Kinetic Properties of DM-Nitrophen Binding to Calcium and Magnesium
Caged-Ca 2+ compounds such as nitrophenyl-EGTA (NP-EGTA) and DM-nitrophen (DMn) are extremely useful in biological research, but their use in live cells is hampered by cytoplasmic [Mg 2+]. We determined the properties of Ca 2+ release from NP-EGTA and DMn by using Oregon green BAPTA-5N to measure ch...
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Published in | Biophysical journal Vol. 88; no. 6; pp. 4421 - 4433 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
United States
Elsevier Inc
01.06.2005
Biophysical Society |
Subjects | |
Online Access | Get full text |
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Summary: | Caged-Ca
2+ compounds such as nitrophenyl-EGTA (NP-EGTA) and DM-nitrophen (DMn) are extremely useful in biological research, but their use in live cells is hampered by cytoplasmic [Mg
2+]. We determined the properties of Ca
2+ release from NP-EGTA and DMn by using Oregon green BAPTA-5N to measure changes in [Ca
2+] after ultraviolet flash photolysis in vitro, with or without Mg
2+ present. A large fraction (65%) of NP-EGTA, which has a negligible Mg
2+ affinity, uncages with a time constant of 10.3
ms, resulting in relatively slow increases in [Ca
2+]. Uncaging of DMn is considerably faster, but DMn has a significant affinity for Mg
2+ to complicate the uncaging process. With experimentally determined values for the Ca
2+ and Mg
2+ binding/unbinding rates of DMn and NP-EGTA, we built a mathematical model to assess the utility of NP-EGTA and DMn in rapid Ca
2+-uncaging experiments in the presence of Mg
2+. We discuss the advantages and disadvantages of using each compound under different conditions. To determine the kinetics of Ca
2+ binding to biologically relevant Ca
2+ buffers, such as Ca
2+-binding proteins, the use of DMn is preferable even in the presence of Mg
2+. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Address reprint requests to Istvan Mody, Dept. of Neurology, University of California, Los Angeles, Reed Building 710, Los Angeles, CA 90095. Tel.: 310-206-4481; Fax: 310-825-0033; E-mail: mody@ucla.edu. |
ISSN: | 0006-3495 1542-0086 |
DOI: | 10.1529/biophysj.104.057745 |