||Archaea Halobacterium salinarum
||Claassens NJ, Volpers M, dos Santos VA, van der Oost J, de Vos WM. Potential of proton-pumping rhodopsins: engineering photosystems into microorganisms. Trends Biotechnol. 2013 Nov31(11):633-42. doi: 10.1016/j.tibtech.2013.08.006. p.637 left column 2nd paragraphPubMed ID24120288
||Kirchman, D.L. and Hanson, T.E. (2013) Bioenergetics of photoheterotrophic bacteria in the oceans. Environ. Microbiol. Rep. 5, 188–199 & Birge, R.R. (1990) Nature of the primary photochemical events in rhodopsin and bacteriorhodopsin. Biochim. Biophys. Acta 1016, 293–327PubMed ID23584962, 2184895
||"Basically, the maximal proton-pumping rate is determined
by two biophysical characteristics: the length of the
photocycle and the quantum yield. Once the photocycle is
complete after the absorption of a photon, the PPR [proton-pumping rhodopsin] is ready
to absorb and pump another proton. However, not a lot and
consistent photocycle lengths are available for most PPRs.
The quantum efficiency is the part of all the absorbed
photons that results in a proton being exported. Determining
quantum efficiency is rather complicated and different
values have been reported for the well-studied bacteriorhodopsin
from H. salinarum, but its quantum efficiency is
generally assumed to be approximately 60% [primary sources]."