 2,6-dicarboxamidopyridine units. Squaraine encapsulation also occurs in highly competitive media such as mixed aqueous/organic solutions, vesicle membranes, and the organelles within living cells. The highly fluorescent inclusion complexes possess emergent properties; that is, as compared to the building blocks, the complexes have improved chemical stabilities, red-shifted absorption/emission maxima, and different cell localization propensities. These are useful properties for new classes of near-infrared fluorescent imaging probes.
Gassensmith
Jeremiah J
JJ
Department of Chemistry and Biochemistry and the Walther Cancer Research Center, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Arunkumar
Easwaran
E
Barr
Lorna
L
Baumes
Jeffrey M
JM
DiVittorio
Kristy M
KM
Johnson
James R
JR
Noll
Bruce C
BC
Smith
Bradley D
BD
D000818:Animals; D016466:CHO Cells; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D018360:Crystallography, X-Ray; D003470:Culture Media; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000494:pharmacology*; D007700:Kinetics; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry; D012997:Solvents
D003470:Culture Media; D005456:Fluorescent Dyes; D009930:Organic Chemicals; D012997:Solvents