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Nonlinear dielectric spectroscopy as an indirect probe of metabolic activity in thylakoid membrane.

Fang J, Palanisami A, Rajapakshe K, Widger WR, Miller JH - Biosensors (Basel) (2011)

Bottom Line: Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity.We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system.Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204, USA. jfang@mail.uh.edu.

ABSTRACT
Nonlinear dielectric spectroscopy (NDS) is a non-invasive probe of cellular metabolic activity with potential application in the development of whole-cell biosensors. However, the mechanism of NDS interaction with metabolic membrane proteins is poorly understood, partly due to the inherent complexity of single cell organisms. Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity. We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system. Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.

No MeSH data available.


Related in: MedlinePlus

Continuous measurement of the 2nd harmonic response. (a) Time dependence of the 2nd harmonic response with a 3,072 Hz, 8 Vpp driving sinusoidal voltage. Every point is a 4 s average of the 2nd harmonic response. (b) The measurement of the O2 concentration of the suspension was taken simultaneously with the 2nd harmonic response seen in (a). The measurement was carried out with 0.2 mg/mL chlorophyll in 5 mL suspension buffer with 1.0 mM K3Fe(CN)6 as described in the text. The O2 concentration increases in the dark due to O2 absorption from the atmosphere.
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biosensors-01-00013-f003: Continuous measurement of the 2nd harmonic response. (a) Time dependence of the 2nd harmonic response with a 3,072 Hz, 8 Vpp driving sinusoidal voltage. Every point is a 4 s average of the 2nd harmonic response. (b) The measurement of the O2 concentration of the suspension was taken simultaneously with the 2nd harmonic response seen in (a). The measurement was carried out with 0.2 mg/mL chlorophyll in 5 mL suspension buffer with 1.0 mM K3Fe(CN)6 as described in the text. The O2 concentration increases in the dark due to O2 absorption from the atmosphere.

Mentions: The time dependence of the 2nd harmonic response is more explicitly monitored in Figure 3. Upon light exposure, the 2nd harmonic response is seen to gradually reduce in magnitude. A key point here is the irreversible nature of the change—the 2nd harmonic response does not return to its original value after the light is turned off. Thus the 2nd harmonic response is not directly probing ETC activity, but some related aspect. To measure the change in the 2nd harmonic response, a convenient measure is the difference of the 2nd harmonic response before and after light application. To this end, we measure the average 2nd harmonic response over 1 min immediately before (Vbefore) and after (Vafter) 2 min of light application. We define the 2nd harmonic difference as∆V2f = Vafter − Vbefore(1)


Nonlinear dielectric spectroscopy as an indirect probe of metabolic activity in thylakoid membrane.

Fang J, Palanisami A, Rajapakshe K, Widger WR, Miller JH - Biosensors (Basel) (2011)

Continuous measurement of the 2nd harmonic response. (a) Time dependence of the 2nd harmonic response with a 3,072 Hz, 8 Vpp driving sinusoidal voltage. Every point is a 4 s average of the 2nd harmonic response. (b) The measurement of the O2 concentration of the suspension was taken simultaneously with the 2nd harmonic response seen in (a). The measurement was carried out with 0.2 mg/mL chlorophyll in 5 mL suspension buffer with 1.0 mM K3Fe(CN)6 as described in the text. The O2 concentration increases in the dark due to O2 absorption from the atmosphere.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4264345&req=5

biosensors-01-00013-f003: Continuous measurement of the 2nd harmonic response. (a) Time dependence of the 2nd harmonic response with a 3,072 Hz, 8 Vpp driving sinusoidal voltage. Every point is a 4 s average of the 2nd harmonic response. (b) The measurement of the O2 concentration of the suspension was taken simultaneously with the 2nd harmonic response seen in (a). The measurement was carried out with 0.2 mg/mL chlorophyll in 5 mL suspension buffer with 1.0 mM K3Fe(CN)6 as described in the text. The O2 concentration increases in the dark due to O2 absorption from the atmosphere.
Mentions: The time dependence of the 2nd harmonic response is more explicitly monitored in Figure 3. Upon light exposure, the 2nd harmonic response is seen to gradually reduce in magnitude. A key point here is the irreversible nature of the change—the 2nd harmonic response does not return to its original value after the light is turned off. Thus the 2nd harmonic response is not directly probing ETC activity, but some related aspect. To measure the change in the 2nd harmonic response, a convenient measure is the difference of the 2nd harmonic response before and after light application. To this end, we measure the average 2nd harmonic response over 1 min immediately before (Vbefore) and after (Vafter) 2 min of light application. We define the 2nd harmonic difference as∆V2f = Vafter − Vbefore(1)

Bottom Line: Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity.We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system.Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204, USA. jfang@mail.uh.edu.

ABSTRACT
Nonlinear dielectric spectroscopy (NDS) is a non-invasive probe of cellular metabolic activity with potential application in the development of whole-cell biosensors. However, the mechanism of NDS interaction with metabolic membrane proteins is poorly understood, partly due to the inherent complexity of single cell organisms. Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity. We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system. Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.

No MeSH data available.


Related in: MedlinePlus