Chemistry Reference
In-Depth Information
to obtain simultaneous and independent recordings from ion channels via imaging of
single-channel Ca
2 þ
flux [13]. Acetylcholine (ACh) receptor channels were expressed
in Xenopus oocytes where single channel Ca
2 þ
fluorescence transients were imaged
using
fluo-4 as the indicator. Consistent with their passage through the opening of
individual nicotinic channels,
fluorescent signals were seen only when a nicotinic
agonist was present in the bathing solution, and were not observed in the presence of
curare, and increased in frequency roughly with the second power of ACh concentra-
tion. The rise and fall times of
fluorescence were as fast as 2ms, providing a kinetic
resolution that was suf
ciently adequate to characterize channel gating kinetics.
4.6
Conclusion
Single molecule imaging of ion-channel proteins is still not as well developed as that
for water-soluble proteins. Nevertheless, single molecule imaging has such potential
that it is worthwhile developing techniques that can be applied to ion-channel
proteins. Progress, although slow, has been made as demonstrated by overcoming
lateral diffusion [14]. In this chapter we have described an application of single
molecule imaging techniques to simultaneously observe the optical and electrical
behavior of RyR. This is a very signi
cant advance which will produce large volumes
of information related to single channels.
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