Lifetime Probes

Anc er Icmg-lived organic fluorophcne is coronene, which displays a lifetime near 200 ns. In membranes the intensity decay of coronene is multiexponential. 

Coronene has also been conjugated to lipids. Both pyrene and coronene display low initial anisotropies and are only moderately useful for anisotropy experiments. However, as described in the following sections, diae are two types of organmnetallic fluorophores which display long lifetimes and other unique features which allow new types of experiments. 

Lanthanides possess some favorable properties as biochemical probes. They can substitute chemically for calcium in many calcium-dependimLpniiems. A main route of nonradiative decay is Ify cou dii to vibrations of water. For both Eu and Tb, the lifetiiite i n HjO and D]0 can be used to calculate the number of bound water molecules (n)  

Landianides can also be used with proteins which do not have intrinsic Ending sites. Reagents have been developed whidt can be coupled to proteins uid which chelate Ian-thanides. Because of dteir sensitivi to water, Ian thanide complexes designed as labels generally have most sites occupied by the ligand. 

Principle of iime-fesolved detection in tantiMnide immunoassays. Revised ftwn Ref. 130. 

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Microviscosity imaging Identify viscosity-lifetime probes... 

We have characterized some of the available caldum probes as potential lifetime probes using phase-modulation fluorometiy. The lifetime charaderistics and phase-modulation caldum (fynamic ranges are summarized in Table II and in Figure 12. 

It is important to notice that the use of a long-lifetime probe allowed measurement of overall rotation of the... 

The foot that both the acid and base forms of these probes are fluorescent suggests thdr use as lifetime probes. If only one fotm was fluorescent, then the lifetime would not... 

For completeness, we note that Ca probes have also been developed using azacrown ethers as the chelator, rather than BAPTA." However, these probes have been studied mostly in organic solvents and used to study the effects of Cif on dectron transfer. Such probes have not found use in cell physiology. Magnesium-sensitive probes are also available (Table 19.4), " and some have been characterized as lifetime probes. These probes typically have the AFTRA chdator, father than BAFTA, as can be seen for the calcium probe Indo-1 and the analogous magnesium probe Mag-Indo-1 (Hguie 19.52). 

L etimes and Oxygen Quenching In Section I9.4.B, we stated that a short-lifetime probe can serve as an intensity reference in an oxygen sensor. Assume that the lifetime of the [Ru(Ph2phen)3] oxygen sensor is 5 is and that the lifetime of the reference fluorophore is 5 ns. Describe Che relative encs of quenching for each probe. 

Thrae ate numaous biophysical applications for long-life-time anisotropy probes. These include studies of all types of macromolecular assemblies. The use of long-lifetime probes in biochemistry is just banning. We have chosen to show just three representative applications studies of DMA dynamics, measurement of domam-to-domain mo-... 

The emission spectra (Figure 2034) reveal that the probe is iuminescent in both the protonated and the unpio-tonated form. This suggests drat it can be usdiil as a lifetime probe because each fiiim is luminescent and may display distinct decay times. TD or FD measurements could be used to recover the mnltiexponenfial decqr ex-... 

Time domain Suitable for long-lifetime probes Consecutive acquisition of time... 

Recently a lifetime-probe (Newport Green DCF) for imaging Zn + has been described [124], and also reports have appeared of non-ratiometric lifetime probes for quantifying Na+ [ 125] and for Mg (magnesium-green, Mag-quin-2, Mag-quin-1), Cl (MQAE,SPQ), heavy metals (bis-BTC) andK+ (PBFI) [126]. 

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