Light-Driven Ca2+ Ion Pump

How Does It Work?

Cheng Tsung Lai, Yu Zhang, George C. Schatz

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Work done by Bennett et al. [ Nature 2002, 420, 398-401 ] demonstrated that Ca2+ ions can be actively transported through a lipid bilayer membrane by an artificial photosynthetic machine. However, details of the pump process, such as the oxidation state of the shuttle molecule and stoichiometry of the shuttle-ion complex, are not fully understood, which hinders the development of ion pumps of this type with higher efficiency. In this study, we combine all atom molecular dynamics simulations and quantum mechanics calculations to estimate the time scale of the shuttle-ion complex diffusion process and charge transfer step. We find that the process of shuttle-ion complex diffusion across the lipid bilayer membrane is the rate-limiting step, with a time scale of seconds to minutes. Other processes such as charge transfer between the redox reaction center and the shuttle molecule have picoseconds time scales. We also show that a shuttle-ion complex with 2:1 stoichiometry ratio has a lower energy barrier across the lipid membrane than other choices of complexes. The calculations show that the Ca2+ ion is likely to be shuttled by a semiquinone type of shuttle molecule as this has the lowest free energy barrier across the lipid bilayer membrane, the fewest electrons transferred in the redox cycle, and it does not generate (or require) proton flow. Estimates of ion flow rates are consistent with measured values.

Original languageEnglish
Pages (from-to)15110-15117
Number of pages8
JournalJournal of Physical Chemistry B
Volume119
Issue number49
DOIs
Publication statusPublished - Dec 10 2015

Fingerprint

Ion Pumps
ion pumps
Pumps
Ions
Membrane Lipids
Lipid bilayers
lipids
ions
membranes
Energy barriers
Stoichiometry
Molecules
Membranes
Charge transfer
stoichiometry
charge transfer
molecules
Redox reactions
Quantum theory
estimates

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

Light-Driven Ca2+ Ion Pump : How Does It Work? / Lai, Cheng Tsung; Zhang, Yu; Schatz, George C.

In: Journal of Physical Chemistry B, Vol. 119, No. 49, 10.12.2015, p. 15110-15117.

Research output: Contribution to journalArticle

Lai, Cheng Tsung ; Zhang, Yu ; Schatz, George C. / Light-Driven Ca2+ Ion Pump : How Does It Work?. In: Journal of Physical Chemistry B. 2015 ; Vol. 119, No. 49. pp. 15110-15117.
@article{678959c3f106477d814e44f67d8fe47a,
title = "Light-Driven Ca2+ Ion Pump: How Does It Work?",
abstract = "Work done by Bennett et al. [ Nature 2002, 420, 398-401 ] demonstrated that Ca2+ ions can be actively transported through a lipid bilayer membrane by an artificial photosynthetic machine. However, details of the pump process, such as the oxidation state of the shuttle molecule and stoichiometry of the shuttle-ion complex, are not fully understood, which hinders the development of ion pumps of this type with higher efficiency. In this study, we combine all atom molecular dynamics simulations and quantum mechanics calculations to estimate the time scale of the shuttle-ion complex diffusion process and charge transfer step. We find that the process of shuttle-ion complex diffusion across the lipid bilayer membrane is the rate-limiting step, with a time scale of seconds to minutes. Other processes such as charge transfer between the redox reaction center and the shuttle molecule have picoseconds time scales. We also show that a shuttle-ion complex with 2:1 stoichiometry ratio has a lower energy barrier across the lipid membrane than other choices of complexes. The calculations show that the Ca2+ ion is likely to be shuttled by a semiquinone type of shuttle molecule as this has the lowest free energy barrier across the lipid bilayer membrane, the fewest electrons transferred in the redox cycle, and it does not generate (or require) proton flow. Estimates of ion flow rates are consistent with measured values.",
author = "Lai, {Cheng Tsung} and Yu Zhang and Schatz, {George C.}",
year = "2015",
month = "12",
day = "10",
doi = "10.1021/acs.jpcb.5b07578",
language = "English",
volume = "119",
pages = "15110--15117",
journal = "Journal of Physical Chemistry B Materials",
issn = "1520-6106",
publisher = "American Chemical Society",
number = "49",

}

TY - JOUR

T1 - Light-Driven Ca2+ Ion Pump

T2 - How Does It Work?

AU - Lai, Cheng Tsung

AU - Zhang, Yu

AU - Schatz, George C.

PY - 2015/12/10

Y1 - 2015/12/10

N2 - Work done by Bennett et al. [ Nature 2002, 420, 398-401 ] demonstrated that Ca2+ ions can be actively transported through a lipid bilayer membrane by an artificial photosynthetic machine. However, details of the pump process, such as the oxidation state of the shuttle molecule and stoichiometry of the shuttle-ion complex, are not fully understood, which hinders the development of ion pumps of this type with higher efficiency. In this study, we combine all atom molecular dynamics simulations and quantum mechanics calculations to estimate the time scale of the shuttle-ion complex diffusion process and charge transfer step. We find that the process of shuttle-ion complex diffusion across the lipid bilayer membrane is the rate-limiting step, with a time scale of seconds to minutes. Other processes such as charge transfer between the redox reaction center and the shuttle molecule have picoseconds time scales. We also show that a shuttle-ion complex with 2:1 stoichiometry ratio has a lower energy barrier across the lipid membrane than other choices of complexes. The calculations show that the Ca2+ ion is likely to be shuttled by a semiquinone type of shuttle molecule as this has the lowest free energy barrier across the lipid bilayer membrane, the fewest electrons transferred in the redox cycle, and it does not generate (or require) proton flow. Estimates of ion flow rates are consistent with measured values.

AB - Work done by Bennett et al. [ Nature 2002, 420, 398-401 ] demonstrated that Ca2+ ions can be actively transported through a lipid bilayer membrane by an artificial photosynthetic machine. However, details of the pump process, such as the oxidation state of the shuttle molecule and stoichiometry of the shuttle-ion complex, are not fully understood, which hinders the development of ion pumps of this type with higher efficiency. In this study, we combine all atom molecular dynamics simulations and quantum mechanics calculations to estimate the time scale of the shuttle-ion complex diffusion process and charge transfer step. We find that the process of shuttle-ion complex diffusion across the lipid bilayer membrane is the rate-limiting step, with a time scale of seconds to minutes. Other processes such as charge transfer between the redox reaction center and the shuttle molecule have picoseconds time scales. We also show that a shuttle-ion complex with 2:1 stoichiometry ratio has a lower energy barrier across the lipid membrane than other choices of complexes. The calculations show that the Ca2+ ion is likely to be shuttled by a semiquinone type of shuttle molecule as this has the lowest free energy barrier across the lipid bilayer membrane, the fewest electrons transferred in the redox cycle, and it does not generate (or require) proton flow. Estimates of ion flow rates are consistent with measured values.

UR - http://www.scopus.com/inward/record.url?scp=84949525585&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84949525585&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcb.5b07578

DO - 10.1021/acs.jpcb.5b07578

M3 - Article

VL - 119

SP - 15110

EP - 15117

JO - Journal of Physical Chemistry B Materials

JF - Journal of Physical Chemistry B Materials

SN - 1520-6106

IS - 49

ER -