# IGEM:UNAM/2009/Notebook/Modeling logbook Claudia/2010/04/06

UNAM-Genomics-Mexico team Main project page
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## Objective: Calculate the photon flux that saturates the LovTAP receptor.

In Strickland et al. is reported that LovTAP is saturated with 20 mW/cm^2 irradiance at 470 nm.

• Conversion to photons:

Using the following formula:

``` The energy E of a photon is
E = hc / λ
```

where h is Planck's Constant, h = 6.626176 x 10^-34 J•s

The velocity of any photon is c, the speed of light=3 * 10^8 m/ s

And λ the wavelength of the photon that in this case is 470 x 10^-9 m (470 nm).

Thus,

``` E=  ((6.63 * (10^(-34))) * (3 * (10^8))) / (470 * (10^(-9)))
E= 4.23191489 × 10^-19 J
```

```The photon flux density (Φ ) at a given light intensity is:

Φ= P/ E
```

where P is the light intensity in Watts and E the energy of a photon in Jules.

Substituting:

``` P= 0.02 Watts and E= 4.23191489 × 10^-19 J.
Φ= 0.02/ (4.23191489 * 10^-19 ) = 4.72599297 × 10^16 photons/s•cm2
```

## References

Strickland, D., Moffat, K., & Sosnick, T. (2008). Light-activated DNA binding in a designed allosteric protein. Proceedings of the National Academy of Sciences, 105(31), 10709. National Acad Sciences. Retrieved from http://www.pnas.org/content/105/31/10709.full.