Hi Rakesh
Your lifetime of singlet oxygen seems to be off by about 3 orders, if the publication below is to be believed.
http://pubs.rsc.org/en/Content/ArticleLanding/1972/F2/f29726800586
It says the lifetime is about 12 microseconds in (organic?)solution.
The following paper says it would be about 48 microseconds in aqueous solutions:
http://pubs.acs.org/doi/full/10.1021/ja800926v
In the nucleus of a cell, the following paper estimates the lifetime to be about 3 microseconds. This looked the most convincing to me:
http://pubs.acs.org/doi/full/10.1021/jp051163i
They seem to be comfortable with using the diffusion coefficient of aqueous oxygen (2 × 10-5 cm2 s-1) to calculate the distance traveled by the singlet oxygen species in 2X lifetimes (6 microseconds) as 268 nm.
However, I am not convinced that singlet oxygen, a mono atomic species will be as sluggish as molecular dioxygen. You could probably find cross references from this paper and estimate the diffusion rate of singlet oxygen, I am sure.
But this could be a good starting point.
Hope this helps.
Hi Rakesh
I made a mistake in my earlier comment. My apologies.
Singlet oxygen is indeed a di-oxygen species. I suppose you could use the diffusion rate of molecular oxygen after all.
Hello,
I am surprised, how long distance and time the singlet oxygen can diffuse according to the data you both stated. I am not familiar with chemistry or physics of reactive oxygen species, but my idea is that it should react as quickly as possible with the first organic molecule it would meet in the place of its origin or in close proximity from there, shouldn't it?
Hi Stepan
The actual ability of singlet oxygen to diffuse out to any distance will depend on two competing but independent factors: 1) Rate of diffusion and 2) the presence of other molecules that are capable of quenching singlet oxygen. While the rate of diffusion can be considered relatively constant inside most cells (although it will depend on the viscosity of the medium and ambient temperature), The abundance of quenchers (Eg. chemicals with electron rich double bonds like linolenic acid, and aromatic amino acids) may vary considerably depending upon the nature of the membranes and proteins in the vicinity of the sites that produce singlet oxygen.
The paper I quoted (http://pubs.acs.org/doi/full/10.1021/jp051163i) states that BSA in bulk solution with singlet oxygen can quench 96% of it almost instantaneously, preventing it from diffusing to any significant distance. However, if a large enough quantity of singlet oxygen is produced, then sufficient quantities can diffuse to a larger radius. Under the conditions mentioned in the above paper, 30% of the singlet oxygen produced inside the nucleus could diffuse out to the cytoplasm across the nuclear membrane.
Please refer to the following paper for some good basic information on singlet oxygen in biological systems:
http://www.imamu.edu.sa/Scientific_selections/abstracts/Chemistry/Chemistry%20and%20Reaction%20of%20Singlet%20Oxygen%20in%20Foods.pdf
Cheers
Hello
The lifetime was estimated to be 3µs in water and 14µs in membranes and the diffusion length was calculated to be 200 and 400 nm respectively.
The biological effect of singlet oxygen was very nicely investigated in this paper (for plants though, but similarities should be present among different organism)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556806/?tool=pmcentrez&rendertype=abstract
Cheers
Hi, Perumal,
thanks a lot for the brief intro to singlet oxygen behaviour. I will check the papers...
Thanks to all for the comments,
In my view :
Using the Einstein–Smoluchowski two-dimensional diffusion model, singlet oxygen diffusion constant in water [Moan 1990], and considering that cells are predominantly aqueous systems, the maximum distance that singlet oxygen could diffuse is ~270 nm (~0.3 µm) (Wilkinson et al. 1995, Baier et al. 2005, Skovsen et al. 2005). This is a very small distance on the scale of cell dimensions. Typical eukaryotic cells have diameter of 10-30 µm, chloroplast are around 3-10 µm in diameter whereas bilayer thylakoid membrane is 5 -7 nm thick. The thickness of plant cell membrane is 100-200 nm (0.2 µm -0.3 µm) (Lodish wt al. 2000, Redmond et al. 2006). Consequently, the primary reactions of singlet oxygen in a cell occur within its short diffusion distance, i.e., at a molecular level. The singlet oxygen can cross the membrane depending on the vicinity of formation but mostly, if membrane is present in the vicinity of formation than more chances of diffusion traveling very less distances.
- Badges
- Science topic
- Similar topics
- Biological Science
- Botany
- Plant Biology